Crf250r Wont Start After Full Rebuild

[rm_racer]

hey everyone,
man has it been a long time since ive posted here..
Anyways, I blew the big end crank bearing in my 2006 crf250r. it has sat for a while but i've finally got it back together. (new crank, piston, rings)
I've been trying to get it to start with no luck. every 20 kicks i get a pop or a backfire, and on occasion like its going to start to run but it stops. I know the motor is assembled correctly.
No matter how many times i kick it will not start.
I've checked the valve clearances (original head and valves but shimmed with in spec) , adjusted the cam timing because i had thought it was a tooth off. Checked the electrical, it has spark (im going to get a new plug though), tried unhooking the kill switch, cleaned the carb including pulling out and soaking the all the jets in a cleaner. it has a clean airfilter.

This is driving me crazy. i dont know what else it could be. If anyone has ideas please send them my way.

thanks

 

[Ol'89r]

Check your carb again especially if it sat for any length of time. Make sure you can see daylight through the pilot/fuel jet and check the little check ball in the float bowl. That little check ball can stick in it's seat and not let fuel into the accelerator pump. Check to see if fuel is coming out of the accelerator pump when you twist the throttle. Also check the diaphram in the float bowl. The fuel we have today can clog up a carb pretty fast.

 

[jaguar]

push it down hill and try to bump start it

 

[Ol'89r]

push it down hill and try to bump start it

Noooooooo! Don't do that. :COOCOO: That is the best way to damage a rebuilt engine. If by chance your cam timing is off, it could cause bent valves. Find the problem first before trying to bump start it.

 

[jaguar]

If the piston is hitting the valve then bump starting it or kickstarting it is not going to be different.
When a bike is real hard to start then you can bump start it going down a hill and then jump off and start adjusting the carb to keep it running.

 

[Ol'89r]

If the piston is hitting the valve then bump starting it or kickstarting it is not going to be different.
When a bike is real hard to start then you can bump start it going down a hill and then jump off and start adjusting the carb to keep it running.

A properly rebuilt engine should start within the first few kicks. If it won't start then something is wrong and it's better to take the time to take it apart and find out the problem before rolling it down a hill or bump starting it. Further damage could occur. Just sayin'.

 

[rm_racer]

Thanks for the replies,

Well after poking around a little more i have narrowed it down to an electrical problem. It had weak spark when i first tryed to start it (i assumed the plug was getting pooched). Got a new plug today. the bike now has no spark at all. checked all the wires with a ohm meter for continuity. everything checks out. all resistance values in spec. i pulled the magneto side cover yesterday, and found some small metal shavings on the pick up coil. Could this be the culprit? i had cleaned it off as best i could, but i may have picked up more. I changed the engine oil because i had to take off the cover.

Im going to pick up a magnetic drain plug, and I am going to change the filter and oil as soon as i get it running.

But could the shavings on the pick up coil be the problem (no spark, lost the small amount of spark it had after i had re assembled it).

Thanks again,