Seeking soot free spark plugs

I have recently rebuilt cylinders, pistons, rings, head and valves on my early 850. I'm running a singe 34mm Makuni and getting sooty plugs. It runs just fine on the top end but has a little lull on the bottom end especially if not completely warmed up. Should I stop where I am since I feel I am definitely not running too lean or are clean plugs something that I should try for?

Clean plugs is a good target, the sooty plugs indicate richess which could cause premature wear, the excess fuel will be washing the oil off the cylinder walls. You need to get the bike turned by a Mikuni expert or buy a good tuning manual eg the one by Panic available from the Victory website, you don't want to go too lean and be in a worse postion.

Got an identical 850 set up. VM34 works well. Modern fuel can be sooty but avoid excess leaness. Try this VM34 spec:

Main Jet 240

Needle Jet P2 or P4

Needle 6DH3 or 6DH4

Pilot Jet 30-35

Air Jet 1.0

Slide 3

Go smaller on the main jet if you are at altitude above 3,000ft

Also try NGK Irridium spark plugs, almost clog free and trustworthy.

I do run the Irridium plugs. I will compare your Makuni recommendations to what I am running now. Thanks.

also look at the float level as it can make it rich if it is to high.

windy

Are there significant setting differences with a VM34 on a 750 vs an 850, does anyone know?

FWIW, if you're running the stock settings that came with the Mikuni, maybe you just need to experiment with leaner settings.

My experience with two sets of Keihin FCRs (great carbs, BTW; one set was on a Norton, memorialized in far too much detail in another thread, and one on a Ducati) was they came jetted WAAY too rich - and both came "set up" for the intended applications by folks who know what they're doing. Perhaps the thinking is that applications may vary and too-rich settings may waste some fuel, foul some plugs, but too-lean settings may trash an engine (and worse).

Dunno, but I'd start leaning out mains, needle-clip settings, and idle mixture screws (not all at once or you'll never keep track of what did what) and keep checking your plugs, mileage, and performance.

Good luck. - BrianK

When are yiou checking your plugs,it is no point checking after riding back through town and puttering into your garage,if its a bit spluttery and erratic before its up to full temp but does every thing right when it hot then it must be very close to being correct. their is a fair bit of mikuni info on this forum. The only thing I have seen most people change is to use a #3slide although a#2.5 is easier when cold. Cruising at 60-70 mph you are still using the slide so it would make sense to get that as lean as safetly possible.