78 replies to this topic

[spuker1]

Hi,

I'm going along with my bike carb project fine, I have got set of bike carbs that I think I want to use (Keihin carbs, they come from Honda CBX550 F2). I have been reconditioning them. I have also got an wideband afr sensor and gauge to help me out with it all. I know I'll need a fuel pressure regulator and I'm looking for spare manifold that I could chop up or someone that can make me a custom one.

Recently I've found out (DUH!) that there are things in my Civic that need vacuum to actually work like brakes, for instance, and all of those things get it from the stock carb's outlets.

I have read loads of different threads about bike carbing various engines and also consulted it all with a friend who has done it loads of times himself and he has put it all in a way that you just whack it on and it works...

So the question is: Do I need to know anything else that is required to get the whole setup going?

Tell me most obvious things because I might not know it anyway...

Please help!

Thanks,

Tom

Edited by spuker1, 31 May 2013 - 09:43 AM.

[CRXfanatic]

http://www.redpepper...470/bike carbs/

[spuker1]

Yea I have read that too. Cheers.

[cbstdscott]

Good luck with this project, I will be following your progress. Is your car currently carb'ed?

I started out a project to add Individual Throttle Bodies to my fuel injected EW engine. But I was told by really smart people that ITBs are great at Wide Open Throttle but that partial throttle was a not always so great.

So I studied the issue and a few things became clear: Single carb, dual carb, stock FI or ITBs the ports in the head stay about the same size. Yes, it is possible to clean them up and make a bit larger and flow a bit better. But the basic size and shape stay the same.

Next came runner length: Longer runners encourage low end torque (used the most in street driving) and short runners encourage top end HP. So if you are driving on the street, runner length is something to think about.

My EW has the stock fuel injection. The intake manifold is a two piece design, the runners are separate from the plenum and the two pieces are bolted together. The runners are long and they mate to the ports in the head perfectly. The "problem" is the plenum is tiny and allows only a stock throttle body to be bolted to it.

My "Ah Ha!" moment was when it occurred to me to make a new bolt on plenum. A bigger plenum will allow more flow down the runners to the ports and a larger throttle bodies to be mounted.

Right now I am in the process of building that new plenum. As handy and DIY as I am, there are some skills and tasks that must be shopped out to people who actually know what they are doing. Right now I am hoping my really cleaver buddy will create a CAD program to do the cutting necessary to make everything line up properly. As my buddy is doing me a favor I can not harangue him on the phone every day asking, "Where is that damn CAD file?" But it will show up eventually and I will share the cad file on this site so that everyone can build their own plenum.

Good luck with the bike carbs,

Scott

[PuddleSkipper]

Buford and RedBaron might be ones to consult, they had a set up awhile back they were selling on here.

[zakats]

How dedicated are you to going this specific route? You'll likely end up putting much more time, effort, and money into this endeavor- I did and my 'finished' product was crap. Sidenote: looking back, my bike carb projects were really more proof of concept than anything else.

 

If you absolutely must go with bike carbs (which is silly for a 1.3, really): build the manifold using an OE flange, have your (26 or 32mm ID 'IIRC) aluminum runners welded @ 10 deg, and have the flange planed to straightness after welding. Having it all done professionally should cost a few hundred, I'd expect. Some peppers have opted to make a steel flange for an all ferrous route- personally I don't see much benefit in that unless you have scrap steel lying around. Keep your vacuum requirements in mind, you may choose to add nipples to supply a small vacuum manifold though you don't really have to employ a manifold- I generally prefer symmetry. Do you really want power brakes? vacuum advance ignition?

 

 

 

I hope you don't mind cleaning, tuning, synchronizing, and troubleshooting four carburetors every time something isn't perfect!

