My scooterengine keeps seizing. Just mounted a 70 cc kit.

[MXer50]

Anyone?

Excuse my english. I an Norwegian and new to this forum.

Can anyone help me. I just fitted a 70ccm Polini cylinderkit on myKymco MXer50 ATV. The ATV has a normal 2-stroke 50cc scooterengine in it.

My problem is that the piston keeps seizing from overheting. It has only seized once and luckally it didnt do any damage to the kit.

But everytime i have driven about 2 kilometers i get the metallic noise i got right before i seized the last time. It also loses power and eventually it chokes when i give throttle. After a good cooling down everything is fine for another 2 kilometers.

I have rejetted from 80 to 94. I also bought the spark plug recommended.

What is my problem? Anyone with good knowledge of 2-stroke scooterengines?
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Kymco MXer50 ATV
Polini sport 70cc cylinder

[mr.z]

There could be a blocked oil way so its not getting the right ammount of oil in the right places.. the oil/fuel mix is not being delivered propperly.. i'm guessing its air cooled, if its water cooled look at the cooling system..

To be honest the soloution to an overheating engine is not fiting a biger bore, this will heat it up even faster!

Could be wrong on these, never had a 2stroke myself.. somebody should be able to give a better idea of whats going on..
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>RidingSkills<->Tech Tips<->MyBikes<

[MXer50]

I only have this problem with my 70cc kit. The original cylider has no problems.
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Kymco MXer50 ATV
Polini sport 70cc cylinder

[mr jamez]

Have you checked the mixture? take the spark plug out, should be a nice brown colour.

https://www.spark-plugs.co.uk/pages/technical/diagnosis.htm

It is either running lean, is not geting enough oil or the cooling system is not up to it. Can't think of anything else as long as you have installed it correctly.

[Thet2]

sounds like the petrol/oil mixture is off, so could be the oil pump not giving enough oil, you can regulate these (theres a little screw on the side of the pump) if that don't work, make your own mix, going back to my 2 stroke era i think the ratio of petrol:oil was 2% to 5% oil in 10litres, if you buy a bottle of oil it should have the right ammount listed on the back of the bottle.

[lilredmachine]

Agreeing with Thet2, most likely your fuel mixture is off so even though you have rejetted, it is likely you need loads more oil in it.
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Bikes: too many, too much for one man to maintain anyway.

[mchaggis]

Have you stuck a K&N air filter on it or anything like that? Chances are you're running lean, or the bore isn't large enough for the piston - sounds ridiculous I know.
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