123+

Well, its official.  Joe Taylor's 1939 61 cubic inch Knucklehead now holds the world record in the MPS VG 1000  class for the Bub Speed Trials at Bonneville!

The record runs were made on Tuesday with Terry of Gunner's Cycle piloting.  The record now stands at 123.526, just over 14 mph higher than the previous class record held by Sid Biberman's Vincent. 

Terry feels that there is  more mph to be found since the newly added AFR gauges showed the jetting still quite rich, however rain precluded any further attempt for this year.  Dyno testing was not in the cards for the Gray Goose this past summer, and though the speed is well short of the team's goal, they wisely decided to fore go any tuning changes until after the record was in their possession. 

Congratulations to Joe, Terry and John for reaching this milestone in only their second year on the salt with the Goose.  And if you would allow me to indulge in a little patting myself on the back, I would like to mention that I not only built the motor, but I also supplied the 2.060" valves and guides used to set this record. It is always a nice when you can add "World Record Setting" to a product description! 

Now, if the boys can just add another 16-1/2 mph next year...   

The Grey Goose 2013

As promised, here is a little more prospective on the hole in the rear piston phenomena which may be prominent on the Salt Flats.  As you may recall, just two posts ago I told the sad tale of the season ending piston failure in the Grey Goose; Joe Taylor's 1939 Knucklehead Bonneville racer.  To review what we already know:

1. In order to raise the compression ratio without having another set of custom pistons made, I welded the domes to fill in unneeded valve pocket clearance.
2. Despite the welding and re-machining, the piston dome thickness remained at a reasonable .200".
3. The engine was not run too lean, in fact just the opposite. 
4. Rear cylinder piston failure is common on Harleys with dual fire (aka wasted spark) ignitions at Bonneville.

The small holes were drilled after the fact to check dome thickness 

Exhaust pocket had also begun to "sag"

To clarify, for those not up to date on Harleys old wasted spark ignition system, it works like this.  On all but the latest offerings from Milwaukee, the timer, whether it be a battery/points ignition or a magneto, turns at half the speed of the engine.  This timer has two lobes (or notches for later electronic ignitions) which open the points, initiating the spark.  One lobe is set to open the points at the correct time for the front cylinder and the other at the correct time for the rear cylinder.  In the case of the Goose, that time was at 42 degrees BTDC (before top dead center) on the compression stroke.But  since these lobes both open the same single set of points, each cylinder gets a spark from each lobe, once at 42 BTDC on the compression stroke, and once on the exhaust stroke. 

Now you need to remember that the two cylinders on a Harley form a 45 degrees angle (thus the term 45 degree V-Twin).  That means that at any given point in time, the front piston will be at a point 45 degrees behind the rear piston in crankshaft rotation (I know that sounds backwards, but its not).  For instance, when the rear piston is at TDC on the compression stroke, the front piston will be 45 degrees away from reaching TDC, but it will be on the exhaust stroke.  This 45 degree offset is what makes things interesting.

Obviously if the rear piston is the one that normally takes the hit at Bonneville, there must be something that differs front cylinder to rear which is the culprit. And if it seems to be exclusive to wasted spark ignitions, then that would be a good place to look.

First lets look at the front cylinder.  After plotting the SS Cycle KN420 camshaft that the Goose employs, we find this:  At 42 degrees BTDC on the compression stroke the rear cylinder spark plug fires, and the wasted spark is produced at that same instant in the front cylinder.  However, the front cylinder is not at 42 BTDC on the exhaust stroke, but rather 87 degrees BTDC (remember it  trails the rear by 45 degrees).  At this point in time the front intake valve is still on its seat, in fact still about 6 degrees before it comes to the opening ramp on the cam.  The exhaust valve is just starting to close, but still near full lift.  OK - no problem.  That spark in the front cylinder with the exhaust valve open and intake valve closed won't do much.

Now for the rear cylinder.  When the front cylinder spark plug fires at 42 BTDC on the compression stroke, the rear cylinder is in a much different position.  Because of the the 45 degree offset, the rear piston is at 3 ATDC (after top dead center); technically not even still on the exhaust stroke, but rather beginning its descent on the intake stroke.  The exhaust valve is closing, but still .135" off its seat.  The intake valve on the other hand has already started to open to the tune of .185" off its seat.  Valve overlap is the common term.  Now that gives one something to think about doesn't it?

