Questions? Looking for parts? Parts for sale? or just for a chat,

The WD Motorcycle forum

WD Motorcycle forum
Start a New Topic 
Author
Comment
piston rings

The engine smoked badly (black) recently and lost compression, so I took the head and cilinder of yesterday.
Turned out the cilinder liner looks fine, no scratches ore anything (it has first oversize)
And no ridge at the top, indicating wear.
I put in a new piston ring, just to see, about one inch below the surface.
The pistonring gap is more than the factory figure; about 0.40 mm instead of the max 0,30 mm.

Can this have caused the smoking ?
Or is it more likely the inlet valve guide ?

The head was VERY black indide, full of coal - especially round the exhaust valve. It didn't close properly anymore.
It's obvious i have to do something, can't go on like this.

So;
What should be done; next oversize, new piston ?
Or just new rings, would that do the trick ?
Or a new inlet valve guide ?

Hope you guys get the problem.
Thanks in advance.

Re: piston rings

Hi,

First off, I would de-coke the head, lap the valves and pay particular attention to the exhaust valve. The valves have to seat properly or you will lose compression and burn things out.

Make sure the de-compressor works properly too i.e the valve can shut.

If you have a solid copper head gasket, then anneal it and re-fit. You will have to tighten down again once the engine cools. If you have a composite head gasket, then throw it away and get a solid copper one.

If your compression is fine after that then great. You may wish to check that the engine isn't running too rich too.

Your liners should have honing marks if it was re-bored a while ago.

At this time of year I wouldn't worry too much about the ring gaps. More of a winter job, when the sun isn't shining!

Regards

Pat

email (option): sacombsashtrees@hotmail.com

Nieuwe pagina 1