# engine compression for Stihl BR 400?



## jgr (Aug 30, 2017)

I have a free but well worn BR 400 blower that I tested compression at 60psi as best I could get out of four pull tests. Debating a rebuild kit. Wont start after new carb and ignition fully tested. Nothing in manuals about what compression should be. Thanks


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## LegDeLimber (Sep 16, 2017)

Have you checked the compression gauge in a known good engine?
60 psi is pretty worn sounding.
I would want to see at least double that number.
140 or more, would be better or it will struggle to get to full rpms.

Since you say it's "well worn" I'd figure at least a ring job and perhaps a fresh piston.
Have you removed the muffler and looked into the exhaust port for any scoring or other damage?

You need look for any cylinder or piston damage before spending any more money.

The recoil may have taken a beating from people yanking it hard
due to that low compression.

What shape is the rest of the blower in?
Any cracked or broken parts.
Leaking fuel anywhere or damaged fuel tank.
Stripped bolt/screw holes.
crushed air pipes or elbow worn at the housing, etc.
throttle controls or cables.


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## ironman_gq (Sep 19, 2017)

Make sure the compression tester you're using has the schraeder valve in the tip and that it reads accurately on a different small engine like a chainsaw. If the compression test is correct it's time to dive in and see why it's low. Could be scored cylinder, worn rings or leaky seals. If the cylinder is clean then I would replace the piston and rings and do a pressure test to make sure the crank seals are good.


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