Anyone have any idea why a Yamaha 4 stroke would only run for 20 minutes at a time?

It was not being "pushed hard" and the terrain was semi-flat. It just dies. When I try to re-start it will start for only a second or so, then it dies out like it has run out of gas. It tries to run if you keep it just above an idle but dies out a higher (or lower) RPMs.

I have tried fresh fuel, cleaned the carb, adjusted the valves, and changed the motor oil.

ANY IDEAS? (Thanks).

 

What year and model Quad is it?

 

Sorry... 1987 Yamaha Moto4 100cc 4 stroke, 4 speed autoclutch, no reverse, shaft drive, engine rebuild 2 years ago.

Thanks.

 

I could be wrong, but it seems to me, that years ago, either myself or a friend had trouble with one of our bikes quitting after it got warmed up, and it turned out to be the CDI box. You might want to check that out.

 

The only thing it looks like you didn't change is the fuel filter if it has one. It should. Is it cold where you are riding? Maybe you got some water icing in the fuel line.

 

Check your air filter, clean it if necessary. did you check the sparkplug, it could show you the probleme by the color of it.

 

We had/have the same problem with our snow blower some times we just adjust the carb.

 

My friend has a atc 110 and it had pretty much the same problem when we got it back to the house we saw that it had a vacume leak where the air box goes into the carb becouse the bolts had vibrated out. So you might want to check the bolts around the air box and carb.


Ryan Harris yz490 blaster ke100

 

Its got to be in the carb. No doubt! Float stuck, trash, water. Check adjustments, take apart and clean again. A compression check will tell alot also. Pull plug and look at condition. Wet or Dry? Good Luck!

 

If it were a car I'd jump on the ignition coil as the likely culprit. It's a classic no brainer for that application. I'd test your coil cold and hot to see if it has a short then if that checks out okay I'd next try the CDI box. If it runs great for 20minutes it is very unlikely that it's a carb problem.