650hucker 0 Posted November 10, 2010 I'm hoping someone here will know of some magic fix that will make the bike start...maybe it's a common issue with 426s that I haven't read about..wishful thinking anyways So, 2002 YZ426F. Won't start. I know the starting procedure, so it's not rider error...for once. I rode it at pala, and it sat un-started for about a month. I know, I know, my bad. So, I've cleaned the carb twice, making sure to get every hole and jet...no luck. I got the new jet from motorworld, bumping it up from a 42 to a 45, supposedly makes it start/run better. No luck. Got ONE start with it, but it wouldn't idle. I took it out on the street with the choke on, and it had about the same power as my 70. Makes me think it's the valves...But I don't have the tools for THIS engine to check it...the valves are hidden....Really starting to hate this bike... So, any ideas? Things I've done(Keep in mind, I tried to start for about an hour after each fix, didn't change more than one thing at a time): Drained out all the gas, Put in premium (used the gas treatment stuff that revitalizes old fuel during the first week of storage) Drained the carb Rebuilt the carb, inspected and cleaned, twice Changed the main jet to a 45 Broke my foot trying to start it Checked the spark plug to see if it was sparking New spark plug (Man those plugs are a PAIN to get out...8 inches into the engine >.< ) Threw wrench across the garage Looked for wrench Checked the ingnition wire Checked the valves...didn't look slammed or anything, no way of measuring them Hit bike with rubber mallet Messed around with the idle adjuster... What I think: Timing Valves ??? Oh, and it does LOVE to backfire and shoot blue flames out of the pipe from time to time...not getting enough air to start I guess. Tried using ether, didn't help, but I did set the bike on fire once. Thanks! Share this post Link to post Share on other sites
tntmo 887 Posted November 10, 2010 Could possibly be a valve, I am working on a CRF250 right now that won't start due to tight valves. It starts if it is push started but can't start it with the kick starter. It should take about 15 minutes to check the valves, they are not difficult. If you have pulled the carb and cleaned it, that is more difficult than the valve check. I have tomorrow off and can help you out if you want. Share this post Link to post Share on other sites
ARGMISTER 0 Posted November 10, 2010 My bike is different, but my problem was tight exhaust valves one time and another time one of the idle circuits was completely blocked even though i cleaned twice and had someone else clean once. Share this post Link to post Share on other sites
PbdBlue 46 Posted November 10, 2010 You really need to check the valve clearance. How is the compression? Can you push the kickstarter through without using the compression release? I just finished doing the head on a friends WR426 for the exact same problem. It's got the same head as the YZ and both have Ti valves. The center intake is usually the culprit. You will not be able to see any problem visually but if you measure the clearance it will be 0. If it is the valves you can replace all the valves in the head with 2000 YZ426 valves which are stainless steel instead of Ti. If you decide to go that route you must change the valves and the springs as the stainless valves require a heavier spring. The stainless will last much longer and cost about 80% less than the Ti (ss intake valve = $13 each, Ti intake = $90 each). The average rider will not be able to tell the difference. If the valves are ok then it's in the carb. Sounds like you've already done a thorough clean. Make sure the slide plate is installed on the slide correctly. The cutout should face down. It is possible to put it together with it facing up which results in symptoms much like you are describing. Share this post Link to post Share on other sites
robertaccio 406 Posted November 10, 2010 simple stuff first got air? (filter clean) got spark?(fresh plug is good too, kill switch short to ground check) got fresh fuel? (got fuel getting in to engine, petcock screen, water in tank, inline filter) got clean carb? (all clean and jets unclogged) got valve clearance? (important, very) got compression? got good cam timing? (cam chain stretch throws off cam timing=hard or no start) good luck and go step by step easy stuff progress to the more labor intensive (dont jump the gun). good suggestion posts above Share this post Link to post Share on other sites
650hucker 0 Posted November 10, 2010 Thanks guys, I'm going to tear into it here in a little bit, hopefully it's just the valves...I'll keep you updated... Might do that switch to steel valves And no, I can't kick it through without the compresion release...My dad can though, I don't have enough kick in my 130 lbs haha Share this post Link to post Share on other sites
socalhodaka 104 Posted November 11, 2010 Did you really pull the pilot jet and clean it, it has more to do with starting then the main. You must pull the pilot. Share this post Link to post Share on other sites
dirt dame 559 Posted November 11, 2010 Did you really pull the pilot jet and clean it, it has more to do with starting then the main. You must pull the pilot. And pull the fuel screw also, then blow air through that passageway. Share this post Link to post Share on other sites
650hucker 0 Posted November 11, 2010 Yep, I completely removed every jet and part in the carb and squirted carb cleaner through the holes, and made sure they were clean. Share this post Link to post Share on other sites
