Mikuni jet thread size

[ticega306]

I'd like to buy a tap to try and clean the threads on a set of 38mm mikuni's.

Can anyone confirm which tap ill need for the pilot and main jets.

Thanks


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[DAG]

Main is a M5x0.8 just taped some threads a few days ago.

 

[js/sj]

Better double check info be for you ruin/damage someones carbs.
5x.75 =main
4x.70 =low
But what do I know. Just trying to save a headache

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[DAG]

I ran a 0.8 pitch up the return and a main fit nicely. I didn't know what pitch to use when I was testing I just drilled a few holes in some plastic I had and started tapping and the 0.8 fit best, it may be wrong but not a number from thin air in my defence.. I apologies if you ordered the wrong one

 

[Mdavies_02]

I ran a 0.8 pitch up the return and a main fit nicely. I didn't know what pitch to use when I was testing I just drilled a few holes in some plastic I had and started tapping and the 0.8 fit best, it may be wrong but not a number from thin air in my defence.. I apologies if you ordered the wrong one

I can't puzzle out what your doing in this picture. It looks like your tapping a fuel return line, but what is the benefit. Never heard or seen anyone do this.

 

[DAG]

By drilling out the internal return restrictor on each carb and running a single return restrictor (jet) not only does it allow all the carbs to operate at the same fuel pressure it also make it easy to fine tune the pressure. You are also less likely to clog a single large fuel orifice than the 3 tiny built in ones. Most people just stick a jet into the fuel line and zip tie it in place. I just taped the last carb inline barb so this way years from now when I get alzheimer's I don’t cut out the fuel line and forget there was a jet in there.

As far as the 0.75 and 0.80 threads per mm goes. I drew it up on CAD because it felt so smooth going threading in so I intrigued myself. Since the jets threads aren’t but 2.5mm the mismatch pitch over that short distance does not have an interference fit, although I agree it’s still not right and if the jets were much longer they would bind.

0.80 = .0315” pitch
0.75 = .0295” pitch

 

[ticega306]

Thank you for the info guys. Ordered 5x0.75 for main and 4x0.70 for the pilot.

 

[azwaveracer]

Found this page...

http://www.jetsrus.com/FAQs/FAQ_identify_that_jet.htm

 

[Kaylee.S]

By drilling out the internal return restrictor on each carb and running a single return restrictor (jet) not only does it allow all the carbs to operate at the same fuel pressure it also make it easy to fine tune the pressure. You are also less likely to clog a single large fuel orifice than the 3 tiny built in ones. Most people just stick a jet into the fuel line and zip tie it in place. I just taped the last carb inline barb so this way years from now when I get alzheimer's I don’t cut out the fuel line and forget there was a jet in there.

As far as the 0.75 and 0.80 threads per mm goes. I drew it up on CAD because it felt so smooth going threading in so I intrigued myself. Since the jets threads aren’t but 2.5mm the mismatch pitch over that short distance does not have an interference fit, although I agree it’s still not right and if the jets were much longer they would bind.

0.80 = .0315” pitch
0.75 = .0295” pitch
View attachment 245160

Nerd...

 

[Big Kahuna]

Good Info

 

[DAG]

Nerd...

I miss how much free time I use to have