Boyeseen CV40 carb float bowl / adjustable ACCELERATOR (NOT Fuel) pump

[JamesButler]

Anyone use this product? Replaces the stock CV-40 carb float bowl and has an adjustable fuel pump.  Seems like they also make one for the S&S Super E carb... 

Straight-forward swap and claims to be "The most effective way to add performance to your stock CV40 carburetor"..."Made in the USA"
The company is located somewhere in PA...

While I don't necessarily believe the claim, I was wondering if anyone has experience --good, bad or indifferent-- with it?

[turboprop]

Not an adjustable fuel pump, its an adjustable accelerator pump. Big difference. Boyseen also makes them for the Super E and G carbs. I have on on a Zippers G3 carb. Not sure about it making any more horsepower but it does provide another point of adjustment.

[black bart]

I purchased and installed the Boyesen fuel bowl with an adjustable accelerator pump. Installed it straight out of the box onto my CV carb. Never bothered adjusting the accelerator pump due to it's working perfectly as is. There is no power gain with this product, and it's expensive. If you're not currently experiencing accelerator pump/fuel bowl problems, you don't need this product. It bolts up perfectly, no leaks, no misalignment issues. and it very well made. All of the CV carb jets and needle are located in the main carb body, nothing in the bowl, just the accelerator pump.

[JamesButler]

Not an adjustable fuel pump, its an adjustable accelerator pump. Big difference. Boyseen also makes them for the Super E and G carbs. I have on on a Zippers G3 carb. Not sure about it making any more horsepower but it does provide another point of adjustment.

Yep, meant accelerator pump.  Correction made.  Read it correctly and lost it in translation when processing then typing it.

[JamesButler]

I purchased and installed the Boyesen fuel bowl with an adjustable accelerator pump. Installed it straight out of the box onto my CV carb. Never bothered adjusting the accelerator pump due to it's working perfectly as is. There is no power gain with this product, and it's expensive. If you're not currently experiencing accelerator pump/fuel bowl problems, you don't need this product. It bolts up perfectly, no leaks, no misalignment issues. and it very well made.... just the accelerator pump.

Thanks.  In other words, "If it ain't broke...", But if it is, then maybe it's worth experimenting albeit the extra cost...

[Hossamania]

Usually a new stock accelerator diaphragm and spring, clean the orifice, new o-ring (or 2 depending on the carb), will take care of any problems with that circuit, for not a lot of money (less than $20 I think).

[turboprop]

Most of you have missed it, but the useful feature of that is to be able to reduce the volume of spray from the accelerator pump.

The pump on a CV has no adjustment and the one on the Super E & G can be adjusted only for when they stop spraying, not for volume.

Additionally, the unit for the CV has a removable bowl drain plug that allows easy main jet changes and it has a drain plug, something that the later CV carbs lack.

While not endorsing these devices, I bet if the regular barstool crowd here were to drill into these things the way they do lifters or oil, there would be countless features and differences exposed. Funny how these things go.

[JamesButler]

...The useful feature of that is to be able to reduce the volume of spray from the accelerator pump.
The pump on a CV has no adjustment and the one on the Super E & G can be adjusted only for when they stop spraying, not for volume...

So, the benefit of the adjustable accelerator pump is to better fine tune the air-fuel ratio with the slight turn of the screw, instead of changing jets - particularly handy in areas of changing climates / seasons and altitudes?  What else? 

On the other hand excluding the price-facor, it may not be desirable because it's viewed as frivolous, and / or another component that adds more time to understand rather than keeping it simple...   

[Hossamania]

The accelerator pump has nothing to do with jets, it is strictly a pump that pushes raw fuel into the throat of the carb when twisting the throttle to keep it from stumbling. The kit may or may not be necessary, I haven't really had a problem with the stock set up. It also sounds like the Boysen kit has access to the jets to make it easier to change them, again, I have not really had a problem needing multiple jet changes once the carb is tuned. The CV carb adjusts itself pretty well for changing conditions and altitudes. If you were using it for racing and wanted to fine tune for the track, then it might be a convenience, but for the average rider, I don't see it as being necessary.

