broken washer hiding in 426

Another YZ question posted to WR side…

I had a problem in the past with the retaining nut on the main gear coming loose and the counterbalancer drive gear key getting rounded off. I simply replaced the key and the retaining washer and retorqued the nut and went on my way. But because I never figured out why this happened to begin with I rechecked the torque and the key about five rides later and about twenty rides after that. No problems.

I don’t know which is the Chicken and which is the Egg here but it happened again (loose nut, rounded straight key). But this time I didn’t catch it early enough and the retaining washer broke in pieces after ruining the case. There was probably a teaspoon of aluminum trapped on my oil filter from the case. I changed the oil and filter right before a 2 hour plus race and then discovered the problem, so this occurred during the course of the event, so at worst my motor ran for two hours with restricted oil flow and a bunch of aluminum filings floating around. What worries me more, however, is I cannot locate all of the pieces to the steel washer. With the motor on its side (clutch side down) and using various magnets and gravity I have located what looks to be more than half, but definitely not all, of this broken part.

So now I would like some advice as to how to locate the other pieces or insure that they are no longer inside my motor, waiting for the right moment to grenade something, short of the obvious splitting the cases.

But if that is all I can do then, aside from a flywheel puller, are there any special tools I need to split the cases (like special snap ring pliers)? Has anybody here done this? Do any parts, aside from gaskets, need to be replaced as a result of this (like seals, bearings or snap rings launched into orbit etc.). Yes I have a manual and no I haven’t read it yet but that thing is not the greatest guide in the world, other Yamaha owners on thumpertalk are much easier to understand and often more accurate.

What else should I be worried about as a result of all that aluminum flowing through my motor? On the HLSM parts site on the oil pump fiche there is an oil strainer (reference # 17 from link below) 0YZ426FMTA+2000YZ426FMB1+2000YZ426FMB1.GIF

I am sure this screen is filled with alum. Can I get to it without splitting the cases? I have not checked the oil pump for damage yet but plan on doing so.

This really sucks, by the way, so some sympathy for my plight would also be appreciated (i.e. “I told you so” comments won’t help me at all).

I don’t necessarily blame this on the bike, I should have continued to keep an eye on this problem but I can be an extremely lazy individual. And yes, I installed the washer properly and torqued the nut correctly.

Any and all advice, observations and comments appreciated (unless they involve replacing my bike with an orange one).


[This message has been edited by Hick (edited 09-25-2000).]

I am sorry to here this. I remember dropping the valve retrainer ring down the engine when I was doing my valves once and I almost started crying. Luckily I retrieved it blindly with a magnet extender.

However, I know if I was in your situation right now, I'd be in the corner curled up in the fetal position sucking my thumb crying like a baby on the phone with the dealer getting ready to be wallet raped by him.

I give you big props for attempting to do this yourself. Good luck.


Dougie, '99 WR400 with a lot of dumb, stupid, here take my money, I have to have them but they don't make me a better rider extra mods.

(Except the dampner :))

LOL...That was funny Dougie.... don't ya just feel like that sometimes?

I can't tell from the picture but I wonder if there is a way to blow compressed air or possibly some cleaner backwards into the oil pickup. We used to de-sludge oil pick up screens on autos in this manor.

That is a great idea. I already removed and blew out the external lines with a little ATF to help pick up all the particles, maybe I can remove the pump and run some ATF backwards through the screen and out the crankcase drain. I didn’t blow any air inside the motor for fear of just drying up and scattering the particles everywhere.

I checked my oil pump and was scared because I couldn’t turn it by hand but aside from some tiny scratches here and there it looked like new, tight clearances make it hard to turn. It looks to me like the pump has two sides, one a basic impeller that takes oil from the frame and pumps it through the filter to the top end and tranny. The other or inner side looks like it operates like an automotive pump (unlike the impeller) and picks up the oil from the tranny and crankcase (one or both of which must pass through the oil strainer or pickup) and pushes it out the left side of the motor back into the frame. I think.

What looks to be the balance of the missing washer pieces was wedged harmlessly against the pump cover (but not inside it). I guess when the new part gets here I can weigh it and compare this to the weight of all the pieces I’ve recovered :)

But the motor is still sitting on my workbench and I may dive in and split the cases yet, just to be sure.

