A Head Scratcher

Nobody likes one of those “head-scratcher” comebacks, though any honest mechanic will probably have a few tales that they are willing to share.  Of course, when the comeback winds up being no fault of your own, then the telling comes a little easier, accompanied as it is with a sigh of relief.

But to shift into reverse for a moment, in case any readers are uninitiated, a “comeback”, in the mechanical repair game, refers to having a customer returning with the same (or closely related) problem which was recently “fixed.”  A head scratcher, on the other hand is something that is confusing, mysterious or hard to understand.

One of the first useful things most “techs” (as they are called these days) learns is that when attempting to find a problem with a bike, the first place to look is the last part of the bike that was worked on.  That rule of thumb is valid whether said previous work was done by the owner, another shop, or the ace mechanic you consider yourself to be.

The tale of this particular head-scratcher is presented here, not only for its educational value in general, but also in the hope that it might save someone else from chasing an elusive problem.

Earlier this year I had occasion to do a stock valve job on a set of late model Twin Cam heads. The heads were carried in, by a customer who we will call John. We’ll call him John for two reasons.  One is that “John”, being a very common name will grant the customer a certain degree of anonymity, and secondly because that is his name.  While not a professional, John is also not a stranger to R&R (Removing and Replacing) top ends. The reason the heads were brought in was basically as preventative maintenance due to about 70,000 miles on the clock.  The top end was off to install some big-bore cylinders and pistons, so John decided that it would be worthwhile to be sure the valve job was up to snuff at the same time.  The job appeared to be about as straight forward as they come; the exhaust guides were bell mouthed past service wear limits so I replaced them, sized them and cut all four seats.  John also brought in a new set of stock valve springs and guide seals purchased from the local Harley dealer where he had acquired the cylinder and piston kit. He requested that I install them as part of the valve job.  I wrapped the job up in short order and life was good.

Then, a few weeks later, John returned with the rear head.  As an aside, let me tell you how much I appreciate this type of customer.  Most of us who have been working on bikes for a few decades have had to deal with the customer who returns with the attitude that you have screwed up his bike and he’s not going to put up with it (after all, his bike was perfect before you fixed it)!  John was the opposite of that.  He explained what had taken place, described the symptoms and calmly asked what I thought might be causing it.  

The symptoms were that once the engine reached full operating temperature, it would begin smoking profusely from the rear head.  John reported that his first thought was that he may have inadvertently installed a piston ring upside down, which only goes to show that the guy is no hack, since that also would have been my first suggestion to check.  However, the rings were in correctly, and there was no sign of oil leaking in the head gasket area.  Yes indeed, it did seem as though a close re-examination of the head was in order.

Which I did promptly.  But here is where it gets to be puzzling.  The valve seals were still in place.  The valve to guide clearances were good: right where I had measured them when freshening the valve job.  I put lacquer thinner in the spring pockets to see if I could detect any porosity: none detected.  I even went so far as to give each guide a solid rap to ascertain that they were not loose in the head: they were not.  

Keeping in mind that the engine in question did not have any symptoms prior to pulling the top end for the big bore kit, there was only one other possibility concerning the head itself that I could think of. If the rear head had porosity between the spring pocket and the port one would have expected that to show up pretty early in the life of the bike (and remember this one had about 70K smoke free miles in its history).  However, for quite some time now, Harley heads have been powder coated before they are machined in the manufacturing process.   Because of this practice, the inside of the ports (and to a lesser extent the spring pockets) leave the factory with a nice thick durable coating.  Of course, when cleaning up the heads for a valve job, media blasting removes the carbon and along with it the powder coat.  What do you suppose the chances are that by removing the carbon from the port, I had also removed the coating which had been sealing porosity, and in this case porosity which only opened up at operating temperature? 

If the scenario of a porosity which only opened up at temperature sounds bizarre, I might have agreed had I not seen it in the past. Way back in the early 1980s, the dealership I was employed by had a new Superglide, still in its 90-day warranty, return with similar symptoms. Under the tutelage of the dealership owner/ head mechanic (and when is the last time you heard of anyone holding that dual title?) I put the head on a burner of the shop’s electric stove with oil in the spring pocket.  Sure enough, once the head got enough heat into it, the oil started dripping through into the port at a brisk pace.  Rare?  You bet; but if I ran across one 35 years ago, why not another one now? 

