hi peeps,

i thought i would share my diy solution to fitting bike carbs to an afh. it is a work in progress so bare with me and dont be too critical! i sourced a set of gsxr600 carbs, a set of bolt down mounting rubbers, an off cut of 19mm alu, and a carbide burr. with some careful marking out o have managed to aline all the inlet runners and mounting holes and made up the adapter plate as pictured. the carbs will mount up very close to the head, but i have the option to space them out a bit using some tube as spacers. i have yet to sort a vacuum feed for the bake servo. i will update as i go along.

mounting rubbers

19mm plate

mock up

view from head side with rubbers bolted down

Edited 14 November, 201015 yr by danh73

good work mate

do the carbs you have fit the spacing of the afh head, or are you going to have to split the bodies and space them out?

looks good though, arun (phataz1) uses the bolt down rubbers on his mk1 golf gt, essentially making a manifold that fits to the head, fitted by runners to another flange, that flange then has the correct spacing for the carbs, and gives a longer inlet tract.

FYI the ports on the afh head aren't the same as the holes in that avy gasket you have... i do like that method of bolting the flanges straight up to the head but i think you will need more length on the runners or you'll kill the lower rpm torque

Nice work! Seen this method done a few times, much easier then bothering with a manifold! Shame the same method can't be done with the 8 valve engines

ps I wouldn't bother extending the inlet tract, it'll be perfect the way it is :)

Edited 14 November, 201015 yr by Phataz1

cheers thanks for the good replies, especially as its coming from the members who really know their stuff!

do the carbs you have fit the spacing of the afh head, or are you going to have to split the bodies and space them out?

looks good though, arun (phataz1) uses the bolt down rubbers on his mk1 golf gt, essentially making a manifold that fits to the head, fitted by runners to another flange, that flange then has the correct spacing for the carbs, and gives a longer inlet tract.

grunge the gsxr600 carbs have 36mm chokes and are spaced 80mm apart and the afh ports are 82mm, so no i have not needed to re-space the carbs. i just very carefully placed the rubbers (which are slightly oval shaped at the port end) so none of the mounting holes fouled each other then ground away the spare metal until everything flowed nicely.

Edited 14 November, 201015 yr by danh73

FYI the ports on the afh head aren't the same as the holes in that avy gasket you have... i do like that method of bolting the flanges straight up to the head but i think you will need more length on the runners or you'll kill the lower rpm torque

already ahead of you there, as the engine is sat on the floor at the moment i will be taking the carbide burr to the ports and doing a little 'metal massaging'!

interesting what you say about the inlet tract length. i was wondering what effect shortening would have on the power delivery. i think i will make up some different length spacers and have a play around once the engine is in.

my next problem is sorting a vacuum feed for the brake servo, with some tricky drilling i can get a feed off each port. i was considering a separate vacuum pump, like an automatic pump as fitted to some volvos or a combined alternator and vacuum pump as fitted to some diesel cars, but all i would be doing is solving one problem by creating another! btw the small rubber pipes on the rubbers will be linked to provide a vacuum feed for the dizzy advance.

Edited 14 November, 201015 yr by danh73

If you were to leave the trumpets on the carbs, or find longer ones, you would effectively be creating the same effect as lengthening the distance between carbs and head as the overall inlet tract is increased. So whilst I don't think it will make enough of a difference to notice, that is another way of doing it

Edited 14 November, 201015 yr by Phataz1

my next problem is sorting a vacuum feed for the brake servo, with some tricky drilling i can get a feed off each port. i was considering a separate vacuum pump, like an automatic pump as fitted to some volvos or a combined alternator and vacuum pump as fitted to some diesel cars, but all i would be doing is solving one problem by creating another! btw the small rubber pipes on the rubbers will be linked to provide a vacuum feed for the dizzy advance.

You can get hold of GSXR rubbers that have vacuum take offs integrated, would save you having to drill/tap/mess about welding pipes to the plate

cheers Phataz