# Help Performing Leak Down Test Stihl Kombi System



## Sam R (Jun 30, 2018)

Hi all,

I've got a Stihl KM 131R in the shop that I'm going over. Per the owner - and I verified this by starting it - it'll start and run for a few seconds, dies under load or when you give it any throttle. I've gone through the engine check diagnostics, I'm thinking it's in the carburetor, which I'll replace and freshen the intake gasket on - but in the interest of being thorough and to expand my own knowledge I want to do the leak down test on it.
My specialty of course is chainsaws and other small 2 strokes, so I've never really dealt with something that has valves (except I did the timing belt on my car once).
I've been searching around found a few videos on the subject mostly detailing dirt bikes, cars and bigger stuff like that.
A couple things I'm unsure of: how exactly to calibrate the leak down tester (I've got my hands on Stihl's tester), how much pressure to use. How to actually run the test and how to interpret the results. Just about everything, see?
Can anyone with more experience give me some pointers, or just a brisk walkthrough of the process?

I do know - the engine has to be at TDC w/ valve cover in place - I know it's easy to verify TDC w/ the cover off and I may do that since I'm going to check valve clearance and therefore put a new gasket. Stihl has you line a mark on the flywheel to another mark on the coil. I also know the tester goes in through the spark plug hole, and I know in a general sense if you're showing >10% leak down you have some issues. And that you should be able to hear the air leak either at the valves, intake, exhaust or crank case.

Thanks for the help folks.


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