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Discussion Starter #1
Long time Harley rider here. I've had everything from 96" Shovels to 120" long rod Evo's. I have used every S&S carb from Super B's to Super D's and 42 and 45mm Mikuni's. However the best carb I ever used was believe it or not a CV. Check out woodcarbs.com The guy is a former Funnycar racer that builds CV carbs for Harleys. I have never had better throttle response or made more power than with his CV carbs. In 2005 I switched to Triumphs, first a Rocket III and now a Thruxton. I noticed that all the guys who are serious about making power in a Triumph dump their CV's. I am wondering if similar mods could be made to the carbs on our Triumphs and maybe end up with a better carb. After all the first thing most Harley guys do is throw their stock CV in a box and buy someting else when they actually have a superior carb already on the bike. It just needs a few mods. Go check out Bob Wood's website it has dyno comparisons ect.
 

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They're not that bad . I've tried both . Generally jetted right and without an airbox they're great . A heck of a lot easier to tune than CRs and stay in tune a lot longer plus they're not as sensitive to weather conditions compared to the CRs . Overall power CRs / FCRs are better . Overall simplicity to performance the CVKs .
 

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my mikuni HSR 42mm carbs kick the crap out of the stock carbs.

The stock carbs are too small. Maybe some larger CV carbs from a Sportster would help, but I don't think we'd need cv's with pumpers like the sporty has. Another problem would be making 2 separate carbs work in unison well. Then you get into actual money, then you realized that there are already carb kits on the market that work a lot better than a loose pair of cv carbs...
 

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Discussion Starter #4
I guess it's all wishful thinking on my part since nobody offers the mods on Triumph CV's like Wood does. Maybe someday it will happen. I can gaurantee you one thing though, you will never go back to a Mikuni after you have experienced the throttle response of a well tuned CV. You should really check out his website. The carbs are bored out so they will work with larger motors, up to 140 horsepower. He is a guy with an extensive racing background who was not satisfied with the performance of available carbs and took it upon himself to do something about it. Many hours of dyno time later he came out with a better product. I can't help but wonder if the same mods could be done with the carbs on my bike.
 

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Discussion Starter #6
Jeff, That sounds great,I was getting ready to do the same thing myself.
 

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I was couple of days ago keeping in my hands a set of Kawasaki ZZR1100 40mm CV carbs and thinking if that would work on Triumph. My friends ZZR is doing 160 rear wheel horses with those so a pair stripped from four should be enough for 80 rwhp on Triumph ( of course with other necessary mods to engine ). That is something like 95 crank horses. Thunder bike people said that they have seen over 75rwhp with stock 36mm carbs so this should be possible.

Of course it is also possible that a lot of trouble could be coming too because of engines being so different. However, carburetors job is to mix necessary amount of fuel to quantity if air going throuhg so it should work if carburetor size is not way out of scale.

Also a pair of Harley CV Mikunis could be a choise too.
 

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Discussion Starter #8
MONTTU,I would love to have 75+ rwhp on my 865cc Thrux. When I get past my current state of financial embarassment I am going to dump the airbox, flow the head, and install Thunderbike cams. I already have Predators installed. A set of worked carbs should push it a little higher. It would be especially fun to ride with the crisp CV throttle response.
 

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FWIW, my bonnie (former 865cc, same cams as thrux) makes 75 rear wheel hp.

engine mods:

904cc Wiseco kit
Bonneville Performance HSR 42mm carb kit
+2mm intake valves
+1mm exhaust valves
ported/polished head
Thruxton headers, thruxton Predators
Stock cams (I'll probably get South Bay 813 cams eventually)
 

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Discussion Starter #10 (Edited)
sweatmachine, sounds like a real nice motor you got there, nice bike too!! Like I said I am new to the Triumph twins. Stock horsepower is terrible but I didn't want to pull my motor down. I am looking for maximum gains without major surgery. Thunderbikes power claims seem very optimistic to say the least. When I get the bucks saved up we will find out. I will take it and get it Dyno tuned. One of these days I hope to run a 989,that will probably satisfy my craving for power....
 

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A friend of mine owns a shop that does custom work on Harleys. He said that a lot of customers want a Mikuni setup. He showed me a stash of CV carb take offs. He loves them and said that most people don't know how to set them up, but once dialed in they can't be beat.
The Mikuins are bullet proof and don't need much fussing with but won't give the response of a CV.

Mike
 

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The Mikuins are bullet proof and don't need much fussing with but won't give the response of a CV.

Mike
um, WRONG! I'm gonna have to call BS on ya here.

I'm sure you know this but...

The mikunis, being flatslides, give INSTANT throttle response since the slide is connected to the throttle cable. As soon as you move the throttle the slide opens.

The Keihins, or other CV carbs, the diaphragm has to open up in order for the carb to allow for accelleration, which takes a little time, and dulls the throttle response.

If you had actually ridden a bonnie with flatslides you might realize that you are mistaken. The difference is night and day, and it has nothing to do with properly setting up CV carbs.
 

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I can't argue this point because I'm not farmiliar with the Mikuni flat slide. I have only worked with what I would consider a standard Mikuni, similar to the old Amal MkII carb.

Mike
 

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Point taken, I guess carb technology has come a long way in 30 years.
I need to get out of the dark ages.

Mike
 

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Here's a good reference manual that discusses these carb issues

Another Haynes Manual. NOT to be confused with the standard Haynes Bonneville Manual. Chapter Four starts off with a section describing advantages and disadvantages of slide carbs, followed by a section describing advantages and disadvantages of CV carbs, Seems to be an 'application-driven' thing. Much of the fuel theory sections of this manual are too deep for a poor ex-marketing guy like me, but little pearls of wisdom pop up throughout.

http://s115.photobucket.com/albums/n284/bcgilligan/?action=view&current=HaynesFuelSystemManual.jpg

Also ..... a heads-up for you Scrambler owners - there's a good hop-up article in the January 2009 issue of "Motorcyclist" describing a Scrambler build-up by Bill Himmelsbach, who works at what was formerly Martin Eurosports, north of Philadelphia. Uses lots of pieces and parts from aftermarket suppliers commonly discussed on this site.

Bob
 

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I guess it's all wishful thinking on my part since nobody offers the mods on Triumph CV's like Wood does. Maybe someday it will happen. I can gaurantee you one thing though, you will never go back to a Mikuni after you have experienced the throttle response of a well tuned CV. You should really check out his website. The carbs are bored out so they will work with larger motors, up to 140 horsepower. He is a guy with an extensive racing background who was not satisfied with the performance of available carbs and took it upon himself to do something about it. Many hours of dyno time later he came out with a better product. I can't help but wonder if the same mods could be done with the carbs on my bike.

With all respect, you can't compare CV carbs with flat sliders.
There is an enormous difference in Performance in favor of the flat slide carburetors.
Cv's are like using a restrictor plate when you compare with flat slide carburetors.
We extensively modified the CV carbs for Bonneville's and it's a waste of time.
 

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+1 Ohiorider, that Haynes manual is an excellent first stop for learning about the different carby types. I'm sure there's plenty of more in depth stuff out there for folks who really want to get into it too.
 
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