GSX250 build

[GregT]

So I've got to make the riding position the same as the macchi do I ?......

Yeah, you on it for Methven is a possibility.

A bigger holdup at present is not having access to a big lathe until Lloyd comes back from holiday...

[fast pom]

Hi Greg only just found your build thread, Must say looks a real cracker look forward to seeing it in the flesh, If you are looking for a rider my youngest is only about 45Kgs wet and if he rides it like he dose his Dirt bike ?, Hmmm hold on he is faster than me on the dirt don't want the little bugger doing the same on the track so scrap that. Cheers Dave

[GregT]

How old is he dave ? One of the reasons for building this is the 125 2 stroke/250 4 stroke limit on young riders up to i think 16....

i figured to finish it, race it with "guests" aboard and sell it.....gotta be a better buy than an old RS125...

Having said that, it looks like there's a queue forming to ride it - and Kev's at the front lol.

[fast pom]

Only just turned 13 not showing any interest in riding on the track so my wallet is safe for a little while.

[Triplenut]

Have just been speaking with the club president over a bottle and bourbon, he has agreed to a new min weight limit for the class.... rider must now be a min of 95kg ...and slow...... and a ginga.... ahaha

[fast pom]

Bugger!!! i am all of the above but Gray and balding

[GregT]

And while you lot are enjoying the silly season, an old bugger slogs onward..

Bottom end together. cases cleaned, paintstripped, TEN helicoils inserted...probably par for the course for one of these.
Bearings all good, still on the tight side actually...Camchain good. Don't know this motor's history but I'd say quite low mileage. Gearbox fine..

The shells for the balance shaft I've put in just so i don't lose them, lol...
The oil galleries for the shaft, I've tapped 3/8 UNC and will pick up a couple of socket head grubscrews along with the shopping list of ZP capscrews for the covers...This will be an all capscrew motor except for the case bolts, easy and cheap.

Next, build up the clutch and oil pump etc.

Then, mock up the pistons and the barrel, check head gasket thickness and see if the barrel has to be machined to achieve the approx .035in squish clearance i want

[GregT]

Squish is fine - around .038in with the gaskets i have.

Clutch good, oil pump in, shift mechanism in - and working, always a bonus...

i realised i was coming to a point where i was going to have to pause so made up a manual camchain tensioner...another weight saving,lol...

Need to get a heap of fasteners - and it's the practise day for the NZ GP friday so I'm into town....

Probably do the balance of the head porting on the weekend unless i score a free pass to the GP. I've built a lot of GSXR's and seen the pics of Ray's headwork. I'm quite surprised at the 250 head, no filling of the bottom of the ports needed IMO - and what little enlargement I plan will be done at the top. They're already quite a lot higher at the carb flange than later GSXR's - a surprisingly good shape IMO.

[GregT]

Some progress to report....some negative. the pair of Mikuni 29 smoothbores I wanted to use won't fit. Frame too narrow...just.
So alternatives were found - a pair of 30mm Mk1 Amal concentrics. I'll make up a pair of slightly curved manifiolds for them - they'll angle inwards slightly.

Positive - i got onto the swingarm. Worked out the dimensions and angles i needed to bend the arms. Used a jig I have here to holesaw the crosstube position accurately in both legs.
Pic shows how I do it - the axle hole is 15mm and there's a stepped register in the top of the pillar. Bolt it on there, clamp it to the jig and both arms are the same...Crude but effective.

[GregT]

Once the legs are finished - the 3 X 15mm holes drilled get filed into slots on each arm and everything gets deburred - it's jig it up for welding.

Usually any arms i make are short enough that the box jig in the pic can be used with through bolts for axle location and pivot tube....This one is just too long to go in the jig so it's sitting on top. Not as rough as it appears as the jig is dead flat and true...

So it's tack everything up including a cross tube. Low on gas as i expected but the suppliers reopen on Monday.

Once fully welded, the bearing carriers will go in the ends of the crosstube. I use 15mm bore double row angular contact ballraces...not a common answer to the swingarm bearing problem but i like them. They'll take a small amount of misalignment without problems...

I align the bearing carriers with cones in the open ends when they're welded in place so any prior distortion of the crosstube is irrelevant.

At the NZ GP last weekend I had a talk to an old friend/customer I hadn't seen for years who was running a genuine Harris in the Post Classic GP. It looks as though I've got most of my mini copy pretty right....Except for one thing - he can't get the cam cover off with the engine in the frame but I can...

[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.