replacing butterfies on mikuni carbs

[feartheride]

Anyone ever relace the butterflies on mikuni carbs.I just changed out a set and they don't seem to close as tight as the originals. I will have to double check my full rectums when I get home from work,but I seem to remember them closing to the point where you could not see light through them.
Just want to make sure before I peen over the screws and call it a day

 

[keefer]

The throttle plate edges are ground on an angle and will not seat properly if you have them in upside down. It is hard to tell by looking at them, I always just remember where the numbered side is on the ones I take out and orient the new ones the same way.

 

[feartheride]

I thought they might be angled but couldn't even tell under a magnifying glass

 

[Kennay]

if you are holding the carb by the fuel pump (Cradling it in your hand) and looking in from the bottom of the throat, the numbers should be facing up like they normally would

This is how a set of blackjacks I have sitting here is

 

[sflsurfrider]

theyre definitely angled.

also, dont tighten/loctite the butterfly untill all the other linkage is in place.

 

[keefer]

Yep, let them align themselves by opening & closing the shafts to normal closed position and then tighten the screws. Use some red loctite and if you peen them be sure and put a buck on the screw head so that you do not damage the shaft when you smack em.

 

[sflsurfrider]

Yep, let them align themselves by opening & closing the shafts to normal closed position and then tighten the screws. Use some red loctite and if you peen them be sure and put a buck on the screw head so that you do not damage the shaft when you smack em.

a spring-loaded centerpunch is what i use the 'damage' the threads.

 

[keefer]

Yeah those things are great and you won't have to worry about bending the shaft. Good call Sir Charles.:bigok:

 

[sflsurfrider]

Yeah those things are great and you won't have to worry about bending the shaft. Good call Sir Charles.:bigok:

....and theyre only like $5 at harbor freight.

i just peck at where the threads meet the shaft and booger it all up w/ the punch about 10 times. theyre really easy to work with in that confined area too.

 

[feartheride]

Yep, let them align themselves by opening & closing the shafts to normal closed position and then tighten the screws. Use some red loctite and if you peen them be sure and put a buck on the screw head so that you do not damage the shaft when you smack em.

Yes this is what I did but still not completely happy with the fit compared to the set of full specs I have sitting here.
The butterflies have no 3's on them but I can see the angle when I look close ,did have them the right way ,besides you can see they fit worse when you flip them around
I center drilled the end of the screws so I could pean them over but maybee I should still use loctite to make sure they don't loosen and allow the butterflie to move

 

[feartheride]

To be able to pean these screws safely I made a plug to go up the throat of the carb.It is same dia as the bore with a 78 degree angle cut on top and bottom and 2 grooves cut on top to clear the round part of the butterfly shaft(.090 deep by .190 wide)
I dimmpled the end of the screws with a small drill wich is pretty difficult without a good drill press and vice or in my case a mill so I would say not required.

Then loctited with 701 high strength and used small punch to peen and also a small chisel to put a cross in the top.
There never coming out but at least they won't go threw the motor

If you don't have access to make a plug I would say get a piece of round stock and try to dimmple the end.Put it in the vice with one end resting on the bottom of the vise and have someone hold the carb so the screw rests on top.