[SpudRider]

Originally Posted by max_damage

Hi
Past 5 days, my Zongshen sierra started to loose its power. The bike has over 25 000km, looks like its time for service.
I think it is loosing compression. Does anybody know what is normal compression value for 200cc (1:9,5) engine ? My manual doesnt say anything ??? Ive checked the compression, it is 125 psi ? is it low ?

Thanks

Max, I just checked the engine compression on my Zongshen Sierra 200GY-2. I followed the instructions posted at Dan’s Motorcycle Repair website.

http://www.dansmc.com/compression_test.htm

I followed Dan’s advice and tested the engine cold. However, I did forget to hold the throttle wide open. Also, I live at 4,400 feet above sea level. In addition, the temperature was about 45 degrees Fahrenheit. I tested the compression three times, and I got 105 psi from my Harbor Freight compression guage set.



I am positive this compression gauge set is not the most accurate. Also, this gauge set has a very long hose, and an extra connection that might lose some air. :roll: Finally, I tested the engine cold, at 45 degrees Fahrenheit, at high elevation, with the throttle closed. However, it still seems to me that your reading of 125 psi is not too bad.

Later I will check the compression again, with the engine warm and the throttle open. However, I doubt I will gain much more than 20 psi when I do it. :?

My engine is running very well. Perhaps engine compression is not the cause of your problem. :?:

Spud