Mikuni on a Sportster

Re: Deluxe Tuners Kit+

The advantage a CV carburetor has over the Mikuni is a CV's slide is self regulating since it is moved by vacuum. Whereas a Mikuni's slide is regulated only by the throttle. What this means in terms of tuning is the CV is far more forgiving in the mid range and rarely needs rejetting when riding in higher altitudes. The CV also has an adjustable mixture screw to dial in the A/F mixture in the range just off idle.

Looks like you have everything covered with your parts selection.

Re: Deluxe Tuners Kit+

I would hold onto the original CV carburetor. Over the years I built or resold hundreds of carbs for people that were dumping their Mikuni's and Super E's to go back to the original. Someday if you or the next owner feels the same way you may wish you hadn't of sold off the original. Also the 60-70 bucks you can get for it today will double in cost if the time comes to buy another one.

Re: Deluxe Tuners Kit+

I would actually have to disagree on a couple of points here. The CV carburetor is not the limiting factor on power - displacement and flow are. Dyno sheets show that on a standard 883 to 1250 conversion, HP remains neck and neck with both a CV40 and Mikuni up until 5000 rpm and then the MK breaks away slightly. On that stock 1250 conversion the CV40 tops out at 74.1 and the MK (HSR42) reaches 75.7... but that is at almost 6000 rpm's! I don't know anybody (except racers) who constantly run that high on a regular basis.

Improve the heads ('04-06 1200 stage 2 heads), new cams, and ignition, and now the CV40 can produce just over 98 hp while the MK excels in the upper rpm's to peak at 103. Again, this is only above 5500 rpm, otherwise both are even up until that point.

In my opinion, if you are already dropping the ca$h on heads, cams, and ignition, then by all means the extra 300 on a Mikuni HSR42 is not going to break the bank. But for anyone just trying to achieve good power out of a carburetor that still maintains good MPG and doesn't need adjusting when riding at all altitudes (the MK can't) then stick with the CV40.

My last point would be concerning fair price for a CV40 carburetor. I honestly believe there is a disconnect between what a used CV is worth and what some people on ebay have tried to inflate them to. I started building CV carbs back in 1989 when they first started rolling out, and people were pulling them off in exchange for S&S (old habits). While the price has naturally gone up from around $30-40 a few years ago to double that today due in part to lesser supply, the most I've ever paid for a CV40 was 90. And that was for a carb pulled off the bike on the showroom floor that still had the factory inspection marks on it. Looking at this from the standpoint of someone who may need that carburetor as opposed to a builder who has to turn a profit, a 13 year old carburetor in excellent condition would be fairly priced around $60 including the shipping. Then again, it's all about what the market will bear so if you can get 100 by all means go for it.

Looks good.

I had your message thread moved out to the Motorcycle Tech Talk forum category since the subject is no longer concerning CV Performance products.

If you believe everything you read about performance
parts and what they can do for you, then for about $4K
you can bolt on 8000 horsepower with Joes heads, bobs cams
toms intake, reds exhaust, bills' carb LOL it's nuts.

FWIW I'll echo Kens sentiments on the carb change.

JMO unless the engine requires a larger carb, changing it
is no better than tossing the money in the trash can as far
as performance gains.

Mik will work on the carb, as long as it's a 42, and while you
might feel a little more power up top, it's doubtful unless the cv
carb was so poorly dialed in and you just happen to pop on the 42 and
it's setup right.

Only the dyno knows for sure, take the bike over, get a dyno pull (3 runs)
with the CV, now, go back and do the Mik after it's on, that way you know
if you made the right move and if it's tuned correctly.

JMO I'd have dropped the extra green on PAB....