I run a stock Keihin on my '85 FXSB Lowrider. Well I took off the stock pipes and put on some gooseneck drags. About a week later, I rode the bike all around town to unstress and the bike did great which was awesome cause it was my first long ride on the scoot since I had it.

Well about 6 days later, while a little colder out, I was riding to the hardware store and the bike would just stop running while I had the throttle goin and everything. Just all of a sudden boom, it seemed like it stopped getting gas and the bike would completely shut down. Took it home, went out and tried it again and it did the same exact thing about 1/4 mile from the house. Now before I left that morning, the carb was sputtering a lil out of the rear pipe (which it had been doing since I put the gooses on) so I figured, yeah she's running rich. But since the bike seemed like it just stopped getting gas, maybe something was plugged up somewhere. I took it back home, took the carb apart, cleaned it and now tonight leaned out the air/mixture screw.

Now the peculiar thing is even though the pipes sound like things evened out since i've leaned the air/mixture screw out, when I shut the bike off and restart it, a quick puff of smoke comes out of the carb and sometimes even (1 out of 10 times) backfires. In addition the carb idles high, when trying adjust the idle screw, the idling still sounds high and I'll back the damn screw all the way out to where there is no tension left on the spring. Its like the high idle is stuck somewhere in the carb itself.

This is the newest year bike I've owned and my first Keihin, so my questions are:

1. Did I adjust the air mixture screw too lean?
2. The hell is wrong with the idle screw?
3. Thinking of upgrading to a CV carb or Super E and want your opinion on that. Or just keep the stock Keihin?

Thanks

 

I would put some baffles in those pipes & change to a CV carb , the CV is a up to date carb & will self adjust if you go into the high country or down to the flat land

 

Drag pipes hurt performance, especially if unbaffled. You are probably too lean on your af mixture, not too rich. I would lose the drags, or at least get some kind of baffle in them, and definately upgrade to a CV.

 

This part sounds like it is sucking some air somewhere it shouldn't. Check and make sure the throttle cable isn't binding,if not check for leaks around your intake or even loose screws on the carb.

As for the adjustment it sounds like it is starving for fuel.
My guess would be you bumped the carb maybe changing pipes(?) and have a major leak around the intake.Couple that with the unbaffled pipes and the fact you leaned out the fuel, I'd say it's starving out. Just my guess.

 

It sounds like you have a lean mixture, it could be from carb adjustment, but it also could be an intake leak.

Your bike has the old design compliance fittings that connect the intake manifold to the heads, these were a common source of intake leaks.

I wouldn`t spend the money to replace the compliance fittings or rebuild that carb, you money would be better spent upgrading to a CV, S&S or Mikuni carb. The CV upgrade would be much less money than the others.

My bike came with the same carb you currently have, it is a good dependable carb, but it is a total performance dud.

Upgrading your carb is the biggest single upgrade you can do for your bikes performance.

To mount the CV you would need:
Backing plate and air filter.
Manifold and mount flanges.
Manifold seal rings.
The seals, mount flanges and hardware are available at the dealer, the rest you can round up on ebay , also check the classifieds section of the forum.

 

1989 FLHS here, upgrading to a CV made my bike much better all around.
It's a good change.

 

I saw someone selling a CV carb off an '81 Ironhead. Would that one be fine with mine or do I need to get a specific year/model CV carb?

 

Do you know what kind of baffles I can get for them? Maybe flex baffles? Cause I really like the goosenecks and want to keep them.

 

Guys have had a certain amount of success using "lollipop" baffles in drags. Just google it, tons of info about them.

 

There is no way to know what carb that is, because the CV carb was not used until 1988 on Sportsters....

You want a CV carb made 1989 or later (1988 Sportster CV carbs do not have an accelerator pump, you don`t want that carb).

It won`t be hard to find one.