VM26SS Carbs

[mike1414]

So I sucked on the vacuum and gas flowed well from the "on" position. I changed my pilots to 15, and after trial and error with the air screw, seemed to find a range that somewhat works. As I was experimenting with the outs and ins of my air screw, I heard what sounded like an open vacuum port, and further investigation took me to the picture below which is a vacuum port coming off of the block between carbs 1-2. I plugged it up with my finger, and the bike actually seemed to run quite well. What exactly is this vacuum port? Typically I have the vacuum from my tank connected between carbs 3-4, so I'm not sure what this one is. Thoughts?






I know that it's very blurry, but you can see the lost coming from the top left middle and the opening in the center. When I took my finger off, it sputtered and then stopped, throttle response was gone. When I plugged it up, it all came back

[GregT]

That's the stock vacuum takeoff. Between 3 & 4 is something done by a PO. Cap one of them....

[allojohn]

That pipe is in a weird spot! Where does it lead? The vacuum to the petcock comes off carb 3, not the vent between 3 & 4 - the vents on carb 2 & 4 should run over your pods into open air. Carb 1 has no vent. Is this how you're set up up or are there other strange things on your carbs?

[mike1414]

The pipe-type thing, which has some suction to it, comes off of the bottom of the part of the block that connects to the intake boot of carb number two. It points downward at about 7 o'clock towards carb 1. The PO had the vacuum line connected to the vent of carb 4, so I will switch it to carb 3. But it still begs to question what exactly is this thing coming off of the bottom of the block/carb 2?

I tried to start it up today (with the vacuum from the petcock connected to the vent between carbs 3/4) with the pipe off of the bottom plugged, and it didn't want to seem to stay running. It started with choke and, once it heated up, revved up to 3k with popping and smoke. Seemed to run a bit better yesterday, but maybe I just have to adjust my air screws a bit better.

[allojohn]

Connect up the petcock vacuum to carb 3 and things are going to start getting better. That pipe thingy looks like it's the connected to vacuum sync port and must be plugged, there should be a screw in there not a hose. You better check the others as each intake has one. Your bike will never run right with it sucking air in freely.

[allojohn]

[IMG][/IMG]

This is the vacuum sync port with the screw plug.

[GregT]

For what it's worth that pipe is in the correct position for the factory vacuum takeoff for VM26's without idle mixture screws.
When the factory deleted the pipe from #2 carb boot they put the vacuum takeoff on the LHS of #2 carb.
Given you've got early type carbs, I suspect there is actually no vacuum takeoff on the carb bodies and you're hooking a hose up to the carb float chamber vents.
I'd try it with the petcock vacuum line going to the pipe under the inlet port - and check when it's running if there's a vacuum at any of the carb breather pipes.

[mike1414]

Well put, fellows. Well put. Unfortunately I fly out of town for the weekend, so I'll be anxiously awaiting getting back to working on it next week. I'll be back with an update once I'm back to town, and I'll give each suggestion a try and see what works best. Can't wait!

[mike1414]

Alright guys, so I got out to work a bit. I changed over to the vacuum port between cabs 2/3 and it made a seemingly significant difference. With the air screws 1 3/4 turns out, 15 pilots and 117.5 mains, it ran surprisingly well. Response was good, but slight popping and smells rich. I'm sure with a vacuum sync, though, I can fix that. A weird new occurrence, don't know what the issue is. I went to take it for a ride, clutch pulled all the way in and down shifted from neutral to first, it bucked forward and cut off. Never done that before, not necessarily because of me having been working on my carbs. What could be this issue, and I assume that a good vacuum sync will solve the rest, yeah?

[mike1414]

So today I went on another ride to check the surf, short ride, just to see how she'd do. It's definitely still running rich. You can smell the gas burning, the throttle is shoddy at first turn, there is slight popping, it's idling around 2000rpm, and my plugs are all black. The reason that I initially started working on the bike (outside of it eventually having stopped running) was because my V&H 4-1 began bluing at the manifolds. So - my bike has this exhaust set-up and K&N pods. The PO had it factory jetted. I started tweaking with the air screws, no go still. I went up to 117.5 and 17.5 - gas was leaking out of my overflow tubing. I went back to 15 pilots, and it's better, but I still have slight leakage out of the 4th overflow tubing, and the drain plug on 1 is wet (I need new drain plugs, but still). My carbs are only bench synced, not vacuum synced, but is this all it is gonna take (vacuum syncing them) or does it sound like I still need more trial and error with jetting? Can I just wire brush my plugs or should I start fresh? Anyone?

[allojohn]

If you're overflowing gas, the floats are sticking which could explain why you're running rich. On another note did you check where the e-clip is on the needle? It needs to be moved down 2 positions from stock.

Edit:Also, the petcock could be failing causing gas to run down the vacuum to carb 3.

[mike1414]

John, I moved it down 1 position which seemed to help slightly. I will move it down one additional position. Why would this make such a difference, though, for carb 4 when none of the others are leaking (aside from the slightly wet drain on 1)?

[mike1414]

I realize that I worded that poorly. Only my carb #4 drains from the overflow, but each of my carb's float heights have been set to stock since getting the bike. Should I set each float height to -2 to help the rich running issue (only slight "wetness" around my carb #1 drain plug with gas)? Why is it that just now they have begun to give me problems? I also feel as though I should make it known: the bike will start with the choke, but I immediately have to close it and give it slight, but continuous throttle up to a couple thousand RPM's to keep it going. It will then idle relatively normally at about 1300 or so until I ride it, it then just up to 2000 or so. I know this further confirms my running rich, but, does the choke issue mean anything else in particular?

[allojohn]

I realize that I worded that poorly. Only my carb #4 drains from the overflow, but each of my carb's float heights have been set to stock since getting the bike. Should I set each float height to -2 to help the rich running issue (only slight "wetness" around my carb #1 drain plug with gas)? Why is it that just now they have begun to give me problems? I also feel as though I should make it known: the bike will start with the choke, but I immediately have to close it and give it slight, but continuous throttle up to a couple thousand RPM's to keep it going. It will then idle relatively normally at about 1300 or so until I ride it, it then just up to 2000 or so. I know this further confirms my running rich, but, does the choke issue mean anything else in particular?

Forget about moving the e-clip, moving it down makes running richer - you don't need that right now. If everything was good with your carbs it would make sense.

You have too much fuel in the bowls, so it's running too rich. If the float heights are correct and they are not sticking (catching on the gasket) then the needle valve is failing, letting excess fuel into the bowl.
Did you check the petcock? Suck on the vacuum and hope you don't get a mouth-full of gas!

[mike1414]

Haha I did in fact suck on the petcock, only enough to make it work, luckily not to give myself gas poisoning. The vacuum from the petcock worked, fuel flowed when I sucked.

How do do I go about checking whether or not the floats are stuck?