HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
BIGBLOCKBRAIN

'00 YZ426F Transmission problems.

13 posts in this topic

The transmission on my YZ426 took a dump when it was 5 months old. The problem started with it jumping in and out of 4th gear very rapidly at WOT. It started occasionally then progressed worse. It was finnally diagnosted on a Dyno where we could actually see the chain whipping around because it never actually pop all the way out of gear. After being tore down, 4th and 3rd gear were thrashed and apon further inspection, using the service manual for reference, we discovered that a shim was installed in the wrong position. After a long wait for for replacment 4th gear the trans was assembled with new gears according to the service manual and since then has been trouble free. Any comments?

Share this post


Link to post
Share on other sites

It has happened to some people here in this forum (to me also).

Please check old messages...

My 426 is still in reparations for this problem.

(S.M.)

Share this post


Link to post
Share on other sites

I went back and looked at past posts about transmission problems, but I never really found an definitive answer as to what is really wrong here. Did anybody else find incorrectly assembeled tranmissions from the factory? Is this a heat treating problem like with rm250 years back? Or is the gear just not up to the task on the 426.

Share this post


Link to post
Share on other sites

Yo brain- go to http://dirtrider.net/forums2/Ultimate.cgi

and go down to the thumper forum. I remember someone posting on there about this problem, seems like I remember reading somewhere that the 4th gear was the same part # as the YZ250 and there are some weak ones out there. Let us know here what you find out if you would...

Mike

Share this post


Link to post
Share on other sites

BigB,

Hey, I am the one that lost 4th gear in my 426 way back in May. I waited for two months for the parts and finally got my bike back around Aug 1st. I don't know if it was assembled wrong since I had a race shop do the work instead of Yamaha. They were backlogged with work for three weeks it wouldn't have mattered in hindsight. Of all of the failures that I've heard of (7 or so) it was always 3rd and 4th gear, or just 4th. My friend had the same thing happen to his 00 250. 4th gear went. He works for at a Yamaha shop and said that the part numbers were the same as the 426's. I'm curious if a dozen 426 motors were disassembled if we found out that these shims were installed wrong on a number of these bikes. I know that I'm still very scorned from my bike failing. Just like someone said in other forum, when your house is burgularized, it's just not the same after that. I don't trust the thing now.

Do let me know what Yamaha does for you. My gut is that Yamaha knows about these problems but they are hoping that the victims fade away. I don't think this will happen if I have anything to do with it.

Cheers,

Daveyg

Share this post


Link to post
Share on other sites

By the way, what shims are you talking about ?

I don't see any shim on the trans parts in the owners manual...

Are you referring to the shafts circlips ?

(S.M.)

Share this post


Link to post
Share on other sites

Hey daveyg,

My thoughts exactly on the possibility of a number of bikes being assembled wrong. The purpose of me posting was to try and find out exactly that. When my mechanic found the shim out of place we attributed that to the failure, but we've never been able to confirm that entirely because we only have this one experience to make that judgement on. Since Yamaha seems to confessing up to very little I think it will take a little more prying. And why should we care? Because like you daveyg I want to know if my problems are over. Should I dump this thing now while blue book is high or can twist the throtle and have a bunch more fun?

Thanks for your input

BBB

Hey sm,

It's almost been 6 months now so I'm having a little brain fade now on the excact misplacement of the shim, but looking at page 4-86 and 4-87 if you look at the trans exploded views you can see the patterns; clip, shim, gear and it looks like fifth goes gear, shim, clip right to left. This all brings up a point that the trasmision failure didn't pop or mangle a clip that would allow the gear to move causing engagement of more that one element that caused tooth breakage, but our feeling was that the slight misalginment caused by the shim may have caused a slight multiple engagement. We just can't say for sure and there's the posibility that it didn't have nothing to do with anything and it was batch of junky gears.

Thanks for the input everybody.

