I posted this in the carb section but go no response. Bike is a dyna and you guys are always helpful.

2003 lowrider, carb has never been rebuilt as far as I know. When I got the bike, owner said he was running it with the enrichner out just a bit. I found keeping it out enough to hold the idle 1000-1200 seemed to do the trick once she was warmed up some. Still getting some coughs through the carb when cold, but not too bad. Plugs need to be changed, they are black. Should I just adjust the idle (I think it needs to be higher) and air mixture or go ahead and do a full clean and rebuild on the carb to start from square one? Gasket kits are cheap enough. What is a good brand if I should go that route?

 

If you're running with the enrichner out a bit to help with your idle that's why your plugs are black. I'd pull the carb and give it a through cleaning and see exactly what is what. Sounds like you perhaps need a re-jet of the pilot and to properly adjust the air mixture screw and set the idle.

Stock pilot is a #45, you may find a #46 or #48 is more appropriate, depending on your A/C and exhaust. With the carb out it's not a bad idea to replace the #27002-89 ring seal and the 2 #26995-86B intake manifold seals. Also you'll want to confirm the brass plunger/starter valve on the enrichner is fully closing; an enrichner not fully closing will blow any attempts at a proper tune. Any question on that, replace the entire enrichner, isn't at all expensive.

The CV carb is actually rather easy to work on; some of the parts I use on them come from the hardware store like stainless allen's for the carb top and the bowl Much better than the cheesy CV screws.

A few tricks I've found: You can improve throttle response and smooth out the off-idle transition by using 2 #4 brass washers on the needle. Don't use M4 washers, they'll hang up the needle in the spring seat cage. With the CV carb and the Twin Cam 88's the air mixture screw seems to have the sweet spot right around 2 - 2 1/8 turns out from light seat. If you find you need to go too far past that you'll most likely need to step up to the next size pilot jet.

If this is your first go-round with a CV carb do a google search for 'Joe Minton and CV carb' He's posted up some great information that's still floating around out there on the interwebz.

Any questions you run in to just post them up, there's quite a few of us in the Dyna forum that still remember the good old days of carb tweaking

 

Good advice from tincup. I think I would change the plugs and limit the time I use the enricher, get the idle back down to 1000-1100 at operating speeds then see how she runs for awhile.

 

Some Good Advice Here Saved me a lot of Typing I basically did all this when bought the 05 for the simple reason it was 12+ Years Old and had sat a lot .. Anytime need to use the Enrichner for other than a Cold Warm Up, at best you have Trash in the Carb .. But as old as yours is and never rebuilt follow the above ..

 

I just rebuilt the carb on my son's sporty. It was acting exactly as you describe...ran well hot, but had to use the enricher for the first 20-30 minutes of riding to prevent stalling and intake popping.

Once apart, here is what I discovered:

Carb and jets were stock, so they were not the issue.
The intake popping melts and distorts the nylon slide diaphragm retainer...so plan on replacing the slide assembly.
The popping also coated the entire carb with carbon, which was not helping the slide action any.
The main culprit was the rear cylinder intake seal. It was leaking air.

I guess the moral of our carb was to also replace the carb mounting and head intake seals while you are there.

 

All the above is good advice. Joe Minton knows his stuff.

I'd add the following...

Tuning is USELESS unless everything else is right. Make sure the carb is clean and leak-free. Make sure the ignition is right (timing, plugs/gaps, wires, etc.). Make sure the intake and exhaust is leak-free.

Perform all tuning on a warm (operating temp) engine.

Carbs have multiple circuits that add onto one another as throttle and rpm increase. Start at idle and move from circuit to circuit. Main jet is least important. You seldom use it. Accel, cruise, and idle are always in use.

I like to use diagnostic tools while tuning. That is, more than plug reading. I use a tach and vacuum gauge at minimum. Set idle speed and adjust idle mixture to max vacuum, then reset idle speed and adjust idle mix to max vacuum again.

I'm not familiat with CV carbs, so I'm not sure if they have accel pumps or not, but if so, they are often overlooked and have a HUGE impact on throttle response and driveability. I think Minton touches on that. Again, not sure if applies to CV.

 

Few things..

Keihin carb has a fuel mixture screw not air. Function is the opposite of an air screw. Has the screw cover been pulled and mixture adjusted?

I doubt blow-back in the carb is melting anything but heat from sitting in traffic probably can.

Main jet will effect everything above the idle as it controls fuel level around the emulsion tube in a CV.

One thing to look at is accelerator pump. Make sure it's functioning properly and not dribbling into the intake.

Coughing will blow back crap in the motor. Even slight oil leakage past the guides. It coats the insides of the manifold.

The map sensor may have issues. It can cause the ignition to run retarded during cruise which will carbon things up, cause the cough and kill mileage. Diagnostics are not smart enough to toss a code.

 

Thanks everyone for the tips and comments. Ordered the baskets etc today. Screw cover has been pulled and adjusted

 

Probably both. I know the backfiring burns it as there is a huge burn mark lined up with the vent tube going to the carb throat. At that spot there are distinct signs of melting. In addition the entire nylon discs were distorted.

 

Hoping mine isn't that bad. Hesitant to tear it down as the weather is getting awesome and i always seem to need another part but I may tackle it in a week or two. Would be nice to have it 100%.


Plug wires look great, is there any other check or replacement interval. I can google or check the service manual but trusted real world opinions trump both IMHO.