Building a bike for Taupo

[bucketracer]

I have just got a Suzuki GP125 and want to get it race ready for Taupo. Anyone know any tricks for making one of these go? I am looking forward to meeting with all the other F4/F5 racers there. In my imagination its like the Isle of Man for buckets. Can't wait :banana: Looking forward to the flag drop and that first corner rush. :chase:

[F5 Dave]

Oh my! What a quality machine.

Isle of Mann for buckets?!? That's quite some imagination you have.
Well the link track leading back onto the main part of the top section could be bumpy & tight enough to qualify for that statement I guess? Apart from that it looks very much like a racetrack.

Whatever you do buy some decent tyres (do a search on this site) & also search, there are a few threads about GPs. You should take some lower gearing, road gearing will be too tall.

[speedpro]

Ignore F5, everyone else does. The best person to ask about GP125s is TZ350. Him and his workmates have a fleet of them and they have done LOTS of development. Their bikes seem to run well and are reliable. Come out to Mt Wgtn for the next meeting and have a look and a chat with them.
Decide where you want to go with the bike. As F5 says, get decent tyres but first decide what wheels you want/need. No use buying tyres for wheels you are going to toss in a short time.

[F5 Dave]

Surprisingly for such an old chap Spe’s dementia sometimes subsides & he says something useful. :bleh:

You have less than 3 months so how much time & effort are you going to put into it is a valid question. To make a very competitive bike in such a short time will take some coin & dedication. If you just want a laugh then aim at only doing the things you are likely to get done by then.

[racer40]

yeah the ESE team have a fleet of GP 125s sure they can help, but not much time to get alot done & get ontrack before Taupo so just get the basics done. Who is speedpro?? PS & get your entry in quick

[Buckets4Me]

change the tires tt100 would be good for those rims
or get better rims
there will probably be some 17's you can lace up at the track next time $400 (good price)

and finding slicks isn't hard
the gearing for taupo on a standard engine I dont think changes much but for mt Wellington you will want an 11 or 12 frount sproket and maby a 15 16 for taupo {i have from memory a 15 and 54 back sproket but the engine is not standard and on 17's} i think they have a 17 on standard but dont quote me
remove the oil pump and use premix
remove everything etc change where the pegs are and change the handlebars clipons are nice you will find that the exaust and bike stands scrape around corners if ridden hard lol



best to come to the track if you can and have a talk

[Buckets4Me]

also make sure everything in the engine is up to a good thrashing ie rebuild if you can

they are a good engine standard and heeps more fun warm
rg250w pipes modify easily to fit ask how at the track may even have 1 or 2 spare now lol depends if they get used for the new engine lol

[speedpro]

Leave the bars that are on it. Most of the seriously fast guys have fairly wide and not too low bars on their bikes for the kart tracks.

[Buckets4Me]

like gary and dave lol

[Buckets4Me]

whatever is easier but I found the high bars a pain couldn't get enouch wheight on the frount tire and it would flip over backwards on a good start
especialy with the standard engine and the right gearing to run in 5th around Mt Wellington

Gary and Dave run clipons Karl has mx bars reconds he can fight it to the tarmack that way

[Buckets4Me]

have you seen how high those handles are like ape hangers

:scooter:

[speedpro]

Nigel Duff(AK #1), Jim Steadman(winner of more Ohakea GPs than everyone else put together)

[F5 Dave]

Nigel was talking about putting lower bars on for taupo, Jimmys bars are hardly high or wide like mx bars. I rode Nigel's bike, it was seriously hard to get your head around those bars & lets remember that I used mx bars on my H100 & I dirtbike a fair bit. Some people like them & fair call. for the H it wobbled enough & the pegs were far enough forward that it suited point & squirt style.

[Buckets4Me]

hardly compair to the standard gp125 bars at all

[TZ350]

The real deal for GP125’s is Skim and “O” ring the barrel, no porting, KX80 ignition, RG250 chamber, 97.5 main jet.

Read Keith Code's books. You will have to experiment with riding style to find what setup works for you.

Some pictures of our GP's at Mt Wellington where we race wet or fine. In the last 2 hour (run anti clockwise) Keith Biddel was consistently clocked at 31's and Joe Mead at 30.5's on these GP’s. The really hot boys were about 30’s so our bikes are right up there. See you at Taupo.

