GX240/GX270 Piston Question

bfeeney

New member
Hi. New to the forum here. I work at a hardware store that offers rental lawn equipment, needless to say, it has its perks. I've managed to get a GX200, 240 & 270 for free off junk equipment. I'm in the process of building a go kart and finally decided to use the 270 rather than the cheaper 200. I do the porting myself on all my engines, so when I had the head off both 240 and 270, I was a little surprised. Why does the 240 have valve reliefs in the piston but the 270 doesn't? The only thing I can think of is the cam is different since the heads are the same and the stroke is the same. I couldn't find any real specs on the oem cams for either of these engines. If the cams are different, can I swap them? Thanks.
 

bfeeney

New member
If anyone happens to know the cc's of a GX270 head, I've been looking all over the place for that info.
 

bfeeney

New member
So I figured out the answer to both my questions, I'll share the info since there is exactly jackshat information on these engines. I got 33ml of fluid in the combustion chamber. I did the measuring correctly, but the number seems high. I guess the numbers can't lie. The reason the 240 has valve reliefs and the 270 doesn't is because the 240 has a flat top piston, thus needing the reliefs. The 270 has a dished piston which acts like reliefs, just worse for performance.
 

alvin l nunley

Premium User
So I figured out the answer to both my questions, I'll share the info since there is exactly jackshat information on these engines. I got 33ml of fluid in the combustion chamber. I did the measuring correctly, but the number seems high. I guess the numbers can't lie. The reason the 240 has valve reliefs and the 270 doesn't is because the 240 has a flat top piston, thus needing the reliefs. The 270 has a dished piston which acts like reliefs, just worse for performance.
Have you done a cc check on both engines. That's the only way to tell what the compression pressure is, unless you have a compression gauge, which will tell you the pumping pressure.
What are the bores and strokes of both engines.

It's nice that your trying to understand these engines, but you need to find pertinent information or have the tools to measure the bore and stroke.

It might be that the 270 needs the dished piston because of the longer stroke, if it has one. Measure the valves also. The lift and duration and the diameter.
 
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