Discussion
Hi,
I am hopefully going to be fitting some bike carbs to my 205 gti over the summer. I have read quite a bit about bike carb conversions and in general people tend to go for carbs of Yamaha R1 or other 1000cc+ bikes. My question is is there any specific differences between how bike carbs work with repsect to their choke sizes in comparison with other carbs.
The reason for me asking is that I have access to quite a few sets of Yamaha R6 carbs for free, these have 38mm chokes, I was told that these would be too small for my engines and should get R1 carbs as they are 40-42mm I think.
The thing is I was under the impression that as a rule of thumb you tend to go for throttle bodies that are 5mm smaller choke diameter than the equivalent weber as they are that diameter straight through and dont taper to a smaller choke size such as webers.
The carbs I have are 38mm so therefore equivalent to a weber 45, so surely would be able to flow enough air for my engine easily (150-160bhp). This is why i thought that maybe bike carbs work slightly differently and the id isnt comparable to throttle bodies. Also i thought that they must work like SU carbs as they as constant vacuum from what i can see by looking at them.
Cheers
Alex
I am hopefully going to be fitting some bike carbs to my 205 gti over the summer. I have read quite a bit about bike carb conversions and in general people tend to go for carbs of Yamaha R1 or other 1000cc+ bikes. My question is is there any specific differences between how bike carbs work with repsect to their choke sizes in comparison with other carbs.
The reason for me asking is that I have access to quite a few sets of Yamaha R6 carbs for free, these have 38mm chokes, I was told that these would be too small for my engines and should get R1 carbs as they are 40-42mm I think.
The thing is I was under the impression that as a rule of thumb you tend to go for throttle bodies that are 5mm smaller choke diameter than the equivalent weber as they are that diameter straight through and dont taper to a smaller choke size such as webers.
The carbs I have are 38mm so therefore equivalent to a weber 45, so surely would be able to flow enough air for my engine easily (150-160bhp). This is why i thought that maybe bike carbs work slightly differently and the id isnt comparable to throttle bodies. Also i thought that they must work like SU carbs as they as constant vacuum from what i can see by looking at them.
Cheers
Alex
Edited by bales on Saturday 3rd June 14:51
38mm carbs will be fine. Opinion varies as to the angle bike carbs should be mounted at. Get a look at the carbs whilst still on a bike if possible and try to get as near to that as possible. This can cause bonnet clearance problems especially if an airbox is used. I have seen some successfull installs where the carbs are mounted much more near a horizontal angle though.
You will need to replace your injection fuel pump with a low pressure fuel pump and fit a fuel pressure regulator. 2 or 3 psi is enough on bike carbs.
What about an ignition system?? If you fit an aftermarket system,OMEX, MBE or similar you may find that the throttle position sensor on your carbs sometimes (often)won't work and will need replacement. The experts seem to be Bogg Brothers. Talk to them. They can supply manifolds and take care of jetting etc.
If you are going to have to buy an aftermarket ignition ECU why not go for full engine management, keep your fuel pump etc. and go for bike throttle bodies?
You will need to replace your injection fuel pump with a low pressure fuel pump and fit a fuel pressure regulator. 2 or 3 psi is enough on bike carbs.
What about an ignition system?? If you fit an aftermarket system,OMEX, MBE or similar you may find that the throttle position sensor on your carbs sometimes (often)won't work and will need replacement. The experts seem to be Bogg Brothers. Talk to them. They can supply manifolds and take care of jetting etc.
If you are going to have to buy an aftermarket ignition ECU why not go for full engine management, keep your fuel pump etc. and go for bike throttle bodies?
spyder dryver said:
38mm carbs will be fine. Opinion varies as to the angle bike carbs should be mounted at. Get a look at the carbs whilst still on a bike if possible and try to get as near to that as possible. This can cause bonnet clearance problems especially if an airbox is used. I have seen some successfull installs where the carbs are mounted much more near a horizontal angle though.
You will need to replace your injection fuel pump with a low pressure fuel pump and fit a fuel pressure regulator. 2 or 3 psi is enough on bike carbs.
What about an ignition system?? If you fit an aftermarket system,OMEX, MBE or similar you may find that the throttle position sensor on your carbs sometimes (often)won't work and will need replacement. The experts seem to be Bogg Brothers. Talk to them. They can supply manifolds and take care of jetting etc.
If you are going to have to buy an aftermarket ignition ECU why not go for full engine management, keep your fuel pump etc. and go for bike throttle bodies?
You will need to replace your injection fuel pump with a low pressure fuel pump and fit a fuel pressure regulator. 2 or 3 psi is enough on bike carbs.
What about an ignition system?? If you fit an aftermarket system,OMEX, MBE or similar you may find that the throttle position sensor on your carbs sometimes (often)won't work and will need replacement. The experts seem to be Bogg Brothers. Talk to them. They can supply manifolds and take care of jetting etc.
If you are going to have to buy an aftermarket ignition ECU why not go for full engine management, keep your fuel pump etc. and go for bike throttle bodies?
Cheers for that, Bogg brothers were the main people I was considering as I have heard quite a bit about them being experienced in this side of things. I was planning on using the existing distributor, can you not use the exisitng fuel pump with a pressure regulator? or is that not possible. Bikes run very low fuel pressures I think and some are even gravity fed if I remeber correctly. I was planning on going to Bogg brothers making me a manifold and re-jetting them, however one issue is mounting as the carb inlets have no specific mounting points and most manifolds i see seem to have just some silicon hosing right at the inlet to allow some flexibility in the manifold.
Cheers
Alex
Edited by bales on Tuesday 6th June 15:31
littlegearl said:
has anyone got a link or phone number for them? do they do manifold fabrication too?
cheers.
cheers.
www.boggbros.co.uk/index.html
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