-
Enjoy XS400.com? Consider making a donation to help support the site.
XS400.com receives a small share of sales from some links on this page, but direct donations have a much greater impact on keeping this site going.
Thanks Dave!
Alright time for another update. So I got the new ignition module and I swapped it in. Unfortunately, the timing did not change but after a little research I found that the pickup coil can be rotated slightly to change the timing. After a little coil adjusting I was able to get the timing perfect. Again unfortunately, I went out for a long test ride only to find that it did not fix my vibration problem at all
I did an oil change and although it was black I did not find any metal shavings or the like. At this point I guess its something out of balance or not tight in the engine that's causing this awful vibration. Ahhh well I guess this is going to have to wait until next spring.
I did an oil change and although it was black I did not find any metal shavings or the like. At this point I guess its something out of balance or not tight in the engine that's causing this awful vibration. Ahhh well I guess this is going to have to wait until next spring.
did you determine that/if your engine has a counter-rotating balance shaft and, if so, if it has/could somehow have gotten out of phase, causing the vibration?
Thanks for the reply Lou but after a bit of research (mainly this website http://www.motorcyclespecs.co.za/model/yamaha/yamaha_xs400%2077.htm) I've concluded that the SOHC engine does not have a balance shaft.
Sorry to hear that. And yet, the bike vibrates on - even while sitting still in neutral.
So, if a piece of metal hasn't fallen off part of a balanced system, then what goes out of balance.
Could it be something like a failed internal baffle on one pipe which results in a large differential from one to the other thus setting up some sort of acoustic interference at a frequency achieved when the bike revs to 4,000?
Or one cylinder pushing its piston much harder than the other thus creating an imbalance in a critical rpm range?
Not sure if either of those or other crazy ideas we could come up with are even possible
So, if a piece of metal hasn't fallen off part of a balanced system, then what goes out of balance.
Could it be something like a failed internal baffle on one pipe which results in a large differential from one to the other thus setting up some sort of acoustic interference at a frequency achieved when the bike revs to 4,000?
Or one cylinder pushing its piston much harder than the other thus creating an imbalance in a critical rpm range?
Not sure if either of those or other crazy ideas we could come up with are even possible
Yeh unfortunately it vibrates on, even while in neutral. What I meant as an imbalance was more of a loose gear or something, that would wobble and therefore cause a vibration. Wouldn't the H pipe help equalize any pressure differentials? I gave it a compression test and both cylinders came right around 130psi if that helps. How would I even test those theories
The compression numbers are good and you are correct with the Hipe creating equal pules for the exhaust.
The H-pipe on your exhausts does help equalize some of the pressure differential but if there is something loose on one side the acoustic interference could still occur. Only way to really try it is to swap your exhausts with someone else's. Compression test reading the same value should rule out pistons pushing harder on one side, as long as you have well-synched carbs.
Unfortunately it seems like there is something going on inside your engine. So yea a loose gear, a crankshaft bearing, or something else that is spinning inside your bike's guts. How about a complete teardown and engine rebuild
good luck with that
Unfortunately it seems like there is something going on inside your engine. So yea a loose gear, a crankshaft bearing, or something else that is spinning inside your bike's guts. How about a complete teardown and engine rebuild
good luck with that
If I took off the exhaust would I be able to reuse the copper gasket (they are new from the last time I had the exhasts off (I really wish I rembered if it still vibrated from then)). Unfortunately I don't really have the time to take on an engine rebuild the most I can probably do is take off the clutch cover and check out the gear. Before I do that can someone tell me if there is supposed to be some play in the clutch basket large gear.
the most I can probably do is take off the clutch cover and check out the gear. Before I do that can someone tell me if there is supposed to be some play in the clutch basket large gear.
This my album detailing a debacle. With that said, take a look at the photo in that album. There is no slip or play in any part shown here. Your bike should be very close to what I have shown here. Note if you have a skinny washer behind your circlip. Beyond that the flywheel clutch basket, and clutch boss will have limited movement for each perspective item. Clutch boss will like to move the distance of the clutch rod will send it. the flywheel will be solid while its firmly connected to the crankshaft. unless the clutch is pulled. I hope that seems straight forward.
The basket is attached to the flywheel, the boss, is what is pushed by the clutch. the part with all the plates.
Is the play in and out, or is up/down/all around? In out, could be a sign of missing shim/circlip, the other sign isn't a pretty concept.
Thanks for the reply. So looking at the bike from behind it wiggles left to right (I guess that means washer missing. It may just be my imagination but there might be a very very slight front to back play. Do you think this can cause such a bad vibration?
from first post in this thread?
Is that how your getting your play facts?
I am going back to see what vibes he is having. after re-reading that my first thought jumped to tires under inflated. But that doesnt withstand the smooth as glass feel he had when he powered down. and coasted Or does it?
So here is my surmises, if the tires are good, and don't need balancing. Your going to need to order some gasket kits, and take off the right clutch side panel, and then do the same for the Generator side, I don't know where the Spark Rotor unit bolt is, but I think the TCI/CDI is not your problem. Somewhere the PO jacked it up good and till you decide to dig into to it, You shouldn't need to do a full rebuild, but you should be able to open up some of the panels and see what is going on there.
Look up magnets and oil bolt, consider pulling out the strainer basket, perhaps you can look up in that hole and see that bolt, (someday I will find it) Perhaps its something stupid like a wooddruft key not in place on the generator shaft. Not adequately spinning the magnet, and thous creating the vibes at higher RPMs. I don't know. but it seems we have exhausted what we can do with out taking anything apart.
Its not that hard, if your careful you can reuse the gasket, that side you just have to take off the kickstart kicker, and hope the guts don't come out with the panel. for ease, take off the foot peg too. You can do it.
drop the oil first, or lean it on the side kick stand. so its tilted over.
drop the oil first, or lean it on the side kick stand. so its tilted over.
