Will this CV Carb work?

[Sanch]

I've read many forums here about how well the CV works on our old bikes, so does anyone know if this CV carb will work on my 73 XLCH? The part number is 27492-96a and I'm wondering if it has an accelerator pump for starting or if it matters?

Sanch

[motomotard]

dont know about the accel pump, but yeah CVs will work. you have to get the manifold adaptor from vtwin or something. most are rubber and apparently dont work very well.

[GA_Ironhead]

... does anyone know if this CV carb will work on my 73 XLCH? The part number is 27492-96a and I'm wondering if it has an accelerator pump for starting or if it matters?

It will work, but isn't a bolt on item. Like Motomotard says, you'll need some sort of adapter. The three adapter schools of thought are: (1) rubber flange w/clamps (think metric), (2) press on adapter w/JB Weld and (3) adapter w/original CV mounting seal. The last option is what I used and got the pieces from Fog Hollow.

You may need to modify the throttle cable direction of movement (pull-on) and method of attachment. You may also need a new A/C if the carb doesn't have one with it. You'll also need a spot to mount the enrichener cable and provide support for the carb. All these were things I needed to address.

I believe that post 1988(?) CV's are the desirable ones. A '96 will have the accelerator pump, which makes kick starting much easier.

An installation tutorial (and more) lives here: http://www.sportster.org/tech/

[Fe Head]

Yes it is a conversion well worth doing and if your handy yourself or have a good place to do some of the mods it can be achieved with minimal cost.

This is what I wrote on another thread having the same topic. It is a bit lengthy but will give you a rough idea of how I used step #2 in GA Ironheads post for my conversion.

************************************************** ****************

I put one on my '79 XLH with minimal changes. I used a 3/8" piece of aluminium plate and traced the shape of the old manifold attachment face and the two bolt holes onto it. I then cut away the excess, drilled the holes 1/4 " and tapped then 5/16 X 18 for the old Keihin studs that I reused.

I then drilled and bored out the centre orfice ( using a lathe) so it was a interference fit over the CV's O.D. where the rubber coupler used to be clamped. I then put the J B weld on the O.D. of CV's ridges and mounted the new homemade manifold adapter plate letting it set up over night in a warm spot. This is the trickiest part as it needs to be oriented correctly and square before gently hammered over the O.D of the CV's throat.

The enricher cable and knob fit perfectly into the original choke hole - it is just long enough to reach.

I then set about re-shaping the backing plate for the original air filter by heating hammering and a little grinding till it fit up to the face of the CV and still used the two original brackets that hold it to the engine. I then drilled the three new holes to match the CV intake side and filed the orfice of the original air cleaner's opening to mate up smoothly. The chrome cover needed to be cut out to allow it to go around the CV vacuum diaphram cover. I then refitted the new cut edges with the 'U' shaped rubber edging on both the backing plate and the ham can cover to make the two components seal.

A new K&N filter was used replacing the original sponge one but needed to be cut out around the same CV diaphram cover and siliconed with a flat strip of soft rubber to keep the filter membrane's cut ends sealed against the CV housing.

The original throttle cable works but the holding bracket on the CV was cut off and turned 90 degrees and welded back on so it lined up right over the throttle plate actuator.

In the end from the side one can not tell the conversion has occurred .

Looking down you just see the chrome slide diaphram cover and the 3/4 " knotch cut out of the original ham can breather cover. Even the crankcase vent hose hooks up as before.

It made a huge difference when combined with the conical lollipo;ps in the 1 3.4" drag pipes and was easy to tune using the typical indicators providd by the plugs and performance over the full RPM range.

If your handy with a few tools its a stealthy approach that keeps most people guessing.




All the best with your decision should you choose to make the conversion.

Cheers;

[Gone]

yes, as has been stated, the CV will work. If you do a google search on CV carburetor conversion to Sportster IronHead you will find a site with pretty much step by step instructions.

