Running lean, suggestions

[SpaghettiOs]

I have a 60mm Mikuni carb with a pod filter attached to a 2 into 1 manifold, also straight exhaust. It runs strong and has plenty of power but is too lean, white/grey smoke out of exhaust. I can't seem to find a local place that can suggest the correct main and pilot jets and all that stuff to get it to lose the smoke... Help me out, anyone running this type of setup?

 

[crazyorigin]

Smoke to me sounds like bad rings. If its lean just start bumping up your main jet until it starts running better.

 

[SpaghettiOs]

I've had it adjusted every which way, smoke gets worse or a little better but never gone. Motor is completely rebuilt.

 

[crazyorigin]

Did you swap out the actual main jet? Adjustments on the needles will not effect your main jet setting, that can only be adjusted by swapping jets or drilling out the one you have which I wouldn't recommend really. Find a jet kit and tinker with that, I doubt you will be able to find some one who can tell you exactly where you need to be, carb tuning is a lot of trial and error.

 

[NONclow]

Welcome! Not trying to be harsh but how 'bout an intake "manifold" without a pair of abrupt V bends in it?

What do yer plugs look like?

 

[SpaghettiOs]

I haven't tried changing the intake... here is what the plug look like after running for 20 min or so also I have changed both the main and the pilot jet but I only bumped them up to the next one not knowing exactly how much to jump.

 

[crazyorigin]

I would keep bumping up the Jets until the plug looks nice and light gold colored. Is there any hesitation or dead spots in your RPM curve while riding?

 

[SpaghettiOs]

no, the bike pulls strong and hauls butt. Ill see if I can find a jet kit and keep going up.

 

[rybeatty]

Yeah I'd also get a different intake. That thing can't flow very well

 

[TwoManyXS1Bs]

White smoke usually is oil. Black smoke is usually rich. The plug looks fine to me. May want to break it in a little more. A 60mm carb would be almost 2.5" throat, you probably have a 34mm or a 36mm...

 

[scabber]

I would trash can that setup . Your plugs are not indicating a lean condition. The white smoke as TwoMany said was an indication of oil smoke is correct. That also means you could be washing the cylinders and ruining your nice rebuilt motor. Put a good set of carbs on it.

 

[Tomterrific]

I see someone has already mentioned a rich mixture of gas washing the cylinder walls of oil. Hence, the gray smoke. Black from rich, white from oil.

Tom

 

[gggGary]

Yeah, what size is the carb really? plus what ever the plug looks OK. Sorry to say that rebuilt doesn't always = right. I might try some baffles in the exhaust. Never heard of an XS that ran all that well with unbaffled straight pipes. reversion, back pressure what ever, the engine can probably pull raw mixture right through to the exhaust without some baffles.

 

[CDNTX650]

Get rid of that intake....joe wiseguy used to make a nice one with very smooth tracts. Teecat made it work.

 

[ippytattoo]

I have to agree with what has been said already plug looks good to rich (if that was only 20 minutes or running). The black section on the frame behind the exhaust says you are either running rich or burning oil. White smoke usually means burning oil. Did you do the rebuild, did you buy it "rebuilt" or have some one else do the rebuild? How long ago was the motor rebuilt? What kind of break in was done?

 

[SpaghettiOs]

sorry guys, I didn't get any messages there was new responses on here... here's what I have so far. The "new" coil was bad and replaced but the bike is still running poor. the plugs are both black now and it will rev high then bog and die also still starts hard. the engine was built and broken in professionally but not with this intake/carb setup. She ran just fine like this maybe a slight black rich smoke until the coil bracket broke and ever since then it have been down hill. Can't figure her out.

 

[SpaghettiOs]

also the carb is a Mikuni vm38 with 35 pilot 200 main

 

[650Skull]

Imagine how the air flows through a carb bolted straight onto the motor. There should be a min, (but some as a necessity), of turbulence to mix the air and fuel to an even consistency

Now look at that manifold and imagine how the air is flowing through that into the motor. The turbulence would be phenomenal and it is trying to draw air through that small restricted filter.

Standard BS36 CV cabs had a Max main jet of 135, and your running a VM38 with a 200 main.