A friend of mine just purchased a new '06 1200 custom, it has a pretty nasty stumble to it whenever you first crack on the throttle, he has not gotten his pipes on and no jet work yet. Local dealer says they all do that but another guy I spoke to said you can tune it out.
Any suggestions on this, is the dealer right? Are they all this way?
I deal a lot with drag cars and when something like this is happening it's usually in a carb tune.
Thanks.....

 

Simple job; it's just a Keihin CVK. Probably an off idle lean condition. Pilot adjustment screw out might solve it. On CVK's out is richer, in leaner. I'd turn it out a bit and see if that helps. On CVK's there is some overlap/transistion from the idle circuit (pilot jet) to the mains. so.....

Along with the pilot adjustment, it's probably not a bad idea on new bikes to go up one size on the main jet and perhaps shim the needle (or lower the clip it it had one) to slightly richen up the cruise. Your @ss-o-meter will tell you when its right. Your buddy can do this for a couple bucks and 20 minutes of his time.

PS, also make sure there's no leak at the intate side. Make sure everything forward of the carb is tight/clamped down.

 

Thanks alot, I'll pass on the info.
Will the dealer (or stealer) do this when they install his pipes and rejet? Is this something he should wait on until that's done.
I know when he bought it the bike wouldn't hardly idle, so the mechanic just turned up the idle screw.

Makes me that much happier I went with the dyna with the efi, I do nothing.....and no problems!

 

I like the DYI aspect of carbs myself and have always jetted, shimmed and tuned them myself. Didn't matter if it was CVK's, Mikuni VM's, Carter AFB's, Holley 3310's or Amal's. All do the same thing regardless of vehicle; principals identical.

There's one main think holding back carb tuning on modern bikes and that is the needle. The lack of taper on the needle creates midrange lean points. To compensate for the lack of taper on the needle, we use a larger main jet size then is usually required. Getting the needle taper is crucial on CVK's because if there is too much taper on the needle, kiss gas milage good bye. This is why the factory pro jet kits are pricey. They take the time to find the optimal needle/mains combo that delivers the best performance.

In most cases, we can just keep the stock needle, pop a shim under it and go up on the mains and have a great running bike. Sooner or later, your buddy will be adding a modded intake to compliment his pipes so it's not a bad idea to know basic tuning and doing it yourself.

 

Just my opinion but your buddy should have Never Accepted the bike in that condition. Especially a 06 model.
My 2 cents....


LV

 

Dont you just Luv that Sheet. Hey harley my bike just exploded and caught fire.
Harley dealers says oh, dont worry they ALL do that. Either that or they say Oh drive it awhile
and we will fix it at the 1000 mile service. What a Crock.....

LV

 

I always look at the simplest explanations first, so forgive me if this seems too obvious:
If not idling well, and stumbing bad off-idle, and no mods as of yet, and it's a brand-new bike, it sounds like an intake leak to me. It could be that the carb just wasn't seated properly onto the intake manifold during assembly at the MoCo, and eyeballing it won't verify. Only when no leaks can be found would I look at jetting/shimming, etc. Oh and FYI, the slow jet is sealed in with a plug for EPA reasons and needs to be drilled out to access it so - the dealer would do this when rejetting. Good luck!

 

Thats it. Check out the do it yourself forums, great info on tunning a CV carb. Its usuallly a good idea to tun it before you start rejetting.

 

Sounds like fuel mixture is too lean or you got a vacuum leak.
You said it is new so I would say warranty issue.

 

He needs to go back to the Dealer and take a firm stance that the "bike is not running right" and make sure that they know he knows that it is their problem to fix and fix NOW! He can be friendly in doing this. They just have to know he means what he says. It might not hurt to confirm by letter to the Dealer everything that he expects to be corrected. Letters always worry Dealers because they know the letter writer means business and is not apt to just "go away".

The engine is not right in something. They don't "all do that". If left for too long, this condition could lead to damage within the engine.

On the practical side, if he is going in in the next few days for the upgrade exhaust and jetting, he could let them know that, cut a deal and get everything taken care of in one trip to the Dealer. .................. BC