Any one put RG150 chamber on a GP125?

[ellipsis]

....you just keep it as standard as possible, its getting lonely down at the none too modified end of the track....

[TZ350]

Carb spacer has been made and fitted thanks for the info.
And will definitely run the bike on the dyno to tune the jetting and timing. Last thing we want is to seize it on its first outing.

My partner in this bike has never ridden on the track so the broadest power we can get will be helpfull to his learning process (and probably mine).

I need to check out the carbs and rotary valve, I think this bike was a GP100 now fitted with a 125 head. Not sure if the previous owner changed the carb and valve as well as the head.

Cheers
Red

Hi Red

There is a very std GP125 that goes very well here at Mt Welly.

The 100's 22mm carb rotary valve and rotary valve cover all need to be changed if you want a 125 24mm spec inlet, the cover and valve can be cut/ported and the carb bored out, or just swaped out for 125 ones. The engine number on the case will start with GP100 or GP125 depending on what size it was originaly.

[Triplenut]

....you just keep it as standard as possible, its getting lonely down at the none too modified end of the track....

Lookin forward to duelling Neil , we fully expect to be at the blunt end of the pack!

See you at the pre 89 cup

Cheers

[Triplenut]

Hi Red

There is a very std GP125 that goes very well here at Mt Welly.

The 100's 22mm carb rotary valve and rotary valve cover all need to be changed if you want a 125 24mm spec inlet, the cover and valve can be cut/ported and the carb bored out, or just swaped out for 125 ones. The engine number on the case will start with GP100 or GP125 depending on what size it was originaly.

Thanks, just checked out the cases, bottom end is definitely GP100.
Will check out the carb etc this arvo, it came with what he called a bigger carb so hopefully this is the 24mm one.

I'm up page 150 of your ESE post, great stuff!

You mentioned bracing the frame swing arm etc didn't really improve handling.
Our budget on this one doesn't allow for a donor frame, would you recommend bracing the frame and swing or am I wasting my time? Both riders are around 90kg so it'll be under a bit of pressure.

Cheers
Red

[TZ350]

TBH it seems that the more they were braced the worse they were, mine would chatter very violently front and back, it was so bad it would throw my feet of the pegs and hurt my back.

The one that was ridden the fastest was basically std, except for foot rest position, both had proper rims and slicks, never figured that out.

My guess is that resonable rear shocks and fresh oil in overhalled front forks would be a good start.

They are good till they let go, and if you have improved the point where they let go they let go more violently.

I think a basically std frame and attention to the suspension would give you a resonable ride.

[TZ350]

Thanks, just checked out the cases, bottom end is definitely GP100.
Will check out the carb etc this arvo, it came with what he called a bigger carb so hopefully this is the 24mm one.

I am glad your enjoying the thread. The rotary valve cover and valve are different too. The inlet on the 100's valve cover is about 22mm the 125 24mm, the 100 has (from memory) 135/35 inlet timing and the 125 145/55 both the valve and cover need to be changed/modified too.

100 on the left 125 right hand side in each picture.

[Triplenut]

I am glad your enjoying the thread. The rotary valve cover and valve are different too. The inlet on the 100's valve cover is about 22mm the 125 24mm, the 100 has (from memory) 135/35 inlet timing and the 125 145/55 both the valve and cover need to be changed/modified too.

100 on the left 125 right hand side in each picture.

Brilliant, thanks.

Bummer, looks like i've got GP100 rotary valve, cover and 22mm carb with a 125 barrel.
The bigger carb that came with bike is a 24mm but not from a GP and wont fit.
On the plus side I just hit the buy now on a 24mm GP125 carb on trademe

I'll run it like is for now until the carb and expansion chamber turns up then mod the 100 intake to 125 specs and tune accordingly.

Cheers

[Triplenut]

TBH it seems that the more they were braced the worse they were, mine would chatter very violently front and back, it was so bad it would throw my feet of the pegs and hurt my back.

The one that was ridden the fastest was basically std, except for foot rest position, both had proper rims and slicks, never figured that out.

