Need more info about the Keihin. Best to post pics of the top and of the forward and rearward facing sides.

The 99484-85 FSM contains pics of various Keihin butterfly carbs and the original jet sizes. The 99484-78 FSM is helpful for the Late 76-78, 38 mm Keihin butterfly. With clear pics of what you have I can provide good info.

 

Here are some pictures. Hope this helps.

 

The single throttle cable makes it 1980 or older. The tall tower for the low speed mixture screw makes it 1979 or newer.

The main difference between the '79 and '80 is that the 1979 originally had a cap on the mixture screw whereas the 1980 had that screw sealed.

1979: main jet #165, slow jet # 65
1980: main jet #160, slow jet # 68

If the carb is in good condition it should in my experience run well with main jet #170 or #175, and slow jet ~ #70.

<B><I>Main jet is 170 and flow jet 88. Air/fuel mix valve opened 1 turn.</I></B>

Keep the # 170 main jet. It is quite possible that there are or have been intake leaks, and that that caused the PO to install the oversize slow jet.

Reduce slow jet to about # 70. Then follow the instructions in this thread to set the # of turns on the pilot [low speed mixture] screw, and to choose a better slow jet ...

<B>Setting The Pilot Screw on Your IronHead</B>
http://xlforum.net/vbportal/forums/s...ad.php?t=71361

This may also be useful ...

<B>Intake And Exhaust Leaks Tests</B>
http://xlforum.net/vbportal/forums/s...ad.php?t=39766

 

Got it all open again and notice a strange thing. Carb has hole coming from air/fuel mix valve but manifold don't have it? Should I just drill hole to the manifold to get it working?

Thanks a lot in advance!

 

I do not have one in hand to compare to, but i recall that hole from some time ago. I did not ever drill a matching hole. It should be OK as is.

 

Got 65, 70 and 75 slow jets. Installed 70 jet and what a huge difference. Idle is nice and acceleration sounds great. Looks it's still gets a bit too much gas so trying 65 today. Thanks a lot