[LJRead]

The idle jet has a small opening in the bottom which is below the level of the fuel in the float chamber, so the mixture screw wouldn't cut off the fuel completely as the idle jet is continuous with the air inlet orifice for the idle circuit.  I guess some fuel is being sucked up through this small hole by air passing over the orifice.    When I turn the idle mixture screw in, it will speed up the idle as the fuel becomes richer in air, but it never reaches a stutter phase, so maybe you have something that I should check.  I probably should check the fuel level, but as I recall this is fixed by the plastic tabs connecting the inlet needle valve with the floats and wouldn't appear to be adjustable.  I will check it though.  Problem might be that I have no data on what the chamber level should be.

[clamp]

The fuel mixture setting screw for the pilot jet may not necessarily be fuel ,--it can be an air screw that controls air into the emulsion tube.

   However being able to move it right in or out without much difference shows something is wrong there. Is there a pilot jet in it.

  Is this a constant velocity or a slide,--has it a diaphragm?

    With a bit of work "Googling" you may well be able to find an exploded view of your carb. If you do , post it.

     A motorcycle carb works in 3 stages , we have to find out which stage is rich then its easy.

[LJRead]

I wouldn't say you could move it in or out (mixture screw) without much difference.  As I recall, it speeds up as you move it in (more air) until you get it right in, then it just stays the same as just before you reached the end.

It isn't really smoking now, just a balck haze really, and if you increase the throttle a bit, there isn't even the hze.  If you tweak the throttle from full off, you get a bit more smoke, then it quits, sort of like blowing smoke rings. 

It is a slide type of carburetor, not a CV.  There are two versions made by Dell'Orto, one has an air enrichment toward the air intake, the other has a mixture screw toward the manifold, mine is this latter type.

I did run it up a bit more yesterday, leaving it in second up to about 40 km/hr, then in third up to over 60 km/hr.  I really can't complain at all about the way the bike is running, in fact I wisdh it would always run this well (never wear out!).

And now it is really idling nicely, very slow without any pause, just thump, thump, thump.  Like that.  I'm thinking just to make sure I blow it out each time I ride by giving it some good revs, sort of blow any accumulation out, but the thing is, apparently the idle stage and the main pilot stage, before 1/4 th throttle sort of work together, and since throttle response is so smooth, I might be loath to put in a smaller idle jet.

Did some more adjusting of a general nature,  I'm becoming sort of a gentleman mechanic - not a serious one yet.  Just polish, then tweak and dither around.

[clamp]

If I move my mixture control screw I have only to go 1/2 a turn and the engine will stop.

     You must have a fast tick over there.

   Or are you increasing the tick over to max and then making final mixture adjustments? .

    If your not ,--you could,--it is a recommended procedure for some .

   Increase tick over to say 1500,- then adjust mixture of primary jet adjustment screw to achieve max RPM., then re set tick over. You should be on the nose there.

[LJRead]

Thanks clamp, I'll give it a try.  Today I'm building shelves.  Lived here for well over ten years and still have stuff scattered around - I'm ashamed.

What I need is a duck that builds shelves.

[LJRead]

Some time has gone by without a cure to my black smoke problem.  I had posted about this on the Yahoo forum as well as this one and received some ideas from people like Pete Snidal,clamp and others but still no cure.  I had sort of given up and since the amount of smoke was slight, had just gotten used to it. Maybe, I thought, it will go away after break in. Then I got a belated personal email from a gentleman named John from India.  He has the same Dell'Orto carburetor and suggested that it might not be clean enough, going through the steps I should take in doing the job properly.  He mentioned that some of the channels are narrow and tend to get obstructed.  Well, I had thought I did a thorough job in the cleaning, although I hadn't taken apart the choke mechanism.  John mentioned this so finally I again stripped the carburetor down and cleaned everything with paint thinner.  While I saw no obstructions, I simply flushed everything out and reassembled.

No black smoke at all !!!!

A couple of lessons 1) Dell'Orto carburetors (and probably others as well) must be kept clean and, probably, the first sign of trouble may mean a dirty carb. 2) I feel it may well have been the so called fuel enricher or choke that was the culprit, maybe a small particle of debris restricting flow at choke-off idle.  This seems logical because it would mean a too rich idle mixture.  Being used to simple choke systems without an orifice like this one, I just didn't suspect it as the problem, but think now it was.

Hopefully, end of story and a big thanks to a man named John from India!

[LJRead]

Here is a photo of the plug taken moments ago.  Before I cleaned the carburetor it would have been entirely covered with soot.  Maybe slightly lean now, but I think I'll run it that way for now and maybe clean out some of the soot residue. The plug temperature seems right on as judged by the heat band on the ground strap.

[clamp]

looks pretty good actually the 4 threads discoloured on the plug show a perfect heat range.

      I have heard tell that modern bio fuels these days make plug reading difficult and if one strives for a perfect straw colour that was once considered perfect one might be too lean.

        I would guess mine looks similar to that and I am happy with it. I dont want a hot engine and since I have raised the needle now to maximum to accomodate for my little mods on breathing, I no longer get tappet noise that I used to get on a hot engine.

     I now ride with my head held high and look at the passing trees instead of head down to the tank listening for noises and feeling temps.