VM 26 bleeder question

[jknappsax]

Thanks for the suggestion. It gives me another avenue to pursue.

[jknappsax]

Hey,49er, I had achance to think about the fuel screws

The fuel screws on the bottom of VM carbs does not come to a sharp, fine point like the air screws. The fuel screws are tapered somewhat, but the thinnest part is about 1/3 the thickness of the widest part. The ones people are warned about breaking are the air screws, on the side of the carbs. I've had these carbs apart to do a complete cleaning, and the fuel screws are identical. Unless somebody REALLY cranked down on them, I can't imagine that the seat would be damaged, and that is a part of the carb body, not a seat that can be changed. The fuel screws are pretty much set and forget. And none of the fuel screws had any damage to them.

[chef1366]

The fuel screws ( by the float bowl) should come to a point and the air screws (on side of carb) has a blunt end.
If the fuel screw isn't sharp the tip may be broken off in the carb. Can you blast carb cleaner into the throat without the fuel screw installed?

[49er]

I agree with Chef. It's the fuel screws that are prone to getting broken off when they're screwed too tightly against their seats. They should have fine pointed tapers. If yours don't, you have got the wrong fuel screws fitted to the carbs.

I just checked my spare set and it's not possible to have the fuel and air screws mixed up, as the thread sizes are different.

[renobruce]

The fuel screws ( by the float bowl) should come to a point and the air screws (on side of carb) has a blunt end.
If the fuel screw isn't sharp the tip may be broken off in the carb. Can you blast carb cleaner into the throat without the fuel screw installed?

This is correct. Here are some pics:

This is what the fuel screw underneath should look like:




And this is the side air screw:


If your fuel screws don't come to a sharp point, they are most likely broken off inside the small port that they screw into, as already stated. That would also explain not having any changes to performance after adjustment.

[jknappsax]

Hey guys, I just got back in town after being away for a week. Bruce, I appreciate the pictures, and wonder ir I have the screws reversed? I'm going out to try and sort his out today. Thanks everybody!

[jknappsax]

Cranial Flatulence clearing!

The screws were as Chef, Bruce, and 49er said, and I must have had Cranial Flatulence when I was picturing it in my mind, because that's how mine were. After all the good advice I got here, I pulled the carbs and checked, and there WAS a fuel needle with the tip broken off. The good news is that the PO managed to get the broken piece out. BTW, squirting carb cleaner into the hole where the fuel screw goes does get into all 4 carbs. The bad news is that the hole is opened up compared to the other three, and has some scratches in the carb throat. I have other fuel screws identical to the good ones, and that makes sense why carb#4 needed only about 1/2 turn out as opposed to about 1 1/4 on the other three. Are the scratches on the carb throat around the fuel orfice a big problem (turbulence, etc.)? Should I try to buff them out somewhat with a felt wheel on a Dremel? Sometimes I have a mind (or what's left of it by all the gas fumes) like a steel trap! Nothing gets in! I appreciate everyone persistence until it finally started to sink in!

[chef1366]

You can either
Get another carb body
Play around with the air and fuel screws until you get the correct mixture

I don't think scratches in the carb throat will affect the air flow as long as they aren't gouges. If you looking for a "pretty" factor buff away.

[49er]

Yeah, unless you're wanting to create work for yourself, just set the fuel screw in closer to the seat and adjust the air screw accordingly. Any turbulence around that area will be minimal.

[jknappsax]

I hooked up the Morgan Carbtune sychroniser and put in the Colortune plugs, and checked sync, still floats a little, but is real close. I set the mixture at 3 grand while checking sync. Mixture looked good, with a little richness when punching the throttle up to about 6K-8K. When I set the idle back to 1100 rpm, all cylinders seem rich. The air screws are all set at one turn out; haven't adjusted them by the max idle method, as it started raining, and I'm working outdoors, but under my front porch by the garage door. And Murphy's Law, my tank took a tumble while off for synchronizing. A lot of little scratches and a teeny dent, all on a bike with nice paint!

Any thoughts on the richness at idle? The 1.5 pilot jets are the ones that came with the DJ Stage III. Should I try adjusting the air screws, then go back and reset the fuel screws to lean out the mixture at idle?

[49er]

Bad luck about the tank, Murphy's struck again!

Try adjusting the air screws. They are usually set in the 1.5 to 2 turns region. If it's richening up in the 6-8K range, you probably need to lower the needle a notch too.

You really need to do plug reads when the bike is under load, at the correct throttle position for each of the pilot, needle and main circuits.