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Carbing woes

Old 09-26-2011, 06:40 PM
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Carbing woes

So I am looking for some knowledge on carbing the SH with a shorter rear header. I have a custom exhaust that is a 2 into one but the rear header is much shorter.

So it never had much bottom end but since I have "tuned" it it has no bottom. Does anyone have experience in this area?

It has a jet kit so adjustable needles but does the shorter header mean richen or lean the rear?

Any help would sure help.....
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Old 09-27-2011, 07:04 PM
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So after overwhelming response I have another question. I got the bike riding pretty well today (3rd slot from top front; 4th from top rear on the needles) but it still lacks throttle response just off idle and low rpm. After 2-3k it RIPS.

anyone??
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Old 09-27-2011, 07:30 PM
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Check the sync and a/f screw for low down tuning.

If you're running rich on the a/f circuit it will stumble and then jump.

I found the best way of checking this is just by leaving the choke on and (if you have PAIR removed) seeing the way the engine decelerates from 5k to idle in second gear or so.

If it pops and ignites in the exhaust tubing, it's rich, if it gets to where there is no hesitation then you're good. Lean is when you'll have stumbling and surging in any range of the a/f, jet, or needle positions.

As well, have you checked your TPS? Small things are what make the difference in tuning.

Outside of regular service stuff (Air filter, spark plugs, gas quality) it's just working out the kinks of it.


I don't have experience with difference in tuning outside of older model bikes where the exhaust runners were seldom even remotely close to the same length.
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Old 09-28-2011, 12:30 AM
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It might be an idea to add a small restriction to the rear header, balancing them out slightly... It's probably going to make it a lot easier to get the performance across the whole range...
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Old 09-28-2011, 06:29 AM
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I have the fuel screws at 2.25 front & 2.5 rear. Which direction would lean towards initial throttle opening response. Carbs are just cleaned and reassembled.
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Old 09-28-2011, 11:10 AM
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Originally Posted by smokinjoe73 View Post
I have the fuel screws at 2.25 front & 2.5 rear. Which direction would lean towards initial throttle opening response. Carbs are just cleaned and reassembled.
clockwise=lean.

The closer they are to being grounded, the more lean they will be.

The service manual does have a pretty good walk-through of tuning the screws even with AFM parts.

I slotted mine and use a 90 degree flat head screwdriver to adjust. It's a pain, but it works nicely.
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Old 09-28-2011, 11:41 AM
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Yeah I went to the trouble of slotting mine as I replaced the plastic choke collars with the brass polaris models. Figure I can use 1/4" socket extensions/ universal joint and a slotted bit to turn it
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Old 09-28-2011, 04:52 PM
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Ok so forget that, even slotted I cant get at them to turn them while the bike is running. Can I use this tool or do I need the right angle motion pro that is gear driven?

NEW!! LISLE CARBURETOR CARB ADJUSTING TOOL #55250 | eBay
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Old 09-28-2011, 07:22 PM
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Originally Posted by smokinjoe73 View Post
Ok so forget that, even slotted I cant get at them to turn them while the bike is running. Can I use this tool or do I need the right angle motion pro that is gear driven?

NEW!! LISLE CARBURETOR CARB ADJUSTING TOOL #55250 | eBay
It really depends on how flexable that line is.

The pilot settings should be smooth and easy enough to do with little finger effort so you wouldn't have to worry about having the line snake and twist under torque, but the radius on the bend might be a little much with the head coolant lines right there.

And since our pilot needles have no shoulder covering the screw, I have a sneaking suspicion that if you put that on there, the bit would just pop off of the head and you'd be S.O.L.

You could J.B weld a small finger adjuster, like an 1/8" extension, but I don't know how small your hands are to fit on there.

I've had my little sister do some adjustments on my CBX hahahahahahahaha.
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Old 09-28-2011, 08:38 PM
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Ok so its hugely poping on decel & even steady throttle at lower rpm. I am going to lean it tomorrow with the needles and maybe turn the fuel screws. I cobbled some tools together since I really want to turn them when its running.

I ordered this tool since its a right angle and looks like the tool for the job
BIKEMASTER EXTRA REACH ADJUSTMENT SCREWDRIVER | MotoSport
Attached Thumbnails Carbing woes-tool-004.jpg  
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