[rallyxcrx]

I lost my battle with bike carbs. I got to the point where I needed to change my fuel delivery set up to have a chance at making them work, and I wasn't willing to do it. Bike carbs run on gravity feed pressure, so you have to simulate that kind of delivery, regulator alone isn't enough. Bikes generate a different cornering force as they lean, and they don't need as much gas as they are light. So I decided to get, you know , car carbs! Webers, Dave    

[PuddleSkipper]

Here's a dual Weber setup, might be less money and time, well maybe less time.............

http://www.pierceman...roductCode=K704

[spuker1]

Hi thanks for all the answers. My Civic isn't my daily and I drive it only couple of times a month so I don't mind pull it all apart and take my time about it all. I think bike carbs will make this project. It's going to be a main point. I don't do it because I hope it will make my car fast. I just want to have it done and I want to do it myself. I'm aiming mostly for a personal satisfaction rather then engine power gains


I was looking at webers before but it's way out of my budget.

The way I was planning to do it is to just have a spare stock manifold and just cut it in half and add silicone joiners to join it up with my carbs and blank spare things off etc. alternative to that (that I will probably go along with as I can't find a spare manifold anywhere...) I wanted to just have a metal plate and just stencil ports and bolt holes off a new manifold gasket and just weld appropriate pipes for runners to it, probably tap into those for necessary vacuum lines (I don't mind not having power brakes if that's an option, not sure of vacuum advance ignition, not sure how that works and how important is it). I was told that those carbs need around 2psi so I was hoping to use my stock fuel pump with a regulator there. I have got my wideband on now so I was hoping it will sort of work and just fine tune it over a time with what I've got....

Am I far off?


 

Edited by spuker1, 02 June 2013 - 05:17 PM.

[zakats]

Am I far off?

The nearest la grange point would be closer I'm afraid.
I don't know of any successful setup using 'joiners.' I advise strongly against that to save yourself the time and disappointment. Hypothetically there is at least one way to achieve the necessary geometry by using a series of angle fittings and your flexible joiners/couplers... It would likely look and perform less than ideal, have a propensity for leakage, and will be an all around pain in the hindquarters to install/service.

If you make a manifold from scratch, you are in control of your finished product so you can focus on tuning which is no small task in of itself.

[spuker1]

What's the better way of connecting my carbs to the runners of prepped manifold then? I thought that short sections of silicon hose jubilee clipped on would be perfect. They'd have to be as short as possible and outlets on carbs would be touching the runners with those joiners on top of it... I know that silicon hose can't deal with vacuum as it just squishes down but if it's short enough and it's just on top of the actual pipe work then it should be fine right? What's the problem with installing/un-installing the carbs using this setup? It's only going to be two screws per carb to get them off?

And yea, I know tuning them will take a while, I want to focus on getting them on and getting all the necessary bits on as well, so I don't find out that I need something else halfway fitting them.

The nearest la grange point would be closer I'm afraid.

Hopefully with your experience and good advice, I'll get there There's no rush and I'm quite positive about it all still so yea, It's gonna be alright

Edited by spuker1, 03 June 2013 - 02:42 AM.

[zakats]

I don't want to sound discouraging, I'd like to see it done for its novelty if nothing else.
A stock, cut runner, manifold is generally more trouble than it's worth because the runner spacing is likely nowhere near identical to that of the bike carbs and their OD's are probably very different. Possibly worse, most bike carbs that I'm aware of require a ~ten degree angle to keep their floats level.


Does your engine have CVCC? I know it's a UK model but I wouldn't know about all the different trims sold there.

[spuker1]

Carbs I've got are very narrow, haven't actually measured them up with the stock manifold but I'm pretty sure they would fit quite easily. Also those carbs operate in 0 degrees, they are mounted completely flat on the motorbike.

My engine is non CVCC. It's 1.3L 70bhp one.

[Mark L]

I am curious how people are jetting the bike carbs after installing.

 

Has anyone actually dial in a set of Bike Carbs? How far off is the jetting?

 

Mark

[spuker1]

I think it depends on what carbs and what engine you want to mate together mate, but as far as I'm concern the only way to do it is to get a spare set of jets and them drill them out a bit more and then check if it's better and then repeat until it's right.

Edited by spuker1, 04 June 2013 - 03:12 AM.