My bike carbs conversion thread
Discussion
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
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
Edited by paulrhodes on Friday 2nd March 16:28
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