A new 50cc 2 stroke scooter out on its first ride. Idled for a minute or two, rode gently for 2-3 minutes, up to 50% for a few miles around the suburbs. Temperature was low 40s. I recall going up a slight grade then riding mostly down slope for a few minutes. Got to a stop sign, accelerated thru the intersection.. then lost all power seemed like the motor was seizing? There was quite a bit of smoke coming from the exhaust. Oh no! I thought. Did I just burn a new engine? I thought I was being gental! Looked at the suction filter there was oil in it, though still the green of the previous oil (new oil is royal blue) I did drain the tank and put different oil in it. Fuel is a blend of VP, and True fuel. bike stalled out twice. Both times it was off throttle coasting. Idle was high by the time I got home. Rode for 4 miles. Cooled it off and rode again a mile or so and it started and ran great! I didn’t do much coasting on second ride though. Hopefully it’s going to be fine now. I thought maybe the oil wasn’t pumping. Checking the hose or the intake I see it is now blue so, oil has been flowing. I have Phillips 66 oil in the tank right now. Also added a splash of oil in the fuel.
Cold seizure?
- Thread starter jkhawaii
- Start date
I did also suck out whatever they had in the tank as well. It looked like some oil was added to the tank prior. Since the scooter runs fine, and cranked fine.. I’m hoping whatever was going on didn’t permanently damage anything. I was probably running on the previous mix for a little while. I am assuming Vp and Trufuel are basically the same…. On the first ride I only had a bit of Lucas UCL in the tank
Just a guess, maybe the needle valve in the carburator stayed open too much when you backed down the throttle. Gummed up, or a small piece of dirt, that cleared with more running.
The quite a bit of smoke from the exhaust could have been because it was super rich of fuel.
If it was just grabbing the piston because the cylinder was too cold, there would not have been smoke.
Back in the day, we use to throw big snowballs at the cylinder of my 175 Yamaha to cause the engine to grab the piston and stall the engine, when we took turns riding it. That motor lasted many years, and it did not seam to hurt it.
The quite a bit of smoke from the exhaust could have been because it was super rich of fuel.
If it was just grabbing the piston because the cylinder was too cold, there would not have been smoke.
Back in the day, we use to throw big snowballs at the cylinder of my 175 Yamaha to cause the engine to grab the piston and stall the engine, when we took turns riding it. That motor lasted many years, and it did not seam to hurt it.
The volume of metered 2 stroke oil will be at a minimum when the throttle is shut so perhaps that's why it seized after "riding down a slope for a few minutes"
Opening the throttle intermittently would feed some oil through.
Opening the throttle intermittently would feed some oil through.
yes, if using premix, there's virtually no oil being fed when coasting.
I thought this was a more modern oil injection system but oil would still be at a minimum when coasting. It also depends on the system being adjusted correctly and being new would be no guarantee of that. There is usually a very simple way of checking the adjustment which would be included in the owners manual.
If it was my bike, I would pull the plug and clean it. Second thing, would be to check and tighten the carb and intake manifold. Sounds like it's flooding at one point, then sucking air the next.,,
This is certainly cooler than the expected usage for a scooter, therefore, it was certainly running lean unless it has been rejetted? Did you check the color of the plug? It doesn't matter how much oil you have in the gas of a 2-stroke, lean is lean and will lead to trouble.
I haven’t pulled and checked anything yet. I just got it trucked in from out of state and took it on a test ride. It’s all stock. Perhaps I should pull the carb and check/clean it. It is a 2022 with less than 2 miles on it. Years of sitting. If it was an oil issue like, the oil pump had some air in the line, it wouldn’t start back up and run fine right? Well, I have another scooter I need to finish putting back together this one is going in the corner for a little while
A quick and easy check is to pull the exhaust system and view the piston skirt. The exhaust side is hottest, and the most likely side to have damage.
Yes, a 4 corners seizure will often unseize when cooled off.
Yes, a 4 corners seizure will often unseize when cooled off.
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Pull the spark plug and see what color it is, very light or white, the air/fuel mix is lean. Black is very rich air fuel.
My old snowmobile does the sputter and smoke after going down a hill with the trans pushing the engine a bit. I think its actually the needle valve letting the carb bowl overfill, when the motor isn't burning much fuel, so it nearly floods the motor, and the plug is very black. To clear a flooded engine you hold it WO and kick it over.
Is this a chinese moped? Some carbs don't work well from the start, and maybe they left junk in the tank? If yours doesn't have a fuel filter, its not a bad idea to add one.
My old snowmobile does the sputter and smoke after going down a hill with the trans pushing the engine a bit. I think its actually the needle valve letting the carb bowl overfill, when the motor isn't burning much fuel, so it nearly floods the motor, and the plug is very black. To clear a flooded engine you hold it WO and kick it over.
Is this a chinese moped? Some carbs don't work well from the start, and maybe they left junk in the tank? If yours doesn't have a fuel filter, its not a bad idea to add one.
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The air cooled ones low performance sleds have lots of piston clearance, and aren't too picky on warm up. But the liquid cooled ones are a bit tighter its a good idea to let them warm up gently until they open the thermostat slowly and trickle in the freezing coolant. Usually factory pistons are fine, but some rebuilds or race engines are a bit tighter and more sensitive.
Any pictures of the scooter 
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