82 kat Re-build

[jwhelan65]

That Kat looks great Joe, I have been anxiously awaiting the unveiling of the EZ but now the Kat is making me drool

Ez is getting close

[posplayr]

Very nice project
Does your front end come from a GSXR 1100?
I would be concerned by ground clearance with this type of fork?
Having a 4 into 1 will help but it will still be very low...
I did a project with the RSU version of this fork and here's the result.
The unloaded fork length was 745 mm ( front axle to stanchion top)
In the end I used Bandit Ph1 stanchions at 775 mm to regain the lost height.

John Kat,
The 89-90 GSXR 1100 triple with Bandit Station is a very nice combination, but the 1991 GSXR 1100 is also a viable option as I think it is only 0.5" less than yours.

I have attached a spreadsheet showing the relative comparison. The two other big factors for your GS1000 are that you have a stock exhaust which has almost the best in ground clearance (even better than a 4:2:1) and you did a mono-shock which could have increase your rear ground clearance.

In the spreadsheet I gave you 0.5" for both shocks and exhaust and with your bandit forks you end up only -0.31 on your mid ground clearance. Depending upon Joe's exhaust and shocks I have him loosing -1.33". In comparison I may have went over board but have no ground clearance issues as a result. I went with 18" wheels, extended shock and a 4:2:1 so I actually ended up with 0.49" positive according to the calculations in the spreadsheet.

Jim

P.S. let me know if you want a copy of the spreadhsheet.

[jwhelan65]

Jim,

Are you accounting for the 954 triple? This will add an inch in fork length, not sure of how much it will increase ground clearance.

[posplayr]

Jim,

Are you accounting for the 954 triple? This will add an inch in fork length, not sure of how much it will increase ground clearance.

How much do you thing it drops the top of the clamp? I can add that in one of the column "O".

Column O comment:

Distance from the top of the fork to the top of the head set; compensates for drop triples

I changed column "O" to -0.5 v.s. -1.0 and the overall clearance went from from -1.33 to -1.11. I still think you are loosing about 1". On the other hand the USD forks with cartridge design do not need as much clearance as they don't tend to dive as much.

[jwhelan65]

It dosnt drop the clamp, the top clamp has a step in it so you gain an inch. So I gues it actually pushes the head up 1".

[jwhelan65]

Mocked up the calipers and rotors

[jwhelan65]

Still some spacing to address and some fabbing to make the rear m/c actuator clear the swingarm..

[jwhelan65]

[jwhelan65]

[John Kat]

John Kat,
The 89-90 GSXR 1100 triple with Bandit Station is a very nice combination, but the 1991 GSXR 1100 is also a viable option as I think it is only 0.5" less than yours.

.

Hi Jim, I agree it seems very little but if you consider it from a lean perspective it shows a very different picture
On top of that,I believe you have computed the clearance at the mid-distance between the two wheels?
The issue on the GS's is the side stand and the left crankcase cover that are closer to the front wheel...
Personally, I don't feel confident if a bike does not have a minimum of 45° static lean angle.
Don't forget that at this angle of lean the bike is subject to 1.41 times it's static weight that further reduces the ground clearance.
This is somewhat compensated by the fact the bike rolls on the circumference of the tire and not on it's center.
Let's suppose the bike was at 150 mm from the ground initially with the 45° lean capability.
Now we lower the bike by 15 mm, the lean angle now becomes arctg .9= 41.9°
Definitely in the danger zone to me
And we haven't hit a bump mid-turn yet!

[posplayr]

Hi Jim, I agree it seems very little but if you consider it from a lean perspective it shows a very different picture
On top of that,I believe you have computed the clearance at the mid-distance between the two wheels?
The issue on the GS's is the side stand and the left crankcase cover that are closer to the front wheel...
Personally, I don't feel confident if a bike does not have a minimum of 45° static lean angle.
Don't forget that at this angle of lean the bike is subject to 1.41 times it's static weight that further reduces the ground clearance.
This is somewhat compensated by the fact the bike rolls on the circumference of the tire and not on it's center.
Let's suppose the bike was at 150 mm from the ground initially with the 45° lean capability.
Now we lower the bike by 15 mm, the lean angle now becomes arctg .9= 41.9°
Definitely in the danger zone to me
And we haven't hit a bump mid-turn yet!

John,
I agree with most of what you say and for that reason the calculation is intended to only be a relative calculation at laden (bike and riders) weight compression of the suspension as measured mid point between the axles.

All of the design variables of fork length, rear shock length, triple clamp height, fork rake, tire/wheel size can be embodied in this single calculation. So it is useful in evaluating the various design options and the net effect of each on this single parameter (mid axle clearance).

For example, when you go to a 17" wheel size it is very hard to keep from losing some ground clearance, on the other hand it is unnecessary (with a modern USD fork) to maintain the full stock clearance. Having said that there are certainly examples of excessively low 17" conversions that have had turning issues and an application of the spreadsheet will show that. From what I recall, you will have issues if you loose more than about 1.5" at center.

There are certainly other factor, if your springs are too soft (with excessive compression in bumps or turns) or you have large case guards. Those factors are not included. As a another argument in support of the validity of this calculation, one of the main ground clearance issues I have seen even with a stock suspension is running over speed bumps and hitting the middle of the exhaust on a 4:1 exhaust. So in terms of relative ground clearance for speed bumps, that is basically what the calculation does.

Jim

[Sadsak]

This is 4 or 5 pages late but this is what a Canadian 1982 750 Kat looks like, circa 1985(ish):

[jwhelan65]

So much for the build thread..

[akckhim]

Lol got off track there. They both look great!

[Sadsak]

So much for the build thread..

So is it a build thread or are you flipping it? By the way if I could find a decent one for sale that wasn't too far away I'd be all over it. I loved my Kat. Rode it for about 4 yrs, guy I sold it to wrote it off the first day he had it!