new GS racer

[ozman]

whats the measurement from top of fork triple clamp to axle centre on your front end ?
just curious as to your lack of ground clearance

727mm is the measurement on my XR69



722mm on the McIntosh





ozman

[John Kat]

Here are a few fork lenghts I measured some time ago:
http://www.thegsresources.com/_forum...d.php?t=186805.
I bet the engine sits much higher in the XR69 frame

[ozman]

Here are a few fork lenghts I measured some time ago:
http://www.thegsresources.com/_forum...d.php?t=186805.
I bet the engine sits much higher in the XR69 frame

its a double cradle frame very similar to the GS1000 frame, motor is positioned higher
McIntosh engine sits higher in its frame
but im wondering how much shorter the forks are on patrinos racebike
considering that the std measurement was 775 on a GS1000 compared to around 725 on these race bikes
seems he has lost alot of clearance

ozman

btw top clamp on both these bikes have 15mm drop and im measuring from top of top clamp to centre of axle only the fork cap is protuding above top clamp on both these

[patrino]

765mm from the top of the upper triple clamp to the axle center. That's with the bike on the rear stand without me on it.

The fork tops are currently 8mm below the top of the top triple clamp. I'm not comfortable going that much lower.

John Kat, those are some helpful measurements.

I schlepped some aluminum to my shop on the back of my XR400 and cut out the bits to make an aluminum seat pan. Turns out I already have an aluminum wire spool for my MIG outfit, so I'm going to build it up on Wednesday. Should save a couple #s compared to the current steel seat.

[patrino]

PS ozman that's a good looking xr69!

Patrick

[ozman]

765mm from the top of the upper triple clamp to the axle center. That's with the bike on the rear stand without me on it.

The fork tops are currently 8mm below the top of the top triple clamp. I'm not comfortable going that much lower.

John Kat, those are some helpful measurements.

I schlepped some aluminum to my shop on the back of my XR400 and cut out the bits to make an aluminum seat pan. Turns out I already have an aluminum wire spool for my MIG outfit, so I'm going to build it up on Wednesday. Should save a couple #s compared to the current steel seat.

if you wanted to raise the front a stepped down top triple clamp is alot better than extending tubes or dropping forks 8mm through the clamps
how many mm are your forks ?
downside is that raising the front does slow your steering
reading the entire thread and looking at the pics bike does appear to be low in the rear compared to alot of other similar race bikes
do you have a good side on pic of bike not on rear stand
how did you go with getting sag back to 20mm ?

ozman

[patrino]

Ozman, good idea about the dropped upper triple clamp. I have a friend who might be able to machine one for me pretty easily.

Per John Kat's measurements, my forks should be 767mm (they're first-gen GSX-R forks.) John Kat's are unladen, I reckon.

I'll grab the sag measurements the next time I'm down at the shop, they're in my notebook.

The steering's just fine at this point, especially at a fast, flowing track like Portland International Raceway (my home track). Might be a different story at tighter tracks, though. The wide bars offset the penalty of slow steering a bit (easier to jockey the thing around compared to a clip-onned bike).

I have a set of 43mm Ohlins RSU forks in my basement, they're even shorter than what I have now, but I'm going to see if longer tubes are available. (When I get some more $, of course!)

[ozman]

i see you mention putting the s fairing on, that might be a backward step for handling
the fairing on cooleys bike was not handlebar mounted it was on a bracket coming off steering head angled down and lower than a normal s model

ozman

[gs58]

Initially I was running standard GS1000 forks on my race bike and used '89 GSXR triple clamps to bring some modern steering geometry to the bike. Then I raised the rear end by about 40mm to give the forks a steeper rake which gives a better turn in, plus more ground clearance. I could adjust the length of my shocks so was able to tune the trail depending on the profile of the tyres I was using. If you are looking at doing this you will need a steering damper for those times when you decrease the trail too much.

In the end I fitted a pair of GS1100GKZ 41mm forks which were longer, stronger, and met the period requirements. I'm not sure how much longer they are, but I'm sure someone on this forum could give you the length.

[gs58]

Another mod I did that may help you was to move the location of the oil drain plug to the front right of the sump plate. This was done by drilling a hole (about 25mm) in the sump plate at the new location, then welding in a short length of alloy bar that had been drilled and tapped to accept a sump plug. This was pretty easy to do and made draining the oil a lot less messy. The new location was at the front as the sump sloped down this way when the bike was on its race stand.

