Carbs?

[Chopped HS]

Gentlemen,
Here is what I have. 81 XS 650 with new stock cam and straight pipes. VM 34 Carbs with 190 main jet. I just put the motor together after putting in the new cam. Before the cam change the bike ran fine. after the swap I started the bike (one kick) and broke in the cam for 15 min at about 2000 rpm. bike ran fine. after I turned off the bike the carbs were dumping gas out of the over flow. Instinctively I pulled the bowls cleaned them and lowered the floats a little bit. After that the next time I started the bike it was only running on the right cylinder. took apart the carbs and adjusted the floats back to where they were. Started the bike again and it was only running on the left cylinder with popping on the right. Messed with the floats again and got it running running rough but when I took it out it goes and runs on both cylinders above 2500 rpm, rough and popping below that. took it apart and raised the floats again and now I'm back to only running on the right cylinder below 2000 rpm; it does pop and kick in intermediately! I checked the spark and it looks strong. I put new plugs in it as well. Does any body have any suggestions. I have been adjusting the carbs mirroring each other each time. Thanks!

 

[XSLeo]

You can't fix bad float valves by adjusting the float levels. Take the carb off the bike, pull out the floats and clean and inspect the float valves for damage. They may just be dirty.
If the float valves are dirty the rest of the carbs probably are too. Clean the carbs while you have them off.
Reset the floats to spec. Test for operation. If they still leak, replace the float valves. Reset to spec.
Once you get the float valves to work the bike might run better.
www.amckayltd.com/vm34-36.pdf is a carb guide for your carbs. Readit, print it out and read it again. Between that and the Sudco book you might get tose carb to work.
Leo

 

[Chopped HS]

Thanks for your advise xsLeo. I would assume that you feel that it is the cabs as well?

 

[grizld1]

Right, Leo; and here are a few questions for you, HS.
1. If your bike was running so well before you stuck a new, stock camshaft in it, why did you install the new, stock camshaft?
2. Did you use a fatass Athena or XS Performance head gasket (both are .013" thicker than OEM)?
3. Did you check valve timing on the new camshaft with a dial indicator and degree wheel?
4. Do you know what the correct float level range is for the VM34, and did you set float levels within that range to a tolerance of +/- .005", equalized on both float arms of both carburetors, measured at the point of contact with the float pins?

 

[OakBehringer]

Check that your float levels are even with sight tubes. It's the only way you can be sure.

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[Chopped HS]

Right, Leo; and here are a few questions for you, HS.
1. If your bike was running so well before you stuck a new, stock camshaft in it, why did you install the new, stock camshaft?
2. Did you use a fatass Athena or XS Performance head gasket (both are .013" thicker than OEM)?
3. Did you check valve timing on the new camshaft with a dial indicator and degree wheel?
4. Do you know what the correct float level range is for the VM34, and did you set float levels within that range to a tolerance of +/- .005", equalized on both float arms of both carburetors, measured at the point of contact with the float pins?

Grizld1,
I changed the cam and rockers because the genius that I got the bike from decided to put in an oil pressure guage and drilled thru the oil passage into the well. My top end didn't get any oil. Of course he "never bought a guage" and plugged the hole. I know the bike ran because after I put it together it fired on the first kick and I broke in the cam with out any problems; after I shut the bike down is when the over flows started pouring. Not thinking it through, I messed with the floats. I couldn'nt find anything on the float specs other htan the manual said don't touch them. Oh, I used the XS head gasket and I just installed the cam according to the marks. I think I got the carbs back to where they were, but now my coil is giving weak spark. I thought that building a bike for a while would be less problems than a hot rod, oh well.

 

[grizld1]

What VM manual told you not to touch float adjustment? It's not one I'm familiar with, that's for sure! Float level range for the VM34 is 23 mm. +/- 1 mm. from the surface on the carb body where the gasket seats to the point on the float arm that contacts the float pins. Equalize the height of the float arms first, then set level by adjusting the tang.

 

[Chopped HS]

Thanks grizld1, I appreciate the info!

 

[Chopped HS]

Update
just figured out what the problem was. After beating my head against the wall over and over, I took one last look at the VM manual and relized that the carb slides were in backwards (opposite carb). this created more pressure thru the pilot system and was flooding the bike. Thanks again for all your help!