My daughters' BMS 50 has developed a problem that I need help with. It starts and runs fine for 5-10 minutes, then dies. When I try to restart it, it will start and idle only. Once any more throttle than an idle is applied it will simply die again.

I have tried unscrewing the gas cap thinking it is a possible venting problem, but that did not seem to help. Finally, once the engine cools down completely it will run fine for another 5-10 minutes.

Any ideas will be greatly appreciated.

Thank you.

 

Welcome to the forum erikdane!

Next time it dies i would check for spark..you can do that by taking the plug out and holding it next to the engine(while its hooked up to the plug wire and your cranking the engine over) If it doesnt have spark then but gets it later Id guess the coils fails when it gets hot....

 

Thank you for the quick response.

If it starts does that rule out coils? It will start, but won't run any faster than idle. I am at work right now but will check for a spark tonight (assuming no rain).

 

Im wondering if it has a weak spark, should have been more specific...a good spark will be blue...a yellow spark is weak...

Does the fuel line get close to the engine and or exhaust pipe? could be vapor locking when it gets hot?

 

Fortunately no rain so I was able to investigate further. I was unable to remove spark plug (one of the kids got into my toolbox) but I was able to keep the engine going by choking it and feathering the throttle carefully. One thing I did notice was the rear brake would get extremely hot after riding. It was as if the brake locked and wouldn't release. I took an allen wrench and slightly loosened the nuts, which seamed to release some of the pressure on the brake. However, the brakes would not work well enough to trust my 5 & 6 year olds driving.

I tried to grease it but the zerk is plugged. Is it possible this could be part of the cause of my problems? The engine seemed to run better the longer it ran. After about 45 minutes of constant running it barely hesitated except when under the most strain.

I guess I have two questions...first, how do I properly adjust the brake so it doesn't hang up and put undo resistance when the brake isn't applied, while still having enough braking to stop the atv when necessary? Second, I'm planning on replacing the zerk, any other suggestions?

Thanks in advance.