[Slingshot]

The real deal for GP125’s is Skim and “O” ring the barrel, no porting, KX80 ignition, RG250 chamber, 97.5 main jet.

Read Keith Code's books. You will have to experiment with riding style to find what setup works for you.

Some pictures of our GP's at Mt Wellington where we race wet or fine. In the last 2 hour (run anti clockwise) Keith Biddel was consistently clocked at 31's and Joe Mead at 30.5's on these GP’s. The really hot boys were about 30’s so our bikes are right up there. See you at Taupo.

I thought the GP100 & GP125 bottom ends were essentially the same but looking at that photo they're quite different.

[Buckets4Me]

whats so different ???
apart from the kx80 ignition and the oil pump removed and plated over the hole

or am I missing something

[Slingshot]

whats so different ???
apart from the kx80 ignition and the oil pump removed and plated over the hole

or am I missing something

I've just been tinkering and have realised that what I thought was different probably isn't different on a stock version.

On my GP100, the casing around the carb has been cut away, on further inspection tonight, it looks like the casing for the airbox has also been cut away. The bit that looked different was the bit with the sieve attached to it.

<img src="http://www.kiwibiker.co.nz/forums/albums/thumbs/8/2065b829584cb17bc092c53dac577061_8791.jpg?dl=12228 54102"></img> (http://www.kiwibiker.co.nz/forums/picture.php?albumid=80&pictureid=8791)

[TZ350]

GP100 and 125 bottom ends are much the same just different carbs 22mm for the 100 and 24mm for the 125. Different rotary valve timings which can easily be changed and the rotary valve cover on the 100 has a slightly smaller inlet tract which can be opened up to suit the 125. Everything else on the bottem end is the same. I did try a 125 rotary valve in a 100 once but it made the 100 motor very peaky.

Here are some pictures of one of our team enjoying a closer look at the Taupo track.

[Slingshot]

GP100 and 125 bottom ends are much the same just different carbs 22mm for the 100 and 24mm for the 125. Different rotary valve timings which can easily be changed and the rotary valve cover on the 100 has a slightly smaller inlet tract which can be opened up to suit the 125. Everything else on the bottem end is the same. I did try a 125 rotary valve in a 100 once but it made the 100 motor very peaky.
I've been thinking about putting a 125 rotary valve in, but may just alter the existing one. I've got an spare uncut case which I suspect is off a 125, the inlet tract looks bigger in diameter than the one on the motor at the moment. I'll have to pull it off and compare them.

What are your thoughts on altering the rotary valve timing on the 100?



Here are some pictures of one of our team enjoying a closer look at the Taupo track. That nylon is doing a nice job in that first pic.

[TZ350]

I will look up all the timing figures for std 100/125's tomorow and get back to you.

Std. Suzuki GP100 inlet opens 135 BTDC closes 45 ATDC, Ex opens 94 ATDC, Trans1 opens 123 ATDC Trans2 125 ATDC Trans3 126 ATDC.

Std Suzuki GP125 inlet opens 145 BTDC closes 55 ATDC, Ex opens 91 ATDC, Trans1 opens 120 ATDC Trans2 121 ATDC Trans3 122 ATDC.

Std 1975 Suzuki RM125 inlet opens 88.5 BBDC, Ex opens 87.5 ATDC, Trans opens 116.5 ATDC. 23hp at 10500 rpm.

Read Graham Alexander Bell's book on engine tuning. You chose the revs you want to make power at and he gives you the timing figures for the ports.

[Slingshot]

I will look up all the timing figures for std 100/125's tomorow and get back to you.
Cool, thanks.

[F5 Dave]

Re Taupo Pic; Yeah but look at those fancy coloured leathers, that was bound to happen.

Keith can peddle fairly well for an old fella. That's a good time, but anticlockwise is faster that clockwise I believe.

