2 stroke help please

ChasF · Feb 22, 2009

I don't know much about 2 strokes.
Last week my sons Rieju 50cc (Minerelli AM6 engine) just stopped as he was driving along at about 35km/h. I checked the obvious things such as the plug and petrol, compression which is difficult to judge but there is some but it doesn't seem quite as much as before. In the end we took the head off to check the piston which seems fine. We notice that if we try and bump it is does 'chuff' occasionally in the carb/airbox. The reed valve is well glued onto the crankcase so before I take it off for inspection I wondered if anyone knows how likely it is to just fail whilst driving along or if there are any other suggestions.

D6 · Feb 22, 2009

check the rings arnt stuck in the piston, try easy start/wd40 into the carb inlet, then try start it, if it does it points to compression, reed valves can fail but they usually still run, but really badly

vilguy · Feb 22, 2009

+1 on the rings.

Itll feel like there will be compression if you put your finger over the spark plug hole while you turn it over but its not enough.

D6 · Feb 22, 2009

needs at LEAST 90 psi to run properly, if it cant blow your thumb away off the plug hole, its fecked

ChasF · Feb 22, 2009

Thanks for the replies.

Turns out it didn't just stop but seized although the boy is still having a problem with the terminology.

The piston is a complete right off but the barrel has only relatively light scoring at the bottom. I don't know whether it's possible to rebore the cylinder and fit an oversize piston. The alternative is to fit an aftermarket kit which is what he'd like to do but muggins here is paying.

The bike has only done 2700kms is the seizure just one of those things or is there another problem?

captainpugwash · Feb 23, 2009

kids a scooters , they just thrash them to death and you cant tell them anything as they know it all , just as cheap to buy a big bore kit , you get a barrel and piston etc , use a top 2 stroke oil

ChasF · Feb 24, 2009

captainpugwash said:
kids a scooters , they just thrash them to death and you cant tell them anything as they know it all , just as cheap to buy a big bore kit , you get a barrel and piston etc , use a top 2 stroke oil

It seem the oil pump is suspect so we'll be using pre-mix from now on.

Big bore kits are all very well but then (apparently) you have to fit stronger crankshaft bearings, bigger carb and a stronger clutch.

The barrel has been passed as OK so we've just ordered a new piston and should be back on the road for the weekend.

2 stroke help please

ChasF

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D6

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vilguy

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D6

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ChasF

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captainpugwash

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ChasF

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