GSX250 build

[GregT]

Well the gas is lasting better than I hoped....Arm almost finished - just a brake anchor point to go on when i have a caliper and carrier sorted.
Still to make the alloy pieces to go inside the arm where the axle passes through plus the alloy end plates for chain adjusters.

Brakes - the small Brembos won't happen so as at this point the front is a Lockheed twin piston caliper which I will have to rebuild. For the rear i have an FZR250 Yamaha caliper and mastercylinder coming.

I've also bit the bullet and bought a triple clamp setup from a Suzuki RG150....the offset is what I want but I'll have to bush the clamps for the 450 fork legs. Not a problem, done it before...

 

[Kiwi Canuck]

Awesome job Greg, wish I was in NZ to "offer my services to test it" as I almost meet the 95KG minimum weight.

Look forward to seeing the progress and I love that you are doing it the old school way with brazing the frame.

Cheers.

David

 

[GregT]

Awesome job Greg, wish I was in NZ to "offer my services to test it" as I almost meet the 95KG minimum weight.

Look forward to seeing the progress and I love that you are doing it the old school way with brazing the frame.

Cheers.

David

Whadda you mean, old school ? I am old......Is there a different way ?

At least i know the difference between brazing and bronze welding...lol...

Did you know Dave Freeman ? Would have been from levin back in the day. It was him with the Harris.

 

[Triplenut]

Swingarm looks good Greg, will it need gusseting as well ?

What is the wheelbase you're aiming for? looks quite compact.

Cheers
Dave

 

[GregT]

Swingarm looks good Greg, will it need gusseting as well ?

What is the wheelbase you're aiming for? looks quite compact.

Cheers
Dave

Around 52 in....the motor's well forward too. Swingarm in 2in X 1in 16G rectangular...stiff as...Got an old one here in the same tube,you're welcome to try and bend it....

Stretched the gas out further today, made clip on bars, it all adds up.

 

[GregT]

Too much outside work on hand to get a lot done today...

Hydrauliced the lockheed caliper pistons out - grease guns are useful...
Paintstripped the caliper and wire buffed it. the pistons are reusable but I'll lighten them - they're pretty thick wall. I'll take the caliper in to a brake specialist in town and get seals off the shelf.

The triple clamps are at the courier depot in town - the seller obviously never listens to what the buyer wants - I told him post was the only way as there are no courier or street deliveries out here...but no....So I've got to go and collect.
So I got onto the fork legs...I'd already had the sliders polished, knowing I'd want them soon. I'm doing an old trick to shorten and limit travel - this little bike doesn't need the 5.5inches of travel the 450 legs have as std..,and they're rather long too.
So, they have two compression springs in each leg - roughly equal length and straight wound....I cut one spring from each leg into equal lengths.
The leg then goes together with one of the short pieces added to the rebound spring and one piece in the compression spring stack.
Result - the exposed length of stanchion is shorter and the travel is cut - to roughly 3 inches actually. This will suit the low steering head height I'm building in and the amount of travel is pretty much what a small well braked racebike needs...It doesn't affect the damping either.

 

[GregT]

Sorted the steering head today.RG stem was too short - I'd made the headstock quite long as there are a lot of tubes meeting there... Old trick of using bearing carriers at each end joined by threaded rod. Did it slightly differently though with a bearing carrier pressed and welded into the bottom triple clamp. Then cut the top off the RG150 steering stem and pressed and welded a threaded plug into that....Join the two pieces with a piece of threaded rod with the ends locked at the right distance apart and you've got a steering stem which retains the OE adjustment for bearing play.
Still to pick up some tube to machine the bushes needed to adapt the 35mm RG yokes to the 33mm GS fork legs.

 

[GregT]

Managed to get a little more done today. Adapter bushes machined up for the fork/triple clamp mismatch. Wheel bearings changed to 15mm bore from the motocross originals - 22mm bore. Spacers made to center the wheel in the forks. Steering stops tacked to frame tubes - 12mm bar tapped 6mm for a screw and nut as adjustable stops.

Put it together and took a pic....starting to show some bling...

Next the rear axle blocks and adjusters then center the rear wheel.

Sorted out availability of sprockets too. The rear hub is a Honda clone and i can get locally 35 - 52 teeth sprockets. fronts locally again, 13 - 15 teeth...plenty of options and quite cheap too.

 

[guzziboy]

i really wanna spend some time in your shed mate...your a mad scientist!

 

[GregT]

i really wanna spend some time in your shed mate...your a mad scientist!

Hmm - define the difference between mad scientist and (slightly) premature senility.....

 

[fast pom]

Good to see it coming together.

 

[guzziboy]

Hmm - define the difference between mad scientist and (slightly) premature senility.....

i think there the same aren't they! MORE PICS!

 

[firsty]

Greg
have been watching this thread and was thinking about Kiwis building bikes
like the Britton and then remembered the "plastic fantastic" (carbon fiber monocoque Suzuki) built by Steve Roberts and raced by Dave Hiscock in the 80s and went searching for photos and came up with this video of the bike in action
and I though you might like to see it

http://www.dailymotion.com/video/x9ixrj_wanganui-road-race-1983_auto

I was racing that day in the 125 class so it brings back lots of memories

great build by the way

-

 

[GregT]

Yes, i was around at the time too.

With the race meeting last weekend and an influx of work, things have slowed down slightly. Next priority is finishing the motor as i need to establish chain line - and if i have to machine the sprocket flange of the rear wheel...

tyres won't be a problem - got offered my choice of top of the line 250 production race rubber yesterday. Only used for two meetings - and cheap....

 

[GregT]

Apologies for lack of progress - several days in hospital will do that...

Still to catch up on outside work before getting back into the 250 - but I will.

 

[Guest]

Hey Greg, haven't logged in for a while but she's looking real good!

Hospital? Hope you're ok!

 

[GregT]

Feeling a bit better so finished off the head porting incl raising and moving the inlets inwards slightly.
Went for a mockup of the head and top end so as to measure valve to piston clearances....only to find that the cam grinders have given me the wrong profile...severely p'd off....

I need the motor complete so as to do the chain line so it's wait for the cam grinder to redo the cams....

I did however pick up some good used rubber for the bike last week. bridgestones from a local 250 production racebike, used at two rounds of the National champs. latest super stickies at a very good price.

 

[GregT]

For what it's worth - and for anyone else who wants to do a GSX250 - pic of the GSXR750 springs Vs std 250. As far as i know, GSXR750 G H J and K are all the same springs and I believe GSXR1100 up to the J are the same springs also.
Same fitted height as the 250, drop onto the OE spring seats and fit the 250 retainers perfectly.
Seat pressure is up - but not an enormous amount - and they'll take more lift than the 250 springs with out coil bind. Being a double spring setup they're also more resistant to surge at hign RPM...

Note that I'm using STOCK GSXR springs - I do have aftermarket springs here but for the 250 size valves i consider them overkill. I'm only using stock GSXR cam profiles too so no need for enormous pressures.

GSXR springs on left, OE on right.

 

[Guest]

all 3 of my cylinder heads have the double spring arangement, your gsx 250 must be a low power version. in england they are 29 bhp standard.

 

[GregT]

all 3 of my cylinder heads have the double spring arangement, your gsx 250 must be a low power version. in england they are 29 bhp standard.

Interesting....No idea if it's an early one or if those were the oe springs.
What I can confirm is that NZ never ever got a restricted version of any Suzuki, LOL. History shows we got the really quick ones...see the black pipe 1100's and wire wheel Katanas...
Cam lift - before the regrind - measured up as same as you'd have in the UK.