OK the title isn't exciting...but this is in response to several people saying I should document one of my builds, so here it is.
The aim - a GSX250 powered racebike built to NZ pre 82 rules - as interpreted in the South Island...which means a bit more latitude.
We are allowed frames which are appropriate to the period rather than insisting on exact replicas...The South has always been big on specials lol.
Why ? Well locally it would get two class rides per meeting at least. A local club runs a 150 2T & 250 4T class with a limit of 2 cylinders. Given what i plan, it won't be the slowest pre 82 out there...And we run on some pretty tight tracks too.
Right - recipe. i have a GSX250 motor which on stripping seems in pretty good nick. The cams are away at Kelford in ChCh to have a standard GSXR750 profile put on. With the GSXR springs and an appropriately ported head, there's going to be some power there.. I also have a part set of Mikuni 29mm smoothbores which i cut up into a pair many years ago. i'll respace them for the 250 and that's that sorted.
I'll remove the balance shaft - plug the oil galleries too. Not irreversible if it proves necessary to put it back. Alternator is coming off too - total loss battery powered ignition. Starting by powered rollers - or find a young pusher lol...
Frame and running gear. Scratchbuilt frame - quasi Harris...but twin shock to comply with our rules. Chinese piggyback shocks already sourced...cheap. GS450 33mm fork legs in home made yokes to get the required offset. Wheels - scored here, Motard style wires 17 x 2.5 and 17 X 3.5 - RS125 sizes so probably used RS slicks. I've ordered a TZ250 G/H seat - high wedge with deep sides, and a Gilera Saturno front fairing - narrow but with deep sides again. i don't expect those before Xmas from our local glass guy...Brakes, have a line on a pair of Brembo 05 calipers - the small twin pots. i'll run a single 300mm front disc and a small rear. The small Brembos will be OK for both ends. Scored a GSXR750 tacho too...
What may surprise some is the amount of scratch building I'm prepared to do - i have the time but not the $$....
Progress so far - frame is probably half done. mild steel, bronze welded. For the technically minded, manganese bronze,no inline fluxer - those cost $$...i have a bender but there's not a lot of bent tubes in this.
Pic is frame and motor in the jig. Sequence was front and lower rear engine mounts ( front was a pain ) then locate the shock tops, tubes to lower crossmember, then top frame tubes steering head to where the top of the swingarm gusset comes...then fill in the gaps lol.
There will ultimately be a rear seat loop once I have a seat....
The aim - a GSX250 powered racebike built to NZ pre 82 rules - as interpreted in the South Island...which means a bit more latitude.
We are allowed frames which are appropriate to the period rather than insisting on exact replicas...The South has always been big on specials lol.
Why ? Well locally it would get two class rides per meeting at least. A local club runs a 150 2T & 250 4T class with a limit of 2 cylinders. Given what i plan, it won't be the slowest pre 82 out there...And we run on some pretty tight tracks too.
Right - recipe. i have a GSX250 motor which on stripping seems in pretty good nick. The cams are away at Kelford in ChCh to have a standard GSXR750 profile put on. With the GSXR springs and an appropriately ported head, there's going to be some power there.. I also have a part set of Mikuni 29mm smoothbores which i cut up into a pair many years ago. i'll respace them for the 250 and that's that sorted.
I'll remove the balance shaft - plug the oil galleries too. Not irreversible if it proves necessary to put it back. Alternator is coming off too - total loss battery powered ignition. Starting by powered rollers - or find a young pusher lol...
Frame and running gear. Scratchbuilt frame - quasi Harris...but twin shock to comply with our rules. Chinese piggyback shocks already sourced...cheap. GS450 33mm fork legs in home made yokes to get the required offset. Wheels - scored here, Motard style wires 17 x 2.5 and 17 X 3.5 - RS125 sizes so probably used RS slicks. I've ordered a TZ250 G/H seat - high wedge with deep sides, and a Gilera Saturno front fairing - narrow but with deep sides again. i don't expect those before Xmas from our local glass guy...Brakes, have a line on a pair of Brembo 05 calipers - the small twin pots. i'll run a single 300mm front disc and a small rear. The small Brembos will be OK for both ends. Scored a GSXR750 tacho too...
What may surprise some is the amount of scratch building I'm prepared to do - i have the time but not the $$....
Progress so far - frame is probably half done. mild steel, bronze welded. For the technically minded, manganese bronze,no inline fluxer - those cost $$...i have a bender but there's not a lot of bent tubes in this.
Pic is frame and motor in the jig. Sequence was front and lower rear engine mounts ( front was a pain ) then locate the shock tops, tubes to lower crossmember, then top frame tubes steering head to where the top of the swingarm gusset comes...then fill in the gaps lol.
There will ultimately be a rear seat loop once I have a seat....
but I suspect my my 6ft 100kg mid pack orangutan carcass would mess up the obvious potential of the bike :lol:
