CV Carburetor or the Mikuni HSR for Your Harley-Davidson

Is the CV carburetor better than the Mikuni HSR? It depends who you ask, some say you're throwing your money away on the Mikuni and you should just modify the stock CV carburetor. If your bike is stock (rare for a Harley) or lightly modified the CV carburetor may be just fine. However if you've got a big bore kit, cams, high compression and head work you'll want the HSR. Swapping an HSR out on a mildly modified bike will net you some gains but the gains increase with a more heavily modified engine. The CV carburetor will work with a high horsepower engine build if you modify it with a thunderslide and large jets, but at that point you will still gain more with the Mikuni carburetor. The Mikuni is a much simpler mechanically operated carb and tuning is a breeze with the best feature on this carb.

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Motorcycle: 2016 Harley-Davidson Sportster XL1200CP (Sportster 1200 Custom)

Custom Parts Installed:
Screamin' Eagle Heavy Breather air cleaner
Harley-Davidson Reach Seat
Harley-Davidson Chrome and Rubber Collection grips
Drag Specialties Offset Clevis Footpeg Conversion Kit
Aftermarket Detachable Back Rest
Harley-Davidson Air Flow timing cover
Harley-Davidson Air Flow clutch cover
Screamin' Eagle spark plug wires
Screamin' Eagle spark plugs
Flipped Down Stock Mirrors

Motorcycle: 2017 Harley-Davidson Sportster XL1200X (Sportster Forty-Eight)

Custom Parts installed:
Harley-Davidson Factory Security System
Screamin' Eagle Exteme Billed Air Cleaner (Black)
Harley-Davidson Burst Collection Foot Pegs
Harley-Davidson Burst Collection Grips
Harley-Davidson Burst Collection Shifter Peg
Screamin' Eagle spark plug wires

[GixxerFoo]

What's you're carburetor preference and why? Maybe you just hate carbs and prefer fuel injection...

[frankmarquet]

Back in the day when cv carbs were stock on the motorsickle and you wanted the Screaming Eagle upgrade when you opened the box there was a 42HSR Mikuni carb in it. That tells you what the HD engineers thought about them

[stevenking]

Just switched to a 42mm Mikuni on my '94 Evo and love it. The instant throttle response is something you can feel for sure.

[tazeredlife]

The CV carb was the first carburetor I’d ever worked on as a younger guy (27), and I have to say I took for granted how good a carb it is. I took it off my bike once to rebuild it when I bought the bike, and the way that the engine vacuum operates the slide basically means you just set your pilot jet right, get a decent sized main jet in there and check your throttle cables and you’re rocking and rolling.

[hawkdsl]

The CV is simple to tune.. it's actually a really good carb.

[scottarmstrong]

I agree with everything you said. CV carbs are fine with a stock or slightly modified engine but IMHO, if you've got a big cam, head work, etc, there's no point in modifying a CV. You'll be much happier with a Mikuni. I bought my 2000 soft tail used about 8 years ago. If it had to idle in traffic it would foul the plugs, didn't like to start when it was warm, etc. I took the carb apart and, low and behold! There was a Dyna jet kit. This is a stock 88 with air cleaner and exhaust. They had the biggest pilot jet available (I think an .048), but the wildest thing was they put 3 spacers under the needle! I figure there must have been 3 spacers in the kit so they just used them all. No wonder it ran like it did. What a bone head thing to do! So I rebuilt it with CV Performance parts and she's been wonderful ever since. Moral of the story - don't let a bone head work on your bike!

[JC-sfph]

Your channel is one stop shopping for basic Harley info. Good source. One of the few channels I subscribe to.

I am prepping to do a top end job and other work myself, on my 80k+ miles 93' Evo Heritage, bike show winner (2010 OKC Fair Grounds Bike Show). It sat for years while I was ill. Now I got to get it running right as cheap as I can. I come here to help me figure that out.

This episode confirms that I am going to rebuild my CV carb. again or have a service mega clean it, since it sat so long. For my autos, fuel injection is fine, but for my Harley, I like being able to tweek it myself with a screwdriver.

To your question, I prefer the CV over others because I already have it and it works well.

Looks like your an OSU Cowboy/fan? Dont hold it against me, but Im an O.U. Sooner grad. LOL!

[rubberduckydiesel]

I have the HSR on my 02 TC and I love it. 3 years, zero issues.

[bradwilliams]

I went with a Mikuni when I had my TC88B slightly modified back in the day. Per Harley-Davidson’s part manual I went with a Mikuni carb, hi flow air intake, Vance & Hines pipes, Screaming Eagle ignition, platinum plugs and a torque cam. I noticed a rather significant improvement in acceleration initially but have grown use to it over the years so it seems normal to me. 19 years later, knock on wood, and she still runs pretty good.

[cassel]

I run a S&S carb. Just used them for over 40 years.

[marshallyoung]

Long live the SU. I bought a shovelhead with a mikuni once. Removed and installed an SU. Ran beautifully. If a manifold was available I wouldn't hesitate to put one on a twin cam.

[aabikrman]

I've ran both carb designs on the Harleys I've owned and I wouldn't lose any sleep worrying about which one to run. I've ran both designs on one of my current rides (a 95" FLSTF with a very mild street cam) and there is very little difference between the two carbs. I would give a very slight edge to the Mikuni for a slightly better throttle response which makes sense given the butterfly of the Mikuni is mechanically operated vs the CV's vacuum operated slide so the fuel/air input is immediate vs, as a result of vacuum change. The difference is very, very, slight especially if the CV is properly tuned. In retrospect and based on experience, purchasing the Mikuni to replace the CV for that bike was not cost effective but if you're needing a larger carburetor to feed a larger engine with a more aggressive cam, better heads, exhaust, etc., then yes, I'd favor the Mikuni.

For one thing, the CV 51mm is the largest available but good luck finding tuning kits and or replacement parts for it such as the vacuum diaphragm. The equivalent Mikuni is the HSR48 which flow testing demonstrates is very similar to actually outflowing the CV51 so don't fixate solely on manufacturers size as a measurement of flow, let alone what is most desirable for your build. I had a 120" Electra Glide, which I just sold, equipped with the CV51 and it had great throttle response but not instantaneous. The difference is so slight between the two carb designs that I consider the point moot and from experience, I knew that changing that bike to a Mikuni wasn't going to materially change the performance so I never messed with it and wound up putting about 60, 000 miles on that engine/carb setup and never had any issues or complaints with fuel delivery including throttle response ! BTW, both carbs are easy to tune and are what I would describe as trouble free.

[kevindonohue]

old time rider. back in the Stone Age i ran a su because i would ride from sea level to the mountains in New York every other weekend. my bike wouldn’t be leaning out upstate. i could just ride without hurting my motor. the cv carb works the same way But, with a acc pump jet it with a cv proformance kit and it’s sweet

[ronford]

CV carbs work great when changing elevations from sea level to mountains.

[larryfromwisconsin]

My 1988 FLHTC Electra Glide Classic was modified by a previous owner with a CV carb, but that owner was in Wisconsin. In Southwestern Texas at sea level I needed to change a jet. It wasn't that hard of a job. Did not need to remove the carb from the bike. Just drop the float bowl and screw it out, new one in. Now runs great. On a Shovel I threw away the stock carb and ran a Lectron. It ran strong. With no other modification I was out running Evos. I think I paid $25 for it at a swap meet. Now they cost more than an S&S. I am happy with my CV carb and will stay with it.

[DOUGLIFE-Caintmakethishitup]

Love the channel! I’m an S&S feller myself…I got nothin bad to say about the CV. I’m actually going to be running my 03’ FXSTB with both carbs back and forth to do my own comparisons on performance/efficiency differences, I’m still just learning how to tune the cv. The S&s is basically really stinkin easy but requires adjustment just about every ride. Which I love to do. Cause I love touchin my girl…GIXXERFOO YOU ARE THE SHIZ. I’ve learned a lot from your babbling ons. The channel is greatly appreciated!

[frankmarquet]

Back when Harley was using the CV carb if you wanted the Screaming Eagle upgrade when you opened the box it contained a HSR 42 Mikuni. That tells you what HD engineers think about Mikuni. Nuff said

[thomasbarnardjr]

Which carburetor to choose is a decision that depends on a lot of different factors. I'd say that for a factory or mildly modified engine, you really can't beat the reliability of the CV, especially when it's properly tuned. And when it comes to repairs, or upgrades, I've found CV Performance to be the best company to deal with. Their products are much better quality, and their knowledge is spot on. The main thing to keep in mind is your application. Don't put a big high performance carburetor on a factory or mildly modified bike. Not only can it hinder performance in general, but it can also prove to be catastrophic. I learned that the hard way with my 1988 883 Sportster. Shortly into owning it, I was hit by a horse trailer that broke loose from the truck pulling it, and ended up totaling the bike. I settled for cash at the scene to avoid dealing with insurance, took the bike home, and began rebuilding a whole new bike with it. Other than the exhaust, the engine was unharmed, so I didn't need to change much. Due to my ignorance of what I was working with at the time, I let a salesman talk me into buying the S&S shorty with a thunder jet set up. I thought it would be needed for the new exhaust. The carburetor setup including the intake was over $600.00, plus the cost of smaller jets to put it on the 883. My best friend(who rebuilt this bike for me), tried to talk me out of it, but I wouldn't listen. Due to not understanding what I was doing, and not listening to advice from friends, I now had an 883, with a S&S shorty, and very short exotic choppers "fuelies" with 2 staggers leading to 2 1/4" pipes at the end. Even with the baffling, the pipes couldn't produce a good resistance, and the carburetor was so big for that little engine, that I could never get it tuned to run quite right. It blew 3 head gaskets, before predetinating on the front cylinder, and disintegrating the piston. The entire top end had to be replaced. After consulting with my best friend, and another professional mechanic, it was confirmed that the predetinating was caused by the carburetor and exhaust system I had chosen, as it was just way too much for an otherwise factory engine. I still have the exact same carburetor and exhaust system on the bike today, but now I have a 2004 Buell XB9 top end, Andrew's v6 grind cams and 4140 chromoly adjustable push rods, Jim's roller rockers, and Accell 35496 programmable ignition with stealth coils. This engine now can definitely handle the large carburetor and exhaust. But I wasted almost $2000.00 originally, and put even more into rebuilding the engine to where it is now, and all of it could have been avoided. The moral of the story is be careful when making decisions on which carburetor you choose, or any major modification for that matter. If I were building a hot rod engine like my Buell conversion, I'd probably go with the Mikuni HSR, but for anything basic, I believe the CV just makes the most sense. Bigger, higher performance carburetors can be cool, but they can also cause a lot of problems.

[eaytc]

I swapped out the CV and installed the HSR. Night and day difference with the throttle response. Definitely recommend it. Thanks for the great video.

[pauldavis]

Some years ago I swapped out my CV carb for the Mikuni 42 HSR on my 2000 Fatboy. I'm running Andrews 26 gear drive cams, 95ci, and have head work done. On trips, I usually get 48-50 mpg, so your analysis about not losing fuel economy is accurate in my case.