My YZ426 completely blew up the other day. Piston, cylinder, cylinder head, rod...all shot. They say it "Dropped a valve." Ever heard of this? It's about a $3500 repair. Trying to get Yamaha to help with something. I'm freaking out! By the way, it just got out of the shop for the "Shift Pin" problem. Any way these are related? Any suggestions???

Yep, mine dropped a valve a few weeks ago. Head, everything in the head, piston, rod, although the cylinder is fine. Around $1000.00 for the parts alone, $2200.00 to use 426 parts instead. Screw it, It can sit and rot.

If yamaha wont help, and you would like another option, I have line on a 2001 YZ426 motor complete no electrical or carb, still in the factory box. I was going to use it in my 400, but decided on a KTM 520 EXC instead. They wany $2500.00 + freight. If interested e-mail me and let me know.


Pretend it's flat and give it the gas.

could you look for score marks on the bore in line with where the wrist pin would come out the end (gudgeon pin to us).

to me the most important area to look at is the piston surface. look for a light silver 'half-moon' colour to the surface in the valve seat pockets. look for carbon build being 'broken away' here.

what does the piston & bore look like. this will be your first indicator as to whether your problems were simply top ned related.

report back.






TOLL FREE 866-782-4600

OUTSIDE USA 818-782-4600


What year was your 426?

Lots of time on it? Had it been rebuilt before?

Just curious...


Hey Guys,

I know this might seem like a real ignorant question, and I apologize for it, however-

What would cause such an event to occur?

And, are there any tell tale signs to watch or listen for?

I'm sorry to hear about your dilemma's and I do sincerely hope Yamaha will assist in the repairs.

Best wishes!

God Bless!


YZ426 Kicks

part your bikes out on the web/ebay and buy another one. Your losses will be minimized.

sorry to hear about your dilemna.


The bike has less than 20 hours on it. It has been maintained exactly as the manual directs and has had NO previous problems. The day before it blew, the shop was working on the shift pin deal and had to remove the motor (without splitting the case) in order to get to the shift pin. Wondering if they neglected to hook up an oil line or pump...or something???

What's the shift pin deal? My 250F is having tranny problems. Something I should know about?


Also, that shift pin maintenance (and it blows up the next day) is way too fishy for me. Did the timing chain snap first? Perhaps they left crap in there.



I don't think you're getting the answer you came looking for.

First of all, you're in a bad situation. I'm sorry to hear about this and it would be good to hear Yamaha doing something about it.

If I were you, I would call Yamaha of North America (assuming you're in the states) and just talk to them about this. Not to complain, but ask them for advice. Or even better, write them, then call. Be very specific in all the details of what took place. Dates, times, cost...etc. And cc the dealer that did the work and sold it to you. This will at least start a case number on the problem, of which they should provide you with.

This will cover you legally and start the process of negotiating a resolution.

Then have someone who is certified with Yamaha pull the top end apart and determine what the cause was. You may be correct in that they forgot to hook something up, or left something out. For all you know, they may have left a rag in the tranny when they did the shift-pin job. If anything looks funny, photo and document it on the spot.

Then follow up with Yamaha verbally and in writing with everything you found. Don't ask for a resolution, wait for them to say something. The more you call and update them, without demanding anything, the better your changes they'll kick in with their share.

Then if you feel you have a case, call them up and tell them what you expect and measure their response. If you get a standard answer, like "it's not our policy", then you're talking to the wrong person.

If you eventually don’t get the answer you deserve, send them a letter of intent. Certified. Then send one to the dealer. This is a legal letter indicating that you have done everything you can and they are not doing their part, and you will take them to court unless they respond.

Then wait. If you don't hear back, either decide to sell the bike off, or go through the hassle of taking them to court.

You would win the court case, but it may cost you more time and money than the bike is worth.

If you race the bike, you're odds are even better since you can show duress.

Hope this helps.


What was the link to that website with the red bike, man this is getting scary!


00' 426 :)



When in doubt, GAS IT!

What are you, YELLOW?


Thanks for the information! I've done almost everything you've mentioned. From pics to talking with YMC to serious talks with my lawyer. He says I've got an excellent case and that cost would be minimal because it'll be a small claims case...just lost time. The repair is almost done and it was done by the same guys that fixed the shift pin deal, so as far as a second opinion...not happening. I thought it was wierd though that the lady in customer relations at YMC wouldn't give me the name of the acting CEO or President so I could cc him. They also won't let me have the damaged parts before they look at them first. YMC has ordered all of the damaged parts back to their facility for an inspection which they say they are 90% of the time successful at identifying the cause. After they give a reason I can go from there. I don't know if my legal proceedings will be directed at YMC (Yamaha Motor Corp)or the shop that did the repair, or both. Any good contacts at Yamaha? I tried getting past this lady at CR, but was unsuccessful. Again, thanks!

The guy that you need to talk to at Yamaha CR is Danny Modina. Really good guy. He'll help you as much as he can. As far as YMC asking for the parts... that's protocall. They alyways do. We as a dealer have to keep all warranty parts for 90 days, because they may request them. In an instance like that, they want the parts to look at, and then make some kind of determination on what they are going to do, IE: goodwill the repair, or tell you "nope". Sometimes though, they will front the parts, and you settle the labor. Good luck.


Mr. Wizard says: "Go BIG, or go home!"

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