crm mk2 engine trouble.

mikey11000 · Post by **mikey11000** » 02 Nov 2006, 10:41

hi ,i would like some opinions on this please. my crm sounds very tight and quiet when cold, but as it warms it starts to rattle from the top end. runs fine but a bit noisy, im not thinking rings as dont these get quieter when they expand. im thinking little ends or maybe somebody on here knows different.maybe power valve. its just if im gonna strip it i dont wanna miss sumet .i have checked the rings for blow back and there looks to be a very small amount, but it looks even ,about 1 or 2 mm past the rings would be my guess.

kinney · Post by **kinney** » 02 Nov 2006, 21:02

Hi mikey,
I suspect the sounds you are hearing may be quite normal for a two stroke engine, especially one that is not brand new.
Your engine could have many thousands of miles in it yet.
Not too sure how you have checked the piston ring \"blow Back\"

as you call it.
Excessive breathing from the oil filler plug can indicate a ring problem on 4 strokes but 2 strokes are a little different.
Is this what you've checked?
As for 1 to 2mm

Ring gaps are considerably smaller than that............if thats what you mean????

Andy.

mikey11000 · Post by **mikey11000** » 02 Nov 2006, 21:56

ive peered down the exaust port to check the piston,there is about 1 to 2 mm of blow back past the rings,this i can see with the pipe of and a torch.
my thinking is if it rattles when warm then it cant be the rings as they expand when warm ,so cant think of any thing but small end bearings.not to sure on the power valve though.

kinney · Post by **kinney** » 03 Nov 2006, 09:09

Ahh.......I see.
The power valve usually sits among a fair amount of carbon encrustment so, even when worn, doesn't usually rattle.
If the engine has done a lot of miles, it could be the little end or the big end which is causing the noise.
When the engine is started from cold, it has oil residue from the last run present in the engine's bearings. After a few minutes running this cold, thick residue is washed away by the fresh fuel/oil mix coming in. This is when a worn engine begins to rattle.
A degree of rattle is quite normal for a used 2 stroke.
If you're keen to get inside, pull the barrel and have a look. You can then check the big and little ends, piston, rings, main bearings and power valve assembily.
All metal parts expand when heated.

Andy.