So her is some other pertinent info gleaned from PipeMax that may shed some light on the issue at hand.
Assume the Goose's engine were running 5500 RPM.  At the point where the rear cylinder receives its "wasted spark" (3 degrees ATDC in overlap), the piston has already started down on the intake stroke, accelerating to 325.5 feet per minute providing a "piston demand" of 10.1 cubic feet per minute of intake air flow.  Raise the RPM to the target 7500 and that becomes a piston speed of 443.8 feet per minute with a piston demand of 13.8 cfm.  All that is at a mere 3 degrees after top dead center.

If you put stock in David Vizard's theories (and I do), you may recall that he puts a large amount of emphasis on the overlap portion of the cam timing.  One of his conclusions is that the low pressure area caused by exhaust outflow results in the single strongest action initiating intake flow during this overlap period (hopefully I have paraphrased him properly).  So what effect does it have when you throw a spark into the middle of that overlap period?  A spark which incidentally does NOT occur during overlap on the front cylinder.  Hmmm.

So here are a few thoughts.  Obviously the rear cylinder is subjected to a spark during overlap which the front cylinder does not.  Since that cylinder is in overlap, there will be a fuel air mixture present to burn.  Now, that fuel air mixture is not compressed, but certainly it can burn none the less.  And what naturally comes along with burning fuel and air?  That's right - heat;  heat that the front cylinder is not subjected to.  I have no way of knowing or even estimating how much extra heat the rear cylinder gets this way, but the evidence would suggest that it may be just enough extra heat to melt a piston dome. 

Here is something else to consider though.  What happens when that wasted spark fires off and the fuel air mixture is richer than ideal?  The BTUs are in the fuel, not the air, so I would assume that you would be releasing even more heat than with a correct mixture.  Hmmm.  Remember that I said that the Goose was not run too lean.  It actually had the baseline jetting that it was dyno'ed with here in Minnesota.  The reason I was pretty sure that the piston did not fail from a lean condition was that I believe that it was "pig rich" (as I like to call it).  Could this be a case of a rich mixture giving the opposite results that one would expect?

But why does this happen at Bonneville, but not on the drag strip or on the street?  Well, my guess would be that it has everything to do with length of time spent under a heavy load.  Remember that aerodynamic drag becomes a huge factor at high speeds.  There are plenty of horsepower/MPH calculators available on line.  Plugging in some estimates (guess-timates?) for weight, frontal area and drag coefficient, we find that if it takes a mere 29 HP to hit 100 MPH, the same bike would need 55 HP to get to 125, and 77 horses to reach 140.  And if that is not enough of a wake up call, if you want to raise the MPH from 140 to 150 you better be ready to call up an extra 17 HP to wring out that 10 MPH.  Bottom line is that high speed puts a tremendous load on a motor, and the longer that load is present, the better the chance for heat build up.

Now we know that a drag motor will not see much time under full load and even less time at high speeds.  If you hit 100 MPH in the 1/8 mile, then you will likely see the 1/4 mile finish line in another 4 seconds. And on the street?  Despite thousands of bar room stories to the contrary, most street motors will never get more than a few seconds at full throttle and high speed before law enforcement rains on that parade.

So where do we go from here?  Obviously a single fire ignition system is in order.  The exact form that will take is still up in the air, with part of the team leaning toward keeping things as simple as possible, and part leaning toward as hi-tech as possible.  The other obvious bit is that new pistons are needed (you didn't really think I would weld them back up, did you?).  That part has been settled.

Four new pistons from Arias arrived this week, with the domes finished as per my sample (the undamaged front piston).  They are down right beautiful, and hopefully the two spares will remain in the box as spares for a long, long time.

