82 Kat resto-mod aka Project Bucket Case

[katman]

NOw, I have a question with regards to the swing arm. I realize you, guys, wouldn't have done it the same way, but would you use it or redo it?

As Rob mentioned, the mounts are pretty far forward and gives me about 25-26 degrees overall rake and stock Katana is around 28 degrees. I was going for a little more rake and not even thinking chain clearance with the swing arm.

So, the issue are chain clearance which can be fixed with custom sprocket (cross my figures) and the mounts themselves. While strong and similiar designs used by others, can be made stronger even if the shock are square.

The serious issue is the trail. Stock is 4.65"(118mm) current sport bikes are (3.6" (90-95mm). Changing your chassis angle by 1 degree will decrease your trail by 1". With the gsxr 750 frontend, bandit back end and pirelli tires my trail is 4.25". This is with the shock mounts placed to equal stock shock angle and ride height in the rear.
There are many parameters that effect the handling including triple offset and swingarm angle. I am told that 12 degrees is optimal for swingarm angle with no sag.
I mounted a frontend less wheel on my bike and fired a laser through the steering stem. Since the stem is hollow I machined a plug that the laser fit into. below is the results of that. The bike attitude as tires just touching the ground but no weight on them. YOu had mentioned that compression of the suspension will help but that is dangerous in my opionion. As you travel down the road and all seems dandy, you turn up the wick and head into a corner (or not). you go over an irregularity which extense the forks, (lets say a bump or rise in the road) you can be in serious trouble. The instability occurs at speed. ONe second your happily travelling along, the next split second your into a wicked tank slapper and skidding accross the road hopefully not into oncomming traffic. Jacking the back end up is not a good idea. If you want more air between the tire and frame, modify the subframe.

Anyways, this is my humble opinion. cut the mounts off and move them back, or, get some extensions for the front forks. If you can change the mounts on your shocks I will send you a set of cnc GS style swing arm mounts for free. IF not, I would like to see new mounts made anyways given the design of the ones you currently have. You know what? I will machine you another set if you want to fit your current set up.

The bolt centers of the shocks should be directly over or just in front of center of the rear weld on the swing arm. One other point. the left hand mount should be outboard of center on the swing arm fork to allow for shock spring/chain clearence.

I used degrees of engine cradle for a base as my garage floor is not level. The setup was with tires touching so engine cradle angle is a point of ref that can be used by all.

[posplayr]

The serious issue is the trail. Stock is 4.65"(118mm) current sport bikes are (3.6" (90-95mm). Changing your chassis angle by 1 degree will decrease your trail by 1". With the gsxr 750 frontend, bandit back end and pirelli tires my trail is 4.25". This is with the shock mounts placed to equal stock shock angle and ride height in the rear.
There are many parameters that effect the handling including triple offset and swingarm angle. I am told that 12 degrees is optimal for swingarm angle with no sag.
I mounted a frontend less wheel on my bike and fired a laser through the steering stem. Since the stem is hollow I machined a plug that the laser fit into. below is the results of that. The bike attitude as tires just touching the ground but no weight on them. YOu had mentioned that compression of the suspension will help but that is dangerous in my opionion. As you travel down the road and all seems dandy, you turn up the wick and head into a corner (or not). you go over an irregularity which extense the forks, (lets say a bump or rise in the road) you can be in serious trouble. The instability occurs at speed. ONe second your happily travelling along, the next split second your into a wicked tank slapper and skidding accross the road hopefully not into oncomming traffic. Jacking the back end up is not a good idea. If you want more air between the tire and frame, modify the subframe.

Anyways, this is my humble opinion. cut the mounts off and move them back, or, get some extensions for the front forks. If you can change the mounts on your shocks I will send you a set of cnc GS style swing arm mounts for free. IF not, I would like to see new mounts made anyways given the design of the ones you currently have. You know what? I will machine you another set if you want to fit your current set up.

The bolt centers of the shocks should be directly over or just in front of center of the rear weld on the swing arm. One other point. the left hand mount should be outboard of center on the swing arm fork to allow for shock spring/chain clearence.

I used degrees of engine cradle for a base as my garage floor is not level. The setup was with tires touching so engine cradle angle is a point of ref that can be used by all.

