Compression Test

Im a newbie at working on atv motors but am pretty decent at figuring mechanical things out. I just bought a compression tester and there really was no manual or anything that came with it, understanding that you really dont need a manual to tell you how to screw it in and then turn the engine over. :-D My question is this, on a recoil start engine the first time you pull it, is the first reading you get the correct compression reading or do you need to pull a few times and let the compression build up? My manual says that I should have between 156-198 for compression and im getting like 95 on the first pull but the motor seems to run fine and have lots of power. I have another motor from a parts bike that i bought and I put the tester in it and pulled and i only get like a 55, which im guessing thats time for some new piston and rings.

Thanks,
Jeremy

[GlennMc]

Hi;
When you do a compression test, you need to perform it with the throttle wide open. If you do this and do not see good compression after giving it a good pull on the recoil, then you have a problem. Also make sure that there is no automatic decompression system that functions when you pull the recoil starter. I know that the 185S had an automatic decompression. If you do have one, disable it and then perform the compression test at wide open throttle.
GlennMc.

One long pull should be all that's needed. They have two types of test for compression, first one is a dry test, the second one is a wet test.

The dry should be taken first, it will have a lower reading than the the wet.

To take a wet reading, coat the inside of the cylinder with engine oil, then test the compression.

I normally insert an oil filled straw in the sparkplug port and let the oil drain into the cylinder. Then I put the sparkplug back in and then pull the starter rope so that the oil coats the cylinder. Now I remove the sparkplug and install the tester and then take the wet test so that I get a wet reading.

[Mobular]

3 full cycles of the engine should get you your proper reading