Carb Brain Teaser

[Peckerwood]

Just for fun, a little input, please-My '04 Mastiff began running a little shitty, so I pulled the plugs and they indicated a rich condition, also verified by soot on the right side of my rear rim. After reviewing the S&S carb set-up video, I warmed the bike up to operating temperature, and slowly adjusted the mixture screw clockwise to lean the mixture out. After a slow FULL turn, the idle speed increased, again indicating a rich condition was present before my adjustment. I then adjusted the idle down a little, took it for a test ride, and all seems ok now. My question is this-how the hell does a carb get so out of tune all on it's own ? The thought occurred to me that the adjustment spring is maybe losing tension, and time will probably tell. It also occurred to me that, since I use the bike primarily as a bar-hopper, that some asshole could have messed with it, but I don't think I've pissed anybody off recently (that I'm aware of). I asked a friend of mine, a professional mc and car mechanic, about this, and he says that mechanical problems like this arise "because they can".??? Any ideas?

 

[standuprick]

Technically, the air mixture screw could be adjusted everyday. What I mean is due to temperature and humidity this affects the way the bike runs. It may not be that noticeable but have you ever noticed on really cool nites your bike runs like a raped ape? It could of been just the fuel that you used. I wouldnt worry about that too much. If somebody was going to mess with you I could think of alot of other ways to really mess with you than carb adjustment.

 

[Bobby Schulz]

Try draining out the gas and getting some from another location.

 

[Peckerwood]

Thanks Standuprick and Bobby, hadn't thought of the fuel; easy enough, will check.

 

[Five Five]

The screw your referring to is for the idle metering circut and plays no role once you roll past an idle ... if you still think it's a little rich it may be your main jet ...but if it's running good, than let it be as most prefer a rich mixture opposed to a lean mixture ...

 

[2004BC]

Just for fun, a little input, please-My '04 Mastiff began running a little shitty, so I pulled the plugs and they indicated a rich condition, also verified by soot on the right side of my rear rim. After reviewing the S&S carb set-up video, I warmed the bike up to operating temperature, and slowly adjusted the mixture screw clockwise to lean the mixture out. After a slow FULL turn, the idle speed increased, again indicating a rich condition was present before my adjustment. I then adjusted the idle down a little, took it for a test ride, and all seems ok now. My question is this-how the hell does a carb get so out of tune all on it's own ? The thought occurred to me that the adjustment spring is maybe losing tension, and time will probably tell. It also occurred to me that, since I use the bike primarily as a bar-hopper, that some asshole could have messed with it, but I don't think I've pissed anybody off recently (that I'm aware of). I asked a friend of mine, a professional mc and car mechanic, about this, and he says that mechanical problems like this arise "because they can".??? Any ideas?

When I'm done dialing in a carb I put a finger full of clear silicone where the screw threads into the carb. Idle, A/F, Accel pump, all of them. These V-Twins vibrate and screws can back out over time. Can't screw in without help but can back out!

 

[ringo]

a good reason to get extended knurled screws, you can just reach down and make little adjustments on the fly, no tools required.

 

[Peckerwood]

Thanks. Great tips, website, and members. Ya'll are OK.