Rob so bottom line how far is he lifting the rear end with the current mount locations with those piggyback shocks? 1"-1.25" is desireable for these old beasts

[katman]

I don't know off had how much lift he is getting. An inch or so isn't critical in the rear but, if you drop the front end by 3" at the same time it gets more critical. Some guys are using gsxr triples so are realizing a 4" change effecting trail before any changes in the back end.
We only have about an inch of trail to work with before things get hairy. The gsxr and cbr triples have much less offset than the kats which works in favor of increased trail offsetting some of the loss by the shortened front end. There are many numbers to take into account for sure but considering the possible outcome of getting things wrong it is best to double and triple check your work.
There are companies around the States that can measure your suspension geometry. Race teams use them. They can be a couple hundred bucks but cheap compared to sliding down the road on your head or even taking out an innocent on the side of the road.
rember also that all the new bikes have steering stablizers. They have to have them in the 90-95mm trail range. If I remember correctly, the TLR1000's first came without one and after several crashes Suzuki added the stablizers.
Handling and stablizing the bike is not a question of one or two factors. My point is simply that modifications can lead to dangerous situations and there are limits that should not be pushed with these old bikes. Many guys out there may not have had any stability issues but these old bikes are all different with different combinations of parts and riding styles and abilities. Because one guy gets away with it doesn't mean you will, or he will for long. Error on safety, these are not race bikes and we are not riding them to their current stock abilities as it is.

If anything we should be dropping the back end not raising it, from a stability point of view.

[ukilme]

Okay, good news is the rear is centered witin a 1-2mm. It took longer to setup and check with the laser then I thought it would. With all the measurement using the center of the cross member and swing arm pivot. I was able to check the alignment again. So, my method worked but is not the best method and I got lucky.

Now with the swing arm, I had to redo the height measurements with the modified swing arm and the stock as I could not find my notes which means I proably forgot to to it. Anyways, there was a big difference between stock and my setup which does have me concerned- just over 3"

And with what you are saying are saying Rob, if I have 25 of rake which is 3 degrees less then stock. It would be about 75mm less then stock and would put me near 43mm for my trail . I did not realize this and I am glad you caught this. The stupid thing is if I had reversed the mounts it would have given 27 degrees or so. And would have put the hole right by the swing arm welds. I went for look on this.-Lesson learned again.

I had a speed wobble once in a 100km/hr corner at a track and just about **** my pants. I caused it by releasing my brakes to fast while trail braking. I also had a 170km crash at the track because of a bike issue at the corner entrance which threw my way off line.

So, this is a no brainer, I messed up and the shock mounts are coming off as there are too many concerns. Good lesson learned here.

A couple of questions:

1. Does aluminum re-act to heat cycles like metal and get weaker with repeated welding? If so, should I go for another swinger?

2. Also, what is the length of shock you guys using? Stock is 13 (340mm) inches and the zrx, I am using, are 14 (370 mm) which will jack it up.

Also Rob, the shock mounts are offset. The inside is 10mm think and the outside are 5mm thick. Any further over, the shock will to for over on the stud.

I will get back to you about your offer. I want to think some more about if I am going to go with the zrx shock or another "GS" type shock.

If I do go with celvis style, I will buy your mounts. No need to give them out. I wanted a honest anwser and I got it.

[katman]

Okay, good news is the rear is centered witin a 1-2mm. It took longer to setup and check with the laser then I thought it would. With all the measurement using the center of the cross member and swing arm pivot. I was able to check the alignment again. So, my method worked but is not the best method and I got lucky.

Now with the swing arm, I had to redo the height measurements with the modified swing arm and the stock as I could not find my notes which means I proably forgot to to it. Anyways, there was a big difference between stock and my setup which does have me concerned- just over 3"

And with what you are saying are saying Rob, if I have 25 of rake which is 3 degrees less then stock. It would be about 75mm less then stock and would put me near 43mm for my trail . I did not realize this and I am glad you caught this. The stupid thing is if I had reversed the mounts it would have given 27 degrees or so. And would have put the hole right by the swing arm welds. I went for look on this.-Lesson learned again.

I had a speed wobble once in a 100km/hr corner at a track and just about **** my pants. I caused it by releasing my brakes to fast while trail braking. I also had a 170km crash at the track because of a bike issue at the corner entrance which threw my way off line.

