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Mr. Jon,

How do You Do? Nice talking to You by this media. After a Year my GG2000 is still running properly. However, I notice that the compression seems to be lower (I haven´t measure yet) because the starting kick is softer than before and the engine keeps turning a little more than normal after stoping it. I would like to know the expected pressure measurement for a new GG2000, which ones are the recommended parts to be changed and the corresponding piston size (and/or tolerance) according to the size of the cylinder (i.e. size A, B, D). Is this information in tabular format?

Thanks very much, Elías


I'm not sure what size engine you have and, as each engine is a little different, the compression pressure readings will vary slightly. The way I've done it in the past is, take a compression reading on the engine with a fresh piston and rings (after appropriate break-in) and consider a top-end rebuild when the reading drops 15% or more. As for the piston clearance, it should be .040 to .045 and a wear limit of 0.10 for the 270/280/321 engine sizes. The pistons come in A,B,C and sometimes D oversizes, in increments of .05mm. This way the piston can be sized exactly to the bore, which is a Nikisil plating and can't be overbored. The ring end-gap is generally .1mm per inch of bore diameter, so you may need to only replace the rings to restore the compression level. Although it is not always necessary, I like to replace the top-end connecting rod bearing when I replace pistons. Your Gas-Gas dealer can help you get all the necessary parts you will need.


Professional tuner and 'Trials Competition' writer Jon Stoodley has very kindly stepped up to the plate to answer your questions. If you're having problems, or need some advice just send an email to Jon. If it's something that could be useful to others, we'll post it on the site.
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