VM26SS Carbs

[GregT]

But the hole doesn't go through to the carb throat...
What you've got looks like a set of VM's I have here which does not use the pilot fuel screws - at all. The holes are just left blank.
The VM26's on GS1000's sold here in NZ didn't have the pilot fuel screws either.
Whether they are used may well be market specific. Try them as is and see what it's like.

[allojohn]

What was the original issue with these carbs?

[mike1414]

Greg that's what it seemed like to me, but I don't know what the fuel screws do, so I was at a loss. What do these fuel screws do exactly?

[mike1414]

John initially the bike just cut off as I was riding one day. It had been running ok when I first got it, then began after a month running relatively oddly, almost like not enough fuel was being supplied, but didn't smell lean or anything. The throttle response was inadequate, and it was bogging down on me by this time. I came to a stop light, it cut off even though I was holding onto the throttle, and it wouldn't start back. Naturally per these old bikes, I pulled the carbs and cleaned them per the writeup, and it starts and runs now with the airscrews at 1.5 turns, and though I haven't fully synced the carbs yet, something still seems off despite my bench sync, so I figured I'd look into this extra space.

[GregT]

Pull the fuel line off the carbs and run it into a container. Try the tap in it's various positions, checking that flow is good - and continues.
Try with and without the fuel tank cap on...What you describe sounds more like a fuel blockage than anything else.
Pull the tap off the tank and clean the internal filter too.

[mike1414]

I'll pull the filter and look at the flow tomorrow. Hopefully it is something as simple as that! That would make my day. I've made some adjustments with the air screw to get it running, and it seems like it should be something simple to get it the rest of the way, so it makes sense that flow is a simple way to start.

[allojohn]

What do these fuel screws do exactly?

The screws regulate fuel in the pilot circuit. It appears you have carbs of a different colour and don't need them! There's always something new to learn! Pretty odd.
As per Greg, check the petcock and filter for blockage and rust in the tank.

[mike1414]

Checked the flow today; "prime" the flow is great, "reserve" it dribbles out, and "on" nothing comes out, all of which I believe are pretty par for the course, right? The tank seems to be pretty good, there is no significant rust in there. So it looks like we're at least ruling out options now. It still seems to be a fuel related problem to me, though I don't know where exactly the problem could lie now. One finding that I forgot to mention could be significant, I don't know - though I have cleaned and rebuilt the carbs, when I open up the bowls, there is little-to-no gas in them. There are no leaks that I can identify, so that confuses me a bit. Thoughts?

[allojohn]

Checked the flow today; "prime" the flow is great, "reserve" it dribbles out, and "on" nothing comes out, all of which I believe are pretty par for the course, right? The tank seems to be pretty good, there is no significant rust in there. So it looks like we're at least ruling out options now. It still seems to be a fuel related problem to me, though I don't know where exactly the problem could lie now. One finding that I forgot to mention could be significant, I don't know - though I have cleaned and rebuilt the carbs, when I open up the bowls, there is little-to-no gas in them. There are no leaks that I can identify, so that confuses me a bit. Thoughts?

Recheck the float height - 24 mm. While you're in there, what size pilot & main jets do you have?

[mike1414]

The float heights seem to be on track. I actually already bought new pilot jets/mains --> pilots are 17.5 and my mains are 117.5, up from the factory jetting. It was running previously with factory jetting, I just recently upgraded them (the PO put 4-1 V&H exhaust and pods)

[allojohn]

The float heights seem to be on track. I actually already bought new pilot jets/mains --> pilots are 17.5 and my mains are 117.5, up from the factory jetting. It was running previously with factory jetting, I just recently upgraded them (the PO put 4-1 V&H exhaust and pods)

I found 17.5 pilot a bit rich and went back to 15, but who knows what's happening with your pilot circuit since you don't have any and don't appear to need pilot screws. I wonder if the holes were blocked off and your cleaning them opened them back up?

Low fuel level in the bowls is down to greater evaporation because you have pods.

I hate to say it....but you may have to dip the carbs again to get this sorted. 24 hours for each carb.

[mike1414]

I guess it would absolutely be worth it to trial/error my 15 pilots and/or 107.5 mains in different combinations. But MAN! Dipping again sounds like a nightmare; although I already haven't been able to ride it for 2 months, whats another week or two I guess, right? I'll do a little experimenting and then see where that takes me, then dip again as needed. Makes sense with the fuel/bowls though, I didn't think of that.

[mike1414]

Could it be an issue of me having to go larger on my mains?

[allojohn]

Could it be an issue of me having to go larger on my mains?

I run 15 pilot and 117.5 mains on V&H 4-1 and K&N pods.

[GregT]

I'd still be looking at the tap. Check it functions in the on position by sucking gently on the vacuum line - running the fuel into a container.
I'd also let it run in the prime position for maybe a minute. If for example you've got a blocked tank vent it won't show up immediately but only after pressures have dropped in the tank.
The little to none fuel in the bowls is strange...