Rattling 426

Hi guys,

Forgive me for posting such a vague question, but I need some guidance. My 426 is making an annoying rattle that appears to be coming from inside the engine. You can't hear it at idle, but when the rpm's run up it is easily heard. I've checked all the fasteners externally (I think) and could not find anything. Several people have listened to it as well and think it is coming from inside somewhere. So, first I went into the clutch and found nothing. My clutch boss needed to be replaced so I did that while I was in there, but the rattle sounds more like it is coming from the timing chain area. Anyway, I took the valve cover off and poked around, everything looked fine. So I went in and took the head off and looked at the piston, rings, and pin. Besides having the rings worn a little out of spec, there is no place where anything is even remotely loose enough to rattle. The connecting rod is tight as well. Now I don't know what to do...do I crack the case and root around for something that looks loose or put it back together and hope the problem magically disappears? :cry: Has anyone experience any rattling from their transmission or anywhere else down there that could lend some advice? I'm up for any advice on the outside that I may have missed a possible rattle could come from. It makes the noise in neutral as well as in gear.



Were the valves in spec., maybe check your chain tensioner and make sure its working properly, remember these bikes make alot of noise compared to other bikes i used to think the same thing but you have to remember there is a lot going on in these motors.

Valves are in spec. I thought about the tensioner too. I need to check that. I've had this bike for 3 years so I'm pretty tuned to it's "normal" operating noise, but this is a new noise it started making, and it is getting louder in a bad way.... :cry:

If it's a 2000 check the key on the RH crankshaft that works the counter balancer. Mine made some wierd sounds when it was worn.

It's Number 9 on this diagram Crankshaft Diagram

I second the crankshaft key for the counter balancer gear.


I assume you have to crack the case to get to that?


No you dont, actually if you pull the left side cover you will see the counter balancer in front of the flywheel, if you can rock it back and forth at all, it is the key. Easy to change, but you will have to remove the right side cover (not the clutch cover) and the clutch basket, then the nut on the end of the crank, change the key and reassemble. This is only applicable if you have a 2000 model, in 2001 they went to a spline instead of a keyway. I just repaired mine and it had quite a bit of slop. The crank and gear had no wear, but the key was grooved on both sides deeply almost ready to shear. I havent started it yet since I am waiting on some parts to get here for another project. I am sure it will be quieter, it used to rattle quite a bit. It rattled for over a year with no problems just concern. However if it shears, it could cause some issues. Order a new key or grind one from some keystock, I used 1/4" X 1/4", try to find some 5mm stock otherwise it will be a lot of sanding to get to right size (2 hours by hand). :cry:


I'll take a look. I hope that's it. Like you said, the bike runs fine, but that noise is driving me crazy.


I take it your bike is a 2000. I am getting ready to do this myself. :cry:

I had the CB drive gear key problem. Here's what I did about it:

There are two gears on the right end of the crankshaft. The outer gear drives the clutch basket, the inner gear drives the counter balancer. This inner gear is the one held in place by the key. My key had little indentations on each side. These "dents" allowed it wiggle a bit in the keyway, in turn allowing the gear some slop. That's where all the noise came from.

It wasn't too challenging to fix. First I drained the oil and coolant, and removed the clutch cover. Next I removed the kickstart lever and the rear brake pedal. Then I disconnected the exteral oil lines (the galley on top, and the line running to the bottom of the right side of the motor. Then I disconnected the fitting from the water pump, and removed the waterpump cover. I removed the oil filter cover and the filter. Then I removed the right side case cover.

At this point I could see all the gears in question. I was able to rock the counterbalancer drive gear on the crankshaft and hear it making the clacking noise. It's not supposed to have any slop at all. This confirmed the problem.

Next I removed the clutch. This is done in a few steps... first remove the pressure plate, then remove the loose clutch plates, then remove the nut holding the hub to the shaft. Finally, when the clutch basket comes off, you can remove the nut on the crankshaft and remove the two gears.

I replaced my dented key with a stock Yamaha key ($0.97!) and cemented it in place with red loc-tite.

Re-assembly is the reverse of disassembly, with the following notes:

Make sure the timing marks on the counterbalancer gears are lined up when you re-install the counterbalancer drive gear. There's a little dot on each gear, they should line up.

Slather all the clutch plates in oil before you put them back in the clutch.

When you put the right side case cover back on, make sure the shift shaft is lined up, with the roller wheel in the slot. The right side case cover holds the shift shaft in place, and with the cover off, it's easy for the shift shaft to slip off the shifting star. An easy check is to work the shift lever after you get the right side case cover bolts in place. If it clicks through the gears, you're OK, if it just goes up and down without changing the gears, take the case cover off and check the roller.

Use loc-tite on the bolt holding the kick start lever in place.

Now my '00 426 is "clack" free, relatively speaking, of course.

Glad to hear you found the noise. You dont have to take the clutch cover off since it is bolted to the right side cover.

You dont have to take the clutch cover off since it is bolted to the right side cover.

True, but some of the clutch cover bolts must be removed because they go through the case cover into the case as well. It's easier to remove all of them than to just guess which ones are the long ones.

You are right, BTW the top 3 are the long ones.

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