Low speed carb issue

[michaelwhaley]

2002 Valkyrie with about 38,000 miles.
Ran fine when I purchased it with 33,000 miles 5 years ago but now I have a low speed issue. The bike runs really rough at low speed when cold. Gets better after warming up but the low speed issue still remains. Once on the gas it runs smooth and strong

I have cleaned the carbs twice following D-Ray videos. The last time i just replaced the idle jets.
I have also replaced the o-rings and gaskets on the carbs including the intake runner o-rings at the heads.
I have the fuel screws set at 2.5 turns. I have not tried to adjust them yet so that is the only thing i can think of that is not quite right. Don't know if that would cause this issue or not.
Any suggestions are much appreciated.
thank you. Mike

[Ramie]

I would double check your clamps on your air cleaner boots and your intake boots make sure their tight and seated correctly.  You could also try a heavy dose of  B12 and ride the bike around at the rpms where it's giving you problems.

[yrunvs]

Would any air connections (airbox to carb runners for instance)
before the carbs have any affect other than allowing unfiltered air into the carbs?

[Madmike]

Would any air connections (airbox to carb runners for instance)
before the carbs have any affect other than allowing unfiltered air into the carbs?

When I was active here several years ago I remember quite a discussion on guys trying to run with modified airbox or no airbox and having performance issues.  I seem to remember through the haze that the airbox is basically "tuned" to the engine was the popular thought at the time.  If you do a search of the forum you may find more info.  Likely about 10 years ago.

Have you balanced the carbs to ensure that they are synchronised??

[rug_burn]

Sounds like you got some cylinders that are running lean and so they misfire when cold, and probably run a little hot when the engine's warm.   You can actually tell by the smell when it's hotter than usual when you shut it down, true story.
    Does that sound like your bike?   If so- then somewhere it's sucking air into the engine at low rpm when there's a lot of vacuum to suck in that air.   
  The first thing  I'd do is check the vacuum hoses that go to the vac nipples on the intake tubes, and the caps as well.  I had two that had holes in them from some reaction with a carb cleaner, so, check well, and if the two going to #3 and #4 seem soft and kind of thin, that may be why.
  If these are all good, and the intake o-rings as well, then try this procedure:

 http://www.valkyrieforum.com/bbs/index.php/topic,110548.0.html

Sometimes after cleaning, they're not 100% like new, and need to be adjusted (a lot).   I hav e one that's out about 4 turns, but runs very smooth.   So don't give up

Paul

[Jims99]

I agree with rug burn, check all vacuum lines and caps. I had two caps start leaking that were only 6 months old. Don’t use auto caps, get ones from Redeye. The auto caps can’t handle the heat and crack. Hopefully it’s as simple as that.

[98valk]

u don't list your location.

if all stock engine,
2.5 turns might be too rich, esp hot summer temps, which cause  even more richness.

put at 2.25 turns and then 2 turns if not better.


http://www.factorypro.com/tech/tech_tuning_procedures/tuning_carbtune,CV,lower_rpm_engines.html

Set for smoothest idle and 2nd gear, 2000 rpm, steady state cruise operation. Set mixture screws at recommended settings, as a starting point. For smoothest idle, 2nd gear, 2000 rpm steady state cruise , and 1/8 throttle high rpm operation.  (pj tuning information)
Pilot fuel mixture screw settings, float level (but, you've "fixed" the fuel level in Step 3 - which you have already done!) AND pilot jet size are the primary sources of mixture delivery during 2000 rpm steady state cruise operation.

    If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn increments. Alternative pilot jets are supplied when normally required.
    Pilot fuel mixture screw settings, float level and pilot jet size also affect high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing pilot jet size will usually cure the problem.
        NOTE: A rich problem gets worse as the engine heats up.
            If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture.
        NOTE: A lean problem gets better as the engine heats up.
            If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, and there are no intake leaks and the idle speed is set at less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm!

[michaelwhaley]

Thanks to all for the suggestions. I am in So Cal. I have sprayed some starting fluid around the carbs and heads and didn't notice any change in idle, but I will keep working on it.

Mike