Rebuild!! And Won"t Stay Running

[KY_YFZ_04]

I just recently had to rebuild my 400ex, parts consisted of a new piston, rings and wrist pin, new valves and new head (dropped a valve had to replace head) I have the quad in time and it cranks and cranks before it will attempt to start. It will fire and take gas only about 3 pumps with the throttle then it dies. Its almost like as soon as I get to let up on the start button it will die. Could I be having and electrical problem with it not letting the quad fire without the starter engaged and that is where i am getting all my power from. I cleaned out the carb. and everything so i don't guess that is my problem.

OH and the quad has sat since November of last year without being started I didn't have the cash to get it fixed until now.

Any help would be appreciated.

Thanks

[400exrider707]

check obvious things like gas, carb, air filter........ tell us what you HAVE checked so far. Its going to be process of elimination.

[KY_YFZ_04]

checked air filter and its ok, took carb. apart after trying to start it many times cleaned it and its ok, check the valves for proper adjustment, checked cam again for timing, gas is fine and flows good out of the tank so nothing stopped up in there.

[bwamos]

Check spark next.

Make sure your getting good spark from your plug. I'd also put in a new plug while your at it.

Your plug may just be fouled out.

[jhoppa]

check your timing, you might be 180 degrees off when you installed the cam.

Take inspection plug off crank and connect a timing light. Should see the timing mark if timing is correct.

[KY_YFZ_04]

its fixed............thanks guys

[JOEX]

Originally posted by KY_YFZ_04
its fixed............thanks guys
What was it?

kill switch was prolly on.

[JOEX]

Originally posted by mittimj
kill switch was prolly on.
LOL I did that the other day:eek:

[plkmonster2]

lol, If my 400 doesn't start in a couple revolutions, I first check the switch. I put some new stuff in my carb the other day, and turned the gas to reserve ( I thought). I ran it around, and it began to bog, and pop, so I went back. I couldn't figure out the problem. I could pump it, and it would fire, then die. If I held it wide open, it would pop, pop, pop, die. I spent 10 minutes on it, until I saw that the gas was on off! doh!

[KY_YFZ_04]

Since you all were curious as to why it didn't start here is what happened.

When I installed the HotCams stage 1 cam last Oct. i removed the cam gear and all the decompression stuff from the factory cam. When that was first installed into the quad it ran fine until a valve dropped and destroyed my piston and head. After all this time passed I bought a new head and put everything back together as correctly as I knew to do. After all was said and done with a HotCam you do not need the decompression stuff on the cam it was allowing my exhaust valve to open and not allowing enough compression to start the motor.

And that brought me to the reason I was having to rebuild the thing to begin with, with the cam allowing the exhaust valve to open that caused it to fall out and drop the valve.

[JOEX]

Originally posted by KY_YFZ_04
Since you all were curious as to why it didn't start here is what happened.

When I installed the HotCams stage 1 cam last Oct. i removed the cam gear and all the decompression stuff from the factory cam. When that was first installed into the quad it ran fine until a valve dropped and destroyed my piston and head. After all this time passed I bought a new head and put everything back together as correctly as I knew to do. After all was said and done with a HotCam you do not need the decompression stuff on the cam it was allowing my exhaust valve to open and not allowing enough compression to start the motor.

And that brought me to the reason I was having to rebuild the thing to begin with, with the cam allowing the exhaust valve to open that caused it to fall out and drop the valve.
Thanks:)

[bwamos]

Makes sense.
I'm not quite used to the complated cam systems in the newer quads yet.. I'm still running the 1980's version.. lol.