[54-FLE]

I'm running a 94' CV on my 1980 iron head and its great. I had to buy the adapter off of the guy on e-bay that sells them, the kind you press on and use some JB weld to seal it up. The adapter presses onto the CV carb and bolts right up to your Iron head manifold. Its darn near a drop in procedure. The adapter only cost around 38 bucks. You will need to find an air cleaner of your choice, I got one from Drag and had to do a little tweaking on it to fit but its on and does great. I love the CV carbs because they are so easy to work on. Get a stock one not a hopped up one though. I bought a stock one and had it hopped up and never could get the bike to run right, just wasn't enough cc's in the engine so I bought another stock one and its running great. The main advantage of course is they are cheap compared to most other choices out there.

[waza]

You will have to do some jetting. The ironheads seem to require a much richer jet set.

Good luck, when you get it sorted, you can forget about it as they are pretty trouble free.

[54-FLE]

You will have to do some jetting. The ironheads seem to require a much richer jet set.

Good luck, when you get it sorted, you can forget about it as they are pretty trouble free.

True. Mine is set at 48/185 as opsed to the original 45/175.

[XLFREAK]

why are the cv carbs so good for ironheads?

[54-FLE]

I had an old Khlein carb that was ok, then I bought a new Bendix and it was better but then I tried the CV at someone elses suggestion and it is far superior in performance. Thats all I can tell you. I can't give you any technical ins and outs but its in the overall performance for sure.

[Sanch]

Great news all around as I expected from reading all of your expert threads that this really should work out pretty well. It already has the manifold adapter pressed on the carb so that saved me some $$$. I've been fighting with the Bendix for 2 years now and even though my plugs are tan and look good even down at the bottom of the ceramic, it just wants to be a bitch some days.

My main issue I believe will be the throttle. Fe Head - Do you have any pictures of how you hooked up the old solid steel cable to the CV?

[54-FLE]

I'm using BDL controls and mine has the brass barrel shaped thing at the end of the cable that goes into the carb body slotted hole. I'm also using a single cable, no return cable (old school way). Ive never hooked up a stock sportster cable to anything. The same throttle cable worked on the Bendix as well. The solid steel part at the throttle itself is for adjusting the slack or tension out of the cable for the optimal throttle response. Hope I'm understanding everything.

I tried to upload some pictures of my set up but I keep getting the exceeds the file size limit thing. I can't upload phots on any website anymore I guess. I dont know if its a software problem or what but oh well.

[Sanch]

You can mail the photos to me at varmit_1973@yahoo.com

[54-FLE]

Pictures sent. Let me know when/if you get them.

[Hopper]

I had an old Khlein carb that was ok, then I bought a new Bendix and it was better but then I tried the CV at someone elses suggestion and it is far superior in performance. Thats all I can tell you. I can't give you any technical ins and outs but its in the overall performance for sure.

When you say better performance, do you mean just straight out acceleration adn top speed type performance?
Or is it better for starting, idling and low speed pick up as well?
What sort of gas mileage do you get?

As far as techinical ins and outs go, I have an old BMW 1000cc twin that uses one 40mm CV carb on each jug. They seem to work well because the slide is closed at idle and opens progressively as revs rise and throttle is more open. The slide is in addition to the throttle butterfly so really alters teh effective size of teh carb throat.

This is like running say a 10mm carb at idle, a 20mm carb at low to mid speeds, 30mm carb when cruising on the highway and a 40mm carb when going flat out. Perfect.

[Fe Head]

Great news all around as I expected...snip.....My main issue I believe will be the throttle. Fe Head - Do you have any pictures of how you hooked up the old solid steel cable to the CV?

Sorry I don't have any. The 1979' s throttle cable was not the solid type as they used the flexible cable with the exact same swedged-on end piece as the newer CV carburetors. I just had to lower the CV throttle cable's holding bracket so at full throttle it was about 1/4" away and tangential (straight in line with) to the throttle plate shaft's curved semicircular actuator plate that carried the flexible throttle cable.

