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Post by rollingbender on Aug 25, 2023 10:37:34 GMT -5
What is this thing and why is it there?  i have 2 of these carburetors (different manufacturers) and on both of them, there are no parts installed behind the plate and the nipple for the vacuum tube is not even drilled.  |
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Post by GrumpyUnk on Aug 25, 2023 10:53:24 GMT -5
With the port un-drilled, it is decoration only. Perhaps the firm that copied the original did not have access to the latest model, but needed to have the diaphragm so it 'looked right' and was an 'exact copy'. I think in most larger carbs the diaprhagm does something with an enrichment circuit or accelerator pump type function. I did not take apart the one on the Kym People S 250.
If you can get the model number, you can likely find a diagram of the internal circuits online somewhere.
tom
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Post by GrumpyUnk on Aug 25, 2023 10:59:33 GMT -5
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Post by FrankenMech on Aug 25, 2023 11:01:51 GMT -5
If memory serves, -and it is not good, it was called a deceleration valve on some carbs. If it was working it was to prevent backfiring on deceleration.
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Post by GrumpyUnk on Aug 26, 2023 8:44:22 GMT -5
If it's a decel valve, then it should be flowing excess air into the intake to compensate for any extra fuel pulled by the stronger intake vacuum when the throttle is closed at higher rpms. When I looked at the pictures, it appeared there was a needle-style or pintle valve operated by the vacuum behind the diaphragm.
That it was totally faked indicates that it does not seem absolutely necessary. OTOH, could be that someone who was supposed to perform a drilling operation on the cover was having a tea break... and no one caught it.
If it is a newly purchased carb, it may be returnable depending on the vendor, etc. It would be interesting to actually remove the diaphragm cover and see if there are any parts at all underneath.
Hgih Qaulity.
tom
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Post by rollingbender on Aug 28, 2023 11:05:30 GMT -5
I ordered another PD24J carburetor on Amazon and this one has the nipple drilled and all the magic parts under the cover. I will say this… even using an A/F gauge, I was having trouble getting either of the previous carbs dialed in. This new one with all the features present and functioning makes this bike run as good as I could hope it would.
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Post by GrumpyUnk on Aug 29, 2023 13:55:06 GMT -5
Who knew? I mean, actually make all the parts like it was designed? Who needs that???
I know bupkis about larger CVs except those made by SU in England. If they skimped on the design, I would expect performance would be different than how the original design with complete internals, would perform.
Good that you figured it out.
tom
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