Need help with 250sx.

[whiteman350x]

Working on 86 atc250sx. It has good spark. I have rebuilt the top end including a bore job and new piston. It will not crank. It will hit and try to run for about 1 second and then die. Here is the histroy so you all will know what I have already done. When I got it it would do the same thing. I cleaned the carb and set the valves: same thing. Then I bored it and rebuilt, set the valves, cleaned the carb again: same thing. Rebuilt the carb with a kit: same thing. Got the electric starter installed so I could spin it over with that because I was tired of kicking by now: same thing. Changed over to a 350x carb that is clean and in good working order: same thing. What kills me is the fact that no matter what I do nothing changes. I must be missing something. Has anybody ever faced this before? I also see a little bit of raw gas leaking out of the exhaust after I crank on it for a while. I have also tried starting fluid and it acts just like it does with just gas. I also ran a compression test and it has about 165 lbs of compression. Any help will be great.

Thanks,
Whiteman

[bigredhead]

Timing... made sure you were not 180 degreez off ?

Have you tried removing the plug and putting a few drops of gas in it, put the plug back in and turn it over ???? if it fires.. it's the carb.. if it does not , and you have spark.. hmmmmmm

[whiteman350x]

Cam timing is right. I have put gas in the plug hole and in the throat of the carb. It will hit when you do that. That is why I changed to a 350x carb. The 350x carb acts just like the sx carb did tho. I am thinking my igniton timing might be off a little, like the flywheel key may be partly sheared.

[bigredhead]

Good flow from the petcok ? Fresh gas ? Clean air filter ? New plug ?

[whiteman350x]

Yes to all of those. Tried several different plugs also.

[bigredhead]

When you say you have good spark,, you removed the plug, put the cap on, touched it to the cylinder and cranked it .. got good spark.. right ? ( just checkin !! lol )

no tears in the carb boot ? all screws tight ?

Checked all the overflow lines and gas inlet, to make sure everything was plugged in the correct place ? ( no gas in the airbox !! )

Do you get gas out of the overflow lines at any time ?

Is your choke stuck on ? ( i realize you tried a different carb tho... so. hmm )

very strange indeed !

[whiteman350x]

Everything is plumbed right. Yes, when you ground the plug, you get a fat blue spark. Gas dosen't leak out of the carb.

[honda200]

is it getting air??

you need gas and air to burn, maybe its not getting enough air?? Jetted incorrectly??

whats the plug look like??


Curtis

[bigredhead]

only thing i can think of from here is timing. sorry.

[bigredhead]

is it getting air??

you need gas and air to burn, maybe its not getting enough air?? Jetted incorrectly??

whats the plug look like??


Curtis

Along these lines.. is the plug tip wet after cranking over a few times ? if so, it's getting gas, if not.. there is the problem.

[Tri-ZNate]

Have you tried starting it with the gas cap off?