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2fastlx
01-03-2014, 05:01 AM
Hey everyone,
I have a 1999 400ex I have had about 10 years. Used to ride it frequently, but due life changes and loss or riding areas I dont get to use it but a couple times a year. Last winter I had a motocross mechanic friend help me rebuild the top end and do a fresh valve job. The bike has run flawless in 4 weekends of riding since. Unfortunately my friend has moved for another job offer, so I lost my go-to guy for atv stuff.

A couple weeks ago I was riding up in central florida and the bike was running great. I hit a puddle, nothing major, and the bike stalled. Not nearly deep enough to get into the airbox, but I double checked anyway, and it was dry. It wouldnt re-start, only sputtered a few times and stalled. I let the bike sit for a while while eating lunch and trying to figure out the problem. After about 20 minutes, I was able to re-start the bike and it seemed fine. Took it for a ride, ran through the gears and all seemed normal for a few minutes. About mid way through 4th it seemed to hit a point where it stopped climbing, then stalled out. I rolled to a stop, re-started the bike and all was fine again. A few minutes later, mid way through 4th again, it did the exact same thing, and has not started back up since.

Once I got back home I checked for fuel and spark and had both. Changed the plug for good measure but no change. Wont even sputter on starting fluid. Unfortunately I dont have a compression tester, but since it ran strong after having the issue the first time it doesnt seem to be a compression issue. Could I have a weakness in the ignition somewhere, maybe the coil? Seems like something got out of whack when I hit that first puddle, but I cant find any wiring issues. Any advice would be greatly appreciated.

Thanks, John

DragonGunner
01-03-2014, 06:21 AM
With info you gave...gas getting to cylinder...right? Good spark..? Did you try a shoot just a little gas or fluid down the plug hole, put plug back in and try and start...? If you pump like crazy on throttle and try and start and it doesn't take plug out...it should be wet...if not then your getting no gas from carb to cylinder.

If after this it has good spark and getting gas..

Engine starts but keeps stopping = improper choke setting, incorrect carb setting, leaking carb insulator, faulty ICM or ignition generator, contaminated fuel.

Engine does not start = test cylinder compression = valve clearance too small, valve stuck open, worn cylinder and rings, damaged head gasket, siezed valve, improper timing.