Yamaha QT50 Timing Issues?

I have a pair of QT50's. Mine has a YT60 cylinder slightly altered exhaust and a K&N style air filter.

The moped runs great but soon after it heats up it starts to bog and then in the middle of giving it gas it suddenly stops and seizes. It almost throws me over the handlebars when it happens.

I turn it off for 5 mins and it runs fine again. I've also turned it off as I feel it bogging however even with the run switch off and ignition off it still continues to run until it dies slowly.

Its very weird I was was wondering if it could have something to do with the CDI or the first or secondary coils. I know for a fact that it's not the piston or rings or the ignition kill switches.

It acts electrical.

Please help!!

Aaron

Re: Yamaha QT50 Timing Issues?

you fail to mention how many miles are on it. just to be safe, i suggest that you decarbonize, that's a very likely cause of that problem. those mopeds go for an incredibly long time if maintained properly.

Re: Yamaha QT50 Timing Issues?

Agree. Given that you have spark and that the timing on these bikes is non-adjustable, I would check carbon buildup and carburetor internal cleanliness.

Re: Yamaha QT50 Timing Issues?

Its not a smiple thing like carbon. I had the muffler hot tanked 3-4 weeks ago. It's a electrical problem I just don't know where.

Re: Yamaha QT50 Timing Issues?

The carburetor is spotless plus I put a brand new inline filter. I 'm guessing the coil heats up too hot. The bike continues to run with the ignition and the run switch on the off position. how do you explain that?

Re: Yamaha QT50 Timing Issues?

Jason Luther /

sounds to me like your engine is soft seizing. an electrical problem wont make you fly over the handle bars

Re: Yamaha QT50 Timing Issues?

The ignition works fine and so does the kill switch. It only acts funny when it gets hot and goes uphill. Are you guys sure it's not the CDI or the first or secondary coils?

Re: Yamaha QT50 Timing Issues?

I'm guessing the timing is being disrupted because of a faulty CDI. Is this possible? Would a faulty CDI cause the timing to be disrupted?

Re: Yamaha QT50 Timing Issues?

The engine has about 300 miles on it. The moped itself has almost 1,500.

Re: Yamaha QT50 Timing Issues?

Jason Luther /

see above

Re: Yamaha QT50 Timing Issues?

Would too hot of a plug cause soft seize? Wouldn't the piston seize and the kickstart be frozen? It kicks over right away after it stalls.

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