Matt P's Flywheel Issue

[PoorUB]

It reminds me of a guy I used to work for. We did HVAC work, but also sold standby generators. We had a customer call in because his generator would not run. I went out and looked at it and discovered it had broken both connecting rods. It just clattered when I spun it over. I verified it by pulling the spark plugs and it had zero compression, and I even stuck a ink pen down against the pistons and spun it over, and the pistons didn't move. (A V-twin Briggs and Stratton) I went back and my boss asked me what was wrong and I spent the next 15 minutes trying to explain how I knew the connecting rods were broken without tearing the engine apart. He wanted me to go back and pull the engine and tear it down to make sure, probable a 3-4 hour job. He just didn't get it. I finally told him I would bet my next years paycheck and he decided to take my word for it.

Another time I looked at one that the valve timing was off. Valve overlap was occurring with the piston about 1/2 way up the stroke. Another 15 minutes wasted trying to explain how I knew the timing gear key had sheared without taking the engine apart.

[PoorUB]

Nope. It can be mounted in any of 5 positions.

IMO, that is really screwed up! If the part needs to be mounted in one position, but can easily be mounted other wise it should be keyed or located with odd bolt placement to ensure it gets mounted as it should. Unbelievable that German engineering would ignore this!

[daz]

Yes, but in this case the bike was being ridden in the mountains! The problem only occurred after it hydro-locked after being left on its side after a tip over.

I don't understand where this flywheel discussion came from. Something changed after the tip over/hydro-lock. Or am I missing something?

[20774]

Matt thoroughly documented his attempts to figure out what was wrong. As far as I can see from what he wrote, he found nothing mechanically wrong with the engine...he eventually got to the point of removing the crankshaft and camshaft. All in all, he found nothing wrong.

His test of running the engine with the transmission removed showed that the ignition was firing at TDC at the very bottom of the rotation, or at 120 degrees advanced as he wrote. If there are 72 degrees between any of the 5 bolt positions, then the flywheel likely isn't mounted wrongly. 120 degrees advanced doesn't agree with any combination of 72 degrees.

I suspect something is wrong with the electrical side, although he changed the Hall sender and looked at another similar setup and found nothing amiss. What would cause the firing point to move like that, I can't imagine.

[Pauls1150]

My original question remains unanswered...

Where it came from is the fact that Matt discovered it in his experienced and straight-forward methodology of troubleshooting. As I said earlier, it's not a Root Cause, but there's NO reason to not attempt to discover Why and correct it as long as everything is already open anyway.

I've spent about ten minutes looking at pictures of airhead flywheels as shown on Google - and I found nothing that indicated they couldn't be mounted "wrong face forward". Ditto the parts fiches for various years on MAX's site (although of course there are differences in flywheels over the years).
Didn't spot anything about it on Snobum's pages.
Likely the authors of shop manuals presume that the mechanic already knows that "this mark has to happen here" and therefore don't bother to caution the reader.

Question for any geometry wizards: If the pattern is flipped over, how many degrees would the timing mark move?
Just as a WAG, let's "assume" it would move by 144 degrees, two bolt holes' worth.
Then the flywheel could be moved two holes; follow that up with a combination of points plate position plus the points' gap, and a few more degrees could be had (either at TDC or full advance).
Would this get the alignment back...?

btw - re my note about the flywheel's starter teeth: Some years had spacers on the 5 bolts that moved the assembly on the shaft; whether or not they are required - or there at all - would affect what happens on the teeth's mating surfaces. But this is secondary to the actual issue.

[20774]

Question for any geometry wizards: If the pattern is flipped over, how many degrees would the timing mark move?
Just as a WAG, let's "assume" it would move by 144 degrees, two bolt holes' worth.

I think it would depend on which axis you flipped it and where the timing mark was relative to that axis.

[STEVENRANKIN]

I want to make it clear, I have nothing against Matt, nor his troubleshooting.

He is one of the best in the business.

I made my comments based on the conversations in this forum regarding flywheel alignment.

Could BMW made the flywheel differently with a key or pin? Yes, they could have but they did not. Could repair manuals/instructions be better, Yes, they can. I have seen You tube videos of repairs that were outstanding. At the same time, I have seen some that were useless. Same with printed manuals.

I stand by my comments regarding some people's actions when making repairs or doing maintenance. Some people should NOT be working on engines.

