Yup, Jim's idea would work for sure Bob.

Our esteemed 2M suggested trying this before resorting to a helicoil.

Hey, peanut, had same issue many years ago. I simply retapped the stripped bowl screw hole to 8-36, not an easily found size, but used in gunsmithing. You could do it with 8-32 std. 4mm is about .157" dia, #8 machine screw is .164" dia, just enuff to get usable threads. 0.7mm pitch is almost 36 tpi.

http://www.shender4.com/thread_chart.htm

From here: http://www.xs650.com/threads/tapping-a-carburetor-float-bowl-thread-size-anyone.31194/#post-315347

Further on in that thread:

It's just barely larger, so you can opt for the helicoil later. I don't recall having to drill out the bowl hole, I think it just barely slipped in there.

Let the screw cut its own threads, use a litle pressure to ensure it goes in, and if you slowly reverse the screw before starting, you can feel the screw drop into engagement with what remains of the old threads, then you start it in.

Careful, this is really a band-aid...

Other option would be to just tap it out to the next size metric screw. Depending on which one is stripped you might need a bottoming tap though.
 
By the way, I meant to add. I am so sick of parts that don’t fit. I try to buy OEM stuff or real Mikuni parts, I always make sure I check the figment charts, but WTH? Three bogus parts on one little carb? Nearly $40 pissed away!
It’s just so frustrating!
:mad:
 
Thanks for the links Robin, I’ll do some reading. I had also thought about just bumping up a size for that on screw.
I was just fooling around and grabbed a little SAE machine screw out of my cabinet and it feels like I could screw it in, a little tight but......
Anyways, I’m gonna think on it.
 
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By the way, I meant to add. I am so sick of parts that don’t fit. I try to buy OEM stuff or real Mikuni parts, I always make sure I check the figment charts, but WTH? Three bogus parts on one little carb? Nearly $40 pissed away!
It’s just so frustrating!
:mad:

BTDT Bob. I have found to ensure I'm getting OEM parts, and real Mikuni parts I have to go to a Yamaha dealer or approved Yamaha parts dealer.
Costs more....yup. Saves headaches and frustration.....yup. Worth it? To me.....yup.

I was just fooling around and grabbed a little SAE machine screw out of my cabinet and it fells like I could screw it in, a little tight but......
Anyways, I’m gonna think on it.

Depending on the size it might just work Bob. Remember 2M's caution that this is really a band aid.
Measure the size and post it up here, you'll get some feedback on whether to proceed or not.
 
The screws are M4's and yes, they make heli-coils that size. You'll need the kit to get started, which will include the special sized tap and install tool. After that, you can just buy more coil inserts if you ever run out. If you own old bikes, heli-coil kits are kind of needed. Eventually you'll need them. I have the 4mm, 5mm, 6mm, and 8mm kits. The kits may seem expensive but I found out years ago that they really weren't after I had one installed by a shop, lol. I could have bought the kit and still had a few bucks in my pocket.

Your original needle jets are probably still fine. Unless the carbs were really gummed up at some point and sat that way for a long time, the needle jet doesn't really wear out. Sitting gummed up can eat it away inside though. So, it didn't really wear out, it was destroyed by the gas varnish.
 
Stripped screw; do a search in here there's a SAE that's either tap n go or it's just enough oversize that it can just be threaded into the stripped hole.
Gaskets; I feel your pain, just spent about 1/2 hour or more "fitting" a set of keystone gaskets, had to remove the flash/fur from every hole in addition to the perimeter trim.
Reused the needle jets but it took some work, they had suffered a bit on the way out cause they were REALLY stuck in there.
Sorry; but with several LOTS of trips to the parts tubs I was able to get these 78-9s back together.
Not show carbs but they will go on the 79 in the shed that's getting a wake up drill "real soon" to see if I got 'em right.
xs650 78-9 carbs 4-2018.jpg
Better than a week ago.
 
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Stripped screw; do a search in here there's a SAE that's either tap n go or it's just enough oversize htat it can just be threaded into the stripped hole.
Gaskets; I feel your pain, just spent about 1/2 hour or more "fitting" a set of keystone gaskets jhad to remove the flash/fur from every hole in addition to the perimeter trim. Reused the needle jets but it took some work, they had suffered a bit on the way out cause they were REALLY stuck in there.
Sorry; but with several LOTS of trips to the parts tubs I was able to get these 78-9s back together.
Not show carbs but they will go on the 79 in the shed that's getting a wake up drill "real soon" to see if I got 'em right.
View attachment 116928
Better than a week ago.

I think those look great! Were those the carbs you were cleaning in the ultrasonic cleaner? The ones with the really corroded bowls? If so, what an improvement!
 
Mailman out of curiosity, which hole was stripped? You can use an oversized screw, and the cost would certainly be cheaper, but the heli-coil saves you from sorting that odd sized screw every time you have the bowls off.
 
This one right here. Right above the choke mechanism you wrote about. I’m off to the hardware store this morning to explore some options.
D61DBAA1-DFB1-48DC-BA75-6C1A889580E8.jpeg
 
I've got the kit and extra coils, But the cost of sending back and forth, as opposed to just buying doesn't pencil out for me. If you want to borrow it though I can send it your way.
 
Mailman; did you look at these?
650 central
Carb Kits
For the 1970 & 1971 Models. Each kit contains:
float bowl gasket, a complete float valve, choke plunger & spring,
slide needle and all jets(42.5 &130) to rebuild (1) OEM Carb.
Order Two.

#CMXS48-1917 ..... $17.50 each
 
That's the hardest hole to repair. The choke casting on the body blocks the hole so a tap won't go through very far. Along with the standard Heli-Coil tap, you'll probably need the bottoming tap as well .....

https://www.mscdirect.com/product/details/99005134
In a pinch one can "convert" a taper tap into a bottoming tap. Just grind the end off till there is only one or two flutes left showing some taper.
 
Yes, that's true, but then you make that tap difficult to use again in normal through holes. The usual routine for a bottoming tap is to start the hole first with a regular tap. Then once a few threads are cut, you switch to the bottoming tap.
 
Mailman; did you look at these?
650 central
Carb Kits
For the 1970 & 1971 Models. Each kit contains:
float bowl gasket, a complete float valve, choke plunger & spring,
slide needle and all jets(42.5 &130) to rebuild (1) OEM Carb.
Order Two.

#CMXS48-1917 ..... $17.50 each

Gary, that won't work on XS2 carbs...
 
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