[Buckets4Me]

that engine was sold on trade me as an ex drag bike engine for something or rather it had been played with but not sure what they had done not a lot I think cant remember how the add went I'm not surprised it's is different :eek:

good luck

[Slingshot]

that engine was sold on trade me as an ex drag bike engine for something or rather it had been played with but not sure what they had done not a lot I think cant remember how the add went I'm not surprised it's is different :eek:

good luck

You're spot on, the guy that I brought it off had built it for the Wanganui drags, it was built to look like an old fashioned drag bike so he'd airbrushed rust onto the motor. I think from memory, he did a 12ish second quarter mile on it. Here's the listing. (http://www.trademe.co.nz/Browse/Listing.aspx?id=112529490)

The transfer and exhaust ports have been cleaned up a bit and it looks like the inlent tract has been smoothed out too but I can't tell yet if the rotary valve has been altered.

[F5 Dave]

yeah that's authentic, 'cause those ally engine cases rust up real good<_<

[Slingshot]

I've managed to get my hands on the article that Performance Bike Magazine did on the GP100 in the mid-eighties. If anyone wants a copy, PM me your email address and I'll send it through. It's 9 jpgs and they're about 2Mb each.

[F5 Dave]

Yeah I probably have a copy of some of it from back then, but not all & I saw that chap had promised a copy. It wasn't exactly revolutionary hi tech tuning, but worth a read I guess.

[TZ350]

Re Taupo Pic; Yeah but look at those fancy coloured leathers, that was bound to happen.

Keith can peddle fairly well for an old fella. That's a good time, but anticlockwise is faster that clockwise I believe.

You are right, its faster but the times for Keith and Joe compaire well with the fast guys going the same way on the day.

[TZ350]

I've been thinking about putting a 125 rotary valve in, but may just alter the existing one. I've got an spare uncut case which I suspect is off a 125, the inlet tract looks bigger in diameter than the one on the motor at the moment. I'll have to pull it off and compare them.

What are your thoughts on altering the rotary valve timing on the 100?


That nylon is doing a nice job in that first pic.


The skate board wheels do a good job of keeping it all of the track.

The first part of the GP's engine number on the crankcases should tell you if they are from a 100 or 125.

[Buckets4Me]

both keith and jo hadent ridden the bikes till that week as well
same with the other rider who was also doing 30-31's
and doing a fine job of holding off nigel at one point till the two of them collided
:shit:

[Buckets4Me]

if I remeber right he was quite proud he didn't scratch his helmit in that crash :jerry:

[F5 Dave]

Hey has anyone noticed that we are 3 pages in of drivel & the original poster has gone awol?

[Skunk]

Yep. However he was here yesterday at 7:16pm...

[nudemetalz]

Maybe he heard what the NWM was about and ran like hell !!! :bye:

[Buckets4Me]

OR MABY he is downgrading his bike so he dosent show them all up

I heard that he was going to keep it all as is so you lot had a chance
specialy the fxr's



:jerry:

[F5 Dave]

Yep. However he was here yesterday at 7:16pm...

check the silverware:confused:

[Buckets4Me]

you stole it on a 50 I hear

[bucketracer]

I have just got some good wheels with TT900GP rubber on them that looks in reasonable condition. The guy I got them off was very helpful, he said it is ok rubber but in his experience when the tires are pressed hard they will induce chatter or at least thats what happened to him. He experimented with frame and swing arm bracing but the problem disappeared when he put 17's and slicks on. It turns out that the STD Suzuki GP125 frame works ok as is with slicks and he thinks the rippling of the TT900GP treads was causing sympathetic vibration in the suspension with a slip grip sort of effect. That was good of him to tell me, and I also would like slicks too but for now I have to start where I can afford.

looking to the future I have a 17 x 3.5 rim that I think I can salvage and need a 17 x 2.5 36 hole rim if anyone has one for sale. Please PM me.

[quallman1234]

TT900's are pretty decent.

[Kickaha]

and need a 17 x 2.5 36 hole rim if anyone has one for sale. Please PM me.

2.15 x17 is easier to find and works just as good (rear of some trailbikes), I've run RS125 slicks on rims as narrow as 1.85 x 17 and hardly been able to tell the difference in handling

[bucketracer]

Many thanks for the info. there is also some pretty clever posts about GP125's on Frankies post http://www.kiwibiker.co.nz/forums/showthread.php?t=81790

TZ350 realy seems to know what he is on about.