I was having a problem with my bike, a 02 Wide Glide fouling plugs out if I babied it around. After some advice from some good people here, I went to nightrider.com and found what I needed. I decided to try adjusting the idle mixture before I tore into the carb. I didn't have to take the carb off as the plug in the idle mixture screw was already removed. After the bike was warmed up, I started turning the screw in and it was almost 2 full turns before the engine started to stumble. Backed it back out until it started smoothing out but still had an occasional backfire threw the carb. Turned it out another 1/8 of a turn and no more backfiring. No more rich smell in the garage after 5 or 10 minutes of idle time. All that to get to my question. Why would the mixture screw be out that far? I have no idea as to what jets are in the carb and the only thing I can figure is the previous owner was trying to fatten it up for pipes or the breather change. I don't want to run it lean and cause any damage so should I go ahead and check to see what jets are in it? Does the idle mixture have any thing to do with it? Again, sorry to run on but trying to get all my info out there. Thanks. Dirt

 

Carb guru's, have any ideas?

 

I'm no carb guru by any means but you can always read the spark plugs and tell if it is to rich or lean. There are plenty of threads/ you tube videos to show you how to read a plug, but basically run the bike, (usually wide open, but it can be done at whatever RPM you are concerned about) for as long as is practical, then clutch it in and hit the kill switch. Pull over and check the plugs. You want to see a little brown on the insulator. Black = too rich, whitish = too lean.

 

I checked the plugs. They are tan. I also ran it to 4000 in third gear, let off about 1/8 of a turn and it didn't surge so I'm guessing my jetting is about right. I guess I'm just trying to figure out why the Idle mixture screw was out almost 2 turns. Maybe the previous owner didn't know about this site and all the info that's available here. He//, it's getting too close to winter to be wondering about a bike that runs good. LOL. Thanks for the suggestions.

 

On a TC 88 or 96, 2 1/2 turns out on the mixture screw will get you in the ball park IF your low speed jetting is right. Aftermarket pipes and open element air cleaner - 45 or 46. Nigthtrider has good info. You can fine tune it with the mixture screw. Once you are happy with how it runs, 1/4 to 1/2 turns out will stop the exhaust popping. CAUTION - beyond that, the MPG goes to hell in a flaming basket and fouls your plugs. As long as it's not exhaust popping on decell, you should be good to go and not have to worry about the jetting. If you can't get it to idle worth a ****, no matter which way you turn the mixture screw, replace the Mixture Screw Packing. CV Performance. com has a good replacement.

 

Why would the mixture screw be turned out so far? Your guess is as good as mine. All it will do is waste gas, foul plugs and run like ****. There's a lot of self-professed carb experts out there.

 

Perhaps the previous owner? Our maybe it backed out, never heard of that but it is possible.

 

It can be hard to find the points where the engine stumbles going in and out with the idle mix screw. I've never had a lot of luck with it. Maybe the previous owner kept screwing it out and out until he finally got it to stumble.

If you have a 45 or 46 pilot jet then 2.5 turns out is just the sweet spot. Hardly worth messing about trying to find the stumble points. If it does need to be a whole turn either side of that then chances are there is a small problem like the rubber seal on the screw having rotted, an incorrect float height, a partially blocked jet, the wrong pilot jet, or somesuch.

Reading plugs to guessimate the mix isn't as easy as it once was. Modern lead-free fuels contain detergents and richness/leanness don't leave the marks as clearly as they used to. About the best method these days is to check the base ring colour as described in the Jetting section here: http://www.dragstuff.com/techarticle...ead-plugs.html. Even so, its not terribly reliable as a one-shot test as you really need to be doing a plug chop on new plugs.

 

The funny thing is most people dont realize the ONLY thing a fuel mixture screw does is allow a PARTIAL amount of fuel to bypass ONLY through the Pilot Jet circuit to an orifice on the engine side of the throttle plate. This mixture screw isnt a tuning tool for anything other than the idle mixture.....

 

Umm, not sure about "most". The clue is in the name "idle mix screw".