With a traditional solid/rigid pull/push throttle wire you need to acquire the carburetor end off of a used or old flexible cable system. There are many sources like ATV's, snowmobiles, dirt bikes etc. as long as the "Tee Barrel " swedged on is able to fit the~ 5/32 -3/16 inch CV actuator plate hole and the flexible cable length is 2 1/2 - 3 inches long. Then using a 5/16 inch rod about 1/2 -5/8 inch long dill a hole length-wise that will allow both the flex and the solid cables to both pass through from opposite sides 1/8 inch I would suspect be enough. Slide each all the way through leaving a little sticking out on each end. Put the rod holding both cables in a vise and squeeze very hard to compress the hole around both cables and secure them.

Take your current throttle holding bracket and cut it to fit to the CV one so your alignment is correct and that it allows the swedged joint to move freely between the actuator plate when at idle and then not hit the solid cable's casing when at WOT.

A small carefully placed tack weld on each side will join the old to the new. You will need to shear off the cable holding part of the CV carburetor as it sits too high up and at the wrong angle.


It is certainly doable and should be easier than changing the entire twist grip and cable assembly.

If it has not been mentioned earlier the right angle vacuum elbow should be left and plugged or capped off ready for future use if you happen to migrate to an electronic ignition system down the road.

Let us know how it works should you decide to make the changes.:tour

Cheers;

[Sanch]

54-FLE - Thanks for the photos and nice job with the bike

Fe-Head - Great suggestion on marrying the two cables, I think I'll try that route. As for the vacuum port, are your referring to the VOES? I just installed a Crane HI-4 and was thinking of adding one. Is it worth the cost and effort installing it? It's an old bike that I do some poker runs, evening get aways and weekly "bike nights" so as long as it starts and runs well, I'm not too concerned about getting a couple of mpg more.

[54-FLE]

When you say better performance, do you mean just straight out acceleration adn top speed type performance?
Or is it better for starting, idling and low speed pick up as well?
What sort of gas mileage do you get?

As far as techinical ins and outs go, I have an old BMW 1000cc twin that uses one 40mm CV carb on each jug. They seem to work well because the slide is closed at idle and opens progressively as revs rise and throttle is more open. The slide is in addition to the throttle butterfly so really alters teh effective size of teh carb throat.

This is like running say a 10mm carb at idle, a 20mm carb at low to mid speeds, 30mm carb when cruising on the highway and a 40mm carb when going flat out. Perfect.

Well you just about answered your own questions. You pretty much described the over all performance i was talking about. The CV idles better and has better/smoother acceleration throughout the entire ranges. The best way I can describe it is with the other carbs, every gear felt wound out too early, really quick like, then it took awhile before fourth gear would get up to optimal speed and the engine would temporarily feel bogged down a bit. I'd have to stay in third gear around town and it felt like I needed to shift into fourth but if I would it would bog the engine down real bad. Now with the CV carb I can wind each gear out with smooth rpm's and I can actually cruise in town on some of the longer roads in fourth gear (40-45) a without bogging the engine down. Every gear is smooth. The whole concept is like driving a four wheel drive truck with all the low gearing and then getting into a nice car. Should have just said that instead of writting a letter:rolleyes:.

[Fe Head]

54-FLE - Thanks for the photos and nice job with the bike

Fe-Head - Great suggestion on marrying the two cables, I think I'll try that route. As for the vacuum port, are your referring to the VOES? I just installed a Crane HI-4 and was thinking of adding one. Is it worth the cost and effort installing it? It's an old bike that I do some poker runs, evening get aways and weekly "bike nights" so as long as it starts and runs well, I'm not too concerned about getting a couple of mpg more.

The VOE switch when added and set up to ground the green (I believe) wire that you now have taped off form the Crane HI-4 allows your bike to run with more advance for better milage and smoother operation when cruising and then to back off the advance when under load or passing another vehicle without that ' Pinging ' sound and the damage it causes.

If you're happy with the current timing setup I would get used to the new CV first then add in the VOE switch if you want to get some added performance or efficiencies.

In my experience -it is ususally best to make one change at a time and then move to the next one. The switch when added needs to be set up for closing at the 3 - 4 inches of Hg (mercury) vacuum as I recall.

All the best with the CV conversion, I know you'll be pleased.

Cheers;