Tap or heli-coil for... ?

[Matt45]

Hello,
My oil pressure (42 WLA) gauge threads (in carter) are dammaged (no possibility to screw the oil pressure gauge in it, then oil is leaking..). Before I remove the gear cover, I would like to know if I can use a tap (I believe that the size should be 3/8"-24, but correct me if I am wrong) or for some other reasons to use Heli-coil insert
Thanks for your helps

[Lyle Manheimer]

Matt,
I am no expert on 45's, but 3/8 pipe sounds mighty big for an oil pressure fitting. I would think 1/8 NPT would be the right size.
Again I don't know if Heli-Coil makes inserts for pipe, because it is a tapered thread so that it seals. I doubt it.
If it has been enlarged to 3/8 NPT, you should be able to put a pipe bushing (reducer) in it, and bring it back to 1/8 NPT. It will not pass the eye of the judge if you are looking for a correct 100 point bike, but if it's a rider what the heck.
If it isn't leaking real bad, try a good thread sealant. Teflon tape is not really a sealant, it is a lubricant of sorts and the threads of the fitting still make the seal.

[cdndewey]

Hello Matt,

First lets get the thread designation straightened out. A 3/8-24 thread is not a pipe thread it is a UNF thread. The thread on the gauge looks like it might be a 3/8-24 but it is in fact a 1/8-27 pipe thread. There are two versions on this thread, one is tapered and the other is a straight thread and then there are variations (specific applications) of the straight thread. The oil pressure gauge on a 45 is a straight pipe thread and requires a copper packing washer under it for it to seal. The part number for this washer is 3572-36C. If you can find a straight pie tap you may be able to clean them up. But without seeing how badly screwed up they are I might be inclined to carefully thread it into the crankcase. Be sure you have that washer on before trying though. I hope this helps you.

[Matt45]

Thanks for your advise, I have ordered the tap, and will take off the gear cover....

[Matt45]

The thread was too damage to be repared with tap then I found this solution (which is not, I agree, correct for 100 points bike) but no more pb and less expensive than changing the cover..