Mikuni carburetor question.

[trooper1954]

Hi all,
So the carburetor from my Mitsubishi generator was seized big time....I had to use an extractor to get the jet in the photos out....in doing so the screw slot got damaged, and also the threads a little. As I cannot identify the carb, it's difficult to find a replacement for this so I was thinking of trying to re-use it.
I'm thinking of using a dremel to cut a new screwdriver notch.......and then use a die to try and re-thread.....any thoughts on this process?
In looking at the bore with a magnifying glass I don't think I damaged it at all with the extractor....didn't go depp enough to do that.
Do you think It's salvageable??
Thanks

 

[trooper1954]

Hi all,
So the carburetor from my Mitsubishi generator was seized big time....I had to use an extractor to get the jet in the photos out....in doing so the screw slot got damaged, and also the threads a little. As I cannot identify the carb, it's difficult to find a replacement for this so I was thinking of trying to re-use it.
I'm thinking of using a dremel to cut a new screwdriver notch.......and then use a die to try and re-thread.....any thoughts on this process?
In looking at the bore with a magnifying glass I don't think I damaged it at all with the extractor....didn't go deep enough to do that.
Do you think It's salvageable??
If so, how best to determine which die to use....looks like M8 1 ...or maybe M8 1.25??
Thanks

 

[trooper1954]

Sorry for duplicate.

 

[RoninB4]

any thoughts on this process?

-Yes but it's not a definitive reply because the photos don't show the possible damage

In looking at the bore with a magnifying glass I don't think I damaged it at all with the extractor....didn't go deep enough to do that.

-Doesn't take much "depth" to alter the flow characteristics

Do you think It's salvageable??

-Maybe, maybe not. Can't see in the photo and I'd want at least 10x magnification on it before drawing a conclusion

If so, how best to determine which die to use

-Measure thread with micrometer, caliper shouldn't be "trusted" for whether the threads have been damaged or not. After measuring the OD you'll want a thread pitch gauge, a discerning eye, and magnification along the entire thread length, there's not much difference between 1.0 and 1.25 except .0098 (inch) and you don't have much thread length to examine the pitch progression. Use the wrong die and you've got large potential for screwing up the emulsion tube threads. Would suggest careful efforts with heat/penetrant/solvent to try backing the jet out and use of Loctite purple (for small screws) if you decide to re-use it. Brass deforms easily. Good luck.

 

[Renegade1LI]

You should be able to find a replacement on Amazon for like 20 bucks, save yourself a headache. Just bought one for a stihl saw, 15$ with filter and plug, works like new.

 

[trooper1954]

Thanks Ronin....
I was mistaken in my terminology....the threaded part of that unit is all one piece.....inother words the whoille thing is the jet....the little threaded part at the end is not designed to come off....its all one piece.
Good guidance for the rest of the post.. I will find a micrometer and give this all a try !!
I have ordered a new carb already, but really wanted to salvage this one.
Thanks again.

 

[kctgb]

Is there a number on the carb? Those carbs were quite common. I had a snowmobile back in the 80’s with a mikuni carb.

 

[RoninB4]

Thanks Ronin....
I was mistaken in my terminology....the threaded part of that unit is all one piece.....in other words the whoille thing is the jet....the little threaded part at the end is not designed to come off....its all one piece.

- Usually, from my limited experience, the jet itself is a really short component threaded into the tube. What a PITA for you.

Good guidance for the rest of the post.. I will find a micrometer and give this all a try !!
I have ordered a new carb already, but really wanted to salvage this one.

-Yeah I would feel that way too. Having trouble imagining the advantage of manufacturing this as ONE piece, considering the already existing tooling and process to supply a TWO piece assembly like their regular applications. Odd. An emulsion tube could be made that allowed a separate jet but that would be reverse engineering for dimensions. A mill and lathe would also be required, don't know if that's worth your time/trouble.

Thanks again.

-Couldn't see the threads in the photo and made an incorrect assumption. Sorry I couldn't be more help.

 

[Fixr]

Hi all,
So the carburetor from my Mitsubishi generator was seized big time....I had to use an extractor to get the jet in the photos out....in doing so the screw slot got damaged, and also the threads a little. As I cannot identify the carb, it's difficult to find a replacement for this so I was thinking of trying to re-use it.
I'm thinking of using a dremel to cut a new screwdriver notch.......and then use a die to try and re-thread.....any thoughts on this process?
In looking at the bore with a magnifying glass I don't think I damaged it at all with the extractor....didn't go deep enough to do that.
Do you think It's salvageable??
If so, how best to determine which die to use....looks like M8 1 ...or maybe M8 1.25??
Thanks

I wouldn't use a die, or a Dremel, at least not at first. I would use a knife-edge jeweler's file to very carefully smooth the damage to the threads with minimal material removal, and the edge of a thin flat jeweler's file to try to clean up the slot without going too deep. This is one of those "slower is faster" things. I also wouldn't expect more than a 50% chance of saving it.

 

[ebj]

The part is called the main nozzle. It is a combination of the main jet and a separate emulsion tube like used in Honda carbs. I believe the jet part is in the short threaded section you buggered up getting it out. If so, you will need to replace the main nozzle to have a functioning jet.
I have had to remove jets before the same way as you and had to replace with a new correct size jet.

 

[NUTTSGT]

Multiple threads merged