[GregT]

Standard GS1000 triple clamps and long shocks (not laydown) give a measured 24.5 degrees of rake and approx 97mm of trail on 17inch wheels.

Ours handles very well like this, and with the pipe well tucked in and side covers slimmed, we're not hurting for ground clearance too much.

[John Kat]

Initially I was running standard GS1000 forks on my race bike and used '89 GSXR triple clamps to bring some modern steering geometry to the bike.

If I may, by using GSXR 89 triple clamps you actually increased the trail as you pulled the front wheel backwards.
Off course raising the rear reduced the trail and you probably ended close to a GSXR spec

I wrote this a while ago on the same subject:

Having installed the GSXR 11 K front fork on my GS 1000 ST, I wondered to what extent the rake and trail had been modified?
The OEM specs for the GS 1000 are:
Rake: 27°
Trail: 116mm
First, I'll assume that the bike's ride height remains constant by adjusting the fork tubes in the triples.
This means that the rake will remain constant at 27°.
The formula that links the different variables is:
a=R*sin(rake angle)-d
a is the trail
R is the radius of the front wheel
d is the offset between the fork tubes and the steering axle
So with the 19" front wheel that has a radius with tire of 344 mm, and the GSXR 11K triple that has an offset of 32 mm, the trail comes out at 124 mm.
That's a lot and the bike will feel heavier to turn.
Second, if we lower the front end by 2.5 cm the rake will decrease by 1°.
With this new rake of 26° the formula will give us a new trail of 118 mm
This is almost the same as the OEM spec!
Is this achievable with the GSXR 11K fork legs?
The answer is yes as the loaded length of the fork tubes goes from 745 mm on the GS 1000 to 715 mm for the GSXR 11K resulting in a shortening of 30 mm that translates in a reduction in height of 26.7 mm
In other words a GSXR 11K fork will give you the same trail as the OEM bike while the rake will decrease by 1° which is good.
You loose of course 26.7 mm of clearance in the front that should be negligeable.
__________________

[patrino]

More detailed race report on the way, but happy to report I fought my way to a couple podium finishes this weekend. Here I'm stalking the SV650 who's leading the Clubman championship, and getting pursued by an Aprilia 125 GP bike. I managed to beat the SV but the 125 beat both of us. A LOT OF FUN!



Props to Talking Parrot Productions for the photo!

[patrino]

More snaps on the way if folks want them, this one's from Bob Edwards. Here I'm entering the chicane.

We run the chicane at PIR two out of six rounds. It's about 2/3 of the way down the ~1-mile long front straight. I loved running it when I raced my 250 but it's a handful on the big bike. Really the only place that the suspension got upset. Big bike, doesn't handle the right/left transition too smoothly!

Raced it in GP Twins on Saturday. Got the holeshot, led for 5 of the 10 laps, then started to get picked off as I got tired out (that's an explanation, not an excuse!) First by a destroked 748 Ducati, then an SV, and in the penultimate lap a Honda Moto3 bike. I tried to hang with the Moto3 bike but couldn't, and finished up fourth.

Sunday's races were better. I started from last place on the grid in the first race (I hadn't raced Middleweight Superbike before, so they put me in back because I didn't have any points in the class). Got a great start and wound up finishing 3rd. The Moto3 bike that beat me on Saturday got ahead of me but I wasn't going to let history repeat itself so put the hammer down and beat him.

450 Superbike finished 2nd, an SV and I were dicing it up for 2nd towards the end of the race, we came up on lapped traffic in turns 7/8/9. I stayed tight on his tail entering nine, pinned it, and popped out of his draft for a pass a hundred feet before the finish line, just barely snagging 2nd place.

All in all a good weekend! Joe Signs and Joe Pethoud (both raced their superbikes at the Phillip Island Classic earlier this year) were there to spectate and both have committed to race their superbikes at our Vintage Day on Saturday, 16 August.

One more race between now and then. I'll keep the photos coming if folks enjoy them - let me know.

You can read more about the races here: http://www.roadracingworld.com/news/...d-in-portland/

[Charlie G]

patrino,

Yes, keep them coming. I enjoy the shots of the races. Looks like a lot of fun.

cg