Stutters and spits fire past 8k

[vfrman]

I was out fiddling with my track bike today and got it running fairly well. It took a while to start. Picked up on the front cylinders first and then the rear came in. Once I got it fairly warm I was revving it on the stand to hopefully clear out some of the fuel that was hanging out in the exhaust. At first it wouldn't rev for shit, and then after a bit it would kick out some black smoke and then stutter and cough at 8k rpm. Almost sounded like a MotoGP bike when the TC is working.

I figured this was just because there was no load on the motor so I put on the helmet and went off for a trip around the block...on slicks with no tag or lights. The bike wouldn't rev past 8k under load either.

I just changed the plugs before all of this started. I have also had the carbs off and cleaned them and balanced them. There is no speedo connected to the harness but I do have some crazy looking box electronic thingy that is connected where the speedo used to be. The air filter isn't in the best shape.

OK, so here is what I think....

• The air filter could be choking the shit out of the motor
• The little box in the wiring isn't fooling the CDI about the missing speedo
• The carbs aren't set up correctly
• My offer to help xivila is phuking my Karma on my own bike

Any thoughts?

Oh, and one more question....does it matter how the coils are connected to the harness?

[porndoguk]

Have you checked jetting and needle height?

[bikemonkey]

How old is the fuel in it?

[alexandervf]

One question and one thought....
The question is, do you have an OEM (original) end can on the bike? (Probably not since it's a track bike, but i thought i'd ask).

And a thought, since you changed your plugs.
Might be a good idea to take them out and reinstall them. It makes me think that they are not fully bolted (seated), BE VERY CAREFUL though not to damage the threads, by the way, did you change the plugs with new ones or used?

Oh, and one more question....does it matter how the coils are connected to the harness?

I do not know if it matters, all i know is that the colored wire from your harness goes to the colored tab on your coil.

[vfrman]

Haven't checked the needles or jets. Assuming they are stock. Did check the float height and they were spot on.
Fuel is brand new, but it is Italian...so no guarantees there.
Can isn't OEM.
Plugs are seated properly.
I'll double check the coil wiring (I think I reversed the rear...)

Keep em coming!

I am going to put a K&N filter in to see what that does. If I can get it to rev cleanly I'll get it on a dyno to see what kind of A/F I have going on. According to Haynes, black smoke means running rich, and the first thing on the list in the troubleshooting section is the air filter. Could it be that easy??!

[Neosophist]

Has it ever run well?

Black smoke usually is the tell-tale sign of overfuelling..

The air-filter would have to be pretty shitty to make it that rich. Easy way is take the airfilter out and see how it runs (expect it to run shit, but a different kind of shit if that makes sense)

Are all your floats sealing? Mabye you've got a sticking float from messing with the carbs and it is flooding the engine... without removing the carbs tap all the float bowls a few times with the handle end of along screwdriver (poked thru the V)

[vfrman]

No. It has never run well. I scrapped this bike together from about two dozen sources....

The floats should be sealing. I wish I had a proper carb dip here to clean the carbs. I really think this is the problem, but I am in denial about it...

[Neosophist]

Well I assume you've already checked float heights, jets and everything are right and the carbs are on properly.

If it really is runnign that rich try it without the air-filter..

The one I replace on my bike was pretty black but it didn't cause the symptoms you had which is why I dont think it will be that, but remoing it all togher might lean the bike up quite a lot becuase of the extra air available and you can at least see how ti runs.

[vfrman]

Thanks guys. Correct me if I am wrong, but won't these bikes suffer if the speedo is removed...like not rev past 8k? I am pretty sure this is it. Bike ran strong as hell up to 8k.

[Neosophist]

Thanks guys. Correct me if I am wrong, but won't these bikes suffer if the speedo is removed...like not rev past 8k? I am pretty sure this is it. Bike ran strong as hell up to 8k.

They will missfire after 5.5k if the speedo ciruit is disconected and there is no ignition box bypass.