Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

I aquired a 5 hp honda snow blower motor.  It wont run and i tested everything.  I ran a compression test on it and am getting a reading or 50 psi!  What should the compression be?

While 90-100 psi would be ideal, I've had engines running with as little as 30 psi (not real well, but they ran). Your Honda engine sounds like it has more than just a compression problem, so you may want to consider a replacement engine if digging into it further isn't up your alley...

Marty

ntr,
Although Honda is one the few small engine companies that publish compression data...they read like this: (Example)  80 psi @ 600 rpm.
That may look good on paper, but how do you know when you are pulling fast enough too make the test valid?
Most of these small engines have decompression mechanisms that make compression tests pretty useless.
I think the best approach might be too shoot a little starting fluid into the carb and see if it fires.
If it does fire, and runs for a few seconds....do a carb clean and see what happens.
Snowblowers are particularly prone too carb problems....because they sit with old gas them longer than the summer stuff does.
Some dont even get used some seasons...and they can really get funky when that happens.

As for your observed 50 psi compression reading, you need 70+ psi for most Honda Engines to run. First, do you know for sure that your compression gauge is reading correctly? You should check the engine with a gauge borrowed from a friend to confirm you are getting a good reading. The compression release, if working correctly, will not cause a problem when checking compression, as it is activated only at lower cranking speeds (around 200 rpm).

Assuming the gauge is reading correctly, check the compression dry. Then, squirt a little engine oil into the cylinder, rotate the engine to distribute the oil & check the compression again. If it is significantly higher (15-20 psi), you very likely have a piston ring problem. If the compression increases very little or none, you may have a sticking intake valve.  

Also, you didn't indicate if your engine is a residential GC Series or a commercial GX Series.