Exciter 440 carb help needed

[Pinto]

I ran across an extremely clean 1979 exciter 440 and couldn’t pass it up. It runs ok but has a midrange lean condition. A little choke makes it come out of it. I’ve had the carb off and apart many times and it’s spotless. No plugged passages, it all looks perfect. Looking at the plugs it also looked to me like it was a little lean at full throttle too. The Kehein carb has a 90 pilot and a 165 main jet. Looks like stock the main should be a 152. Given that it was already jetted richer than stock and still lean I figured there was a good chance of an air leak or bad crank seals. I ended up pulling the motor and had the crank rebuilt because a main bearing was rough. Put it back together with new seals, gaskets, piston and rings. I noticed someone had done some porting on the cylinders. It still runs the same as it did before, Lean in the middle and top end.
Im not sure where to go from here. Find a different kehein? Swap to mikuni? Oil injection has been deleted and I do have a 38mm mikuni from a junk sled I could put on. Not sure where to start on jetting for the Mik though.

Thoughts?

 

[74Nitro]

Is the airbox completely stock?
Also, is the rubber adapter boot between the airbox and carb in good condition.
These will be lean if either of those is not stock or in poor condition.

 

[Pinto]

Is the airbox completely stock?
Also, is the rubber adapter boot between the airbox and carb in good condition.
These will be lean if either of those is not stock or in poor condition.

Rubber boot is new. Air box is stock. Only thing is I’m not sure if there is supposed to be foam on the outside of the air box or not.

 

[74Nitro]

Curious as to where'd you get the new boot as they're not available anymore.
Assuming all the stock baffles are still inside the airbox?
Otherwise, I'm not sure.

 

[Pinto]

Curious as to where'd you get the new boot as they're not available anymore.
Assuming all the stock baffles are still inside the airbox?
Otherwise, I'm not sure.

I believe I got the intake flange/boot from Dennis Kirk.
After your first response I looked online at air boxes. Turns out mine has been cut down. The main part of the box is all there, but the right side has been cut off. Pretty good chance that’s my problem.
Thank you!

 

[74Nitro]

I'm refering to the boot between the carb and airbox, not the one between the engine and airbox.

Yamaha had restrictive airboxes on these and the carbs were calibrated to run with them in place.

Yamaha had stickers on these airboxes stating that severe engine damage could result if engine ran without airbox.

Loading…

www.cyclepartsnation.com

 

[Pinto]

I'm refering to the boot between the carb and airbox, not the one between the engine and airbox.

Yamaha had restrictive airboxes on these and the carbs were calibrated to run with them in place.

Yamaha had stickers on these airboxes stating that severe engine damage could result if engine ran without airbox.

Loading…

www.cyclepartsnation.com

I misread the first time on the carb to air box boot. I’ll get a new air box and see what that does.
Thanks again.