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  #1  
Old 20th August 2012
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Default Kiehin buttetfly tune

Ok, i have been changing jets and stuff 2 weeks now and cant get it right. I now have 170 main and 88 pilot. If i turn mixure out it starts to stumble around 2 1/2 turns . I turn it in and can go all the way to seated and just gets a little rough . I set it about 3/4 seemed ok but after ride it wouldnt idle at all. Also noticed rear cylinder exhaust is real sloppy sputtering. Also popping thru exhaust when i let off throttle. I have adjusted rods and rechechecked. Sprayed intake no sign of leaks. Carb is clean as new. I am lost . I have jetted many bikes before but this one just is not working out... Thanks

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  #2  
Old 20th August 2012
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Do you know if you are running rich or lean? What do your plugs look like? I've finally got mine dialed in and it stalls at 1/4 turn out going in so you pilot jet may be to big for starters.
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Old 20th August 2012
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I had a similar problem after many attempts at changing jets doing timming and push rods .It would run good then after a short ride it would play up again allways fouling the front plug .For the life of me i could not work out why .Then i done a leak down test and found front inlet valve leaking .Pulled the front head and the valve seat insert was cracked.Going by your previous posts you have gone up and down the jet scale. Try doing a leakdown test it dont cost nothin and it will rule out valve and ring problems .
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Old 20th August 2012
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Its running rich... Plugs are black

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Old 20th August 2012
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+1 on doing a thorough check for intake and exhaust leaks. It is impossible to tune up the carb if these are not completely sealed up.

Set the pilot screw when the engine is fully warmed up, as in a half hour ride not in the city, then leave it there. If there is a probem it is not because of the pilot screw setting.

In my experience plugs will always be black after a ride in the city. It has to be out on the hiways. I use the local paved roads with little traffic.

Tuning a carb in the shop is problematic. Best done out on the back roads.
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Old 20th August 2012
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88 pilot is way too big, particularly since you can turn the mixture adjustment screw that far out, and all the way in and it makes almost no difference in how it idles.

Like already said, you must verify all the little things before you try to fine tune the motor. Make sure valves are adjusted properly, timing is set where it should be, advance mechanism is working (if you have it), and most importantly, there are no intake or exhaust leaks. If one of these things is off, you will never get it to run right.
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Old 20th August 2012
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Quote:
Originally Posted by ultra...good View Post
... Like already said, you must verify all the little things before you try to fine tune the motor. Make sure valves are adjusted properly, timing is set where it should be, advance mechanism is working (if you have it), and most importantly, there are no intake or exhaust leaks. If one of these things is off, you will never get it to run right.
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Old 21st August 2012
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If you are running the 34mm Keihin, which is stock your year, the 88 slow jet is most likely too big, which is why you can close the idle mix screw all the way down and it still runs ok. Too much fuel going in via the slow jet at idle.
I run an 88 in my 38mm Keihin so suspect its too big for your 34mm.

Or your float level is set too high and is slopping extra fuel into the carb at idle.

Or you accelerator pump is dribbling fuel through into the carb at idle. Might need the pushrod on the pump shortening so it does not prop the diaphragm open at idle, or might just need cleaning out.l
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Old 21st August 2012
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Quote:
Originally Posted by hopper View Post
if you are running the 34mm keihin, which is stock your year, the 88 slow jet is most likely too big, which is why you can close the idle mix screw all the way down and it still runs ok. Too much fuel going in via the slow jet at idle.
I run an 88 in my 38mm keihin so suspect its too big for your 34mm.

Or your float level is set too high and is slopping extra fuel into the carb at idle.

Or you accelerator pump is dribbling fuel through into the carb at idle. Might need the pushrod on the pump shortening so it does not prop the diaphragm open at idle, or might just need cleaning out.l
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Old 21st August 2012
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Ok tonight i checked intake again no leaks. Went ahead and replaced clamps and seals i had new ones sitting here. Went ahead and took it down to a 80 pilot jet and think i got it.will no for sure tommorow after work.

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