EL Bonnie Wrap Up 2012

Here we are at the very end on 2012, and I have still not finished writing about EL Bonnie (recently re-named The Grey Goose).  Since I was not there, perhaps the best way to sum up the actual Salt Flats portion of the effort is to borrow from the writings of team member John Endrizzi as follows:

"We spent Sat and much of Sunday preparing The Goose for tech. After passing tech Sunday afternoon we had a freak thunderstorm, which left 2 inches of standing water on the Salt. Racing resumed Tuesday morning! We made our first pass that day after waiting in the starting queue for over 4 hours. By the time Terry set off from the starting line a very brisk crosswind had come up. He found the bike being blown from one side of the course almost hitting a marker flag on the opposite side. This was in the measured mile. He backed off the throttle. Later, he said that he was at 1/2 throttle and accelerating when the gust of wind hit him. The result was 115.929 mph. This was enough to break the Sid Biberman Vincent’s standing record of 109.079. By the time that we got the bike back to the pit, the wind speed had not died at all. It was decided not to make the return pass, which would be needed to post a new record. The next morning it was another long wait for our turn to run. Terry got off the line in good fashion and the bike sounded good thru 1-3rd gears. At the top of third, a little change in the motors rhythm was heard. While on the way down the return road, we heard the announcer say that our bike had run 59 MPH! Once back at the pit we found the rear cylinder had a holed piston. That was end of racing for The Goose!"

And, indeed that was the end of racing for the Grey Goose ...for 2012.  The motor is back in my shop, apart and waiting for new pistons.  If you read the previous posts on this engine build, then right about now you are no doubt saying to yourself, "So, welding the pistons turned out to be a bad idea after all!"  Or maybe even, "What kind of moron would weld on pistons anyway?"

I must admit, those were my first two reactions also.  After discussions with various sources ranging from fuel manufacturers to legendary engine builders,  it seems not to be so cut and dried.  (And a big thank you to John for taking the initiative to seek out those conversations!). 

First off, a few clues.  The front piston survived its excursion to the Salt Flats with absolutely no sign of any problem.  The team had not yet even started to lean out the jetting from its Minnesota baseline.  That in itself makes the possibility of a lean condition being the culprit very improbable.  The rear piston not only had a hole through the flat of the intake valve relief, it had also started to "sag" on the flat of the exhaust valve relief.  Drilling a small hole through the center of the "sag" allowed me to get an accurate measurement of the thickness at that point.  It was approximately .200" thick, which was just about the figure I was shooting for when I modified them.  The "sag" along with the appearance of the hole itself lead me to think that it was a heat problem rather than a detonation problem.

But all of that really left me none the wiser as to what had actually gone wrong.  Obviously new pistons that would not require the drastic modifications I performed on the last set were in order.  And I may have left it there, trusting that the hole in the piston was due to my overzealous welding in pursuit of compression, but for one dissenting opinion. One of the experts who John contacted in search of answers was Minnesota's own Mike Roland.  Mike did not think that the welding was to blame.  In fact, were it not for the fact that I personally believe that Mike is one of the brightest people to ever get involved in the Harley performance arena, I would have dismissed his idea without giving it any thought.  But when Mike speaks, I tend to listen; and closely at that!

When John contacted Mike for his thoughts, he immediately asked if it was the rear piston, and if it was a dual fire ignition.  Yes, and yes.  Well, it seems that at Bonneville, it is very common for Harley's to hole (using "hole" as a verb) the rear piston when using a stock style dual fire ignition.  I did not know that.  The team members for the Grey Goose did not know that.  Judging from other Bonneville stories I have since heard which feature "holed pistons", many others did not know that.

John's conversation with Mike Roland suggested a cure for the holed piston phenomenon (single fire), and even a reason for it (dual fire), but not an explanation.  That is not to say Mike did not have an explanation ready; just that John did not ask for one.  This left me with several options.  I could dismiss the dual fire scenario as the cause of the hole in the piston ...but I have too much respect for Mike's reasoning skills to make that mistake.  I could just go with Mike's advice and tell the team they need to switch ignitions. That would be the simplest solution, but hardly gratifying intellectually.  I could give Mike a call and ask for his explanation.  That would certainly be the quickest, but where is the satisfaction in that?  Sort of like turning the page over to get the answers to a crossword puzzle rather than fully exercising you brain to get them.  That bring us to the last option, and the one I ultimately went with: I could sit down and spend the time to figure out why a dual fire ignition could cause the problem.

My conclusions will be the subject of another post in the very near future, Lord willing.  In the mean time, readers are encouraged to submit their ideas in the comments section.  I already have my own explanation worked out and I promise not to borrow from anyone else without giving proper credit.

