Servicing a 2 stroke engine (39 / 49cc)
06 September 2004, 10:30 AM
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What's the motor for? Power tool, mini moto? Is it a routine service, or do you think something's wrong?
Change the spark plug -- strokers are hard on plugs. Check the oil pump setting as per the manual (if it has an oil pump -- it may run on premix).
If you're keen you could remove the cylinder head and cylinder barrel (takes 5 minutes
) and inspect the piston and cylinder liner for scuffing / scratches. Is there a step near the top of the barrel? If yes, it's worn and needs a rebore and oversize piston. If the engine makes a rattling noise but there isn't much evident cylinder wear, it could be the little end bearing.
If they look OK, polish the piston skirts with Solvol or similar. Check the piston rings are free in the grooves BUT MAKE SURE YOU RE-ENGAGE THE PEGS ON THE RINGS WITH THE HOLES IN THE PISTON.
Scrape any carbon out of the exhaust port, off the piston crown and cylinder head. Reassemble using a good smear of 2stroke oil on the cylinder & piston skirt, and make sure the pegs on the rings are engaged as above before you drop the cylinder onto the piston.
Change the spark plug -- strokers are hard on plugs. Check the oil pump setting as per the manual (if it has an oil pump -- it may run on premix).
If you're keen you could remove the cylinder head and cylinder barrel (takes 5 minutes
) and inspect the piston and cylinder liner for scuffing / scratches. Is there a step near the top of the barrel? If yes, it's worn and needs a rebore and oversize piston. If the engine makes a rattling noise but there isn't much evident cylinder wear, it could be the little end bearing.If they look OK, polish the piston skirts with Solvol or similar. Check the piston rings are free in the grooves BUT MAKE SURE YOU RE-ENGAGE THE PEGS ON THE RINGS WITH THE HOLES IN THE PISTON.
Scrape any carbon out of the exhaust port, off the piston crown and cylinder head. Reassemble using a good smear of 2stroke oil on the cylinder & piston skirt, and make sure the pegs on the rings are engaged as above before you drop the cylinder onto the piston.
Last edited by brickboy; 06 September 2004 at 10:32 AM. Reason: Forgot some stuff
06 September 2004, 01:57 PM
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No worries -- it's a doddle compared with a 4 stroke 
Don't know if the motor will have electronic ignition ... if it does, it's one less thing to worry about.
I would leave the carb setting alone, if it's got a foam air filter just go over it gently with your hoover nozzle.
Final thing -- check the exhaust to see if there is a removable baffle tube in the tailpipe. If there is, remove it and wire-brush the carbon deposits etc off it.
The best servicing is preventative -- use a good two-stroke oil like Silkolene, Rock, Motul or the high-end Castrol stuff.
Don't know if the motor will have electronic ignition ... if it does, it's one less thing to worry about.I would leave the carb setting alone, if it's got a foam air filter just go over it gently with your hoover nozzle.
Final thing -- check the exhaust to see if there is a removable baffle tube in the tailpipe. If there is, remove it and wire-brush the carbon deposits etc off it.
The best servicing is preventative -- use a good two-stroke oil like Silkolene, Rock, Motul or the high-end Castrol stuff.
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