Only runs for 15mins

[ItsDANEgerous]

howdy,

I'm very confused! For some reason my 79 Xs400 will only run for about 15min. Just enough time for my mechanic to ride it around the block a couple times come back and tell me it runs fine. Then when I get on it after a couple laps it dies whenever I put the clutch in. At first I thought I was doing something wrong but when let my mechanic rode a second time it did it to him too. I really dont have a clue where to start and he has been to busy to figure it out. What do you guys think? Is it Transmission problem?

 

[bcware]

Fuel starvation sounds more likely. Gas cap not venting, petcock vacuum line has a leak, petcock itself is clogged, carbs are clogged at fuel inlets/float needle seat screens, float height is wrong, etc. When the engine heats up you also tend to run richer and this may be a sign.

Run the bike on "PRI" (prime) and see if the problem goes away. If it does you've eliminated a few possibilities. It should not be a hard fix, but you'll have to take a few things apart.

The clutch-in thing sounds more like correlation as opposed to causation. I cannot see how removing load from the engine would cause it to die. It sounds more like coming to a stop after riding is when it dies. Momentum can drive the engine by itself, just like when you drop it in gear to start it while rolling, etc.

Also, I am thinking there may be a link between a hot engine and dieing at low rpms (idle). Perhaps the idle mixture is contributing as well.

 

[SPUDGUN]

Hi just bought 1980 XS250 with similar symptoms. Can you post your solution if you found one. Cheers.

Posted via Mobile

 

[226dark]

howdy,

I'm very confused! For some reason my 79 Xs400 will only run for about 15min. Just enough time for my mechanic to ride it around the block a couple times come back and tell me it runs fine. Then when I get on it after a couple laps it dies whenever I put the clutch in. At first I thought I was doing something wrong but when let my mechanic rode a second time it did it to him too. I really dont have a clue where to start and he has been to busy to figure it out. What do you guys think? Is it Transmission problem?

Runs 15 min with choke, then no choke after warmed up and dies? Start simple. Not a trans problem.
I try to keep my idle around 1300 rpm AFTER WARMED UP, and that is when the throttle stop screw should be adjusted, after up to operating temp. If too low then when I pull in the clutch, it dies and I upshift and bump start while it is still coasting. (maybe that's why time for a new back tire )