I work on a mix of 4 stroke motorcycles and ATVs... I noticed that Honda almost always uses a Keihin with a butterfly type choke. I know Keihin also makes carbs with a enrichment passage setup that has a choke ****, but I have only seen Honda use them on utility ATVs (CV carbs). Why does Honda prefer this type of choke setup over a carb that would have dedicated enrichment passages?

 

You must be talking about the sport quads, cuz my rancher has an enrichment passage. I think the advantage of the butterfly choke design is that it is a simple design. The passage type has a plunger and other stuff involved, which gets more costly to machine.

 

Because of the way a cv type carbs works, it cant have a choke plate, they need the enrichment circuit. A non cv carb can have either, but on cold days, a choke plate is much more effective, at enrichening the cold motor.
Using the non cv type of carb allows for an accellerator pump, and ease of tunibility. Popping the top off of the non cv type and adjusting the needle isnt a big deal, but on cv types the expensive diaphram is just something in the way, and must be installed just right, and must remain very clean..something hard to do at the track or dunes.
The slide can also be contolled on jumps and whoops...a cv type slide is only held in position in the bore by vacumn and spring, where the slides non cv carbs are held in place firmly by linkage...a jump or bump wont move the slide like on a cv style carb.. The throttle response on a non cv carb is sharper and not modified by vacumn....wide open is wide open, and on a cv carb, wide open at the thumb isnt nessarily wide open in the venturi, its like a vacumn secondary of the old holley carbs, they will only open as much as the engine vacumn demands.
If you have an accord or civic, look at the throttle body....yep Keihin. I think Kiehin is owned by honda, so it makes sense to use that brand on honda vehicles.

 

Well I understand why its not used on some motors vs others.. I was just wondering why they like it over other systems. As an example, almost all Yamahas that use a non-cv Mikuni carbs still use an enrichment passage/jet. I could see how using the plate would cut down on production costs though. I also noticed that the butterfly choke carbs don't let you do much until the motor is warm and ready to do so (thats almost a good thing).

 

Going to a bigger pilot jet, and /or adjusting the mixture screw richer, will help it come off choke faster.