Since the architecture of the Twin Cam head did not lend itself to holding oil in the spring pocket while heating on a stove, instead I chose to coat the interior of the spring pockets and oil drain passages with a product called “Gasoila Hard Set” to seal any potential porosity from the top side.  This had the added advantage of sealing off any possibility of oil getting between the head and the outside of the valve guide.  Still, it was a bit of a shot in the dark since I was unable to actually pinpoint any problem.

That of course still left the rest of the top end as the potential culprit.  Though John had checked to be sure he had installed the piston rings in the proper orientation, he took my advice and replaced the new rings based on my theory that it was better to spend a bit more money than to chance spending a bunch more time later.  Of course if the end result was success, then we might never know for sure whether the heads or the rings were at fault, but that was something we were both willing to live with.

So that is what the John did.  He once again installed the top end, with new rings & gaskets along with the (hopefully) repaired heads.  And all was well with the world, …at least until the engine once again reached operating temperature! Whoa!  Or maybe even Woe!  What in the world could possibly be going on?  At this point he made a trip to the dealership and described the conundrum to the service techs, but none could offer any ideas which had not already been addressed.  Now what?

Well, after a few more test rides to be sure it wasn’t just some left behind oil in the exhaust pipe causing the smoke, John received his first solid clue.  Pulling the “smokin’-hot” bike into his garage (well, …”smokin’-warm” to be more accurate),  he started to unscrew the oil reservoir cap only to be greeted by a sound just as if he had removed the valve stem from one of the wheels.  Suddenly everything pointed to the breather system.  And just as suddenly John thought of the new breather assemblies which came with the kit, the ones he almost didn’t change out but at the last minute decided he might as well install since he had them. You know, the stamped steel ones that come pre-assembled. Yeah, those.

Sure enough.  As it turned out, the umbrella valves in both of them were installed upside down, effectively sealing the engine and turning the crankcase into an air compressor. I must admit to being a bit impressed by how good a job Harley has done with sealing these Twin Cam engines, because evidently there was not a hint of oil weeping from any joint, seal or gasket.

 

The whole situation reminded me a bit of a stroker Shovelhead motor that I built for a customer back in the late ‘80s or early ‘90s.  Harley had recently started to install a little squiggly plastic “oil separator” into the breather pipe passage between the cam cover and breather trap.  When I built the Shovel motor I decided to try one since some oil carryover was not entirely unusual on strokers. Perhaps Harley’s latest technology would help, I reasoned. 

The results could have been a disaster.  The motor “wept” oil from the base gaskets, the tappet block gaskets, the pushrod tubes, and nearly every other place you can imagine.  The customer was not impressed.  When he brought it back, I immediately decided that the new-fangled oil separator was too restrictive, and removed it.  The only question I had was whether the oil leaks, once started, would go away when the added restriction was removed.  I thought it worth a shot, though the customer was convinced that it would not, and perhaps suspected that I was trying to dodge my responsibility to stand behind my work.  But he doubtfully took the bike, and sure enough, a couple weeks later came back to say that the engine had completely dried up – no oil leaks or weeping anywhere.  I felt like I had dodged a bullet and never put another one of those separators in a motor and removed them from any motor I found one in.  Evidently Harley came to a similar conclusion, because they did not make it into many engines.

So, I guess the moral of the story is beware of your Harley's breather system or it might turn into a real head scratcher.

Slippery Slopes and the Letter "P"

I am pretty sure that this post will win me no support among those who willingly go along with every nuance of “popular culture” in its ever-spiraling descent into immorality.  It seems that those who would poke their finger into the eye of their Creator are never satisfied with the present atrocity, but are forever desperately reaching for the next and even more abominable one.  Some will say that the subject matter here is just the old “slippery slope” fallacy, but I would suggest that when one views the terrain above and behind you and then considers that the hill continues down immediately below, it becomes less than a fallacy to predict the trajectory which one finds society to be on.  Certainly, there remains that oh-so-narrow ledge that we are approaching at breakneck speed, upon which we might hope to gain sufficient traction to stop, but the momentum of the slide certainly does not favor halting at any point on the slope.

