New to the forums with 426 project

Just wanted to say hi to everyone on the forums and wanted to show a new winter project I picked up the other night. Its a 2000 YZ426 that needs some TLC. Bike is missing the rear wheel assembly and does not run for some reason. Previous owner said bike was run out of oil and stopped but kicks over fine and has great compression. Kicker feels good with no noticeable noises. Do these bikes have a low oil sensor that will shut bike off? Picked it up for $350 off craigslist and needs some work but I thing I can get it up and going again and still have less than A grand in it when done. What do you guys think? I am not one to part a bike out, You can sell a few high dollar items but a few weeks into it your left with a pile of worthless parts that is bigger than the pile you sold.

yz426POS-1.jpg

Welcome to TT !!

Nop, they haven't got any sensor. It will be nice to check the engine for damage due to running out of oil, for peace of mind, and to avoid expensive repairs if something is wrong inside and you start it.

Greetings and good luck!

If it ran out of oil, the first two things that would happen are the cams might seize, and/or the piston would seize.

Piston seizure seems contraindicated by the fact that it has good compression, but don't be surprised if it burns oil like a steam locomotive once you get it started. The cams, on the other hand may have partially seized, leading to the engine jumping time far enough not to run, or even a camshaft sprocket rotated out of place on the cam.

It's also possible that the carb or ignition system is responsible, and engine damage, if any, is not involved.

Proper carb condition is critical to getting the bike to start well, as is the correct procedure.

http://www.yamaha-motor.com/sport/4stroke_vid/4_stroke_vid_a.mpg

http://www.yamaha-motor.com/sport/4stroke_vid/4_stroke_vid_b.mpg

If its anything like the project I bought then the top end could be in great shape yet the bottom end could be completely toast. You might need the complete crank assembly as well as all the bearings, Most of the bearings you can get at a bearing supply house, but the mains and a couple of others(ie Balancer shaft) will be OEM only.

This site has been very helpful to me over the last little bit.

Good Luck

Thanks, I am not going to rip into until this winter. I am sure all the help I would need is right here.

Here is some wheel info for you:

Rear wheel from any YZ400/426/450 or 250 2 stroke from 99-08 will work for you. You can even pick up aftermarket sets out there for around $500.

Check the 3 basics:

compression

spark

fuel

Sounds like you have some compression. I would drain the oil, filter and remove the frame screen to see what you find in the oil. Then put in new oil and filter. Check for spark, simple there. Troubleshoot if you dont.

Carb, well that is most likely the problem. Clean it out really well. Then spend some time jetting and modifying it when you get it running. The BK mod and JD jet kit will really help you out on the bike. Great find for $350 though.

sweet find, im sure you will enjoy working on it during the dead sesson.

Well, I won a complete wheel on ebay for $150. Also this afternoon, My buddy came over put some frsh gas in it and it started on the 10th or so kick. Would run for about 3 seconds and shut down. Time to clean the carb and check things over. Engine might be OK. Not sure what the truth could be behind the engine problems that were told to me. Looking good so far..

Cool project, please keep us updated with pics!

I bought a 2002 YZ426 with a seized piston after running out of oil. about 15 running hours after I poured too much money into the head, piston and cylinder, the rod bearing went bad. I ended up replacing all of the case bearings and had the crank rebuilt. I am hoping that after dumping ~$3000 into the engine that it will last as long as the unmolested versions out there. That $3000 figure does not include the labor required to split the cases at least three times (transmission issues), but does include having the head professionally rebuilt.

In closing, rebuild the crank since you can't inspect the rod bearing without splitting the crank. Try Mr. Crankshaft, they had my crank rebuilt and shipped in one day. Cheap and fast since he had parts in stock. $17 for me to ship to him (with $600 insurance), $189.95 including shipping from Mr. Crankshaft. Pleasure to deal with, I must say.

that tanks is more than half what you paid for the bike.

Well, A little update, Ripped bike completely apart including motor. Found clutch boss totally ate itself to death and many metal shavings in the oil and botton of cases. Case was damaged anyway from chain flying off so found a set of 2001 426 cases on ebay for $30. Switched parts from old to new cases. Motor is back in bike But now waiting for new neutral safety switch and exhaust clamp.Also in need of a left radiator cause mine is completely crushed. All new plastics also to come. Will update with pics soon.

Be sure you wash out the oil tank in the frame.

I will do that, What would be the best way to go about washing that out??

The best way? Strip the frame and have it cleaned ultrasonically.

Realistically, though, remove the feed screen from the base of the down tube (25mm hex, and usually VERY tight). If you have access to a pressure washer, you can blast it through in both directions thoroughly. Then put a couple quarts of alcohol in it to absorb the residual water, following that with a rinse of 75/25 mineral spirits/ATF, and then some cheap engine oil. If no pressure washer, soap and water and slosh it around as best you can.

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