  

EL Bonnie on the Dyno

Last stop for EL Bonnie before hitting the "great white dyno" AKA the Salt Flats, was a mechanical dynomometer.  Like much of the rest of the project, this too proved to be somewhat less straightforward than planned.  Faribault Harley Davidson had come on board as a sponsor in the form of providing dyno work.  Only one problem; about the time Joe and Terry were feverishly working to install the modified 61 inch motor in the EL Bonnie chassis, the FHD dyno was in the process of taking some time off (I think the term technical description was that "it blew up").  Since repairs to the Faribault  dyno were not possible in time for the Knucklehead, another plan was needed.

A call from team member John Endrizzi to Pat Lehmann of Rochester Harley saved the day.  Pat graciously agreed to come in on his day off to establish the baseline jetting using their SuperFlow Dyno.

The following video documents some of the dyno testing.  A couple notes about the video; the first thing that you may notice is the ingenious starter system that Joe Taylor came up with.  It consists of a snow blower with a go cart wheel attached in place of  the rotor.  Also noteworthy  is that when you see Pat with the welding gloves on, it is because the plug wires kept coming loose from the magneto at RPM.  Eventually he was forced to hold them in place during the dyno run.  Finding this one issue alone, before making the trip all the way to the salt, was priceless.


So, what was the horsepower?  I guess we just don't know.  I knew going in that the dyno would probably not pick up a usable trigger from the magneto.  The lack of a tachometer on the bike was also an issue.  After some initial warm up runs and jet changes, Pat broke out an optical pickup which he set up to run off the engine pulley, but since he had never had occasion to use it before, there was some question as to the readings it produced.  The actual readings showed over 120 horsepower at around 4800 RPM - obviously that was incorrect (at no time during the dyno session did the engine reach maximum RPMs).  The RPM readings from the optical pickup seemed to be right though.

 

After the fact I mathematically calculated the RPM from the wheel speed, confirming that the optical pickup was providing accurate data.  If the horsepower readings  we saw meant anything, my guess is that they were reading double the actual horsepower figure, but since the engine was only taken to about 4800 of what I hoped would be a 7500 RPM top, even that told us very little.

 

Oh well, perhaps the great white dyno of the Bonneville Salt Flats would provide more conclusive results...

      

EL Bonnie - Flywheel Balancing Act

Yeah, OK, I know Bonneville is over, but I am going to go ahead and write this just as I would have had I not run seriously short on time leading up to it.  So with that in mind, here is the next installment.

Balance the flywheels. Simple enough.  In fact if you are familiar with the process you know its normally only about a two hour process. The key word here being normally. Really nothing normal about this motor though. Turning a 1939 engine of any type into a Bonneville racer is not a simple task, but add to the antiquated design, we are also dealing with a small (by Harley standards) displacement which needs to stay that way to remain in the chosen class. In this case, what I am trying to do is make up for displacement with RPMs, and RPMs call for strong and light parts.

Well, we already had some strong parts in the S and S 3-1/2 inch stroke flywheels, and while these flywheels start out considerably lighter than their OEM counterparts at 26-1/2 pounds for the pair of bare wheels, they still needed to be put on a serious diet for this special application.  So... to the lathe!
I lightened the shiny new flywheels - a lot!  In fact, as sometimes happens, I got a little carried away.  Knowing that I was dealing with these tiny little 3-5/16" bore pistons, I "mis-underestimated" how much of the counterweight I could remove.  Oops.  Well, I had planned to make the pistons as light as possible anyway, so....

First thing was to track down a pair of .080" wall tool steel wrist pins.  It seems that I obtained the last set on the planet from Axtell by way of Zippers.  Of course they were for a Evo so I had to shorten them as well as hone the pistons for the .001" larger diameter pins.  Weight savings on the pins alone was nearly 50 grams.  The pistons also went on an extreme diet, with enough material removed from the insides to make any piston manufacturer cringe.  I was careful to try to leave at least .180" thickness in the dome though. 

I went with 55% for the flywheel balance factor, chosen because that is what the factory used for the XR750.  Small motor, short stroke, and high revving - those were the characteristics I hoped EL Bonnie would share with an XR. To get there, not only did the pistons go on a diet, but even such small things as the crankpin nuts were cut down, not to mention adding an internal bevel to the ends of the pin.  Before all was said and done, the finished crankshaft assembly (with rods and shafts, ready to run) weighed but 20 Lbs 5 Oz.   obviously this motor borders on anorexic.

