Stripped pilot jet holes

SuperRat

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I'm re-building a set of carbs for '74 cb350-four and hit a snag. The holes for the pilot jets (or slow jets) are stripped on 2 of the four carbs. The old jets are out but the new ones won't thread in. They bottom out and keep turning. I'm thinking the last guy that re-built them over-tightend the jets and stripped the threads. Any ideas for a fix other than replacing the carbs? My next move is to figure out the thread size/pitch and re-tap, but I'm thinking the threads might be too far gone.
 

jpdevol

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Ouch!
That's an odd thread on that jet; I measured the thread OD @ 3.3mm. That's smaller than a std. 4mm bolt thread @ 3.84 and larger than a 3mm bolt. The pitch on the jet's threads measured .7mm. I question if a 4mm x .7 helicoil will yield a thread that will allow the jet to tighten-up. Most 3mm helicoils are a .5mm pitch and I think they're too small.

Original 2-part JB Weld has been known to durable in other carb repairs, perhaps just glue them in (very carefully with no excess):shrug:

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20230110_015306.jpg
 

SuperRat

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Thanks for the measurements. That may help. I'm also contemplating using thread locker. Possibly red. Although that may complicate future jetting changes.;)
 

dirtdigger

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There are a couple of carbs on ebay right now. Some complete racks and couple individual carbs. No matter ehat you try to glue the jets in with the gas will soften it. Even JB weld fails when under constant contact. You will be better off biting the bullet now and getting the carb bodies while they are available......cb350 four stuff very hard to find!
 
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