If not I could be riding again by this weekend. Should I risk it? Actually, considering my penchant for creating additional havoc during the course of any repair job, checking inside versus not checking is probably a wash…

Thanks for your sympathy Dougie, you crack me up. I dealt with the frustration by getting drunk and taking it completely apart (alcohol diminishes fear of the unknown). Ever hear the phrase “state-dependent memory?” Now I need another twelve pack to remember how she goes back together. :D

[This message has been edited by Hick (edited 09-26-2000).]


Any thoughts on whether the nut is coming loose from an internal vibration? Such as a main bearing?


I think that ation is just a thing with big singles.

The counterbalancer is always spinning in relation to the piston etc, bt with more load on the bike and wider throttle openings there is more force on the piston that the ballancer can't cancel (or try to cancel) out.

I'd deff strip the motor.

The damage I've seen done on ships engines but a very small piece of metal is unreal.. its not worth the hassel and expense later on when you have to replace a heap of bits.

At least now all you'll have to replace is gaskets. :)



**Ride it like you Stole it!**

Matt Porritt

99 YZ400F

Vist the Rubber Chicken Racing Online Shop

Discounts for ThumperTalk members.

A friend of mine had the bottom piece of his cam chain tensioner spring break off and get ground up inside his XR 600 (the cam chain spring is internal on the XR 600). We did the top end-(hone, piston, etc.) cleanded out the bottom end as best we could then flushed the bottom end several times using Mineral Spirits. Put in fresh oil, a magnetic drain plug, fired the bike up and did two quick oil changes.

This bike ran perfectly for another 18 months until it was sold.

On My 95 Husky 610 I crashed and smahed the left side cover into the clutch basket filling the motor with magnisium and other metal shavings. Same drill did a top end clean up - no damages observed, cleaned out the bottom end as best I could then flushed the bottom end several times with Mineral spirits and did the fresh oil and two quick complete oil changes. The 610 ran great for another 2 yrs until sold and the guy who purchased it is still running it.

So it kinda depends on how well you think the oil filter did in doing its job and protecting the lower end rod bearing and crank bearings, the tranny is probably ok. It is kinda your call. But if you feel the oil filter was compremised and bypassed then I would tear it down inspect it and build it back up with a 00 426 top end (rod, piston, barrel)


Thanks for all the advice guys. I went ahead and split the cases once all the parts got here. I ended up ruining a seal getting the water pump bearing out of the old case so now I’m waiting on that. It was a pretty easy job but you are talking about a lot of parts to misplace like o-rings, dowels, springs, seals and snap rings. It will be interesting to see if I can get it all back together properly. :)

The oil filter, while covered with particles, held up well. It was slightly crushed from all the pressure and obstructions but there were no holes in it. There was only a few tiny pieces of aluminum on the oil strainer pickup inside the cases.

The crank, rod, cylinder and gears all looked perfectly fine. I did find several more pieces of the lock washer stuck to the flywheel and there was a few small scratches on the case on that side but nothing serious. So the hard metal fragments did not appear to come into contact with anything other than the clutch basket and left case before some ended up stuck to the inside of the flywheel (BTW my KX flywheel puller worked on the YZ). As far as I can tell the crank and rod are straight and all the gears looked untouched.

But now I am wondering if I should go ahead and put in a WR 5th gear, plus I heard that Wiseco just released an oversize piston and I know a guy who will powder coat my frame for free. Powder coated YZ 440 w/ WR fifth gear?? Sounds like an MXC eater to me!

Does 13.5:1 mandate 50/50 race gas? What is the turnaround time to bore and replate a cylinder?

I may never get to ride the damn thing again…

PS Taffy, if you are reading this I haven't measured the base gasket yet because NCY sent me the wrong one. Check here next weekend.

[This message has been edited by Hick (edited 10-02-2000).]

I'running the Weisco 13.5 to 1 417cc piston and I run 1.5 gallons of VP C-12 mixed with 3.5 gallons of Union 76 92 octain supream pump gas and it runs great.


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