crank case leak?

[Brains]

Hi all

I'm sure that I am sucking in air somewhere causing the bike to run lean. Jetting OK.

Does anyone have a method of checking of air leaks, I don't want to strip the whole motor before knowing for sure.

A thought I had was to make a fitting that bolted in the spark plug hole and preasurise that crankcase with the compressor and then check with soapy water and look for bubbles, but what preasure would I go up to? I don;t want to cause more damage than there allready is.

Thanks to all

Mark

 

[David Trustrum]

EEKK! Don't uase the compressor! :scream:

The best way to analyse the problem is a leak down tester. I’m surprised how few shops have them. Problem is 2 strokes don’t require high pressures. Real easy to build one. Basically I hollowed out a sparkplug (which isn’t that easy) & braised a bit of tube on it & connected a hose. That leads to a low pressure gauge ~$20 on a 3 way gas fitting the spare hole you put a tire valve fitting. Block off the intake by replacing the carb with a piece of plastic or whatever & the exhaust you may have to be a little clever but a block of rubber with a bolt through it to make it expand should work.

Then you just up use a pump to take it up to 8-10 pounds (no more) & see if the pressure drops down quickly. If it hangs around a few min you’re ok. Otherwise squirt some suds around to track the bubbling leak. (usually your test jig first couple of times until perfected).

First off check under the ignition cover for oil which would indicate LHS crank seal. Suspect the reedblock assembly & boots for airbox.

Also check you carb slide hasn't worn a groove in it as they do.