Before final assemble and true, the flywheels received the same oil shedding, heat dispersing coating as the interior of the crankcases.  The underside of the pistons also received the same coating (the idea is to keep the oil moving off the inside of the piston to aid in cooling it.  The domes got a ceramic coating as well as an oil retaining skirt coating. 

Oil pumps on these old motors are becoming a little problematic.  Back in the good old days, it seemed that a guy could always sort through a drawer full of spare oil pump gears to find pairs that would give acceptable protrusion from the body.  As time goes on though, the pickings are getting pretty slim.  The solution actually results in a better pump than what one might come up with if the drawer of spares was still well stocked.  By surface grinding the oil pump gears so that the pairs are of matched thickness, and then surface grinding the pump body, the protrusion of the gears from the body can be "blueprinted" while compensating for the thickness of reproduction gaskets.  Bear in mind that we are talking about doing this on a precision surface grinder, not a belt sander.  EL Bonnie's pump was in medium poor shape, but the surface grinding treatment brought it back - that and some welding and re-machining on the cover.

That pretty well wraps up the story on the bottom end. The heads had been re-worked by Ron Adamson before the motor came to me, so I'll just comment on the rocker arms.  They too received the lightening treatment; or maybe we should call it the "lightning" treatment, since we are dealing with an early Knuck.  Once lightened and spec'd for shaft clearance, all that was left was to resurface the pads and treat them with the same oil shedding coating as the bottom end parts.

After all the trials and tribulations which accompanied prepping the engine parts, final assembly was somewhat anticlimactic - in other words it went smoothly.  And all finished with nearly a week left for the team to install the engine in the bike and dyno it before leaving for Bonneville!

EL Bonnie Part 3: Don't Try This at Home

As I left off with the 61 cubic inch EL Bonnie motor, after a detour to make the cam cover usable, I was finally ready to blueprint the breather timing.  Mocking up the lower end reminded me that I would have to cut the flywheel diameter down to clear the crankcase oil scraper (pre 1940 flywheels were slightly smaller diameter than those used since). Some judicious work on the lathe brought the scraper to flywheel clearance to a snug .006".

With the mocked up crank assembly in the cases, next up was to get the degree wheel mounted and accurately indicating TDC.  If you have never done this, there is slightly more to it than just bringing the piston to the top of the cylinder and lining up the TDC mark of the degree wheel to a pointer.  That gets you in the ballpark, but certainly not close enough to base any timing events from.  Since there was no head installed, here is an easy way to get the degree wheel "degreed in:

1. With the piston at the top, mount a dial indicator and zero the needle
2. Install the degree wheel on the sprocket shaft and align a pointer with the TDC mark
3. Pick an arbitrary number on the dial indicator (example - .050) 
4. Rotate the crank counterclockwise until the needle on the dial indicator matches the number you have chosen.  Note the exact reading on the degree wheel at that point (example - 9-1/2 degrees after TDC)
5. Rotate the crank the opposite direction, past TDC until you reach the same dial indicator reading you chose in step 3 above, and again note the reading on the degree wheel
6. If the two reading from steps 4 & 5 match exactly (unlikely), you are done.  If they don't match, then loosen the degree wheel and move it to split the difference.  For example if your reading from step 4 was 9-1/2 degrees after TDC and the reading from step 5 was 10-1/2 degrees before TDC, then move the degree wheel so that its pointer is on 10 degrees. 
7. Repeat steps 4 & 5 until both give exactly the same number of degrees before and after TDC

(note:  Blogger, in their infinite wisdom, autmatically converted the numbered bullet points I have in the draft form to the goofy looking flowers that you see - guess you will just have to count them)

Once the degree wheel was properly installed, the opening and closing specs for the breather gear was checked, looking through the lifter block holes.  Rather than go through the process here, I suggest you download the excellent instructions available from S & S Cycle here.

Since a degree wheel was installed, it only made sense to check out the cams, especially given the discrepancy found in cam opening and closing specs due to mis-machined lifter blocks.  The lifter blocks seemed to be OK, but the exercise did pretty well make the cam choice for me.  The KN420 cam from S & S checked out good.  The old Sifton, not so much.  One intake lobe showed a 12 degree discrepancy on the opening, 5 degrees on the closing (for a total of 17 degrees less duration) and .020" less lift than it should have, all despite showing no sign that it had ever been run.