With that, I would like to claim for myself the honor of at least partially providing the inspiration for an article from one of my favorite writers.  A short time ago, on his blog, Douglas Wilson embedded a boring but provocative video provided by an organization called TEDx, who describes its mission as sharing “ideas worth spreading.”  The video in question is one featuring Mirjam Heine speaking at the University of Würzburg, Germany, wherein she makes the controversial (at least for now) claim that “"pedophilia is a natural sexual orientation, just like heterosexuality."  Doug had correctly titled the video as “Nah, No Slippery Slope Here” but provided no further commentary.  

After viewing the video, I sent the following to him, which he published in his weekly “letters to the editor” post:

“As to the video under the title “Nah, No Slippery Slope Here” in Thursday’s Content Cluster Muster, I suddenly feel like a prophet. Just earlier in the day, I had vocalized to my wife a thought that had been fermenting in my mind for a few days. That thought? If, as the sexual deviants and their cheerleaders on the left keep telling us, people cannot help their sexual preferences and it is hateful to suggest there is anything wrong with them living out their perversions, then how long will it be until pedophiles are the newest darlings of the Democrats? Of course to keep this all “above board” the pedophiles will only be able to officially molest those children who give their consent. As luck would have it, the groundwork for such consent is already being laid, with leftist’s heartily agreeing that 5-year-olds are perfectly capable of deciding they need a sex change. If they are mature enough to make that decision, then the decision to have sex with men in trench coats can hardly be a big deal. LGBTP anyone? And, even more disturbing, how long before apostate Christianity follows suite?”

Doug’s only comment to my letter was, “Yes, slippery slopes are slippery.”  That’s it; no high praise for my insightful comments; no sincere thanks for getting him thinking; not even a “high five” for being a fellow outcast from politically correct society.  Nothing.

So, imagine my delight a couple of weeks later when Doug posted a full-blown article titled “This Cavalcade of Concupiscence” reinforcing my thoughts as well as expanding upon them. Now in reality, I cannot pretend that Doug Wilson took his inspiration from my letter.  Doug has his finger on the pulse of popular immorality more so than a great number of so called Christian leaders of our day, so its quite likely that the seeds of this post were germinating in his mind well before even the video surfaced.  Still, I can wonder if my input played a part, can I not?

With that, I highly recommend that you follow this link to “This Cavalcade of Concupiscence” and read Doug Wilson’s treatment of the issue.  Doug’s wordsmithing ability is a thing to behold, and coupled with his firm grasp of biblical principles, most Christians will love his writing with the same fervor that most non-Christians hate it.

Under Pressure

[Wow, how time flies when you are busy living life and working for a living.  There have been an untold number of things I have had the urge to write about over the last several months, but could not seem to justify taking the time.  Some of those topics I consider very important, some interesting but not very important, and some perhaps just somewhere in between. This post is definitely not important (in the grand scheme of things), and probably only interesting to a limited audience, but you know what?  I am going to go ahead and write it anyway, if for no other reason than to see if anyone is still paying attention.]

A few weeks ago I had Billy's Iron Head vintage flat track bike here for a little maintenance.  It had been smoking pretty good the last couple times out, and that coupled with the fact that one of the recent races featured extended time spent at 8500 RPM meant it might be due for more than just checking the valve adjustment.  As it turned out everything was in pretty decent shape with only a fresh set of rings required.

Given that I would not have to spend very much time freshening things up, I took the opportunity to fabricate a custom breather system for the bike, something that has been on my "to do" list for some time.

As with most early Sportster engined flat track bikes, Billy's has a magneto and runs without a generator.  Now, having my "druthers" I would love to see the mag mounted in the generator position so it would be out of the way of the pushrods and carb, but that's probably not going to happen any time soon.  So with the generator gone, a gaping hole is left at the front of the motor; easy enough to seal off with a flat plate, but of course that leaves the breather system in a state of chaos.  In stock form, the large diameter washer which resides on the inboard end of the generator serves as as an oil separator allowing excess crankcase pressure to be relieved by way of a tube attached to the cam cover. Without the washer, the breather tube would tend to do a credible impression of the Exxon Valdez (if you youngsters are scratching your head, click on the link for a little history).  Okay, that may be a bit of an exaggeration, but without the washer you will get at least some oil out of the breather tube, something most tracks take a dim view of.

