MOPED ARMY

Put the seal in first, lube the collar and seal lip then gently push the collar in. If your oil pump has been bled just pull the oil line off the carb when it is running just long enough to see if oil is pulsing out of the open end .

Did you upjet accordingly when you put the new kit on? If not that's gonna be more than a soft seize real quick...

You'll know you oil injection isn't a problem when you bypass it and premix...lol. I don't trust injection at all.

When you bypass oil injection, do you remove a gear to the pump? Or do you loop a hose?

Either.

Age is more detrimental than mileage especially with 39 year old seals.

Which method do you prefer? Aren't the two hose ends different sizes?

I run the hoses together because I've had one of those expansion plugs pop out causing immediate engine kill and walk of shame home

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I can see two stroke oil at the carb so I'm sure that the pump is at least functioning. j

What makes the motor "four stroke"? Is that too much fuel/too rich of a mixture at that particular time?

My 60cc kit seems to start "four stroking" between 25 and 30 mph WOT. Wouldn't upjetting, a common practice for bigger piston sets, cause this issue?

I have an express with 5300 miles and still running the injector just fine. The one thing to remember is that they will leak some oil into motor over long term, like several months or years. This will lead to difficult starting and heavy smoke when started again.

The other thing to watch on qt50 is the oil injection hose that connects to carb. It's under left plastic cover. If the bike is ever wrecked or knocked over on that side it can pull the hose loose or break off the brass nipple on carb. I've found that the express and yamahopper run best with injectors on non synthetic injector oil from the dealership.(edited)

You likely already know this site : https://www.jetsrus.com/FAQs/FAQ_identify_that_jet.htm

Not cheap , but , definitely good .

Another question for the group: How can I rule out an electrical issue caused by temperature? This may not be a soft seize issue at all. The bike fires up and cruises great for five minutes or so and then starts the routine of dying out until it cools down. I'm a points and condenser guy so I immediately think about a failing condenser. This is a CDI, something somewhat foreign to me. I swapped out the CDI for a JOG CDI with no difference. I swapped out the ignition coil with no difference. I tried another carburetor with no difference. I replaced the crank seals.

Its either something that I don't understand regarding the 60cc kit or its ignition related (something that I suspect). The stator coils are low mileage (700 miles). Are these prone to failing under heat?

P.S. - I don't really think the motor is overheating. I only have a handheld lase and the max temp that I saw on the head was around 315 degrees. I've read on this site higher functioning temps.

I honestly don't know. I would assume that they are OEM. They looked OEM and all else is stock on this QT (700 original miles on the bike itself)

A picture of the stator charge coil? I'm 99.9% certain its the stock coil but I will take a picture of it and upload it. Sorry, I may have made this confusing, but I'm asking if there is history of QT50 charge coils going bad? And could a symptom be intermittent failure at certain temperatures?

I was saying that the stator coils are low mileage - because I believe them to be original to the bike that has only 700 miles.

What Jack just said and look for rust- remove plastic cover that covers magneto and look around in there. You may have to remove flywheel to really see behind it . Sand the flywheel magnets if they're rusty and tips of all coils,

I was initially concerned with fuel delivery but have ruled it out. The gas tank had horrible varnish which I thoroughly cleand. I replaced the petcock.....twice. I replaced with the original carb with miniky clone (I didn't even bother with the original carb because of the varnish situation and couldn't find a complete rebuild kit at the time). In fact, I tried two different miniky VM12 clones. I've tried various inline fuel filters. I've even cut the screen off the petcock since I was using an inline filter.

My initial suspicion of fuel delivery was because the motor would stop after 3-5 minutes and when I would look down at the clear fuel line I could see a gigantic air bubble move up the line. Then the motor would start after 30-60 seconds, but only for a brief run (less than a minute). One time when it died i shut the petcock off and actually clamped the line above the carb. The float bowl was full of fuel....so I ruled out fuel starvation. FYI - I checked the float height by using eyeballing the clear drain line next to the bowl (while drain was open). Furthermore, had the same results with two clone carbs.