Kokusan flywheel problems anyone?
Posted: 03 May 2013 18:56
Well you learn a new thing every day. Morini actually changed the design of the pickup mounting plate on the kokusan bikes. The one on my bike is from a very late Excalibur and having just compared it to the 2 spares I have (one from an '88 dart and one from an early kokusan Excalibur) I've noticed the following:
The early mounting plates are much less substantial castings. The backplate is more or less the same but the protrusions the pickups mount onto are thin and have lines of weld on the back to form a rib. At first I thought this was a repair, but both of my early ones are the same. By comparison, on the late one the pickup mounts are more substantial with webs extending around the backplate.
I don't know why the change was made- I can only guess they had issues with the early type, and the more substantial later one can only be an improvement in terms of pickup location accuracy & vibration, although I've never heard of any problems with the early type.
So what, you ask? Problem is I have just modified my spare flywheel (which was with the early type backplate) with the trimmed pickup trailing edge mod for more idle spark advance, and went to fit it this afternoon. After fitting it I noticed that when rotating the engine by hand, somewhere around TDC on cylinder 1 the engine went tight (with the plugs out!). To the point that I thought about pulling the head to have a look. To sanity check I refitted the original flywheel and problem gone (phew, no engine rebuild!).
So what's wrong with the spare flywheel? It worked fine on my old engine.
Is it that the old/new flywheel/backplates aren't interchangeable (cant see anything that would bind though)?
Have I got a wonky flywheel (haven't put a gauge on it but it looks to run true)?
Have I got an out of place magnet (they all have the original glue and look/feel correctly positioned?
Why is it only binding at one angular position? That would suggest something out of concentric or a high spot on the inner face touching a point on the backplate somewhere. Can't see any visible contact signs, and the engine cranks over easily and quietly enough (and runs fine for the brief few seconds I let it run).
I now have a bit of a dilemma- I really want to fit the modified flywheel as it will cure the long standing idle issue, but am nervous of possible alternator/crank damage if I don't get to the bottom of the binding issue. Having cranked then run the engine briefly it's not as tight anymore, like it's machined itself some clearance, but no signs of where that happened.
Anyone experienced anything like this before??
Tom
(desperately getting the dart together in time for the AGM weekend next week!)
The early mounting plates are much less substantial castings. The backplate is more or less the same but the protrusions the pickups mount onto are thin and have lines of weld on the back to form a rib. At first I thought this was a repair, but both of my early ones are the same. By comparison, on the late one the pickup mounts are more substantial with webs extending around the backplate.
I don't know why the change was made- I can only guess they had issues with the early type, and the more substantial later one can only be an improvement in terms of pickup location accuracy & vibration, although I've never heard of any problems with the early type.
So what, you ask? Problem is I have just modified my spare flywheel (which was with the early type backplate) with the trimmed pickup trailing edge mod for more idle spark advance, and went to fit it this afternoon. After fitting it I noticed that when rotating the engine by hand, somewhere around TDC on cylinder 1 the engine went tight (with the plugs out!). To the point that I thought about pulling the head to have a look. To sanity check I refitted the original flywheel and problem gone (phew, no engine rebuild!).
So what's wrong with the spare flywheel? It worked fine on my old engine.
Is it that the old/new flywheel/backplates aren't interchangeable (cant see anything that would bind though)?
Have I got a wonky flywheel (haven't put a gauge on it but it looks to run true)?
Have I got an out of place magnet (they all have the original glue and look/feel correctly positioned?
Why is it only binding at one angular position? That would suggest something out of concentric or a high spot on the inner face touching a point on the backplate somewhere. Can't see any visible contact signs, and the engine cranks over easily and quietly enough (and runs fine for the brief few seconds I let it run).
I now have a bit of a dilemma- I really want to fit the modified flywheel as it will cure the long standing idle issue, but am nervous of possible alternator/crank damage if I don't get to the bottom of the binding issue. Having cranked then run the engine briefly it's not as tight anymore, like it's machined itself some clearance, but no signs of where that happened.
Anyone experienced anything like this before??
Tom
(desperately getting the dart together in time for the AGM weekend next week!)