But of course you can't then plug off the breather tube unless you're willing to give up a bunch of horsepower and initiate oil leaks from every conceivable joint.  Okay, you got me.  Another slight exaggeration, but only concerning leaks from every joint; that plugging the breather will result in loss of horsepower is a given.  The temporary bandaid that went onto Billy's bike when he showed up with an rebuilt stock replacement engine last year was as simple as it was marginal.  An elbow in the generator block off plate with about  18 inches of 3/8" hose pointing up, along with an in-line PCV (Positive Crankcase Ventilation) type valve topped with a generic plastic automotive fuel filter. In retrospect, perhaps the filter should have been put in place between the fitting and the one way PCV which would have allowed the oil seperated by the filter to drain back into the engine, but its a moot point now.

The actual breather that I came up with was to a large extent  dictated by the scrap aluminum material that I had on hand (keeping in mind mine is an engine shop, not a fabrication shop). What I came up with is shown below.  Keep in mind that I stressed the part about material on hand.  With more to work with, I probably would have built it with the oil separating baffle before the umbrella valves to keep more of the oil in the cam cover rather than transferring to the catch can.  But, ...oh well, the first prototype of anything is seldom the best or final version.There is a drain plug on the bottom of the canister for easy draining, so it shouldn't be a problem anyway.

1st piece -machined a flat plate for a recess and drilled holes for umbrella valves

Umbrella valves installed in plate

Engine side of plate - center hole of each group mounts umbrella valve - other 4 holes for air transfer

The umbrella valves are from a late 80" Evo engine, which uses only two.  I calculated the cross sectional area of the transfer holes to insure that added together they exceed the area of the new breather outlet. Consider this: due to the common crankpin design of the 45 degree V-Twin engine there will be 90 degrees of crankshaft rotation where both pistons are descending in their bores at the same time.  That means that without a "breather" to alleviate the potential pressure, the air/oil mist in the crankcase will need to be compressed, at the price of the horsepower it takes to do the compressing.  As mentioned earlier, pressure will also tend to seek a way out, usually at whatever gasket has the least resistance.

Now, if one is willing to take the time, they might calculate the amount of air displaced by the downward motion of the pistons that needs to be moved through the breather system, and then factor in the amount of time available to do that at, say 7500 RPM and apply that to estimate the needed cross sectional area of the choke point (smallest orifice) in the breather system.  No, I'm not going to do it either, but barring that, it is at least a good idea to increase the size over stock.  The I.D. of a standard 1/8" pipe x 3/8" hose barb fitting is only .265" which calculates to only .055 square inches. That seems awfully small.  The outlet pipe on my completed breather assembly has a 1/2" O.D. (to take a breather filter) with a .380" I.D. for a cross section of .113 square inches, or double the stock size.  Still seems a bit marginal when just looking at the cross section, but it has to be an improvement.  Oh, and by the way, I did calculate the cumulative area of both the baffle(oil separator) holes and the holes at the umbrella valves to be sure they would not be a "choke" point.

Finished assembly

Orientation of umbrella valve plate when assembled

Tack welded in place oil separator inside canister

Installed on bike - breather filter not installed.

Before I go, one other think to consider.  Some of the breather fittings that go onto a Twin Cam motor are ridiculously small.  First of all, the heads are only tapped for a 3/8" - 16 tpi (thread per inch) bolt so there is little to work with (even the smaller cubic inch Evo motors were tapped 1/2" - 13 tpi) but some of the breather fitting that go into those holes have a through diameter of only .145" which works out to a cross sectional area of only .017 square inches per head or .034 for what are often 103 cubic inch or larger engines.  Its a testament to how well all the gaskets and o-ring in the engine work to keep (what I assume to be) all that excess crankcase pressure on the inside.