Saturday, November 24, 2012

Shovelhead Hydraulics

Now, now, now ...those are not swear words, though many mechanic has used them in a tone that would imply that they are.

Introduced in 1953 to replace the ill fated Panhead "hydraulic in the top of the pushrod",  certainly the 17920-53A was an big improvement since in 30+ years of wrenching I have yet to see its predecessor in working condition.  I did actually meet a man once who claimed that he had a working set in his motor, but I could not verify that he was not either deaf or a liar.  But I digress...

So, what is the first thing to do when you find yourself with noisy hydraulic lifters?  Adjust them of course.  And if that doesn't work, you adjust them again ....and yet again.  After one finally realizes that further adjustment is little more than wishful thinking bordering on the vain repetition of the prayers of the heathen, then what?

Now, we have all seen Shovelhead hydraulic lifters that function flawlessly; quiet and trouble free.  Common sense would tell us that for the most part this would be the norm, after all, the factory used them for over 30 years.  Somehow, though, it is the ones that are noisy that stick in our memory.  To be fair, a number of those that seem to be problematic are not to blame themselves, but take on the role of scape goat for other engine parts. 

Low oil pressure is the first logical root cause to examine before condemning the hydraulic unit.  Most who have been around Shovelheads for any time know to keep an eye on the tappet screen, since all the oil to the lifters must pass through it (hence its name).  Debris plugging this small screen can definitely make for some noisy hydraulics, though the type of debris and the amount of time it took to accumulate may also indicate larger problems.  Remember, the tappet screen is downstream from the gauge or sender, so you could have a good oil pressure reading, but still not enough pressure at the lifter. 

The oil pump itself could also be the culprit, but there again, excess wear could itself be a symptom of worn out parts serving up a metallic oil soup.   And then there are the bushings....  Oil pressure will seek the easiest path to relieve itself.  Fortunately there are only a few bushings in a Shovelhead motor that are subject to pressure, those being the pinion bushing and the rocker bushings.  Now  lifter noise in later Shovels with the multi stage oil pumps should not be affected much by loose clearance between the pinion shaft and bushing, since the pump is designed such that it must build pressure against the top end (hydraulic lifters and rocker arms) before the pressure relief valve opens enough to supply oil to the bottom end via the pinion bushing.  However, badly worn rocker bushings could still bleed off enough pressure to effectively disable the hydraulic lifters. 

But what if you have good oil pressure, the rest of your engine is in good shape, and you still have noisy hydraulics?  Well, maybe it's time to revisit that adjustment one last time.

First of all, I prefer to bring the engine to TDC on the compression stroke for one cylinder, and adjust both lifters for that cylinder at that point.  I'll assume you can find that place in your engine's rotation.  At that point the '59 to '69 FL/FLH-1200 Service Manual tells us to loosen (shorten) the pushrod until we have noticeable shake, and then extend it again until the shake is just taken up (just before it starts to compress the hydraulic unit).  From that point we are to extend the pushrod 4 full turns.  Fine.  I have use that adjustment many, many times with good results.

Now lets look at the '70 to Early '78 FL/FLH/FX/FXE/FXS-1200 Manual.  Here we find two methods.  One, called the "wet" method is identical to the one we just described from the '59-'69 Manual.  The other, called the "dry" method involves removing the hydraulics from the lifter, pulling the two halves apart, and cleaning out the oil (best accomplished with some spray brake parts cleaner or the equivalent).  With the hydraulics cleaned of oil, we are instructed to extend the pushrod past the point where the shake is removed and all the way until the hydraulic unit is bottomed out.  At this point, extending the pushrod length any further would begin to lift the valve.  Here we are instructed to shorten the pushrod by exactly 1-3/4 turns.  Again, I have used that adjustment many, many times with good results.

On to the '78-1/2 to '84 1200/1340cc 4 Speed Manual.  Here we find the old tried and true "wet" method to be missing in action.  And if that is not enough, the dry method has changed just enough to be barely noticeable (I just noticed it this summer after 30 years of valve adjustments).  Now we are to follow the same procedure as the "dry" method from the '70-'78 Manual, but instead of 1-3/4 turns up from the hydraulic being bottomed out, now it calls out 1-1/2 turns.  Hmm.  Do I need to say it?  Certainly I have used this adjustment many, many times (depending on which manual I grabbed) with good results.

