Righty ho, apologies if this has been asked before, I've done a search but the forums are massive now.
Is it absolutely necessary to re-space bike throttle bodies?
I would imagine that for top power then yes, as it presents the easiest path for fuel/air into the motor.
But, respacing only seems possible on a few ITBs, and then you seem to need TIG to extend throttle linkages etc. (I don't have TIG)
I guess what I am asking, is "Would I be OK in using XYZ throttle bodies with a manifold made to suit?
Any replies gladly appreciated, or links to this info 
Don't see why not, but would be a bit of a bugger to fabricate, IMHO. Cheers Ray
IMHO not wholly necessary, it’s the total length that you need so just extend the trumpets on the short middle ones.
Look at car manifolds for instance; v8 rovers have shorter stacks on the end cylinders to balance things.
The length is tuned anyway, so having a couple out will just spread the torque spread a little, will you ever notice? It's doubtful, will be far
better than a single carb/TB setup anyway.
Regards Mark
You dont need to TIG the throttle linkages.
If you use the common R6, early GSXR600/750 and Hayabusa ones they will all respace easily and it makes manufacturing the inlet manifold really easy
too.
David
its not absolutly necesary to respace them, there is pro's and cons. firstly if respaced makes the manufacture of the manifold easier as no
compound bends, and if space is an issue the manifold can be shorter, against respacing is potential problems in remanufacture of a fuel rail. teh
extension of the throttle linkage is quite simple rearly. as later throttle bodies seems to be cast in pairs, respacing is not always an option.
Bogg's do not seem to respace theirs but they are craftsmen when you see their work as opposed to my DIY efforts. bit more info in a how to link
i done on anoteher forum.
re-spacing and manifold link
Good points.
The only messy bit with respacing the "standard" throttle bodies comes from the linkage arms. Everything else is easy on the early GSXR
ones.
You can move them relative to the washers which buys a couple of mm, but that isn't normally enough.
I have bolted on an extension and bonded with chemical metal. This works but is a bi t bodgy. The other problem with this approach is that you end
up moving the link slightly. This can be corrected by adjusting the "balancing screw" but it has a very limited range of action.
The best solution would be to get replacement linkages. The relevant piece is only a short arm with a d-shaped cut-out. This is made out of a flat
sheet, with a fold in it. If someone out in the internet world wanted to laser-cut a decent batch of these (you do make them universal by having a
long arm which could be bent and cut-down). I'd happily pay £10 for a set of 3 of these (actually for a set of 4 as then I could make a mistake),
and I am sure there would be a fair number of customers as this modification is quite popular.
Just a thought.
Matt
quote:
Originally posted by flak monkey
You dont need to TIG the throttle linkages.
If you use the common R6, early GSXR600/750 and Hayabusa ones they will all respace easily and it makes manufacturing the inlet manifold really easy too.
David
Details on respacing GSXR TB's etc on a Zetec engine are on my website - link below, and then go to the throttle bodies page.
I don't see why you need to respace them. Fabbing a new manifold and using the original spacing adds just a couple of mm length.
Leaving the TB's as standard helps with all the oem balancing etc, dead easy to sort any problems, or not have any to start with.
Linkage arms are always steel and about 2mm thick, so no probs migging them.
As for fuel rails, I can supply billet ones, or just the blank extrusion for you to make your own.
quote:
Originally posted by flak monkey
Linkage arms are always steel and about 2mm thick, so no probs migging them.
As for fuel rails, I can supply billet ones, or just the blank extrusion for you to make your own.
The problem is that the distance between the throttle body and head is usually so short that forming the desired bends is almost impossible. This is
why the majority of manifolds I have seen have so-called "cheated" joins between the manifold and the flange plate, i.e. the pipe joins the
flange at an angle, causing a very tight corner for the air to get around.
What I would say is that if you aren't worried about extracting the best power, why use individual throttle bodies? A good plenum system will
give as good or better power than a mediocre throttle body set-up but without the negative aspects of getting a good MAP signal and part throttle
calibration.