The RF9 quandary

[F5 Dave]

Ok here’s my bind

The RF started stumbling a bit, low revs sort of thing. Sometimes runs clean, but more recently is poppin onto 3 it appears.

Had changed the emulsion tubes & fitted a factory jet kit. Ran sweet & was running better than before on the dyno.

Then this problem rears up a few months later.
GSXRs like to kill coils, so I threw some Honda ones in. Ohh heck some of the plugs are pretty sooty. Replace.

Happens again. Check float valves, appear fine, lower float settings a mm. Put in one set hotter plugs. Plug 1 & 2 are sooty, 3 & 4 are fine.

Bike has petrol pump so sidestand side is irrelevant as tank not pressure feeding in that side when parked or nufink. Both coils are affected so can’t be one coil or the ignition. As a precaution change the plugcaps for some spares I have even though the measure up ok & can’t see any tracking. Swap out sooty plugs for two good ones.

Measure compression for the sake of it. All pretty much ok & the cleanest plug is the lowest comp. Bike doesn’t use oil & a rev produces nothing visiable but followed by a couple of big revs produces some black smoke. Little rich, but no blue oil smoke. Oil rings should be fine, but that would be an oily plug, not sooty. CV carbs do get a little confused like that anyway & did it on the dyno when running fine.

Diaphragms should be ok as was doing the business on the dyno & that wouldn’t make a rich mixture. A rev without the airbox on shows they all move.
Air-filter wouldn’t favour sides.

Ride into town & back, same again. This is getting worse.

Plugs sooty, clean up, take carbs out again & pull out all the float jets, all appear new. Plastic float jets seats appear fine. O-rings fine. Swap left carb float, jet & needles for ones on the right. Attach clear tube to floats 1 & 4, open drains & check fuel level with tube ‘u’ held against carb. Both are the same, yet one side is clean plug, one soots. Start engine to see if pump overpowers, no change. Rains yesterday so don’t try it out to see if the problem swaps.

This is getting frustrating. But I have thought of the thing I haven’t checked & is possible. I will check it when I get home. Rep points if you can guess it. Promise of a beer if you come up with the reason if this isn’t it.

Read above before you post.

[riffer]

Hmmmm...

Have you accidentally half-pulled the wires out that lead to the coils, and they are intermittently coming loose? You know, the ones just behind the steering head?

or (hedging his bets here) have you got water in these leads?