Early full spec carb issues, butterfly/shaft need advice

[schicks]

Im helping a friend out that has an early full spec single carb. One of the butterfly screws came out, nuked the motor. Motor is rebuilt, now we are having issues getting the carb fixed or getting parts. Carb worked great, but full spec wont help or sell us parts to fix it and they wont fix it either because its to old. Dont want to throw the carb out since it worked great. Needs butterfly, shaft, screws. Any advice?
49mm carb throat.

About to put screws in with a backing nut just to get on the water.

full spec quoted $900, plus freight for a replacement lol

 

[jeepcreepcj]

I have the same issue with some old bmr/ F/S “47”s and got the same response on parts lol. It looks like the shaft is just the original 46 with the slot widened and screws original mikuni too. I would assume yours will be the same. Not sure yet where to get the butterfly tho.

 

[Jcary85]

Idk who all makes butterflies but I know mark Erickson has made them before.

 

[JetManiac]

I have the same issue with some old bmr/ F/S “47”s and got the same response on parts lol. It looks like the shaft is just the original 46 with the slot widened and screws original mikuni too. I would assume yours will be the same. Not sure yet where to get the butterfly tho.

Good call, if the butterfly is usable, then get a std 46mm shaft kit. Will need to widen the slot to fit the butterfly and then go to go.

 

[Storbeck]

Not sure I would recommend it, but in a pinch, I have had success with removing the butterfly (which can be difficult when it is deformed on the edges like that, and gently, carefully, CAREFULLY, tapping the deformation flat again with a hammer on a nice flat hard surface, and touching up CAREFULLY with a file. There is a lot of very subtle shape to the butterfly, so...it's tricky. It's not just square on the end, it is beveled in a complex shape to match the bore of the carb when it is closed at a slight angle. Fortunately at the edge where they get damaged like that, it's pretty close to just square.



Obviously a new butterfly would be much more ideal, but it is definitely possible to make it a hell of a lot better than it looks in the pic.

 

[Big Kahuna]

@Jr.

 

[Jr.]

I have been close friends with Ed @ Full spec for well over 30 years. Ed holds his carbs in very High regard. Always upgrading and refining them. It is not uncommon for him to turn down rebuilding them, as he feels accordingly. He has done it to me also on more than one occasion. There really is a science to them. And overall performance is what he feels is at stake.
I have done repairs as Storbeck suggested above. That is really the best option. Shaft repair kits are readily available from Mikuni.
just take your time and be very careful not to bend or damage the blades. I also offer this service thru my shop
Having blades replicated is not in your best interest. The angle the blade sits at is a proprietary part of the carbs function. Being off slightly will change overall performance , and how the cab meters fuel. While the carbs would technically function, you will be risking more than performance loss.

P

 

[Storbeck]

Then, shim the shafts so it doesn't happen again. Especially since you can't get a new blade any more.

 

[schicks]

Thanks all! That should set me straight.