Share this post


Link to post
Share on other sites

I haven't experienced any transmission problems to speak of but I DID seem to notice a little notchy feel to shifting in general. There was a short article in one of the dirt oriented magazines that talked about Bel Ray's EXS oil. According to the article, the used test bike had developed hard shifting and after using the EXS oil for a short while, shifting improved dramatically. I usually take such articles with a grain of salt but after checking out the specs for this oil to see if it would be compatable with the 426, I decided that it surely wouldn't hurt to try it. I changed my oil before heading to the locl track Wednesday afternoon and put about 3 hours riding in. To my surprise, shifting became a buttery smooth and clutch action was equally as smooth. One very noticeable improvement is when shifting down from 2nd to 1st. It always took a little more effort to avoid getting neutral instead of 1st before and I had to compensate by applying a longer duration of force on the shifter instead of a simple jab with my boot to get past neutral and into 1st. Oil choice is such a heated issue and probably always will be, but this was my experience and am passing it on.

Share this post


Link to post
Share on other sites
Originally posted by BIGBLOCKBRAIN:

I went back and looked at past posts about transmission problems, but I never really found an definitive answer as to what is really wrong here. Did anybody else find incorrectly assembeled tranmissions from the factory? Is this a heat treating problem like with rm250 years back? Or is the gear just not up to the task on the 426.

Share this post


Link to post
Share on other sites
Originally posted by BIGBLOCKBRAIN:

Hey daveyg,

My thoughts exactly on the possibility of a number of bikes being assembled wrong. The purpose of me posting was to try and find out exactly that. When my mechanic found the shim out of place we attributed that to the failure, but we've never been able to confirm that entirely because we only have this one experience to make that judgement on. Since Yamaha seems to confessing up to very little I think it will take a little more prying. And why should we care? Because like you daveyg I want to know if my problems are over. Should I dump this thing now while blue book is high or can twist the throtle and have a bunch more fun?

Thanks for your input

BBB

Hey sm,

It's almost been 6 months now so I'm having a little brain fade now on the excact misplacement of the shim, but looking at page 4-86 and 4-87 if you look at the trans exploded views you can see the patterns; clip, shim, gear and it looks like fifth goes gear, shim, clip right to left. This all brings up a point that the trasmision failure didn't pop or mangle a clip that would allow the gear to move causing engagement of more that one element that caused tooth breakage, but our feeling was that the slight misalginment caused by the shim may have caused a slight multiple engagement. We just can't say for sure and there's the posibility that it didn't have nothing to do with anything and it was batch of junky gears.

Thanks for the input everybody.

Share this post


Link to post
Share on other sites
Originally posted by BIGBLOCKBRAIN:

The transmission on my YZ426 took a dump when it was 5 months old. The problem started with it jumping in and out of 4th gear very rapidly at WOT. It started occasionally then progressed worse. It was finnally diagnosted on a Dyno where we could actually see the chain whipping around because it never actually pop all the way out of gear. After being tore down, 4th and 3rd gear were thrashed and apon further inspection, using the service manual for reference, we discovered that a shim was installed in the wrong position. After a long wait for for replacment 4th gear the trans was assembled with new gears according to the service manual and since then has been trouble free. Any comments?

Share this post


Link to post
Share on other sites
Originally posted by BIGBLOCKBRAIN:

The transmission on my YZ426 took a dump when it was 5 months old. The problem started with it jumping in and out of 4th gear very rapidly at WOT. It started occasionally then progressed worse. It was finnally diagnosted on a Dyno where we could actually see the chain whipping around because it never actually pop all the way out of gear. After being tore down, 4th and 3rd gear were thrashed and apon further inspection, using the service manual for reference, we discovered that a shim was installed in the wrong position. After a long wait for for replacment 4th gear the trans was assembled with new gears according to the service manual and since then has been trouble free. Any comments?

BigBlockBrain, Glad I found you. I have a 2000 426

with the same trans symptoms. I can feel the trans

surge in and out of gear in the top of third, and almost everywhere in fourth or fifth when in the power. I bought the bike used and for the first 20 hours of riding it was awesome. Then this problem came on and it's made me sick. I spent $400 to upgrade the clutch to 2001 specs but the problem obviously still exists. Am I another unlucky recipient of a lemon tranny or has Yamaha stepped up to the plate and aknowledged this problem ? My dealer is playing dumb (big surprise). I'm a competent general mechanic. Do you think I should tear it down and inspect the gears myself or pay thousands to have a Yamaha mechanic fix it ? Lastly, before you discovered the problem did you see any significant metal chips during oil changes. Mine have been very clean. Thanks, Ernie Otto

2001 YZ426F, 1997 Ducati M900 Monster, 1969 Camaro

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0