Piston skirt difference

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Piston skirt difference

Postby Emerica1975 » Sun Jul 17, 2022 2:05 pm

I rebuilt my 1956st motor last winter and have been trying to figure out why it just won’t run right. I have checked and rechecked timing I’ve done carb cleaning and adjusting, even made sure I tried different oil in my gas to get that correct. I’ve made sure points and condenser and spark plug and coil all checked out. Nothing has changed the engine performance.
The engine will start and run and (the compression is around 95 on my gauge) but has no power and will start to sputter and act as if it’s either to hot or not getting enough gas after about 10 minutes of driving. (I have and old 1955st motor that I have put in the bike to compare against) So I finally took the whole engine apart and expected to find the compression plates to have come loose. But they were fine. Infact everything looked good But then I noticed that the new piston I had bought last winter was different on the skirt from my original piston. The new piston has no notch cut out on the intake side of cylinder. Could this be my problem? I’m usually pretty good with this stuff but I’m feel like I’ve been bested and it’s really eating at me. Thanks
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Emerica1975
 
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Re: Piston skirt difference

Postby Mutt » Sun Jul 17, 2022 5:31 pm

The cut out more than likely is not the problem. That just increases the intake port charge, but motors ran fine without the cutout for half a decade before the cut away came in to use on the pistons
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Re: Piston skirt difference

Postby Emerica1975 » Mon Jul 18, 2022 11:02 am

Thanks for the reply. I thought it was worth checking. What do you think the compression should be? It’s a standard st165 with a .010 over piston.
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