Carb adjusting
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Cruiser
Joined: Jun 2008
Posts: 200
Likes: 39
From: Assonet MA
Carb adjusting
I just put my rebuilt CV carb back on my bike. 94 Heritage.
I did the upgrade per http://www.nightrider.com/biketech/hd_cv_mods.htm.
I am running SE turnouts, SE Air cleaner set up. Went with the 45 and 165 jet combo with the '88 Sporty needle.
She fired right up, coughs when takin a quick blip of the throttle at idle, but out on the road I am backfiring thru the pipes when I let off the throttle. Too rich or lean.
I don't want to play too much with the mixture screw since it is tough to get at. I did replace it with the thumb screw so it is a bit easier to get at, but I do think it will still be easy to lose track of # of turns in/out.
Suggestions?
Thanks,
John F.
I did the upgrade per http://www.nightrider.com/biketech/hd_cv_mods.htm.
I am running SE turnouts, SE Air cleaner set up. Went with the 45 and 165 jet combo with the '88 Sporty needle.
She fired right up, coughs when takin a quick blip of the throttle at idle, but out on the road I am backfiring thru the pipes when I let off the throttle. Too rich or lean.
I don't want to play too much with the mixture screw since it is tough to get at. I did replace it with the thumb screw so it is a bit easier to get at, but I do think it will still be easy to lose track of # of turns in/out.
Suggestions?
Thanks,
John F.
Stellar HDF Member
Joined: Apr 2009
Posts: 3,039
Likes: 11
From: Northern Ontario
Nightrider has some good instructions , follow Step 8: ADJUSTING IDLE MIXTURE:
With engine warmed up and at idle, turn the idle mixture screw inward (clockwise) slowly until the engine starts to stumble. If the engine will not idle on its own during this procedure, raise the idle by adjusting the idle set screw until it does. Make a mental note of the position of the clock position of the screwdriver. Now turn the idle mixture screw outwards until the engine begins to run smoothly, adjusting the idle stop screw as necessary to maintain proper idle speed. Blip the throttle a time or two and observe the results. If the engine responds quickly with a gratifying blast and no backfiring through the carburetor, you have your idle mixture right. If backfiring occurs through the carburetor then adjust the idle mixture screw out another 1/8 to 1/4 turn. Under normal circumstances, the idle mixture screw should be between 2 and 3 turns out. Adjusting the idle mixture screw out to far results in an overly rich, low RPM fuel mixture leading to poor gas mileage and carbon buildup in the combustion chamber.
Big Twin Idle Speed
The proper idle speed for Big Twin engines is 900-1000 RPMs. EVO oiling systems need better than 700 RPM to work properly. Resist the temptation to lower the idle excessively. It may sound good, but improper oiling will contribute to engine overheating while idling in traffic and premature engine failures.
With engine warmed up and at idle, turn the idle mixture screw inward (clockwise) slowly until the engine starts to stumble. If the engine will not idle on its own during this procedure, raise the idle by adjusting the idle set screw until it does. Make a mental note of the position of the clock position of the screwdriver. Now turn the idle mixture screw outwards until the engine begins to run smoothly, adjusting the idle stop screw as necessary to maintain proper idle speed. Blip the throttle a time or two and observe the results. If the engine responds quickly with a gratifying blast and no backfiring through the carburetor, you have your idle mixture right. If backfiring occurs through the carburetor then adjust the idle mixture screw out another 1/8 to 1/4 turn. Under normal circumstances, the idle mixture screw should be between 2 and 3 turns out. Adjusting the idle mixture screw out to far results in an overly rich, low RPM fuel mixture leading to poor gas mileage and carbon buildup in the combustion chamber.
Big Twin Idle Speed
The proper idle speed for Big Twin engines is 900-1000 RPMs. EVO oiling systems need better than 700 RPM to work properly. Resist the temptation to lower the idle excessively. It may sound good, but improper oiling will contribute to engine overheating while idling in traffic and premature engine failures.
Tourer
Joined: Mar 2009
Posts: 375
Likes: 4
From: St. Peters, Missouri
Popping on decel is an indication of a lean condition.
Go up on your jets...46 or 48 should do, but I'd go up on the main as well.
165 probably needs to be a 175.
Let us know what the end result is.
Go up on your jets...46 or 48 should do, but I'd go up on the main as well.
165 probably needs to be a 175.
Let us know what the end result is.
Stellar HDF Member
Joined: Apr 2009
Posts: 3,039
Likes: 11
From: Northern Ontario
Had to set idle mixture on my bike ( just came in ) I have a 45 and it seems happy at about 2- 3/4 turns.
Basicly I set idle to about 1000 rpm and watched tach and listened for change turning in and then out and tried for the middle plus a bit more.
Basicly I set idle to about 1000 rpm and watched tach and listened for change turning in and then out and tried for the middle plus a bit more.
Road Warrior
Joined: Oct 2009
Posts: 1,251
Likes: 1
two things, imo, a 46 is the minimum size the pilot jet should be, period, secondly, im not a huge fan of that needle, ive never gotten one to run correctly in a big twin, and third, the main is entirely too small, u should be running a 175 miniumum. did you drill the slide?
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Cruiser
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From: Assonet MA
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From: Deep in the heart of New Jersey
Reading that the needle doesn't make a difference either way you turn it, I have to ask did you just take it apart and put it back together, or did you rebuild it?. Sounds to me that you have blockage probably from sitting too long. Or possibly an air leak from a ripped diaphragm or manifold seals. I would disassemble it, remove all the rubber parts, and boil it for an hour. The blow all the passages with compressed air. The methodically reassemble it with new soft parts. Any type of carb cleaner won't do much good if it can't flow thru, the part your trying to clean.,,