But here is the interesting thing: for years I assumed that 4 turns down on a wet lifter would result in the exact same adjustment as 1-1/2 (or 1-3/4) turns up on a dry lifter.  It does not!  In fact, if it were not the for the 1-1/2 vs 1-3/4 discrepancy, I may have never realized this.  As it turns out, it takes about 8 full turns to collapse a Shovel hydraulic from its "wet" starting point to its "dry" starting point.  That means that using the "wet' adjustment method results in a hydraulic that is 4 turns up from bottomed out rather than the 1-1/2 or 1-3/4 turn up from the dry method. 

Obviously  the wet method is much less time consuming if you have no other reason to completely remove the hydraulic units from the engine, but it looks as though extending the pushrods 8-1/4 to 8-1/2 might be in order (assuming the factory had good reason to go to a tighter adjustment in later years).  But it also becomes obvious that precise adjustment is not critical if all else is as it should be.  So next time you adjust your lifters don't sweat it if your wrench slips and you think you may have gotten a half turn off.  If its still noisy, better to spend your time investigating whether it is an engine problem or just bad lifters.

7 comments:

Anonymous said...

As my bike is a 72 XLCH I can't comment so much on hydraulic lifters. However, as my bike has shifted her flywheels at least three times I have spent some time debating with myself about the pinion shaft and oil circulation.

My first schooling on the subject was in the late 70's when my brother called from a distant state to say he didn't think all was well with the beast. The rod bearings were gone. As in vanished. The rod races were still round and the crank pin was still round but the bearings had become a metal-flake coating on the whole of the inside of the motor. When I picked up the cam cover the pinion bushing stayed on the floor. The inside of the bushing pocket had been peened with a punch by some previous owner. This must have been the second time.

A couple of years ago, having finally settled in one place for more than 6 years and having sent our last young one off on her own, I took the old girl out of storage. It had some gas from the 80's but I put some more in to freshen it up. I hooked up an old battery with jumper cables and she started on the third kick. Just like she used to. And she ran great! Better than I remember (maybe gas is like wine and old tanks like oaken casks).

Still, she jumped up and down like a five-year-old going to the park. There were many reasons I could not ride her that day and so began the work.

I started taking stuff off to clean and polish and ended up at the exploded parts view. The pinion shaft measured about .125 runout. This must be the third time.

At the time of which I speak (last year) I knew nothing of Harley fly-wheel dynamics. I took the crank to someone with 3 or 4 decades of experience and told him my pinion shaft was bent (or the tapered hole was drilled wrong) and that I strongly suspected it had always been that way. I could tell right away that his estimation of me had fallen some as he said, rather emphatically, "That crank was perfect when it left the factory and the pinion shaft won't bend." He put his hands together as if to pray and rotated them opposite to each other and said: "Your flywheels did this."

It's all back together now, thanks in large part to him (Doc, at Columbus HD in Neb.). But now I wonder. Could there be something wrong with my flywheels that predestines me to this same problem?

Spending much time on the internet I found a blog entry where the guy had installed timkin bearings in place of the bushings in the cam cover. He also bored out the pinion bushing to huge oversize and installed a lip seal, to keep the oil going where it should, saying: "The bushing doesn't really support the pinion shaft anyway and is a poor oil seal."

Putting a lip seal in the cam cover for the pinion shaft seems like a great idea. At least to a fool like me. My oil pressure (measured at the last rocker with 20-50) is 25lbs at cold idle and 0 at hot idle (it rises to 35lbs, wait, 35 psi at 2500rpm). Not that I'm going to take her apart again; I'm just thinking of the next time. An old hand told me the best way to fix my problem was to throw away the oil pressure gauge.

Maybe we all have a knucklehead. Sometimes the knucklehead is the bike we ride and sometimes it's the knucklehead that rides the bike.

Brad Ervin

Anonymous said...

Err, I meant torrington bearing where I said timkin bearing.

Brad

St. Lee said...

Great comments Brad!

At this point in time it is probably impossible to do anything except speculate what was the original culprit that was the source of all your flywheel woes. It is pretty safe to say that the flywheels probably were close to perfect in regards to run-out when they left the factory. I disagree with the statement that a pinion shaft cannot bend however - but it is uncommon.

The disappearing bearing phenomenon could be as simple as a batch of incorrectly hardened rollers finding their way to your engine (it has happened). That would be my suspicion since the rods and crankpin escaped. If it had been lack of oil I would expect the rod races and pin to suffer as much as the rollers. On the other hand, a loose pinion bushing could certainly result in the oil that was meant for the crankpin dumping into the cam cover. Maybe a combination of the two?

