# mcculloch compression test



## kansasnut (Jun 3, 2009)

I have been tinkering with mcculloch 2 cycle chainsaws lately,,,310',320,330...I bought a compression gauge...I have a 330 that runs pretty good ,(after cleaning the carb)...but how can this be when I can only get25lbs of compression?I tried it on another chainsaw that runs...also only around 25...I tried it on my lawn mower and get 50lbs...blower =zero lbs....is there a special compression tester for 2 cycles...it is only a 35cc engine....I just have not made any since out of the compression test yet....do they have to be warmed up 1st...does this make a differrence...as you can see I am at the irritated stage on this...any suggestions?


----------



## rotti1968 (Apr 26, 2009)

something does not sound right. is this a push into the plug hole and hold style (not the best to use) or is it a screw in ? normal compression should be in the 110 to 140 psi range for most 2 strokes. no there is not a different one for 4 or 2 strokes. Some of the 4 stroke engines have a compression release and can affect the reading you get. I would make sure you are getting a good seal and you will want to pull the engine over at least 3 times to get your reading. If after all of this and you are still getting these kind of readings on known good engines I would get a new tester.


----------



## kansasnut (Jun 3, 2009)

it does have a release on it and is the scew in type


----------



## Deathrite (May 21, 2009)

agree with Rotti. 
you need least 90psi to run the engine. and you have to pull it 3 times to get a reading. engines that run and read as that low of compression would tell me i need to get a different tester. 
also ALWAYS remember to release the pressure that is built up in the gauge after reading it. NEVER put the guage back without releasing the pressure. you can damage the seals if you dont do this each time.


----------



## kansasnut (Jun 3, 2009)

ok...I am returning this comp. tester to get a new one,.....can anyone reccommend a make and model that they know of first hand that reads compression on small cc 2 cycle engines?


----------



## Deathrite (May 21, 2009)

this is the one we use. it has done ok so far. we cant afford the higher priced ones as of yet. http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92697


----------



## rotti1968 (Apr 26, 2009)

I use the mityvac mv5520 daily on 2 and 4 stroke engines.. http://www.mityvac.com/pages/products_ede.asp
you can get the same one at sears branded craftsman...http://www.sears.com/shc/s/p_10153_12605_00947089000P?keyword=compression+tester

i have had mine over 6 years without any issues


----------



## kansasnut (Jun 3, 2009)

thanks for the help you guys...update, i cut the hose and bypassed the check valve to the meter, and now it is a 6 inch connection from connector to meter...the meter now moves actively between 0 and about 60 psi....(still low), but a more believeable reading,According to what people say on these post...it shouldn't be able to run at such low compression...so I believe there is still a mystery here to be solved....I will try and locate a second meter to try.I will update when I locate a second meter


----------



## ossaguy (Dec 3, 2008)

The right way to do a compression test is to be sure the throttle is wide open,no choke,and after screwing in your hose,pull it until the needle doesn't advance any more.Depending on the length of hose,depends on how many pulls.The specs called out are on a cold engine.A warm engine will be lower.
The hose is now an extension of your combustion chamber,the air has to be compressed the same as in the chamber.If you only go by 3 pulls,you are not getting a true reading.The shrader valve is special,it's not the same as an inner tube one,also.
I guage set I use is the one made by Snap-on.You see them for sale on CL every now and then,to make it affordable.If it's not accurate,it's worthless I think.
Take care,
Steve


----------



## Deathrite (May 21, 2009)

so far i have not seen the needle raise after the third pull. i agree this might depend on what gauge you are using. i also have yet to find a unit that runs without getting at least 90psi on 3 pulls. but i admit i have not seen as many units as some of yall. 
the few units i have seen that i doubt would pull 90psi after 3 pulls had many more issues and were abandoned by the owner after the estimate. 
how much does the snap-on compression tester run?


----------

