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Short Slow / Pilot Jets - Problem?

sugarmcguinn

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Happy Thanksgiving weekend fellow SOHC/4 Brethren and Sistren!!

I searched this topic for an hour or so and the only thing I found was a passing mention in an unrelated thread that an owner had traced idle problems to short aftermarket slow jets in a CB550... but there wasn't much detail...

Long story long--- Over the thanksgiving weekend I planned to rebuild the carbs on my '78 CB750f (Completely Stock). Over the few weeks prior I ordered and collected everything I thought I would need, as I knew come the T-Day weekend if I didn't have a part I would be SOL...

Anyway, ordered the Complete Rebuild kits from Vintage CB750 and all seemed to check out against what I thought I needed... but upon reassembly yesterday I discovered that the #35 pilot jets that came in the rebuild kit are shorter than the OEM pilot jets I removed. They are shorted on the "bowl" side only, where as the OEM Pilot Jets protrude into the bowl roughly 15mm and the NEW Pilot Jets only protrude about 8mm. Other than this, they are identical. My gut tells me that this is going to cause a problem, but I have no science for saying/feeling that... Conversely, "actual" science would suggest that if the fuel level in the bowl is where it should be, they will be fine... right??

Anyone here with any experience using shorter Pilot jets? I'd just put the OEM ones back in, but two of them are bent... (How does that even happen....?? That's another thread.... :)

Thanks in advance for any words of wisdom :)

Sugar McGuinn
Seattle, WA
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Can you show a picture of how they are bent? If it doesn't affect the holes then they should be ok but I would order some new jets from JetsRUs, they have oem and cheaper then oem jets that work perfect and are caibrated correct. Just clean your original jets and use them for now. I never use the jets that come in "kits"....you never know if the holes are correct calibrated hole or not.
 
Hey Dirtdigger!! Thanks a lot for the tip on Jets R Us. A quick paruse of their site clearly indicated that my pilot jets should be 28mm long. I believe Vintage CB750 sent me the wrong pilot jets. Bummer.

I'm bent the OEM jet back as best I could, threw them in Berryman's overnight and then in the ultrasonic for about 8 cycles. all the holes are clear and I can see light down the shaft and am able to blow air through them.... can't fit a drill bit down them though... I seems to be able to see a "star" pattern when I squint to look through them... not sure if that's real, or just my squint... but they seem clean, I guess... going to throw them back in and hope for the best...

I have to say... the "complete" rebuild kit I bought from Vintage CB750 might be the worst rebuild kit I've ever purchased... many of the parts were wrong, the brass was so brittle that the supplied jets actually broke as I was installing them... some parts fit, but then other OEM parts wouldn't fit after e.g. float bowl pins prevented the bowl from seating... I'm pretty disappointed with these kits, and they weren't cheap...... I ended up reusing more part that replacing with the ones included in the kits....
 
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