So, this is a no brainer, I messed up and the shock mounts are coming off as there are too many concerns. Good lesson learned here.

A couple of questions:

1. Does aluminum re-act to heat cycles like metal and get weaker with repeated welding? If so, should I go for another swinger?

2. Also, what is the length of shock you guys using? Stock is 13 (340mm) inches and the zrx, I am using, are 14 (370 mm) which will jack it up.

Also Rob, the shock mounts are offset. The inside is 10mm think and the outside are 5mm thick. Any further over, the shock will to for over on the stud.

I will get back to you about your offer. I want to think some more about if I am going to go with the zrx shock or another "GS" type shock.

If I do go with celvis style, I will buy your mounts. No need to give them out. I wanted a honest anwser and I got it.

Welding weakens alum yes. If you move the shock mounts back to the weld area you will be fine. I don't think a new swinger is needed. You are at the outside limit of thickness IMHO for mounts. 5mm is minimun thickness. I would not go less than that.
I would check your trail numbers. They can't be 43mm??? If so you can't ride it. I offered the mounts to you because I didn't want your decision to be a monitary one. YOur safety is more important than my cost on some mounts. ONce you move the mounts back you can go to a 17/48 sprocket set which is a smaller diameter set than the stop ones.
YOu are using a GS sprocket hub yes? not the gsxr and, you are using the GS inner bushing for that hub and not the GSXR yes? If not you could explode the wheel bearing.

Feel free to email or call if I can be of more help. parts@suzuki-katana.com

[ukilme]

Welding weakens alum yes. If you move the shock mounts back to the weld area you will be fine. I don't think a new swinger is needed. You are at the outside limit of thickness IMHO for mounts. 5mm is minimun thickness. I would not go less than that.
I would check your trail numbers. They can't be 43mm??? If so you can't ride it. I offered the mounts to you because I didn't want your decision to be a monitary one. YOur safety is more important than my cost on some mounts. ONce you move the mounts back you can go to a 17/48 sprocket set which is a smaller diameter set than the stop ones.
YOu are using a GS sprocket hub yes? not the gsxr and, you are using the GS inner bushing for that hub and not the GSXR yes? If not you could explode the wheel bearing.

Feel free to email or call if I can be of more help. parts@suzuki-katana.com

Ya, 43 is a little small, I was just taking the 1 inch for every 1 degree. In short, it really does not matter. I'd rather be safe then sorry.

GS hub with GS hub spacer is yes.

Here is a close up of the mount welded to the arm. The back is right on the factory weld. Is the swinger still usable?


I hate wasting money but I really not that much into the arm. Well, I'll keep telling my self that...lol

[katman]

Ya, 43 is a little small, I was just taking the 1 inch for every 1 degree. In short, it really does not matter. I'd rather be safe then sorry.

GS hub with GS hub spacer is yes.

Here is a close up of the mount welded to the arm. The back is right on the factory weld. Is the swinger still usable?


I hate wasting money but I really not that much into the arm. Well, I'll keep telling my self that...lol

Email sent.

[ukilme]

Well, after some emails with Rob and a phone conversation today with him.

I have decided to get his mounts for the swinger and get rid of the zrx shocks. We did talk about mounts for my application but we thought it best to go the traditional way.

I guess this is like 2 steps back but that's life.

I have to say thanks to Rob and Jim for hashing this out with me.

[posplayr]

Well, after some emails with Rob and a phone conversation today with him.

I have decided to get his mounts for the swinger and get rid of the zrx shocks. We did talk about mounts for my application but we thought it best to go the traditional way.

I guess this is like 2 steps back but that's life.

I have to say thanks to Rob and Jim for hashing this out with me.

Rob is the real expert. I just know my bike and the set-up ; well I do know a little math

[ukilme]

Rob is the real expert. I just know my bike and the set-up ; well I do know a little math

Ya, I heard you new math. Rob and I spoke about your project for some time.

[ukilme]

So, while I wait for new shocks mounts from Rob. I have been gathering other parts.

