VM36 Float Issue

[SlowMaintenance]

Hey guys, running a 2-1 intake with a Mikuni VM36. Carb is brand new, I've cleaned out the jets several times and can see through them. Brass as follows

22.5 pilot
190 main
6f9 needle with circlip middle slot.
159, p-8 needle jet.
Mix screw out 3/4 turn from seat

Was having a tough time getting it to run reliably so I figured I should check the float level since many say that really should be step one. Here's what I found

Well that's no good! Fresh from the factory, clip isn't even hooked onto the float arm so when the carb is in it's normal upright position, those brass arms would just hang down atop the floats. I'm not sure why exactly that's bad but I know it's not meant to sit that way. Also, the factory setting should be 17-19mm float height, as you can see it's nowhere close to that. I found these photos online of what it should look like, with a handy reference being that the brass arms should point to the upperleft corner of the pilot jet hole. See photo below

I was excited to get this adjusted, but unfortunately I hit another snag. The pin that holds the float arm on refuses to budge. I can't get it out at all. Tried tapping it gently, needlenose pliers, nothing. 100% stuck. Other side is a flat head like a nail, so it can only go out one way. Any tips for getting this loose?

I did what I could to bend the tab to the correct position and did manage to get it pointing to that upperleft corner. However, getting the little clip around it was really a challenge. I think I got it on there decently, but I had to fuss with it a bit to ensure it didn't limit the travel of the float arm, would have been a lot easier if that damn pin would come out!

Overall, I got it back together and tried to start the bike again but an electrical issue seems to be throwing yet another wrench into the mix here. Hoping to test this thing soon to see if my float fix did the trick. I'm THIS close to throwing this whole carb and manifold in the trash and getting that TC Bros VM34 kit.

 

[robinc]

Did something similar on a BS34. Put a small socket over the flat head. Use a small c clamp with a smaller diameter pin and slowly push the stuck pin into the socket. Might help to have an extra pair of hands helping hold everything together.

 

[SlowMaintenance]

Can you expand on this a bit more? I'm not sure I understand what you're describing.

 

[robinc]

Put a small socket against the post over the 'nail' head large enough for the 'nail' head to go into.

Then use a small C clamp, one jaw on the socket and the other with a pin between the jaw of the clamp and your float pin.

Slowly turn the C clamp screw and push the float pin 'nail' head into the socket and out of your way.

It helps to have an extra pair of hands holding all this together.

I think gggGary has illustrated this for BS34 carbs in other threads. Maybe try a search for ' stuck float pin' or something like that.

 

[robinc]

IIRC Fredintoon and grizld1 also start to remove that float pin using a spring loaded centre punch.

 

[SlowMaintenance]

Ohhh I get it now, thank you for clarifying. The socket is just there to allow the nail head some space to move out without hitting the clamp.

I will give this a try.

 

[robinc]

You got it Pontiac! No worries. Good luck.

 

[SlowMaintenance]

Once I do get it out though, and I'm able to set it a little easier, where exactly should that silver clip be set?

I understand the float level is set with the carb inverted, but what level should that clip be set at?

 

[robinc]

Sorry man, I can't help you with that. No experience with VM36's. Just a little with BS34's and a little more with BS38's.

One of the carb guru's will chime in here and help you out.

 

[SlowMaintenance]

I found this photo but I can't see much beyond the fact that the clip is indeed over top of the brass tab

 

[grizld1]

Just hang the the needle on the tab with the clip, as in the photo. To quote John Keats, that's "...All ye know, and all ye need to know."

 

[SlowMaintenance]

She's alive again! Was having some issues with it coughing when kicking, and a quick google search showed that that only happens when it's not getting enough gas. Turned the mix screw to 1/2 a turn out and she roared to life again. Smooth as ever. Timing lined up beautifully with the battery. Switched to a capacitor, runs just as well though the headlight is a bit dimmer at idle (just as bright when RPM's rise).

Now just need to find a solution for my fuel line which is leaking a bit. Unfortunately, my petcock and inline filter are 1/4" but my carb is 5/16" and I just couldn't get my 1/4" line to slip over it with the carb attached and really didn't want to take the carb off after finally get it running.

I'll try again tonight and if I can't make it work, I'll wrap some tape around the fuel filter outlet and switch to 5/16" hose on the lower half of the fuel line.

 

[grizld1]

Glad opening the mixture screw gave you better results, but the improvement didn't happen because it solved the problem of "not getting enough gas." The mix screw on a VM carburetor adds air to the pilot mixture as the screw is turned out, making the mixture leaner. This is opposite to mixture screw operation in the OE BS series carbs, in which turning the mixture screw out admits more vacuum to the pilot jet to pull up more fuel and richen the mixture. Rule of thumb: on carbs with the mixture screw located forward of the slide tower, turn out to richen. On carbs with the mixture screw located behind the slide tower, turn out to lean. Getting 1/4" line to fit the fuel barb on a VM carburetor is a litttle difficult but not impossible. Use Tygon or other high grade plastic line, heat it a bit, stretch it a bit with needle nose pliers, and apply a dab of petroleum jelly (Vasolene).

 

[5twins]

I don't think the style of wire clip on your particular float needle seat was made to hook onto the float arm. It's just there to hold the needle into the seat.

 

[SlowMaintenance]

Glad opening the mixture screw gave you better results, but the improvement didn't happen because it solved the problem of "not getting enough gas." The mix screw on a VM carburetor adds air to the pilot mixture as the screw is turned out, making the mixture leaner. This is opposite to mixture screw operation in the OE BS series carbs, in which turning the mixture screw out admits more vacuum to the pilot jet to pull up more fuel and richen the mixture. Rule of thumb: on carbs with the mixture screw located forward of the slide tower, turn out to richen. On carbs with the mixture screw located behind the slide tower, turn out to lean. Getting 1/4" line to fit the fuel barb on a VM carburetor is a litttle difficult but not impossible. Use Tygon or other high grade plastic line, heat it a bit, stretch it a bit with needle nose pliers, and apply a dab of petroleum jelly (Vasolene).

My mistake, should have mentioned that it was at 1.5 turns out prior to this, letting in a little too much air as I saw the black plugs and thought it must be too rich. That was probably the fault of the incorrect float level being attributed to the pilot jet. Another reason to always check the float first.

Twins, that's interesting. It really wasn't close at all and took quite some bending to get it over that float tab. Maybe it wasn't needed? I was thinking about this because if those brass arms just ride on the floats as they raise up, and the tab is the only part that makes contact with the needle, I'm not sure why it would matter if the arms hang down further.

 

[SlowMaintenance]

One other question though as I was wondering about the petroleum jelly, would that make it more likely to slip OFF the barb as well?

 

[gggGary]

One other question though as I was wondering about the petroleum jelly, would that make it more likely to slip OFF the barb as well?

Not if you use the required clamp.....

 

[gggGary]

A few random VM pics from when I was thrashing on madness. My issue turned out to be the float valves. there are at least two different types of floats used.

 

[SlowMaintenance]

Need me some of those clamps. To autozone!

 

[SlowMaintenance]

Ah, so the clip does not need to go over the tab. I wonder if I should go back in there and remove it.