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Discussion Starter · #1 ·
I know how much you guys love to have new content to read and new problems to solve and I'm sure you guys are getting to know how much I still have to learn... lol

Anyway... I have a "problem" getting the bike to idle when it's cold. One it warms up, no problem. Idles nicely around 1200 RPM. However the thing just won't stay running until it's at least partially warmed up. I usually have to sit on the bike with the throttle partially open (revs at about 1500) for a good two or three minutes before it can leave it to it's own devices. If I adjust the throttle stop screw to increase the revs this works, but then it's idling at about 2000 RPM once it heats up. I've also found that with the choke on, the engine just dies, so I've been having to skip that. I suspect this could be part of my problem.

Not sure if it helps, but I pulled the plugs yesterday and it looks like it's running a bit rich. Carbon build-up on the threads and a little on the insulator tip, but electrodes are a tan color.

Thanks (for what seems like the 20th time in two weeks),
Matt
 

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That's why you have a choke :lol:

My Honda actually does start and run well with no choke. But my W650 is cold blooded. I have to run with the choke half way on for about the first 5 minutes I ride it. It's because the factory jetted the bike on the bleeding edge of lean for emissions reasons. So in your case it's probably some of the same.. too lean and then the bike starts liking it better, the hotter it gets.

Could be due to too small of jets, plugged up fuel passages, improper float height, or misadjusted pilot circuits.

I need to say IF running with the choke on helps out, it's because your primary adjustment without the choke is too lean.
 

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Discussion Starter · #3 ·
I'm led to believe that it's actually running rich. Plug color is on the darker side and choke on actually kills the bike (unless I give it a good deal of throttle).

I'm just wondering the following:
1.) Is my analysis correct? Too rich?
2.) If so, why is that giving me problems when it's cold but not when warm? Shouldn't it be the opposite?

As far as choke goes, how am I supposed to use it without killing the bike? Other models I've ridden seem to have a mechanism that changes the throttle stop to increase engine speed when choke is on, but on my CJ360 the choke only seems to kill the engine and not really help at all... :(
 

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Yeah, if the choke makes things worse, you're too rich. Probably due to dirty carburetors or the float height being wrong or the floats taking on gasoline. If the fuel is too high in the bowls it'll run rich.

Not sure why it runs worse when cold than when heated up though. I've never had that happen. You'd have to figure out if it's truly running rich or lean. I own a colortune spark plug that I use with my british car, but would be useful on a bike as well. It's a temporary (like 30 seconds worth of using) spark plug you put in that is made of clear glass so you can see the color of the fuel combustion.



That's the easiest way I know of to troubleshoot rich and lean. Sometimes you're rich at idle and lean at throttle and vice versa. Sometimes things change with a hot or cold engine. This sort of tool will let you know that.

For me, when in doubt, I pull the carbs, clean them, and adjust them to spec. Most people don't want to do that, but it's the surefire shotgun approach to mixture problems ;)
 

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Discussion Starter · #5 ·
Thanks, luke. I'll take a look at the float height.
I had the carbs apart last week and everything looked pretty clean. The floats seem to be made of some solid synthetic material though, so I don't think they're taking on gas.
 
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