Of course since the motor was mocked up as far as it was, it also made sense to clay the pistons to get a sense of how much valve to piston clearance there was.  The answer to that question was a lot.  In fact, more than a lot; make it a huge amount.  That was a bit worrisome, given the fact that I was already apprehensive about the compression ratio the engine would wind up with.  The custom built pistons claimed a 10:1 compression ratio but the large diameter intake valves were sure to need a little more radial clearance in the valve pockets.  Given my "druthers" I'd have liked to see 12:1 for a starting point.

Time to check the piston dome volume, another fairly straight forward procedure which involves putting some grease on  the rings, installing the piston into the cylinder to a measured depth, capping the cylinder with a Plexiglas plate and a burret to measure the amount of oil it takes to fill the void.  Then by mathematically calculating the number of cc's that would be in the cylinder without the piston dome (using piston depth and bore) and subtracting the measured cc's with the piston dome in the cylinder, the actual dome volume is revealed.

Entering all the figures into my Engine Analyzer program, which takes into account head volume, piston deck height, head gasket thickness, head gasket bore and adjusting for fire ring and fire ring volume, I came up with a very disappointing 8.25:1 compression ratio.  Worse yet, there was no room to shave the heads due to the proximity of the 2.060" intake valve to the fire ring.  Now what?  I was really beginning to worry that this little 61" motor would be badly over-cammed at this compression ratio. 

I decided to call Jim Leineweber of the cam company that bears his name.  While he was not wild about the low compression ratio, he said he currently had nothing on the shelf that would work any better.  Jim did boost my confidence by affirming the clearances that I planned for the various engine parts, but then I always have been one of those who do well on tests.  And it really did seem much like an exam, as he asked what each clearance I planned to use, and then gave each of my answers a "OK- that's good - a lot of guys set that too tight."  One key piece of information that I was not sure of, Jim provided.  Set the ignition timing to 42 degrees BTDC as a starting point.  That tidbit probably made the whole conversation worthwhile; though any conversation with a living legend goes down as worthwhile in my book.

But, memorable conversation or not, it really did not solve my compression ratio problem. In fact it really narrowed it down to the "too deep" valve pockets on the pistons...

Now we come to the "don't try this at home" part of the title of this post.  It was far too late to consider having another set of custom pistons built, even if funds had been available for such a thing.  But out of the recesses of my mind, I managed to dredge up something that might be of value.  Some years ago Mike Roland mentioned to me that he had once welded up the domes on a set of pistons for a drag racer who was on a tight budget.  Hmmm.  Seemed that a consultation with the best welder I know might be in order.  John from PMFR informed me that as long as the pistons were not alloyed with silicone, I should be able to weld on them with no problem.  He further reassured me that I would be able to tell the moment I struck an arc - a silicone alloy piston would immediately result in massive amounts of black soot. 

Still, what would be worse?  Going to Bonneville with a motor down on compression, or missing another year because I screwed up the pistons?  It was about this time that I spent a Sunday afternoon watching "The World's Fastest Indian" again; just for a little inspiration.  The more I pondered old Burt Munro casting his own pistons in the little shack he lived and worked in, the more I knew I had to give it a shot.  Besides, the ceramic coatings I planned to use on the piston domes should give a little extra protection.

That's not to say I wasn't still plenty nervous about it.  What if I managed to distort the ring lands?  What if I screwed up in some other unforeseen manner?  And what might that unforeseen screw up be?  Obviously no point in pursuing that line of thought.  If I could come up with a possible screw up, it would not be unforeseen.

To make a long story short, the pistons welded very nicely.  In fact a steadier hand on my part would have resulted in a nice looking job.  But, despite the lack of beauty in my welding, I was confident that it was structurally sound - well...at least as structurally sound as one can be when welding a piece that normal people would not consider mistreating in such a way.  So, back to the mill to re-cut the valve pockets to a minimum depth, and then mock up with clay once again.  With only a minimum of frustration I achieved valve to piston clearances of an acceptable distance.

