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Finicky fuel screw

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Hey all. Rejetted with the JD kit and followed the guidelines in the kit. Put in the extended fuel screw and all is fine ... except at idle. The kit spec'd 2.5 turns out but the left the bike hanging on idle a bit. It would eventually drop down, or I could bring it down by slipping the clutch a bit and it would settle nicely. So I started adjusting the fuel screw out in small increments and I'm almost at 3 turns out. It still hangs slightly but only for a few seconds. But now it stalls anytime I'm slipping the clutch and blipping the throttle at low rpms in the slow "technical" stuff. (Technical for me cuz I'm a noob). I tried setting the idle higher using the idle adjust on the throttle, but it still stalls out. No problem restarting, in fact since the rejet it starts almost without turning over. No other running issues that I can detect.

It's a new bike - 2017 S. It has the 25 pilot jet, third clip, 155 and the 3X3 mod. I'm basically at sea level (Vancouver, BC) although now that the snow has gone there will be some elevation in my near future. Any advice would be appreciated.

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When I had the Mikuni in mine I usually had the mixture screw somewhere in the 3½ turn out for fall and winter(cold weather) rather than going with the next size bigger pilot. Mine never had a high idle but at the time I didn't have the 3x3 cut yet , maybe tape yours up and try the bike out, may be too much air with the Mikuni carb and no other performance mods.

 

 

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2.5 turns is for stock screw.  extended screw needs about 1 turn less.  move to 1.5 turns from closed, ride the bike and readjust idle speed when engine is hot

Edited by 30x26
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1 hour ago, 30x26 said:

2.5 turns is for stock screw.  extended screw needs about 1 turn less.  move to 1.5 turns from closed, ride the bike and readjust idle speed when engine is hot

I thought that a hanging idle was a sign that it was too lean. So if it's hanging at 2.5 turns won't going to 1.5 make it worse? Or is my understanding on lean/rich flawed? 

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3 hours ago, Frankfurter said:

I thought that a hanging idle was a sign that it was too lean. So if it's hanging at 2.5 turns won't going to 1.5 make it worse? Or is my understanding on lean/rich flawed? 

sounds like something is wrong like dirt in the pilot, or you say its 25, did you change it ? if not it may need to be changed ... check your cables are sorted and well adjusted so that isnt causing an issue, your vac line is hooked up, your boot is on right ect ... then if it was me i would tear the carb back out and go through it and blow it out real good, make sure the oring and everything is right on the mix screw ect ..

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18 hours ago, Frankfurter said:

I thought that a hanging idle was a sign that it was too lean. So if it's hanging at 2.5 turns won't going to 1.5 make it worse? Or is my understanding on lean/rich flawed? 

it also hangs when pilot circuit is too rich and at the same time,  in order to get correct idle speed, you have to run the slide too high .

try 1.5 turns with warm engine and slightly lowered idle.  :thumbsup:

 

according to JD screw should be about 1 turn out from the point where engine noticeably starts to loose rpm because of lean condition. 

 

Edited by 30x26

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In this case the pilot is the known size for most times , to be so rich that he'll have the idle turned up to compensate he'd need a #30- 35 pilot. Also in that case it would idle "normal" rpms when the motor is cold and the high idle and worse hanging idle will come when the motor is fully warmed up.

 

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it's not the known size. 25 is fine for stock screw , extended screw needs stock  22.5 at about 2.5turn  or 25 at about 1.5 turns.   stock and exteded screws have different tapers, same movement from closed position does not generate same effect  . 

it cannot be lean at 3 turns with extended screw and 25. no way

 

Edited by 30x26

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He said the kit even spec'd 2.5 turns out so , 1 turn less isn't going to make that big a difference (Yes I do it all the time going from winter to summer 100º temp swing), the jet he's using would be alright, he's in BC ,Canada (cold) not hot Italy ,That makes a difference, but whatever.

 

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Edited by jjktmrider

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Thanks for the input guys, I really appreciate it. I think what I'll do is run the bike until it's hot and then start to put the screw in and see what happens as I get past where I started. Hopefully I'll find the sweet spot then. I'll check back in with what I discover.  I did notice a difference in the extended screw from the stock screw when I rejetted; the extended screw did not penetrate the carb as far as the stock screw when it was seated. Perhaps I should have backed both screws out until they were flush with the interior surface of the carb body and then noted the difference in the amount of rotation needed to do that. 

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