TC-88B and cough/pop
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6th Gear
Joined: Apr 2008
Posts: 10
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TC-88B and cough/pop
Yes, the age old question... here are the specifics:
2003 Fat Boy
stock engine
K&N air filter
V&H Big Shots
Bought bike w/8,100 miles on it, now has 21,000 (or so). Bike ran well when purchased and until 3-4 weeks ago. Until then, pops on decel and a cough or two only when cold (20 to 40 deg F) outside without warmup. Now, coughs at low RPM all the time (not at idle, but anything above for a little way) and pops on decel at just about any speed.
Here's what I've tested, and the results:
- Exhaust seems solid at the manifolds (doesn't move, tight)
- Intake manifold seems solid, no leaks (WD-40 test)
- rear cylinder plug looks very slightly black
- front cylinder plug had white residue caked on it
- gold jet (toward air cleaner) shoots gas here and there and always when I 'get on it'
- at higher RPM, the main jet seems active, slide rises
- air filter looks a little dirty
I replaced the front plug and cleaned the air cleaner. Bike runs 'better', but displays all the same symptoms as before at a slightly less frequent level.
I know there are several things I could immediately do to improve things, but the fact is that I - knowingly - changed nothing, and the bike's performance has changed. I need to find out why, fix it, and then we can chat about pet improvements!
Ideas guys? I'm not the gearhead I need to be, but I can find the major parts. What needs to be checked next, and how?
Thanks in advance,
R
2003 Fat Boy
stock engine
K&N air filter
V&H Big Shots
Bought bike w/8,100 miles on it, now has 21,000 (or so). Bike ran well when purchased and until 3-4 weeks ago. Until then, pops on decel and a cough or two only when cold (20 to 40 deg F) outside without warmup. Now, coughs at low RPM all the time (not at idle, but anything above for a little way) and pops on decel at just about any speed.
Here's what I've tested, and the results:
- Exhaust seems solid at the manifolds (doesn't move, tight)
- Intake manifold seems solid, no leaks (WD-40 test)
- rear cylinder plug looks very slightly black
- front cylinder plug had white residue caked on it
- gold jet (toward air cleaner) shoots gas here and there and always when I 'get on it'
- at higher RPM, the main jet seems active, slide rises
- air filter looks a little dirty
I replaced the front plug and cleaned the air cleaner. Bike runs 'better', but displays all the same symptoms as before at a slightly less frequent level.
I know there are several things I could immediately do to improve things, but the fact is that I - knowingly - changed nothing, and the bike's performance has changed. I need to find out why, fix it, and then we can chat about pet improvements!
Ideas guys? I'm not the gearhead I need to be, but I can find the major parts. What needs to be checked next, and how?
Thanks in advance,
R
Seasoned HDF Member
Joined: Nov 2007
Posts: 6,790
Likes: 10
From: Hawaii
It may be a long shot but try checking the spark plug wire mostly the rear one where you said the plug was a little black... maybe it's arching? You could grab it to check... but I wouldn't... lol maybe in the garage with the light off? Oh yeah have you put gas at any place then other then your normal spot, bad gas can make a bike run like crap also.
Ultimate HDF Member
Joined: Feb 2007
Posts: 5,578
Likes: 4
From: Northern California
Slow speed jet controls fuel at low RPM, which seems to be your problem. The orifices in the jet are really small, and a bit of crud making its way down can clog the jet just enough. The fuel filter is in the tank, but crud can develop in the lines and passages below and eventually cause a problem. A new jet is cheap, or you could soak the jet and clean the orifices with a bristle from a wire brush in a pinch. Just for drill, and to get to the simplest solution, also change the other spark plug.
Last edited by Dorkman; Sep 12, 2010 at 02:58 PM.
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