Welded

Machined after Welding

Back to the same old drill of cc'ing the newly larger piston domes and entering the results into the computer.  To be honest, by that point in time I would have been happy to see 9:1, so I was quite pleased to find we were up to 9.8:1!  Next up: balancing the flywheels.

EL Bonnie, Part 2: Never Easy

In my last post on EL Bonnie, I stated that the next step would be to mock the engine up to check/blueprint the breather timing. As is so often the case, easier said than done! My intention was to perform this quick and dirty, without regard to cam bushing clearances, but no such luck. I knew that I was dealing with an inferior aftermarket cam cover, and so at some point the bushings would need to be replaced and line reamed for proper fitment, but I thought I could get by with them for now.  The lineage of the cover was quite evident.  A certain company who will remain nameless to protect the guilty, reproduces these covers and puts them on their reproduction Knucklehead motors.  I have seen one other in the past; it too had damage to the bushings from misalignment.  One has to wonder how big a hammer it took to get one of these covers installed the first time.  It seems that S&S made the right call in casting their name into the covers they make, if for no other reason than to keep them from being mistaken for these gems. 

Did I mention that this motor is being done on a budget?  It has much in common with something I would build for myself in that respect; a lot of "spare parts" coming together,  in some cases those parts finding their way to the build based on availability and price rather than on fitness.

Before assembling the case halves for the mock up, I put the cam into the gearcase with the cam cover to ascertain how much it bound up in the bushings- the answer being plenty! Still thinking I could get this done quickly, I chose to line ream the cover bushing an extra couple thousands (the particular reamer I use for this operation is adjustable) since that would surely alleviate the bind and keep things moving. Wrong again! Apparently even the additional clearance was not enough to compensate for the mis-alignment between the case and cover. Time to re- think this.

After an appropriate bit of soul searching (to make the decision sound infinitely more dramatic than it actually was) it appeared to be the perfect opportunity to follow the old adage; when life gives you lemons, make lemonade!

The cam choices available are a (new) old Sifton 110 or an S&S FHP 420.  Both of them happen to be set up for a Torrington needle bearing in the crankcase rather than a bushing (the shaft for a Torrington will be approximately .0007" larger O.D. than one for a bushing).  That means that either the crankcase cam bushing would need to be reamed oversize (the original cam bushing had enough wear that it already fit) or the case would need to be bored for the larger outer diameter of the Torrington.  The bearing would have the added benefit of slightly less friction, so it seemed that the logical thing to do would be to use a Torrington on both ends of the cam.

Now, machining to install a bearing in the crankcase is pretty straight forward:  indicate in the existing hole and bore it to size.  The cover is an entirely different matter though, especially in this case, given there is good reason to suspect it was manufactured with the hole in the wrong place.  I decided to create a template.  I already had a 3/8" thick aluminum plate with the two dowel pin holes correctly located.  By installing the plate on the crankcase half and mounting it on the mill, I was able to indicate in the cam  bushing hole, and then going through the bushing hole, bore the aluminum plate. 

Indicating case bushing hole

Boring hole in template

Indicating template hole

Once I had a hole in the template, it was simply a matter of fabbing a couple extra dowel pins to align the cover to it.  Fortunately, at some point in the distant past I had built a fixture for holding generator cam covers level while installing and pinning bushings.  This made mounting the cover in the mill quick and easy.  Then, by indicating in the new hole in the template, I had the correct relationship between dowel pins and where the new cam bearing was to be installed.  BTW, the original hole in the cover checked as being only .006" off: I expected worse.

Boring cover for Torrington bearing

Once the new hole was bored and a bearings installed in both cover and case, another test fit with right case, cam and cover gave the results I was looking for: a totally free spinning cam!  Since I was in cam cover mode, I also tackled the pinion bushing.  I chose to go ahead and try installing a new bushing and line ream it, rather than going to extreme measures.  Kind of a "why go looking for trouble" approach, and in this case it paid off.  Another test fit with the cam cover bolted on the right case and the new S&S pinion shaft with bearings in place resulted in a very pleasant surprise.  Absolutely no binding even with only .0007" shaft to bushing clearance!  It appears that the cover manufacturer managed to get half of the bushing holes in the correct place.

Checking pinion shaft for binding

By the way, if any of those of you who are anxiously waiting for this motor are wondering, you may feel better knowing that the writing is lagging behind actual progress.

