Jockey Journal Forum banner

V Twin Dual Carbs

54K views 73 replies 41 participants last post by  cpsdeni 
#1 ·
Whats up fellas. I've heard on more than one occasion that a v twin can greatly benefit from running dual carbs. I guess its something to do with uneven vacuum or something like that. I was wondering what everyone's thoughts were on the subject.

-Chris
 
#46 ·
we used to keep the stock manifod inlets on ours also and run a tube/plenum between the heads so each cyl. could draw from both carbs. intrupted flow some but they didn't flow that wellanyway coming out the left on both cyls. works best like setop in pic, ft...left facing rear...rear....rt facing ft. better for port shape. 115 hp. 84cid 139.9 mph (147 mph unofficial) ran a balance tube to idle at all for drags but like xr750 not needed at 7500-8000 rpm. if no plenum between carbs, run big carbs. 38-42 mm. carbs on ours 38 mm amals.
 

Attachments

#47 ·
lets see some dual carb v twins{that work}

since i dont have enough problems in my life i wanna try a dual carb setup on my hot ironhead, if i rememer right branch used to make a dual 38mm kit, anybody running duals? what size? im thinking common plenum to smooth out the tuning ...lets see what you got.
 
#53 ·
I have this VM29 Mikuni supercarbs for shovelheads. People say they are a bitch to tune is that so? I have a pretty cool set-up I was running. S&S heads with the 4 plugs & dual coils. I was also told that it has a big bore. It hauls pretty good with the s&s carb set-up. I was offered $300 for the set-up but dont know if I should sell it. What do you guys think?
 

Attachments

#54 ·
I know this threads been down for some time, but I figured it'd be better to pull up an old thread for a related question than to start a new posting. I really dig the way those mikunis on FabKevin's scoot. The post said its an old Kosman piece. I was wondering if it was a piece they produced, or a custom one off. I know a lot of their business is one-off pieces.

Either way, I was hoping Kevin'd be willing to post a few more pictures of the intake. I'm tossing around big ideas for new exhaust and intake on a bike I don't even have yet, and vintage go-fast pieces like that are the cat's ass as far as I'm concerned.
 
#55 ·
I know this threads been down for some time, but I figured it'd be better to pull up an old thread for a related question than to start a new posting. I really dig the way those mikunis on FabKevin's scoot. The post said its an old Kosman piece. I was wondering if it was a piece they produced, or a custom one off. I know a lot of their business is one-off pieces.

Either way, I was hoping Kevin'd be willing to post a few more pictures of the intake. I'm tossing around big ideas for new exhaust and intake on a bike I don't even have yet, and vintage go-fast pieces like that are the cat's ass as far as I'm concerned.
Cyclexchange sells the manifold and the carb setups. Good guy, I bought some stuff from him and talked to him on the phone. Check out his site and you'll see the kit he sells.

Sixball
 
#57 ·
I have a couple of questions about the factory KR dual tillotson set-up as described in the Competion Racer Model KR, KR-TT, and XLR-TT instruction. I'm working with a pair of HD carbs that appear to be modified in the way the instruction describes with the 12 degree velocity stack on the inlet end and the fixed Idle adjustment screw on the rear carb.

1) The picture shows a lever added to the oposite side of the throttle shaft assembly where the accelerating pump lever would go, but makes no reference to it in the instruction. I was ready to bolt up the linkage and found that the hole on the throttle lever is quite a bit less than the 10-32 ball stud on the P-103-S ball joint. Looking into it I found that I was working on the wrong side of the throttle lever assembly and there was an additional part. Is that correct? Any ideas about sourcing it?

2) The carb pair I have is missing some parts and I'm sourcing from a box of stock carbs. In picking throttle shutters, I have a pair that fit easily but have a small gap all the way around between the disk and carb throat. I also have a pair that fit the throat exactly but not into the throttle lever assembly slot. how important is a tight fit?

3) It appears that there are some additional adjustment needles for where the main jet plug screw would go. Its on the opposite side of where the intermediate adjustment screw is. Should I use them or source stock main jets?

4) I got two diaphram covers in the box o' carbs that look like the snowmobile kind. They ok to use? they fit.

5) For the clamp that bolts to the back of the intake manifold between the cylinders, I'm just going to cut it out of a 1" nipple from a plumbing store. Any better ways?

6) The illustration in the factory material shows no use of choke. I'm going to put this set-up on a KHK for street use and keep the choke. Any advice other than trial and error?

Thank you,

richie

PS hi Patrick, this is the same project from 4-5 years ago on your site. I got married and had two kids in the interim. slowly getting some time freed up after bedtime.
 
#65 · (Edited)
A friend of mine who knew I was looking for heads for my 48 sent me a craigslist link to these yesterday. before I could even decide if this was even an option for me I called the dude up and made the purchase before someone else snagged them up. I was told these were done by Jerry Branch back in the 80's and the guy I bought them from has had them since the esrly 90's and never did anything with them. It will be interesting to see how these work out and the new direction it has taken this project to.



 
This post has been deleted
#67 ·
By coincidence...Friend called today. Got his Outlaw Street DragBike ready with brand spinnin Dual runner Injection system...said to me
"wait till ya see it ..It's Baddass lookin"
I'll see it at the April BowlinGreen Harley Drags...
Maybe even get a Pic for ya!!!!!
 
#69 ·
qoute;"By coincidence...Friend called today. Got his Outlaw Street DragBike ready with brand spinnin Dual runner Injection system...said to me
"wait till ya see it ..It's Baddass lookin"
I'll see it at the April BowlinGreen Harley Drags...
Maybe even get a Pic for ya!!!!!"

Well, i for one, would love to see a pic of that! Not sure what a "brand spinning dual runner injection system" is but i know that from a performance and longevity standpoint, EFI or FI is the way to go! In the last 35 yrs of owning these type vehicles, i believe i`v had just about every type on the market. From the Bosch fuel distributor systems to the std electronic port injected systems, that i consider to be the best. Knowing that the Bosch electronic trigger`d systems were fired in sets of two,led me to mod a single carb Triumph intake for two Bosch injectors, pointed straight at the intake valve. The stumbling block was how to re-map the ECM for a shorter "spray" time for the large automotive style injectors. Nobody was doing that stuff back then, getting your ECM re-mapped now is somewhat commonplace!
However,before i got somewhat competent on these systems, someone gave my wife a very clean Volvo wagon with an engine compartment wiring harness that was irretrievably screwed! [someone had cleaned the engine compartment with an corrosive cleaner that softened up the insulation on the wiring harness to the consistency of peanut butter.] never did see injector reference via the "noid" light nor did it ever kick the fuel pump on. [although i could hotwire the fuel pump and it did pump] So i did the only thing a hillbilly with a welder would do, and thats build a stub manifold for a Weber "sidedraft" carb that i got in a trade! did away with the external hi-pressure fuel pump and added a "clicker" type electric lo-pressure pump. That car ran quite reliably for a # of yrs after. Not as good as if it still had the timed injection system, but good enough for the ole lady to run grocery`s in!
My ? is this, has anybody ever tried the Weber on dual throat Harley? Was the S&S dual throat a Weber type carb? Did they get it right? The Euro-type gearhead i got this carb from said they were a race upgrade for the Cortinas and Volvo engined MG`s and such that required the sidedraft configuration.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top