Carbs are off, I don't want to miss anything!

[Brian.]

Good afternoon all.

I can't get my 98 M750 to run properly.

Carbs are balanced, and it is happy at tickover, and will even hold a very slow tickover steady; but I don't leave it that low, just a normal speed.

The problem is with slow speed riding, even medium speeds. It is seriously "kerchung kerchung kerchung". At bigger throttle openings it pulls really strongly, 60mph in fifth gear and wind it open, it's great. Anything other than a big throttle opening, it really is a pig. Or a kangeroo would be more accurate.

It soots up the plug in the vertical cylinder. Dry dusty soot, not oily at all.

Fuel consumption appears to high. Mid 30s on mixed rural riding.

I've checked the timing with a strobe, it appears bang on. I've put some of those neon things between the plug caps and the plugs, it appears not to be missing a single beat spark wise.

I've swapped the plugs over, and then the ignition boxes, the soot stays with the vertical plug and it still runs the same.

I've done a compression test, it's within the tolerances, and the two cylinders are very close pressure wise, 4psi apart iirc.

So I've taken the carbs off, only taken the float chambers off so far. Someone has been in there before, I can see where someone has removed the starter jets.

That's all I've done so far.

I suspect pilot jets and or pilot galleries have muck in them causing the bad low speed running, and wonder about the float heights or needle valves causing the sooting up of the plugs? The carbs or not overflowing, it is not smoking from the exhaust, but the ends of the silencers is quite sooty, as you would expect I suppose.

I've done carbs before on various bikes, mostly Keihins on older Jap fours, the Mikunis on my GS750, and Dellortos on Laverdas. I've not done this particular type of carb before. ***The carbs are identical to the ones shown in the Haynes manual, so I am assuming now that they are Mikuni BDST 38mm CV carbs, not as I wrongly described them when I first posted this. ***

I don't want to do all the work involved in taking the carbs off and refitting them, and it still not be right because I've missed something needing attention in the carbs that may be obvious to you experienced Monster owners but I would miss, out of ignorance and inexperience. I really do not want to reassemble the carbs, and reassemble the bike and find that I have missed something out that I should have done

Have any of you had the running symptoms I've described in the past? Is there anything at all that I should check?

Would you go as far as completely gutting the carbs, have them ultrasonically cleaned and rebuild them with all new jets and rubber bits etc? Or would you be more inclined to methodically work through to find the actual fault or faults that is causing this? Though obviously replacing O-rings etc as necessary

My bike has done less than 15,000 miles.

Sorry it's been a long-winded posting, but I wanted to give as much background as I could.

Thank you for reading all this; and any help, guidance, advice anything at all, will be very much appreciated.

Thank you!
Brian.