EL Bonnie

Some of fellows from over Wisconsin way have been scheming for several years to put a 1939 61" (model EL) Knucklehead on the great salt flats of Utah - better known as Bonneville. Joe Taylor, the owner of the "project," is joined by Tom Anderson and John Endrizzi in the quest to take home a record in the 1000MPSVG class at the AMA sanctioned annual BUB Motorcycle Speed Trials. For those of you not quite up to speed on class designations (I fit in that category too) the 1000 refers to the maximum displacement in cubic centimeters - hence a 61 inch Knuckle = 1000cc. The MPS narrows it down further, to a frame that is Modified/Partial Streamlining. The final piece of the puzzle is the VG which stand for Vintage Gas, limiting the engine to a production date of 1955 or earlier.

The trio does not walk into this endeavor with no prior knowledge of what they are getting in to; Joe and Tom have previous Bonneville experience racing under the Buell Brothers banner. This build will, however, be their first foray into the vintage side of land speed racing.

As may be expected, a project like this is not without its setbacks. Too small budgets are almost always an issue when regular guys take something like this on. A major setback in this particular build was the untimely death of the engine builder. That will definitely put a damper on a project!

Knowing the predicament that the Buell Brothers found themselves in, I had to weigh my morbidly obese workload against the possibility of being involved in a record setting endeavor. In the end, the deciding factor was this: given my penchant for high performance and knuckleheads, how would I feel if EL Bonnie set a record, but another engine builder's name was associated with it? What could I do but offer my service to build the engine?

Before going any further, it is important to note that a project such as EL Bonnie would be virtually impossible to complete without the existence of a company such as S&S Cycle. S&S has made the commitment to reproduce quality engine parts for these early motors. Witness the parts in the shot below; all from S&S, and all vital to transforming this dream into a reality.

As soon as Joe dropped off the engine, it became apparent that they committed no sacrilege by turning it into a racer. Nearly every square inch of the '39 cases showed evidence of welding repairs. If they could talk, these cases would probably have quite a story to tell. With Joe's permission, I decided it would be worthwhile to do some reinforcement modifications. I added a gusset to the left side of the left front motor mount (which showed evidence of at least one previous repair). Early Knuckle cases are also known to be weak on the left side in the cylinder spigot area. My solution was to weld 3/8" plate to that area, windowed just enough to leave the serial number pad intact.

Moving on to the the inside of the cases, windage is always a concern - at least to my mind. The "pocket" in the right side case quite obviously performs no function other than to save a bit of aluminum during the casting process, and I have always pondered what to do with it. What, if any, effect on windage this pocket has is any one's guess. On the other hand, when it comes to racing, I am a firm believer that the difference can often come down to a matter of adding together all the details. I've heard it before: "Do you really think that will make a difference?" My answer is usually, "We'll see." But the more honest answer is no ....but hopefully when it is added to the other dozen things that are too small to make a difference by themselves, it will!

A couple of thin aluminum plates cut to fit and welded into place smooth out the interior of the right case half. The next step toward minimizing windage was to polish the interior of the cases, including the gearcase. One of the final steps before final assembly on the case will be to treat them with TLTD, a oil shedding thermal dispersant coating.

Now you see it ...

Now you don't

So, if all the previous repairs had not distorted the cases, it was a good bet that with the welding I did, there was reason for concern! Besides, one of the keys to making this motor fast will be to keep the friction losses as low as possible. The first step to ensuring that was to mount the left case to the mill and indicate in the pinion shaft race hole (races removed). Once the indicator showed that it was centered in the hole, I gently installed the right case, torquing all the case bolts. Taking a reading from the indicator in the right side case race hole, I was far from shocked to find .012" runout. A +.025 race in the right case was the cure.

Next, with the cases still bolted together, I decked the bottoms of the motor mounts enough to insure they are true, and then did the same with the cylinder mounting surfaces. Before giving the mill the rest of the day off, I also machined the breather gear bore for the +.030 S&S gear, removing 70 years worth of damage in the process. Installation of the new crankcase races, and line lapping them to size pretty well brings us up to the present. Next is a mock up to blueprint the breather opening in the case and see what kind of piston deck height we are dealing with. To be continued ...