My bike carbs conversion (help needed urgently)

[Paulr1980 0]

I thought I'd start a thread to document my bike carbs conversion.

 

So far I've ordered my carbs and have paid for them.. I've gone for ZX9R carbs from a 51 plate bike that's being broken.

 

Reason being, they have nice big 39mm chokes and are far cheaper than R1 carbs which are more widely used due to Bogg Bros preffering them.

 

In reality the ZX9R carbs are fine and should flow at least as much as a pair of 45DCOE's.

 

The other useful thing is that as they are CV carbs, they are constantly fuelling correctly, kind of like running a live map on an ECU.

 

I initially was going to have the manifold and carbs rebuilt and jetted by Bogg bros, but they charge too much in my opinion for what they do. I was quoted £240 for me to send my carbs to them.. have them rebuilt and a manifold made up.

 

I know that thats still cheap but I was certain I could find an alternative.

 

 

I'm now using KNN manifolds. They normally do Ford engines and hence have all the right CAD designs for the inlet but after some discussion, have agreed to take mine on.

 

I've got to send an inlet manifold gasket off... they'll do a CAD design of it and run a mild steel template for me to line up against the head. I'll need to make any adjustments to the mild steel template and send it back to them (with my carbs).

 

At this point, they'll redisgn the profile of the inlet side of the manifold and rebuild my carbs using an equally spaced design as opposed to Bogg bros spacing the manifold differently.

 

It doesn't make a dramatic difference but could affect the outer two cylinders running slightly lean. Having an equally spaced manifold means that KNN will make up new fuel lines to suit.

 

They'll then jet the carbs for me to a best guess approach which will be good enough until I get to a dyno. They are confident that it'll be 'near as dammit' though.

 

The whole process will take two months which I'm gonna be itching about but still... at least the jobs being done properly and for sensible money.

 

I'll then need to cobble a throttle bracket up and use a push bike rear brake cable as a throttle cable.

 

Lastly I'm going to buy a filter king FPR and set it to a max of 2psi (bike carbs need very little fuel pressure).

 

The whole thing should cost about £350 and at the moment I've yet to see what gains it'll give on a KR but I'm up for something different.

 

 

Before anyone says it. I know that K-Jet will be fine up to 200 bhp but I like being different and the sound should be magnificent. :)

 

I'll get pics up of everything as I go along and will also put a dyno graph on at the end of it all..

 

Not sure if it helps anyone decide what to do but I've been hunting away for weeks looking for fragments of info, so maybe me doing a build review will help.

 

Thanks

 

Paul

[CoxyLaad 0]

i would have thought you would have ditch the fuel injection fuel pump mate.

 

Bike carbs have no return on them, the pump regulates the pressure in the float bowls.

[Kevin Bacon 5]

Wasn't there a chap on here from Norfolk way running a KR on TBs? I think Dave Walker mapped it and it made some serious power?

 

Plenty of cars run bike bodies with injection pumps, check out Practical Performance Car magazine, so it must be doable I would have thought?

[CoxyLaad 0]

are they not running motorbike fuel injection bodies though?

 

carbs dont have a flow and return system, so it will just fill up the float bowls and flood the engine.

[Paulr1980 0]

I was told that if I used a filter king and set it to a low pressure rating then I'll be ok. I'll look into it as I don't want any greif come fitting time.

 

Any suggestions coxy?

[CoxyLaad 0]

how about the fuel pump from the bike?

[Paulr1980 0]

I've heard of people doing that.. Never looked into though as I figured that it would be better to be able to manually adjust fuel pressure using a regulator.

[flusted 0]

thought its better to use throttlebodies instead of carbs?

[Paulr1980 0]

It would be but carbs need no ECU so set up costs are far cheaper. My C was always going to be a budget track car so whatever I do will be at the cheaper end of the spectrum.

[mrbeige 0]

It would be but carbs need no ECU so set up costs are far cheaper. My C was always going to be a budget track car so whatever I do will be at the cheaper end of the spectrum.

