Stock bikes takes a CVK34 with no accel pump - there ARE CVK34 carbs out there that have built in accel pumps in the 34 and 36mm range.

I like the CVK for altitude range handling.

I did a search but couldn't come up with anything - has anyone ever tried to fit one of the CVK accel pump carbs on their KLX250 or big bore KLX?

 

You are stating you know there are pumper CVs or asking?

I'm not sure they make sense. The whole concept of the CV is that the slide opens as needed to keep the mix proper, where the accelerator pump gives a shot into the throat of a slide or butterfly carb without the cv slide.

Not saying they don't exist, just never had or seen one.

 

Do a search for "constant velocity carburetor with accelerator pump" and you get hits for some Harleys, a Vulcan, and some other stuff. I never heard of this, but apparently they exist in some form. I saw no hits for one that was on a dirt bike or modded to fit a dirt bike, but...

 

Hi KLX678,

I am stating a fact - they do make 34 and 36 and 40mm CVKs with accelerator pumps. They make them for Vulcans and Harleys and Arctic Cats, Suzuki 400 quads(?), and probably other things I don't know about.

I am looking at acquiring a 2006 KLX250S with the stock exhaust/ CVK carb set-up and know I will be looking at an exhaust/rejet possible carb swap traditional non-CVK Pumper in the future and then down the line either the 331 or 351 overbore kit.

I was curious if someone had tried to slot in one of the CVK with accel pump for a kind of "best of both worlds" scenario. I'm sure the body of the carbs will fit, might need to replace the throttle cable cam.

If I end up getting this bike I will probably try it just for the hell of it.

Here is a CVK34 for an Arctic Cat 400. You can see the accel pump next to the float bowl. The housing is probably also to keep snow out and keep the cam from freezing/sticking on snowmobiles? Part number associated with this carb is 0470-738,CVK 34-AE(PUMPER). I am not sure if the throttle cam housing would have clearance issues. It may be easily replaceable since the Harley version might not have this cam housing...







The electric choke could easily be replaced with the stock one from the Kawi. I doubt it would be worth it to try and make the electronic choke actually function.

 

falcn, there was time that I would have tended to agree with you about the benefits of a CV carb. Back then I had KLR650's, and I was able to go to CO and hit high elevations without changing jetting from my 1700' elevation at home. However, when I got the KLX, even with mods and added displacement, the bike would not run cleanly at the higher elevations with the 34mm CVK. The reason is that the smaller engine has less fudge factor for performance when the air gets thin compared to the KLR or other big bikes. Even with a pumper, I don't think you'll avoid rejetting, and in fact it may be worse at elevation. The best move I made was going to a flat-slide pumper carb which not only improved response and WOT running, but it actually increased fuel mileage. Not trying to dissaude your effort here.

 

Experience trumps theory! Thank you for the feedback on the high elevation and CVK carb.

Ever try the Dial a Jet kits? I am skeptical, but keep reading good reviews.

I also just like to tinker... So might still try this. Depends on if I get the bike.

 

I think KLX678 is your dial-a-jet guy around here.
I've contemplated adding one to the TM36-68.

 

Off to the Search function it is!

 

The large throttle housing might interfere with installing the pumper CVK34, and and accel pump itself might hit either the header or the cam chain adjuster.

I don't see that much of a gain compared to the 36mm. You'd get better throttle response with the pumper CVK but would still have the butterfly in there obstructing flow.

If you can borrow one or get one cheap it might be fun to see what happens, but in the end you're only gaining throttle response; no overall hp

 

I've been running the Dial-A-Jet in my KLX650 for about 16 years now, running from stock to big bore with full reverse cone megaphone exhaust. It has compensated for the lean mix when removing snorkel, installing 102mm piston (678cc), and adding the exhaust without altering the DAJ setting from the middle setting. Also ridden from about 18-95 deg. F and from sea level to around 5000+ feet in the Appalachians. Again, no alteration in setting. Exhaust tip color stays the same, seat of the pants says not much difference in performance noticeable, although I am sure there is some difference.

I have found the KLX250 must run significantly leaner because I am going to have to do some initial jetting to get "in the ball park" per Thunder Products' instructions for the DAJ. My brother has done the jetting, ridden, then installed the DAJ and found it smoothed out the performance over just being jetted.

It works as advertised, much like the Mikuni power jet, but it does not mix air with the fuel drawn in as the Dial-A-Jet does.