rebuilt motor runs for 30 sec then dies

[cope849]

I rebuilt my top end over the winter and am trying to get it to run now. it starts runs for 30 seconds then dies then won't start again unless i leave it alone for about an hour. the carbs are clean the battery is good any ideas. O and its a 1980 xs400.

Posted via Mobile

 

[Pork Chop]

Does the problem occur if you leave the petrol tank cap open?
Does it do it when you turn the petcock to pri?

 

[Scorpio1963]

when you it runs and dies for 30 secs how does it run poorly or does it sound good.Dumb responce maybe but have you adjusted the valves properly.Do you have an iline filter and can you see gas flowing into it?

 

[cope849]

I have tried it with the cap open and the petcock on prime to no avail. i have a clear filter and it looks like im getting good clean fuel. i did not adjust the valves yet

Posted via Mobile

 

[cope849]

The motor sounds pretty good when it runs

Posted via Mobile

 

[Scorpio1963]

Adjust the valves to proper clearances That should help.

 

[cope849]

K Ill do it tonight after work

Posted via Mobile

 

[cope849]

I adjusted the valves and it helped but still wouldn't run .so i looked a little deeper and found that i was not getting fuel so i put a set of carbs on that i new were good and she started right up

Posted via Mobile

 

[Drewcifer]

I would guess valves first, as Scorpio suggested because it happened after the engine warmed up, but the other common time dependent failure is....fuel. The bowls run dry.

Once I fixed a bike and didn't snug the suction actuator hose to the petcock. The bowls would dry out and the bike would die. Maddening two hours of my life.

 

[Scorpio1963]

Well I started my bike 4 days ago,Then the day after.Then on the 3rd day it wouldnt start.Today I didnt try tomorrow it better start.

 

[bcware]

Don't start it too often if you're not going to be riding it for like 30 minutes or more. If you're just tooling around in the garage letting it idle the battery will die. It won't charge worth a damn at or near idle; the revs have to be up there a bit. What I am getting at is that your battery is probably low.