My guess is that resonable rear shocks and fresh oil in overhalled front forks would be a good start.

They are good till they let go, and if you have improved the point where they let go they let go more violently.

I think a basically std frame and attention to the suspension would give you a resonable ride.

Thanks will focus on suspension.
We are running treaded race compound tyres on standard rims, given they are about the size of mountan bike tyres I doubt the grip generated will tax the frame to much or inspire banzai riding .

[Buckets4Me]

Thanks will focus on suspension.
We are running treaded race compound tyres on standard rims, given they are about the size of mountan bike tyres I doubt the grip generated will tax the frame to much or inspire banzai riding .

tz350 first bucket had dunlop tt900 (race compound tyres) and it would shake so bad he would get it sidways out of corners

start looking for 17 inch rims with 36 holes or a sait of motard rims 2.5 and 3 or 3.5 inches

[Triplenut]

tz350 first bucket had dunlop tt900 (race compound tyres) and it would shake so bad he would get it sidways out of corners

start looking for 17 inch rims with 36 holes or a sait of motard rims 2.5 and 3 or 3.5 inches

Cheers Buckets, your right but rather than spend to much on wheels etc now, we'll probably follow team ESE's lead and save up for a better chassis next year. Maybe FZR, RG, what ever we can get cheap.
Hopefully this will cure all the handling and grip issues we are likely to encounter in one cost effective sweep.

Or maybe build a frame like the Waddon frame in the race chassis thread, looks cool.

Cheers
Red

[TZ350]

I'll run it like is for now until the carb and expansion chamber turns up then mod the 100 intake to 125 specs and tune accordingly.

Good plan, bike should run ok as it is. Good starting point anyway. The FZR250 3LN comes with decent wheels 2.75x17F and 3.5x17R which are near perfect for slicks. Early TZR are slightly narrower at 2.15x17F and 2.5x17R and only just OK ish for slicks.

[Triplenut]

Thanks to everyone for their advice.
I've used what I understood from the TeeZees thread ( about 1%) and finally got the disc and ports reshaped, 24mm mikuni carb fitted and the RG150 chamber cut, welded and tweeked to fit.
Spaced and modified the carb cover for a bit more flow.
The RG pipe JUST clears the front wheel, kickstart and JUST misses the ground when laid over so hopefully will be all good.
I made my own silencer which looks like it belongs on a bucket

Have started rich with a 115main but doesn't feel to bad.

First run up our cul de sac was very pleasing( for me not the neighbours) on the set of the pants dyno.
Prior to these mods I could only just get to 4th before I had to brake, with the mods above I hit redline in top before realising how crap the brakes are.
It revs a lot faster, has a good botom end, flattens a bit in the middle then really good top end that wants 2 revs way past redline if you let it.
Dyno will tell the tale but I'm guessing a 40% increase in power over its strangled previous state.

I'll try to get it properly tuned and first outing will at the Methven Street races at Easter, cant wait.

Also just purchased the next stage of evolution, picked up a 88-89 RGV250 rolling chassis for $150. Haven't picked it up yet but hoping it will be suitable? .
Looking forward to better brakes at least.

Cheers
Red

[ellipsis]

I'll try to get it properly tuned and first outing will at the Methven Street races at Easter, cant wait. Cheers, Red

...i better go and rub a damp cloth over mine then....

[TZ350]

Looks good, please keep us posted, its very interesting to see how someone else is getting on with a stroker especialy a Suzuki GP.

[Triplenut]

...i better go and rub a damp cloth over mine then....

Your talking about your bike I presume? See you down there mate.

Thanks for the inspiration TZ.
Picked up the RGV rolling frame tonight, looks like a bargain and not as heavy as I thought it might be. Should keep me out of trouble over winter.

A question for the wise
What sort of revs can I safely(ish) go to to with a stock GP125 bottom end, I know redline is 8K but this one seems to be making good power well past that.
Am I asking for trouble going past 8K without improving the rods, bearings etc?

Cheers
Red