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Holed my piston


stuartasutherland
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Bad times. I was running at a nice pale coffee colour on the plug and on Friday night the engine sometimes would cut to tick over and struggle to get up the revs again.

Looking back, I should have landed and probably could have saved myself some coin.

So, just in case I'm missing anything, other than too lean, what else should I consider?

Check the carb for dirt?

ps it is a Parajet Volution 1

Thanks

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Yes but only a small thin layer.

Get a thickish piece of glass and some 1200 wet and dry, hold a full sheet (or stick it around the edges with tape) on to the glass then put your head on it and very gently start moving it in small circles you can add some water with washing up liquid as you are doing this. After a couple of minutes wipe the face of the head off and if it is not nice and clean ALL over then the head is not true.

You can carry on doing this until the head is true.

Pete

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Hi Stuart I have rebuilt a couple of paramotor engines , first what type of motor is it ? if a Ros 125 it could be the decompression valve , oring or dirt is carb on the pump side ( look if little filter inside carb is blocked ) If the pop off pressure is to high the motor can run to lean , it can also be a leaking base gasket or one of your crank seals can be leaking , how many hours on the motor and type ? all the best Thys .

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Hi Stuart 200 hours I would defnitaly replace the crank seals and main bearings , that will force you to replace the bottom gasket , not a expensive exercise about 50-60 £ if you do it yourself , I went thru the same with a Blackdevil a couple of years ago it was the crank seals , just make sure you use Viton seals they can stand the heat , you get it from your local bearing suppliers . There is not much to a 2 stroke engine if your seals and bearings is fine it could go for thousands of hours . Most of outboard engine seizures is caused by crank seals . You just need a small press .

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Hummmm,,,

I am not so sure about this.

200 hours, for a full strip down a re-build is a little OTT.... My V1 compact hit just over 1000 hours of School use before the bottom end needed looking at.

SW :D

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Hi Stuart 200 hours I would defnitaly replace the crank seals and main bearings , that will force you to replace the bottom gasket , not a expensive exercise about 50-60 £ if you do it yourself , I went thru the same with a Blackdevil a couple of years ago it was the crank seals , just make sure you use Viton seals they can stand the heat , you get it from your local bearing suppliers . There is not much to a 2 stroke engine if your seals and bearings is fine it could go for thousands of hours . Most of outboard engine seizures is caused by crank seals . You just need a small press .

Hey Thus, the engine had a strip down last year where the bearings were checked and seals replaced. All gaskets too.

Just cleaned it all up and the cylinder has a slight scuffing, hope I can get away with that one!

Carb is all clean, fuel lines okay, reed valve seems fine.

Could it be Pre ignition?

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Hi Stuart here is a link how to check your pop off pressure

http://www.aerocorsair.com/id28.htm

you can go to a chain saw shop or ask around for a pop off gauge , I made mine myself but it better to use one than to built one or buy one because it is expensive . I have other links if this one don't help . The pop off on my PXP Menari 180 is 16 psi and it reseat value 11 . The reseat value is important if it is to low your carb will flood , your carb operates between 7 and 8 psi so ideal your reseat value should be a minimum of 10 psi . You can ask your manufacturer of the motor what the pop off should be , or google it . If the bottom part of your engine is fine it can only be , pop off , leaking head gasket , or your head bolts was loose I check mine frequently and sometimes it need some tightening , or somehow someone turned your high screw . You say that the carb is 2 months old did you tune it with the motor running on your back ? if not this might also be part of the problem , all the best , Thys .

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