Accelerator CVK Carb Install?
Senior Member
Joined: Aug 2009
Posts: 4,650
From: Delaware, Ohio
1st Gear Member
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...
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...
Interesting... never saw one.
I've always wondered about the diaphragm carbs - no float bowl - like Karts run/ran.
Don't know how they'd work.
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Joined: Jul 2013
Posts: 38
Now some CV carbs do allow for an accel pump and the fuel bowl looks about the same with the pump and all but they are connected to the throttle linkage by a control arm.
Senior Member
Joined: Sep 2009
Posts: 5,050
From: Abilene, TX
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The pump in the images you attached are not an accel pump but only a prime pump like you find on some lawn mowers to get fuel into the system when it has been sitting for a while. There is no connection between the throttle linkage and the pump on this Arctic Cat carb. There is a push lever that you can pump by finger to prime the motor I guess in cold weather or if it has not been started in a very long time.
Now some CV carbs do allow for an accel pump and the fuel bowl looks about the same with the pump and all but they are connected to the throttle linkage by a control arm.
Now some CV carbs do allow for an accel pump and the fuel bowl looks about the same with the pump and all but they are connected to the throttle linkage by a control arm.
arctic cat 400 carb diagram - Bing Images
Last edited by TNC; Aug 8, 2014 at 03:11 AM. Reason: add pic
Senior Member
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Joined: Mar 2013
Posts: 866
From: SE Asia
The pump in the images you attached are not an accel pump but only a prime pump like you find on some lawn mowers to get fuel into the system when it has been sitting for a while. There is no connection between the throttle linkage and the pump on this Arctic Cat carb. There is a push lever that you can pump by finger to prime the motor I guess in cold weather or if it has not been started in a very long time.
Now some CV carbs do allow for an accel pump and the fuel bowl looks about the same with the pump and all but they are connected to the throttle linkage by a control arm.
Now some CV carbs do allow for an accel pump and the fuel bowl looks about the same with the pump and all but they are connected to the throttle linkage by a control arm.
You may be onto something OR maybe the accel pump can also act as a primer? I did a quick search for Arctic Cat prime pump and there's lots of results including this:
http://www.arcticchat.com/forum/util...when-cold.html
Senior Member
Joined: Sep 2009
Posts: 5,050
From: Abilene, TX
1st Gear Member
Man, these are confusing carbs. I searched some more and found some with a priming plunger on the side of the float bowl just for priming...found some without any fuel assistance by either primer or accelerator pump...and found some with an accelerator pump. How many of these freaking carbs for one ATV do they make?...LOL!
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Junior Member
Joined: Jul 2014
Posts: 8
From: East McKeesport, PA
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 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 understand your point about the butterfly mechanism itself being an obstruction whereas the slides you lift with the throttle cable don't have that issue. My old thumper GP supersingle race bike used a VM38 round slide.
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Junior Member
Joined: Jul 2014
Posts: 8
From: East McKeesport, PA
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.
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.
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Junior Member
Joined: Jul 2014
Posts: 8
From: East McKeesport, PA
I certainly claim no authority on the knowledge of this particular carb, but that pump rod sure looks like it's incorporated into the throttle linkage. If I could see a better angle of the carb maybe I could tell more. Also if you google a parts diagram of this carb, you get the description of "accelerator pump diaphram" for that part of the carb.
arctic cat 400 carb diagram - Bing Images
arctic cat 400 carb diagram - Bing Images
It is a little crytpic finding information on these.
Here is a pic showing one linked to the throttle cam through a plate: http://ww2.justanswer.com/uploads/So...8_carb_pic.jpg
Perhaps I shouldn't buck the trend and just get a flat slide like everyone else
haha I have a curious personality when it comes to these things though and like the challenge sometimes of alternate solution investigation. Somewhere a Harley/Vulcan rider is laughing at us about our lack of knowledge on CVK accel pump carbs!
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Junior Member
Joined: Jul 2014
Posts: 8
From: East McKeesport, PA
I use a stand alone "vacuum" pulse fuel pump on my DR250SE T-d off the crank vent. My Elefant has one from the factory to get the fuel from the droopy tank wings uphill into the carb inlet which sits higher than the petcock outlet. Mikuni pumps. They are not high pressure so they work with most float controlled carbs as well and don't overpower the float needle as easily as electric pumps. You may have to slightly raise the float clip so it pushes up on the float needle a little bit sooner to avoid too high of fuel in the carb which is worse than slightly low.
I have 15000+ miles on my little DR fuel pump with no issues.
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Joined: Aug 2009
Posts: 4,650
From: Delaware, Ohio
1st Gear Member
I'm not under the impression that a carb adds HP, it only appears to do that if it is not as restrictive as the one it replaces and the engine has the ability to actually flow more air than the original carb opening allowed. The immediate throttle response of the accelerator pump was what I was interested in testing since that is the major point everyone loves about the pumpers.
I understand your point about the butterfly mechanism itself being an obstruction whereas the slides you lift with the throttle cable don't have that issue. My old thumper GP supersingle race bike used a VM38 round slide.
I understand your point about the butterfly mechanism itself being an obstruction whereas the slides you lift with the throttle cable don't have that issue. My old thumper GP supersingle race bike used a VM38 round slide.
I still wonder if that old VM36 would work well on the 250 since they worked for decades on the old big singles. They can be had for about $100 versus nearly $300.
