monty motor

[gordonmichaellee]

my montesa 315r has developed a noise , its not the flywheel I've checked, but it
sounds like it, also at about the same time it seems to be a bit low on power. I've cleaned the exaust completely, changed spark plugs, new fuel. non of it makes any difference. I wondered if it might be the reed. At the same time a noise comes out of the exaust, not quite a backfire but a signifigant ammount more volume than normal. If I put my hand over the exaust I can feel it.
the loss of power is sometimes worse than others. sometimes 60% good give it a hard rev and it comes goodish.other times its at about 90%.
My thought are
1 piston/rings
2 reed valve
3 fuel/carb problem
4 exaust

any feed back would be most appreciated.

cheers Gordon

[David Lahey]

The symptoms sound like a ring sticking in its groove.
You have eliminated most of the other possible causes and a reed problem won't go away with a rev out.

[gordonmichaellee]

I should point out the knocking noise does not go away with a rev out.

[sharvie]

You could try De-carboning the piston, its not a huge job & won't cost you any $.

Just drain the coolant, whip the head off, move the piston to Top Dead Centre. Brake cleaner seems to disolve the carbon well. Spray some onto a rag so you dont get muck running down the clyinder

Steve

[gordonmichaellee]

thanks sharvie I'll try that this weekend. I'll let you know hw I get on.