I just changed the main jet in my rancher to a 135(up from the factory 130) primarily because of suspected lean running when cold.
(I also returned the pilot screw to 1 3/4 out from a fresh start on that setting.)
Anyhow it certainly changed a couple things.
1. Full choke really over does it now- sputters and skips [rich] on full choke cold start. (Is that normal for such a change in honda's choke behavior?)
2. The idle position is about a half turn "open" from where it was to maintian idle speed.
3. I've had it die from idle speed a few times when given a straight throttle punch. ( perhaps tommarrow I can catch wheather it's sucking a big glob of fuel(black smoke)- if it is[rich] do I lower the jet needle a clip position or so? )
4. Related to three- does tuning with the jet needle height affect WOT cruise mix or does it merely affect partial throttle conditions
5. It [135 jet] frankly had little effect on power, but then it wasn't paticularly cold this evening. Lower end torque is up somewhat the front end is easier to raise on level ground-although not livlely enough to worry about going all the way over without a log or something.


My Notes: Forgive me for not leaping with joy, the job was a pain in the rear, could the process be simplified by loosening the isolators, getting a bit of cable slack hitting some armor all or wd40 in there and just turning the carb 45 degrees or so to get at the float bowl? How do the few mechanics out there get it done without nicking customers 100$

 

I don't mean to sound critical but what was you trying to acheive by going up on the main? That isn't going to have anything to do with your cold starting problems, and is not going to give you any more power. On a four stroke engine it takes a little more a jet change or a jet kit for that matter to get any gains. You have a bigger problem now than what you started with. My advise would be to take the thing to your dealer or someone you trust with the job, and have everything set back to the way it was, then THEY can fix your cold start problem. You are gonna end up paying more for this than it would have cost you if you just took it in the first time. As far as the bogging is concerned, that's from fooling around with your air mixture screw. Going up as small as you did, that wouldn't have anything to do with it. Get your settings back to stock and you can start on a clean slate. KNOWSALOT.

 

Yep, Main jet is full throttle only.. but only a .5 increase wont hurt... sounds like your air screw is the prob, I would put it back to factory and call it good. If you dont know what factory is keep trying and rember that only a 1/8th turn is quite huge for a airscrew and also rember the following:
idle: airscrew
1/8th to 1/4 throttle: Piolet jet and Needle possition
1/4 to 1/2 throttle is needle jet and possition
1/2 to 3/4 is needle and main jet
3/4 up is mostly all Main jet ( and never should be floored on cold engine)

 

I should have specified that I'm not talking about cold starting or cold engine... I'm talking about ambient tempereture, you know for when cruising at temperetures below 20 degrees F or so. The bike would run slightly slower at cruise than when the ambient temperture is at say 60 degrees. Tire pressure being equal, and differential oils warm- the increase in power from lower ambient tempertures usually makes up for increased air drag. But that's not what was going on, so I increased the main jet for WOT cruisiing, suspecting a lean WOT condition.

edit added: This bike has no cold starting trouble and I know exactly where the factory settings are/were. I also have been working on engines to some degree or another for fifteen years or so, but have very limited experience with atv/motorcycle carbs.