YZ426...at wit's end!

Any info is appreciated. I have combed the threads prior to posting this. I have tried almost everything so please advise me. My 426 won't start. Never had an issue in the past but now not even a sputter. I have removed the carb and cleaned it. However, I did not remove the bowl because I am not experienced with anything inside the bowl.

I replaced the cleaned carb and changed the spark plug...twice. I checked for spark prior to putting them in and they gave a spark. I kick and kick but I get no fire at all. I am at my wit's end with this. Can anyone offer some advice on this one. Thanks!

Check the valves.

Everything you need to clean when you clean the carb is inside the bowl. If your bike sat for a while, it could be that the jets are gummed up. The manual tells you everything you need to know to clean them out. Are you sure you are getting gas to the carb? When you take out the plug, is it wet? I assume you have a clean air filter. You might want to be sure the Hot Start is not stuck open as well. Have you run a compression check?

Check your valve lash if everything Birdie said has been done or checked out. My neighbour had the exact same issue with his wr250, once we shimmed his valves correctly it started first kick.

Does your bike have a battery? If so try hooking your bike up to a fresh battery. 2 weeks ago my bike wouldn't start. Only change in bike was A. sitting and B. battery had gone dead....bike would not kick start period with dead battery, I could only bump start it. I put in a new battery and 1-2 kicks it fires up!!!

If it was starting before you cleaned the carb, good chance that is where your problem lies.

With the air filter off, can you see the AP squirt fuel when you pump the throttle? Is the fuel on? If you open the bowl drain screw, does fuel come out?

Thanks for your input. Here is what I have done. I removed the carb, broke it all the way down, cleaned it, and reinstalled it. Once I did this, the bike started on the 2nd kick. I was a happy guy. The bike sat for a week while I was out of town. Again, she wouldn't start. A more thorough investigation revealed that my petcock does not shut off, thus letting fuel continually leak into the carb. Could this be the root cause of my issues?

Any advice is appreciated!

I know this sounds like a dogdy thing, but to isolate whether the problem's caused by your faulty petcock (which you should replace anyway), remove the fuel line from your carb and stick a bolt or something in it to stop it leaking. Then see if you have the same dramas in a few days.

Either way, you seem to have narrowed it down to something carb related, as your problem changed once you worked on the carb.

But as already mentioned wouldn't hurt to check valve clearances as well. I've seen guys who couldn't get their bikes to start no matter what they did because of valve issues ( on CRFs in most cases - surprise suprise - not the mighty WRs) .

Hmmm...my petcock must be faulty too as if I switch it to OFF and allow my bike to idle to let the gas burn out of the carb...it will idle forever. You may be on to something. Where can a new petcock be purchased. Any links?

my petcock went once on my old IT 250. Parts for old bikes can get expensive and i was in high school with no money. I went to a small engine repair shop and bought a small plastic shutoff valve for 10 bucks. I cut my line, put it in and never had problems again.

I also had that problem with my WR this past summer. I bought a rebuild kit for it for like 5 bucks and the local bike shop. They had it in stock. It took me like 15 minutes to fix. You just have to make sure the seals are clean and fitten snugly. The old ones didn't even look bad, but they had gotten a bit hard and started leaking.

Hey MrMonk. I found the OEM part at the ThumperTalk store for $19 sans shipping. The ThumperTalk store is a great resource for OEM parts. I have also utilized it for my son's TTR90.

If it started on the 2nd kick after taking the carb apart then the valves are fine. Sounds like the float level too high. I would guess that your petcock does still work but the level of fuel in the bowl is so high it runs out the overflow.Fuel will only run out the overflow because of this. Even if you always left the petcock on the float should shut it off.This is a normal thing that happens to a carb. over time, very easy to fix. I never shut the fuel off on any of my bikes , no need to unless I take the tank off . Also if the level is too high it can sputter over whoops or any series of small bumps, you may not always feel it but it can happen.


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