YS-637 Carb

1950 - 1952, M38, questions, discussions, regarding anything related to the M38.
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stiknruddr
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YS-637 Carb

Post by stiknruddr » Sat Dec 02, 2017 3:10 pm

I've received a lot of great info here so thought I'd pass along my experience. I bought my M38 with a soles and never ran it. Found a YS-637 core and put a kit in it from one of the larger suppliers. I measured the replacement parts left the original metering rod in it was .072" vs.068 in the kit. The main jets both mic'd properly. Ran but not great. After further investigation found the accelerator pump check valve and weight missing. Re mixed everything and put in the missing ball and weight. Runs great. I didn't lose the ball and weight someone else did. Info from this forum and the mil manual put me onto it. Was running really rich now all good great idle sweet mixture only thing is air screw works best at 3/4 out yes I checked for vacuum leaks. Whatever works


stiknruddr
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Posts: 23
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Re: YS-637 Carb

Post by stiknruddr » Sat Dec 02, 2017 5:43 pm

All I'm say is check the components of a rebuild kit for proper specs and make sure the accelerator pump check valve and weight are in place. In my case the carb looked great but the accelerator pump check valve ball and weight were missing replacing it made all the difference

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