help diagnosing a problem
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Ultimate HDF Member
Joined: Oct 2007
Posts: 7,562
Likes: 11
From: Palm Harbor fl.
help diagnosing a problem
The bike starts and idles fine. It also accepts revving fine. It will not run at a constant speed without popping, backfiring, and dying down to idle. changed the plugs and same situation. Been running fine with the same tank of gas as used for last 3/4 tank.
Club Member
Joined: May 2006
Posts: 14,564
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From: the 50s & the 60s
carb or FI??
Big Kahuna HDF Member
Joined: Feb 2006
Posts: 23,881
Likes: 34
From: USA
Idle speed improperly adjusted.-- Adjust operating idle speed.
Inlet system air leak --Correct as required.
Restricted fuel tank vent system --Correct restricted hose. Replace vapor valve.
Dirty or damaged air cleaner element.-- Clean or replace.
Enrichener valve not seated or leaking. --Adjust, clean or replace.
Restricted fuel supply tract.-- Correct and clear restriction.
Plugged bowl vent or overflow. --Clean and clear passages.
Loose or plugged fuel and air jets or passages. --Clean, clear and correct as required.
Worn or damaged needle or needle jet.-- Replace assembly.
Vacuum piston assembly malfunction. ---See Vacuum Piston Troubleshooting below.
Accelerator pump inoperative.
Inlet system air leak --Correct as required.
Restricted fuel tank vent system --Correct restricted hose. Replace vapor valve.
Dirty or damaged air cleaner element.-- Clean or replace.
Enrichener valve not seated or leaking. --Adjust, clean or replace.
Restricted fuel supply tract.-- Correct and clear restriction.
Plugged bowl vent or overflow. --Clean and clear passages.
Loose or plugged fuel and air jets or passages. --Clean, clear and correct as required.
Worn or damaged needle or needle jet.-- Replace assembly.
Vacuum piston assembly malfunction. ---See Vacuum Piston Troubleshooting below.
Accelerator pump inoperative.
Last edited by KBFXDLI; Nov 7, 2008 at 12:14 AM.
Road Captain
Joined: Apr 2007
Posts: 631
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From: MA
? what your saying is that it is dieing while motor is under a load ?
While back a friend had a similiar situation ran fine until he drove a distance, then it would gradually begin to die out, drove us crazy until we removed gas cap. Seems that the gas cap wasn't venting enough and motor was slowly running out of fuel while under load.
While back a friend had a similiar situation ran fine until he drove a distance, then it would gradually begin to die out, drove us crazy until we removed gas cap. Seems that the gas cap wasn't venting enough and motor was slowly running out of fuel while under load.
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Ultimate HDF Member
Joined: Oct 2007
Posts: 7,562
Likes: 11
From: Palm Harbor fl.
here's a picture of my slide. the rubber does not appear damaged that black looks bad though. it will not clean off with carb cleaner. Also does the rubber stretch? I cant seem to get the thing to fit into the groove fully.
It appears as if the problems come when the slide starts to move. It will slide up fully when I blip the throttle wide open.
It appears as if the problems come when the slide starts to move. It will slide up fully when I blip the throttle wide open.
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Road Master
Joined: Nov 2007
Posts: 1,223
Likes: 3
From: Peoria, AZ
KB has a nice list of things to check. Better off just removing the carb and doing a thorough cleaning as the jets or inlets could be blocked esp. the main circuit vice picking one portion of the carb as a problem: I've found if one thing is wrong with the carb, there are probably others too. How's the AFR esp. the main curcuit? As for the diaphram: with bike not running, lift up the diaphram. You should feel a slight resistance and the air being displaced. When you let go it should fall but not snap back into position. If you have any shims in the needle, remove those as they can cause binding. Might also try filing/sanding with 600 grit/polishing the butterfly guides of the diaphram until the wear marks are removed to aid in movement. I also chamfered the square edges at the air in to out (the venturi portion) to aid in airflow and drilled the hole behind the needle to #31 drill bit size. Discoloration is a normal occurance so long as the heat is not melting the rubber or teflon collar. Seal should fit in the groove at top of carb when top cover is placed into position.
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Ultimate HDF Member
Joined: Oct 2007
Posts: 7,562
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From: Palm Harbor fl.
diaphragm checks out. I think that this is an intake leak. I got all the gaskets to replace around the manifold and I have a tool on order for the manifold bolts. Also have dynojet sending me 3 new washer spacers as mine have disappeared. Looks like the bike will be out of commission till late next week.
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