FWIW I think you have done an admirable job tracking down and correcting potential issues. Makes me think perhaps I should check that junk body for a similar issue.
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Carbs are off again. What now?
- Thread starter Its been a long time
- Start date
Thanks.
Easy check first. Screw a mixture screw into the port and bottom it the way you normally would. If it doesn't screw in as far as the pictures I put here, there's a chance there is a broken screw tip in there. Second thing, remove the screw again and take a close look down there. You will see if the port is blocked or not. You need good light. I wouldn't be surprised if you find the same as I did.
On the road a few more days but will try to remember to take a look when I get home.
This maybe an aside, but still relevant. I have been told, by a luminary in the XS650 field, that the VM carburetors are really a design for 2-strokes. The aerated design of the BS carburetor emulsion tube is much better for 4-strokes and makes these BS carbs better suited overall for the XS. I am not an expert on VM carburetors and would be curious to hear opinions.
Mikuni carbs were originally a knockoff of Amal carbs. They weren't designed for either 2 or 4 strokes, they'll run equally well on both. It's all in the tuning. You can tune them for either engine equally well.
tmikeyb
XS650 Addict
If your going to loctite the screws, then why not just reuse the originals?
Good question. Yes, I could and I wouldn't have ordered the M3 x 8mm screws if I had known what I know now. The 8mm long ones that I bought sit deeper into the throttle shaft countersink and as a result are a bit too long. 6mm ones would have been better. 20:20 hindsight is a wonderful thing.
I'd think they peened them over for a reason.
Is it worth sucking a screw into a cylinder?
That's one of those few things I wouldn't leave to chance.
Edit double post.
Somethings wrong with my lagtop.
Is it worth sucking a screw into a cylinder?
That's one of those few things I wouldn't leave to chance.
Edit double post.
Somethings wrong with my lagtop.
Let's play spot the repair 
I would not try to dissuade anyone from doing so.I'd think they peened them over for a reason.
Is it worth sucking a screw into a cylinder?
That's one of those few things I wouldn't leave to chance.
For completeness, here's what I used to plug the drilling on the mixture screw repair. Dropped a disc a couple of mm thick into the hole to prevent the epoxy from going somewhere you don't want it. Then pushed the prepared epoxy down into the hole firmly, ensuring any void is filled. Leave it overnight and the carburettors are going back on the bike to see the result.
Ok, home for a minute so I dug that carb body out. The broken needle does not appear to be my issue so I’m going back to my junk body theory, lol.
Worth a look.
