CV??
- Thread starter prmurat
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The 34 single mikuni on my Cdo is possibly the easiest to twist throttle ever. It may also be the most "just bolt on and ride" of the available options. Got mine from Rocky Point and after a couple needle and jet adjustments( provided in the kit) its been no fuss, no muss for years.
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Thanks for asking prmurat, because I had considered them (CV carbs) at one stage.
Jim, what was the problem ?
Just curious.
AC.
Jim, what was the problem ?
Just curious.
AC.
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AussieCombat said:
When I put the CVs on my otherwise stock MK3 850 it really hurt the throttle response and made the midrange very soft. The bike ran very nice and got great fuel mileage but it was slow. I only rode it for a few weeks that way and tried several things to try to make it snappier but I ended up removing them. I can't say that it was just because they were CVs or if there was something else that wasn't dialed in correctly but I gave up.
They didn't fit very well either. They were too wide and made fitting anything but a sock air filter impossible and the big top hit the frame.
I ended up putting the carbs on a buddies MG midget and he was happy as could be. Jim
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That's by far the universal summary of behavior of vacuum balanced throttle carbs, about perfect behavior for best mileage, which means not fueling in a rush. A single carb spring is half as much to hold and I noticed this going to duals and back close together. Grip twist-hold assist tabs and devices abound to look into. Well at least until comnoz brings us a fly by wire throttle injector kit, then could set grip feedback from zero to dual carb and beyond : )
Me thinks the "universal" view is more than passe .... GSXR etc all had CVs before injection and we all now know that all these modern bikes do not not handle, brake etc but they are anything but slow... My Vmax has 4 CVs and has enough power for me... Some Jotta Laverda owners even adapt GSXR carbs on their bikes to get rid of the Dell'orto... I am trying to remember wich Honda 500 had twin CV and I see only the 500T (detuned CB450) with these 1st generation CVs with the huge metal dome, a la SU... I am thinking more in terms of rubber diaphragms ones.
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prmurat said:
That may have been part of the problem. I did use a dynojet kit that had some needles and drill bits to enlarge the holes to the vacuum chamber.
As I recall the carbs with the larger diameter rubber diaphragms wouldn't clear the web between the downtubes.
Maybe they were too small too? I feel that when going CV it is a must to go 2mm larger than a piston carb???? Thw 1st XS650 (only 650cc) had 38mm... So I guess that a 38mm will be a minimum for a 850 Commando??? Getting closer to the 40mm HD or 39mm from a DR Suzuki quad... Looking around there are all the ones made for Quads, SkiDoo, Jet ski (when 4 strokes of course!)
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I don't remember what size they were for sure. They were bigger than the Amals but they had an oval venturi and a butterfly in the way.
My experience with replacing CV carbs on modern racebikes with FCRs has been the FCRs make quite a bit more power through the midrange and about the same top end. We normally used the next size smaller FCRs in place of the CVs.
My experience with replacing CV carbs on modern racebikes with FCRs has been the FCRs make quite a bit more power through the midrange and about the same top end. We normally used the next size smaller FCRs in place of the CVs.
Anyone tried a Bing carb yet? Different sizes for different models. Also---different springs used but interchangable. The spring rate would allow for a more rapid opening of the slide---then there is the matching up of the vacuum pull on the Norton and the CV carb. The CV carb slide would have to be fully opened at the same rpm as the bike it was removed from---then it would be a matter of jetting. A lot of work--trial and error before getting it dialed in. But it should work.
My js 32pwk's are dialed in. But that won't stop me from a little R&D. As soon as I find a good Mikuni TM 40-6 at a good price, i'm going to try and dial it in and see. They are only 5mm taller than the tm34 and from centerline mount, it is short to the top. That is to say taller at the bottom.
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