Compression specs 48 hp SPL

[Benday]

I did a compression check without engine running but with plugs pulled and only registered 50 psi on each cylinder which seems very low to me. Engine cuts out sporadicly on top cylinder at high speeds. What should the psi normally be. Also the pressure checker is old and was last used about five years ago. But the pressures were balanced. I have the carbs in the shop being cleaned and hope that that is the problem. Engine was running fine until a week ago.<br />Thanks.<br />Ben

 

[ob]

Re: Compression specs 48 hp SPL

I'd get me a known good compression guage and check again.Make sure the throttle is open and engine is cranking strong.Typical pressures will be 100+ and within 10%.

 

[MurdockJr]

Re: Compression specs 48 hp SPL

ob is right on, just make sure engine is at operating temp. 50psi is way to low.

 

[DJ]

Re: Compression specs 48 hp SPL

Ben Day,<br /><br />The advice given is good.<br /><br />If both your cylinders are low, yet close to each other, there are a couple of scenarios going on here.<br /><br />1. The compression guage is off, or the test was done improperly. (throttle open, correct cranking spped-good battery with good connections.<br /><br />2. Your rings are stuck. Do a thorough decarb (use thee search feature using "decarb" as the search word and read on).

 

[Benday]

Re: Compression specs 48 hp SPL

Thanks for the good information. Engine was cold and both carbs were off being cleaned. When I put the carbs back on if engine still cuts out at high speed on the top cylinder will check compression again with other checker. Have a good mechanic available to help me if I need it, hopefully this advice will lead me through. Thanks again.<br />Ben