To all who had to endure my endless conjectures about the idle adjustment. IT WORKS LIKE A CHARM ! ! ! ! Thanks to those who recognized this in the past. Now I just have to put in a little leg work and corellate temperature with throttle slide opening. On a warmed up bike that will be in part where it sets idle and also the number of turns of the screw. As in it's 6o degrees
I just tried adjusting the throttle slide height with the enrichment circuit on (before trying to start it from dead cold). Many thanks to those who use that as a method. Because...IT WORKS!!! of course you have to have the right mixture. Even the mighty Mikuni needs the right mixture. And that's affected by your screw that raises or lowers the slide to control idle. Two kicks. And before all the one kick guys chime in, I have not dialed it in yet. I need to correlate ambient temperature with the correct slide height. My thoughts: those guys who are currently in warm weather (and, yes, altitude affects it too) who like and are proud of a beautiful slow tick over will find the Mikuni pilot jet too rich. And those guys in colder weather who like a high idle will either have no problem or the enrichment circuit wont be strong enough. Scopeing this out by ambient temperature will be a long process. Once you start it, things have already begun to change. But at least I have a starting point and a direction. Now, maybe, my right leg will return to normal size.
It depends. When they say close the throttle you know they don't mean completely. Only down to where you set the height of the slide to get the idle you want. Say your best friend sets his idle 100 rpm lower than you. Does it matter whether you use the cable attached to the hand throttle to raise the slide to get that higher rpm or use the set screw to raise the slide? Of course it doesn't matter. But according to that imaginary friend AND MIKUNI your throttle is not completely closed! Yours is open a wee bit. So the advice from Mikuni must be taken with a grain of salt -- or at least considered in light of what opening the throttle is doing to the mixture. It is very sensitive and using the twist grip is not a very accurate way to affect the very small changes that will have large effects. But using the screw on the side of the Mikuni IS a way to dial in accurately a small but significant change in mixture.
You're probably right about that. I was just throwing out numbers. But I'd rather twist in the throttle slide screw a couple of turns, when the weather was warm yet too cold to start without some enrichment. And then turn it back out whe I got it running than have to replace the pilot jet. Now, there may be some fly in the ointment with this method, but, so far, it seems simple and fool proof.
What you say may be true. Several years ago I followed the jetting advice of a few on this site and Old Brits. Once running it runs/starts just fine. Just starting from cold is, or was, the problem. It was suggested here that the jet for the enrichment circuit may be too big. But that's not a screw in jet. It's a pressed fit. Maybe that's at fault, maybe Mikuni had a variation in there enrichment circuit jet. Who knows? At that point in this discovery process I thought through the enrichment circuit coming to the words from Mikuni that the throttle must be completely shut off if the enrichment circuit is to work "properly". And why is that? And why is it hard starting if you use the enrichment circuit when the engine is even slightly warm? Because the enrichment circuit is "one size fits all". Change even the set idle speed and things start to go off. One persons "shut off" idle is anothers slightly open throttle. I was also using a 900 rpm idle setting. Not good for tappets, I know. But I wasn't thinking about that. That would cause a slightly richer condition. And when I raised the idle speed it started right up. Hard to really know if I ended up with gas wet plugs like before because it ran. I'll bet there is a "flat" spot in the temperature related air/fuel mixture curve that the Mikuni engineers took advantage of to not add additional design complication. But none of this is an either on or off proposition. At what temperature do you switch from enrichment circuit to standard? It would depend on your particular idle speed setting, ambient temperature and altitude -- plus a whole bunch of small jetting and needle variations. All of which are still within a range that might be called normal. With a weak ignition you might notice problems. With a hot mag, no problems. At this point I have something that works, another knob I can fiddle with.
You've just advanced and enriched my knowledge (I think) Thank you
If it's running it's getting air. Maybe it's the cutaway on the slide. But pulling in all that necessary volume of air at even a few hundred rpm requires some kind of opening. And a heck of a vacuum draw. Just a reminder, different idle settings mean one man's "closed" is another mans "slightly open" and mother Mikuni says, "Close your throttle completely!" So are all those variations in throttle openings for different idle speeds irrelevant? Or are those necessarily open throttles still "completely closed"? -- or what? The questions are rhetorical.
The OP’s bike has a plug fouling problem that has manifested as a starting problem.
The term “closing the throttle” in imotoring speak means to put the variable throttle down to it’s lowest position. It always has.
I do understand that point. What I was trying to point out was the variability involved. And that changing this setting made changes in the ease of starting the motor on the enrichment circuit. That was more than likely due to a change in the air/fuel ratio. So, very small changes in slide height on the enrichment circuit had a large effect.
More to your point, I was trying to point out exactly what you said. The slide is always somewhat open. The bike does need air to run.
Just this one more post as I sit next to rattling clattering rumbling beast. I walked out, flipped the enrichment circuit on, turned the slide stop screw in 2 and 1/2 turns. One kick and it was running. After about 30 seconds raised the enrichment lever, turned the slide stop screw back 2 and 1/2 turns. Idle 1,500 rpm and smooth -- except for the rattling and clattering and rumbling. But that's what I bought it for. And, oh yes, to ride!
By the way that should have been 1,050 rpm, not 1,500 rpm idle