I was trying color tune but the bike kept acting really weird. At first it ran OK but would slowly stall with out choke. When i took it for a little ride to warm it up it ran great although i had to take off with choke on then i could shut it off. Then when i came back the engine would ra e up to about 3000 - 5000 rpm with choke on and stall with it off. I reset the mixture screws a few times to make sure that wasnt the problem and turned the idol way down the brought it back up to get the bike to a point where it would run. Later it was racing with our with out choke. Im gonna try getti g a better sync today and if that doesnt work, pull the carbs again and check to make sure the butterflys arnt sticking. Anywhere else i should look?

Classic sign of vacuum leak. Get a can of starter fluid and spray around the throttle shaft seals when it is running, if the idle speed goes up then you have found it. If the carbs are way out of sync that can also cause your problems.

I tried testing with a propane torch didn't get any out of the "ordinary". Got the carbs off right now. Going to go through them make sure nothing is plugged and really bench sync.

Be sure to "wet-verify" the float levels; that could also be part of your problem.

I did set the floats steady but will double check when I take the carbs off the bike.... again. Using starter fluid I found a very small vacuum leak. Will have to change boots and throttle shaft seals.

I was reading another memebers post and some one said something about stock jet size. This made me wonder if mine were stock or not. I looked it up and found that I should have a 110 main fuel jet and a 40 pilot fuel jet. For the air jets it should be 50 main and 195 pilot. What I have in mine is 107 for main fuel and 45 for pilot and 55 for main air and 195 for the pilot. The only one that is right is the pilot air and the rest seem out of wack to me from what I read on what they should be at. This could be a big part of problems.

These bikes are tuned low to meet emission standards right? When I order new jets, should I maybe order a size up? Or should I just go with stock?

Im 1257 feet above sea level if that matters at all too.

Go back to original settings. Once I cleaned, bench synced, and all the other fun stuff according to the book. I also had larger jets. Went back to stock, I ride from the 3500 ft level down to the 1500 ft level. Mine runs 42 MPG. I have it stock except a jardine 4 into 1, I only run my pilots at 2 3/4 to 3 turns out. I have been fighting this carb set-up for months. Good Luck . Be patient and most of all go back to stock settings and start there.

Check ALL your AIR Jets:

Air Jets are OPPOSITE from Fuel Jets.

Main = Smaller [o]
Pilot = Larger [O]

This Illustration is 750 Maxim:


When you make any adjustments:
Seal the Manifolds to the Head.
Bench Sync with the Throttles as CLOSED as Possible:
3X5 Card Strip, Business Card Strip, Resume' Paper Strip or Thin Strips of 35mm Film Negative.

Attend to any possible Manifold Leaks
Fill with Black Epoxy • Coat with several applications of Liquid Elect Tape • Shine with Black Nail Polish.

Vacuum Nipples seated & Air Tight

Cool thanks guys. Back to stock it is then. Im hoping changing the jets will solve most of my problems. gotta get that vac leak fixed too though.

Got the jets changed, throttle shaft seals replaced, carb boots repaired and it starts. Now it is only running on two cylinders (1 and 2). Before I pull the carbs to clean them.... AGAIN. Could this be caused by the sync being off? With the number 3 carb being the main one that you sync everything to, I figure that would be one that is running.

anyone?

Did 2 & 4 fire prior to carb cleaning? Are they sparking? Well -- What does color tune tell you is going on in there (2 & 4?????? )

? OT from your question, but someone will ask if you've done valve gaps

Stock jets should be #110 main and #40 pilot for the 650

Generally cold cylindres would be an electrical issue -- even way out of synch carbs should allow the bike toi run although poorly...

Unless you are providing NO fuel

So, use the color tune to see if 2 and 4 are sparking?

It was running on all four before I changed the jets back to stock. Put them all back together and on the bike and its not wanting to start and only running on 1 and 2 when it does start. I did check for spark too and it is sparking. Yes I did my valves and the floats and cleaned the carbs multiple times and rebuilt them. Im stummped.

Check float levels -- WITH THE CLEAR TUBE METHOD WHILE ON THE BIKE -- got fuel in those bowls? So, it's a fuel issue somewhere? -- go slowly, think carefully, and it sounds like you need to validate fuel level. But, regardless you'll have to pull em and double check all...

Maybe not - it may be weak spark, but I agree seems unlikely however, there is a way to test the strength of the "spark" -- got a manual?

I have the haynes manual. and the XJ CD. I opened up the drain screw on all four and there is gas in them. I really hope its not the floats. I had a hell of a time setting them the first time.