I just picked up a DID ERV3 520 chain which is the thinnest 520 chain on the market at 18.60mm. But here is Canada it can go for $200 or more. The cheapest prices I found was at http://www.bluestreakracing.ca/ base in Toronto or http://www1.petes-superbike.com/ based in Montreal. The price difference was 17 cents by the time you work in taxes and shipping. The chain it self was roughly $143cnd.

Now, if you go for a 520 sprocket and want to stay in Canada. Petes' can get the sprocket but email him first. Or order from your stealership and get them to order it from Steen Hansen Racing. Part number is 1825-48 for a JTR or 6050-48 for a PBI rear sprocket. PBI also has a 50t sprocket.

My front sprocket is coming from Rob.

I have also had some PMs with regards to the zrx 1200 shocks and some issues that may arise. IF you plan on using them ( posting this more if anyone ever searches for these shock).

1. They are 30mm longer then shock GS shocks.

2. This can be fixed by placing the bottom mount over the weld point on the B12 swing arm.

3. Placing the mounts over the weld will cause some more issues, you need a custom mount made with radius d cut (discussed a few post back) and need a 8 degree angle on the bottom as flat bottom will not work. This means it is a complicated/timely machining job and a little more costly.

4. The upper bushings on the shock are 14mm. This can be fixed by a sleeve or getting lower bushing and drilling them out. Not really a problem if you don't let it over heat and get the right drill bit.

5. THe zrx shock is 2.75" wide while Ohlins and Ikon are around 2.5 or less. This means possible chain clearance issues.

6. You can weld the left side mount to the edgeof the swing arm and gain clearance but now you shock will be about 5mm on the threaded part of the upper stud. And now looking at sleeves.

7. zrx shocks can go anywhere from 200-350 used and may still need a rebuild which is roughly 150-200 each.

Now, I am not saying it can not be done but I decided to cut my loses and go the tried and true route.

Currently, I am leaning towards the YSS.

[ukilme]

When I spoke with Rob, he mentioned and agreed with Jim that the sprocket side spacer should be .650" or 16mm which is the stock B12 spacer. He did also mention that there can be little differences. Now, mine is 3mm larger which is a lot. So, I decided to take off the rear tire and check the best I can with the rim. Rob also mention this is best.

Now, I do not have the tools to make the tools that Rob uses and posted earlier. However, I tried my hand at it and think it worked out.

The edges of the duct tape is the center of the swing arm, rods and front cross member(although the cross member wasn't really used). I then lined up a laser to hit the edges as seen it the picture. I did not even consider the rim when lining up the laser. Just the edges of the duct tape.


As you can see, the rear is pretty well center.


The rim is 159mm and center would be 78.5mm. Now, the measurement is a little off in the photo because I was taking a picutre with one hand. It was just shy of 80mm. Which means, I should have added 1-1.5mm to the stock 16mm spacer and not 3mm. However, I believe this should be fine.

This also makes sense as to why when lining the front wheel with the rear the left side measurement was 35mm and the right was 36mm.

[posplayr]

The rim is 159mm and center would be 78.5mm. Now, the measurement is a little off in the photo because I was taking a picutre with one hand. It was just shy of 80mm. Which means, I should have added 1-1.5mm to the stock 16mm spacer and not 3mm. However, I believe this should be fine.

This also makes sense as to why when lining the front wheel with the rear the left side measurement was 35mm and the right was 36mm.

79.5+79.5=159 mm right. You are closer than you think ??

If I remember I got 3/16" by just using a T square off the front of the pivot and a straight edge to the in side of each fork.

[steve murdoch]

A bit of a hi=jack here Andre, but did you see this swingarm for sale near you?

http://ottawa.kijiji.ca/c-cars-vehicles-motorcycles-motorcycle-parts-accessories-1981-Suzuki-GS1100-Frame-for-sale-W0QQAdIdZ254423525

[ukilme]

Jim, I never even notice that. I screw my numbers up all time: phone numbers, house numbers and I even see words that are not there or do not see them. I think this is a condition I have...

Steve, I have seen that a few times on Kijiji-and quickly thought about it- but the shocks aren't worth $600 and the swinger is not after market it looks to be just a GS swing arm with bracing. Thanks for the link-if you are interested and want to go look at it PM.

Anyways, I am leaning towards YSS for shocks right now. Still doing some research.