 

Well given that my mate has put motorbike carbs on a standard 9a with only a KR inlet cam and fourbranch manifold and is seeing 170bhp, the cheaper option isn't a bad one!!

[Paulr1980 0]

I don't suppose he would mind me picking his brains at all?

[StuartFZR400 0]

how much additional power do you reckon this small investment will return?

[CoxyLaad 0]

bike carbs are self regulated pressurewise.

[mrbeige 0]

To be fair he got a mechanic to do it, and he always calls me for advice, like its going out of fashion! What do you need to know, I might be able to get him to find out from the mechanic?

[Paulr1980 0]

That would be great, cheers beige.

 

I need to know whether there is brake servo take off on the inlet manifold. I'm being lazy but the people that are building my manifold need to know and I'm at work in a suit.. not good for routing around under the bonnet.

 

Has the ignition caused any problems?

 

Is he running an electric fuel pump or just standard kit with a filter king/similar?

 

Any space issues?

 

Any general advice?

[CoxyLaad 0]

now theres a thing.

ITBs generate far less vacuum than a normal manifold, certainly on tickover.

 

bikes carbs always have a vacuum take off on each body to enable balancing of the carbs.

 

You could make a bridging manifold to equalize the pressure and and T from that to the servo

[wilkes 0]

page i found on the web http://www.totalvauxhall.co.uk/resource ... h60697.pdf

its on a vauxhall page but helpful non the less .oh and any updates ?

[Paulr1980 0]

Yeah.. thanks, I saw that the other day. All useful stuff.

 

All I seem to be doing at the moment is saving and buying bits to complete the set up.

 

KNN have been a little slow in that I'm still waiting for a template to check against the head but have explained that they are so cheap as it's all done as a cobble.

 

We agreed yesterday that I'd send my carbs off to be jetted, cleaned and spaced now and also send my ITG backing plate so they can cut the holes to fit.

 

It should only be another month before I'm ready to do the conversion.

 

I'm currently trying to work out how I'm going to fit ram pipes on and what length they should be... I'm a bit stumped there.

 

I still need some detailed conversion pics so I can work out where to mount everything and how much/what pipe I'll need (if anyone can help?)

 

Ta

 

Paul

[wilkes 0]

another link ,if you go down to fpr009 you may be able to get away without switching fuel pumps .. http://www.scarbro-racing.co.uk/fuelregulators

[Paulr1980 0]

Ok, I'm getting there but need a little help from my peers.

 

I received this from KNN today....

 

 

Paul, good news ish at last. Have got the Template and need your address to post for a trial fit.

 

A slight problem is that the current inlet holes on the plate will need to be made slightly larger to take the tube, once the trial fit is complete. This leaves insufficient plate in some areas to stop it bowing the edges when being welded. The main area is the water inlet in the centre.

 

We can incorporate this in the manifold itself. However we dont know the hole centres to do this. Would like to chat on the phone when you go to Trial fit.

 

Could you also send a pic of the head close up and square on with the water outlet uncovered.

 

Could you also make the pic as big as possible 1mb+ with a rule to show scale .

 

 

I figured that it would be better for me to supply KNN with the lower part of the manifold to take all the measurements from.

 

I'd also like to take the measurements etc but don't have a spare head and haven't got the time to strip my car down this weekend.

 

Does anyone have a head and could help me out on this one?

[mrbeige 0]

I've got a spare head, are you local to cambridge? Posting it would costa fortune....

[Paulr1980 0]

Not particularly no. Any chance you'd have a spare ruler... five minutes and a half decent digicam??

 

 

Naturally a couple of beer tokens would be offered for the service (or a donation to the site if you'd prefer)

[wilkes 0]

the triangle bit you have mentioned is the water outlet ,it sits on the head ,surely the manifold would have to go round it like the original ,heres a pic.

[rolex 0]

updates updates updates??!!

 

 

is there any?