I have seen new guys make mistakes out of ignorance, I have also seen guys with years of experience make mistakes out of ignorance or carelessness.

Taking an engine on an Airhead apart to change a main seal is not all that difficult, if a person follows the correct methods of doing the job.

If someone cannot take the time to put the flywheel back in the proper position it was in when it came off, I most certainly do not want that person working on my bikes. Same goes for blocking the crankshaft so it does not shift and loose the shim.

I am looking forward to Matt's article explaining what in fact the problem turned out to be. St.

[Pauls1150]

By "flipped over", I'm referring ONLY to the front and rear faces. THAT is the overall question.

[20774]

But it seems to me that the fact that the bike was running up in the mountains, was dropped, and then ridden back from the mountains before quitting near Matt's house should suggest that nothing mechanical about the flywheel is wrong...at least the way I read it. That ride back from the mountains had to be a good 15-20 iles. Matt's in Colorado Springs and while the mountains are visible, the roads too and from have to cover some distance.

I think one can put the flywheel back on in any orientation as long as the timing marks are adjusted accordingly. The flywheel is just a mass as well as something that carries the teeth for the starter to mate with. It doesn't really have anything to do with when the spark fires.

[20774]

By "flipped over", I'm referring ONLY to the front and rear faces. THAT is the overall question.

I probably am not seeing this visually right. So you're looking at the rear facing part of the flywheel, hand hands holding it at 3 and 9 o'clock. Flip it around the vertical axis so that the 3 o'clock position becomes the 9 o'clock position. You're now looking at the formerly forward facing part of the flywheel. But what if you flipped so that 12 o'clock went to 6 o'clock. Wouldn't that be different? Especially if the timing mark was initially at say the 3 o'clock position, or the 4:30 position, or... Obviously, the 5 bolts have something to say about where it can be flipped to.

[Pauls1150]

Makes me wonder what (else) was happening when the Enduralast ignition was installed, how was the timing set?
And you take us right back to the original question... and IF it can be flipped over, that gives you ten possibilities instead of five.

[Guenther]

I don't have a clear picture of the flywheel of my '89 R100GS. But I think this picture shows that the front and back sides are different and you cannot mount it with the wrong side facing you.

DSC02255sm.JPG

/Guenther

[GTRider]

I don't have a clear picture of the flywheel of my '89 R100GS. But I think this picture shows that the front and back sides are different and you cannot mount it with the wrong side facing you.

DSC02255sm.JPG

/Guenther

Yes. The clutch carrier (flywheel) is dished and only one face can be mated to the end of the crank. Matt’s article indicated that he verified that OT on the flywheel was in the window with pistons at TDC. He also verified that neither the crank sprocket nor the cam sprocket had sheared their woodruff and spun on their respective shafts, and after reassembling the engine set valve clearances which would again be done using the OT marking on the flywheel. So I think it’s safe to assume the crank, cam, and valve train are in their correct relationships.

It seems the problem as it presents now is one of ignition timing, not valve/piston/flywheel relationships so I’d tend to agree with the opinion expressed by 20774 that it’s an electrical/ignition issue. Bean cans were swapped, to no avail, and the bean can only fits one way due to the offset on it’s engagement tab. And the corresponding slot it engages could only be off if the crank and cam sprockets were not properly aligned on assembly—and Matt verified those marks. That leaves coil and ICU as the next items in the chain, and while we are used to seeing these items fail suddenly, usually after a period of presenting intermittent issues, certainly other failure modes could be possible.

Definitely a good puzzle and one I trust Matt will successfully solve. Can’t wait to hear the final diagnosis and solution.

Best,
DeVern

[44006]

93 is too new for me to have had the parts in my hands - my newest is 1980 R65 with bean can points

Everyone commenting here seems to be focused on the rear end of the engine

I ask this as food for thought for those who have actually had the pieces in hand:

How does the front end of the camshaft drive the bean can?

Is there any way for whatever fittings are affixed to the front of the camshaft to be loose or have slipped
relative to the actual position of the cam lobes?

Is the camshaft one piece of machined metal or is the front narrow part made separately and heat fitted
into the larger rear part with the lobes?

[GTRider]

I just happen to have a new camshaft on hand, just waiting for time to get at that particular project. I can verify that yes, the cam is a billet piece and not built up. Also noted the slight offset of the slot that drives the bean can; that offset pretty much guarantees the bean can cannot be installed 180 degrees out of phase with the camshaft.

Best,
DeVern