[JamesButler]

...The CV carb adjusts itself pretty well for changing conditions and altitudes. If you were using it for racing and wanted to fine tune for the track, then it might be a convenience, but for the average rider, I don't see it as being necessary.

Might be better suited then for the S&S carb, which does not adjust itself for changing climates and altitudes...

[sneakypete]

I've been tuning S&S carbs for years, one thing I can say about them is they don't need to be retuned for changing seasons or altitudes.
I just moved from 300 ft. to 3000 ft. above sea level and the S&S e in my old softail runs the same as it did flawless.
One of the best things about the S&S is that its a set it and forget it component. Changing jets have never been a big deal, while you must drop the float bowl to get to the pilot jet the main jet is accessible from under the float bowl.
Easy to use easy to work on.

[turboprop]

...The useful feature of that is to be able to reduce the volume of spray from the accelerator pump.
The pump on a CV has no adjustment and the one on the Super E & G can be adjusted only for when they stop spraying, not for volume...

So, the benefit of the adjustable accelerator pump is to better fine tune the air-fuel ratio with the slight turn of the screw, instead of changing jets - particularly handy in areas of changing climates / seasons and altitudes?  What else? 

On the other hand excluding the price-facor, it may not be desirable because it's viewed as frivolous, and / or another component that adds more time to understand rather than keeping it simple...   

As stated by others, the pump has nothing to do with the jets. That being said, there have been many times in the past that I would have liked to reduce the amount of fuel sprayed by the accelerator pumps in both the CV and Super E/G carbs. This bowl for the CV and the piece for the Super E/G allows just that.

In comparison, the Mikuni HSR 42/45/48 carbs have accelerator pumps that can be adjusted for when the pump starts to spray, when it stops spraying and the size of the nozzle can be swapped out (three sizes available). Bottom line is the accelerator pump will not affect the AFR during steady state conditions, but it will affect the AFR during periods of acceleration and will/can smooth the transition areas.

The drain plug on that Boysen bowl would make it very easy to change the main jet.

Most of these features will probably not important to the masses. I think if any of my bikes ran a CV carb I would probably buy one of these just for the ability to tune down the volume from the accelerator pump and be able to easily change a main jet.

Also, if I were in the business of dyno tuning carb'd bikes I would probably want to have one of these on hand. Swap it in at the first jet change, swap it out after the last jet change.

[Hossamania]

That's what I was thinking, would be nice for tuners to facilitate easier jet changes while tuning.

[turboprop]

Update to this old thread on the Boyeson Twin Shot float bowl with adjustable accelerator pump.

A local guy that I see around town sometimes asked me to tune his 88" evo (3-⅝" bore x stock stroke). Nice little engine, heads have been rubbed on, little EV-46 cam, 10: compression (cranks at 192 lbs), and a Thunderheader.  The carb setup is an oem manifold, CV41 from a late model TC with an adjustable idle jet and a float bowl spacer. The AC is from HPI and has a little venturi built into it.

The engine put out the typical numbers expected of this combination, but used smaller jets than typically used. He has been riding the bike for a few weeks since I tuned it and reports fuel mileage to be around 53 mpg. This is in a naked FXR platform with 32/70 rear gearing and 24/37 primary drive.

I rode the bike after tinkering with it on the dyno over the course of a week. While it cannot compare to the 124" TC FXRs that I typically ride, this little engine was a lot of fun and ran really smooth.

Bottom line - I thought the adjustable acceleration pump was very useful and attributed the better than usual gas mileage to it. The removable plug on the bottom of the bowl allowed the main jet to be easily changed. If I were running a bunch of bikes with CV carbs, I would install one of these at the onset just to have easy access to the main jet and then swap the oem bowl back in when everything was finished.