The flywheel shifting, likewise could have been from the crankpin nuts not receiving sufficient torque during the rebuild to repair the rod bearings.

With no hydraulic lifters, there is really no "need" for oil pressure, just oil flow to all the parts. However, without oil pressure, there is no good way to monitor whether or not you have oil flow. A seal inboard of the pinion bushing would be a band-aid that would not be needed if a properly line reamed and sized pinion bushing was in place. A Torrington, on the other hand would need a seal since it would not restrict the oil flow enough to route it to the crankpin. As to a bushing not being a good oil seal, I would say "if not good, then sufficient." I have taken a number of Big Twin Evo engines apart which had clocked over 100K miles, and found crankpins, rod races and rollers showing absolutely no sign of problems. Obviously the pinion bushings in them were keeping enough oil going to the crank to avoid undue wear.

My advise would be to ride it and enjoy it - but then, I am an admitted knucklehead!

Anonymous said...

It's awfully hard to look back and unwind what may have happened; as you surely know. The bike came into my possession with a built in problem, the loose pinion bearing. This may, or may not, be due to a slipped flywheel that wrenched the bushing loose.

I wasn't riding it when the bottom end failed but I have assumed that the flywheels slipped, the pinion bushing spun (again), and oil quit going to the rod bearings; with the likely result. I may be wrong; it's all lost in the mists of time. I knew nothing then but arrogance, and we all know where that gets us. I only hope I have it right this time.

Replacing the cam bushings with torrington bearings looks, on the face of it, a good idea. After all, bearing have less friction than bushings, right? Bearings last longer than bushings, right. Hmm, maybe, maybe not.

With oil, bushings provide 100% surface support. Bearings contact only on the tangential surface of the bearings magnifying the force delivered to them monumentally. I've often wondered if Harley bottom ends would last longer if they used the split bearings common in car engines. (setting aside the enormous engineering this would require)

I'm also a little suspicious of flywheels that are driven into compliance with a brass hammer. If a hammer blow will move them into alignment then the hammering they get from the pistons can't be good. And, what worked 50 years ago with 30 HP may not be so great at 100HP. Not to mention the asymmetrical way power is transmitted through those flywheels.

I do not wish to bore you with my lunacy but I also have a 91 XL that I got cheap because of a little rod knock. No more front rod bearings. The crankshaft was trash as the spline that the drive sprocket rides on was hammered. I got another crank that was disassembled. Looking closely at the tapered hole that the perfectly smooth crank pin mates into revealed a Saturn's rings constellation of coarse, thread like, ridges and grooves. It's possible that a tightened crank pin may only touch the tapered hole in a dozen places.

If I had a proper lathe (not the Chinese toy I really have) I would mount the flywheels in a 4 jaw chuck and turn the tapered hole smooth and concentric with the pinion (or output) shaft (lapping it in with the crank pin) so the pin is seated immovably. This would invariably cause other problems as the space between the flywheels would shrink; but, as I haven't a real lathe, or the experience to run it, it won't happen anyway.

Maybe we should talk about re-assembling that crank.

Thanks for your kind words. Not to shift subjects but your Bible commentary is great. I started out on your pages from 2007 or 2008 and have worked backwards to your Pastor leaving.

Thanks again
Brad Ervin

St. Lee said...

The flywheel taper for the crankpin sounds very suspicious. It should be total smooth. You are right about re-machining it. You would lose rod end play. May be time for a new crank assembly.

It would SEEM that a Torrington would have less drag than a bushing, but from what I have read, the difference is negligible. One thing about a bushing, it does not fail catastrophically, which can't be said for a bearing.

You may be interested to know that the Harley VL models (1930 to 1935) used a bushing instead of a bearing to support the pinion shaft. It was several inches long, and if I recall it had a slight internal taper.

The 100K mile Evo's that I mentioned above were both in the 85 to 95 RWHP range, and never showed any signs of shifted flywheels, but on the other hand, Twin Cams are becoming notorious for it even at stock HP levels.

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St. Lee said...

Adorable? Really Jennifer? I'm pretty sure that your comment is spam, given the link you added, however I am going to leave it up strictly for entertainment value. ... for anyone reading this, the link has absolutely nothing to do with Harleys, so don't waste your time.