Stihl 029 leak problem at the carb

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Bob95065

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I rebuilt a Stihl 029 for a friend at work. He had me put a Meteor 039 P/C in it. I replaced the seals, impulse line and intake boot with OEM parts. The saw held vacuum and pressure with the muffler blocked off and a block off plate in place of the carburetor. Needle didn't move for an hour.

I put the carb on it and started the saw to find it idled like it had an air leak. I used a can of brake cleaner with a straw and sprayed near the base of the carb and found the leak. I removed the carb box cover, drove the studs out and used a metal bar with sandpaper to sand the mounting interface flat. I put a piece of sandpaper on my tablesaw and sanded the carburetor flat. I measured the rubber flange if the boot to find it was 0.110" and the outer metal ring was 0.080" so the rubber sealing surface is proud of the metal ring. I tried removing the outer metal ring and it still leaked.

I am getting ready to pull the carb then put a block off plate on either side of the carb with bolts through the mounting holes. If one of the plates had a barbed fitting I can do a pressur/vacuum test to look for leaks. I would use a piece of fuel hose between the impulse barb and fuel inlet. If the fuel pump side cover or metering side cover isn't sealing that would cause the leak I am experiencing when the saw is running.

Has anyone had this happen to them with a 1127? Has anyone tested a carb for leaks this way?
 
I rebuilt that carb including the plugs. I've replaced many and never had a problem.

That saw was used and used hard for decades. I believe the throttle shaft hiles in the body were leaking excessively. I bought a new carburetor and the problem went away
 
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