Stihl FS90R vacuum leak, Ugh

Robrote

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Oct 1, 2014
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I'm in a full on battle with my Stihl FS90R. It's running poorly so I decided to dig in and rebuild the carb, then I replaced the carb, did the plug and adjusted the valves. No carbon issues in the muffler.

So, while it was idling on the bench, I took some carb cleaner and sprayed around the carb mounting surface and it immediately stalled. I have pulled the carb and changed gaskets, changed carbs, no luck. Same issue. I also pulled the intake off and cleaned everything up. The gasket looked good and I didn't have a replacement for that.

What's my next step? gasket sealer on everything? Any help would be appreciated.
 

upupandaway

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Jul 3, 2015
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Go to auto parts stores, they sell cork gasket material. This will give u more spongy to fill the leak. double ply if u have a major problem.
When u cut the gasket, punch 1 screw hole and use a drill bit to line that up while u punch hole 2 etc. and don't forget the small hole below the main air passage(small drill bit will suffice). makes lining up a lot easier.
That is strange though unless parts warped major, it shouldn't leak. Being the carb screws to a plastic block, should be no warp... Just clean both mating surfaces and cork should fix your problem.
 
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