BUILDING AN I.C.B.M. KATANA 1100

[Anonymous]

Re: Sawing on swing arm.

Re: Sawing on swing arm.

Just read your post on the limits of rear ride height being the chainline intersecting with the nose of the swingarm. That is the practical limitation on the amount of swingarm droop that can be obtained on these older bikes . Often the handling would continue to benefit with even more swingarm angle but it just isn't physically possible. you can sometimes by additional clearance by using the largest countershaft sprocket that is posssible and then running the largest rear sprocket that makes sense in terms of your gearing rquirements. Generally, most bikes optimise at about 12.5 degrees of swingarm droop from horizontal when both front and rear suspensions are topped and both tires barely touching the ground. I measure fom the ground to the center of the swingarm pivot and the ground to the center of the rear axel and the length of the swingarm from pivot to real axel. Then I divide by ten(to keep the size reasonable) and plot it out on paper to scale and measure the angles with a protractor. The ground must be level and the bike must be raised enough so the suspension is topped out but the tires are touching. I use an under the frame stand, properly adjusted for height and a floor jack to raise the bike. 12.5 is the most common sweetspot, but difficult to acheive on the older bikes. Each bike is different but this is a goood place to shoot for. Most bikes are far from optimum in stock form even the modern ones. This is more of an issue with high powered bikes with lots of traction. your bike qualifies on both counts. One last comment, lowering the front of a bike reduces swing arm droop. This means lowering the front improves corner entry because of the reduction in rake and trail but hurts the ability to finish off the turn because the reduction in droop results in an unloading of the front under power. Steve

You can make it a lot easier on yourself by using some trig.

Subtract the rear axle center distance to ground from the swingarm pivot distance to ground, then divide by the distance from the swingarm pivot to the rear axle center. This is the cosine. Use a calculator or table to look up the associated angle.

You posted some good info BTW. I checked my swingarm drop on the project bike and it's at 9 degrees right now. In order to get the 12.5 degrees that you stated as optimum I need to add around another 1.25".

Once I get the front raised a bit more, I'll look into just that. I'm using a 2002 GSXR750 swingarm and it's easy to adjust the ride height using spacers. I'll have to look at the chain clearance real close.

 

[Anonymous]

droop

droop

Hi Sammy. Just make sure the suspension angle is topped out front and rear, with the tires both just skimming the surface. You can not check this measurement with the bike sitting on its suspension or you will get a false reading. Also be aware that if you raise the fork tubes which lowers the front end of the bike you reduce swing arm droop. It is generally recomended that you get the rear sorted out first and then do fine tuning on the front. Raisng the rear really helps the bike finish off the corner, while it can also help on entry. Dropping the front seems to help more on entry but can can make corner exits worse. If you go too far on rear ride height, the bike will sometimes want to spin the rear tire on exits if you really drive it off the turn. This tendency can be reduced by running between a quarter and a half inch more total sag in the rear as an alternative to reducing swing arm droop. Many of these adjustments are simple on the modern bikes as their suspensions are so adjustable but sometimes mean a change in parts on the two shock set ups. I recomend that anyone who is running lots of rear ride height have a steering damper. The bike should handle fine without it, but you should still have one just in case as your trail figure is going to get pretty short with tons of rear ride height. The bikes I have built with these figures have handled really fantastic, like night and day from original, you can start dialing in throttle so early in the turn you wont believe it. Steve

 

[Anonymous]

bike attitude

bike attitude

One last comment about ride heights. I have found that a bike with too little rear ride height will leave a wider chicken strip on the front tire than the rear. If, for example you have a chicken strip that is a half inch wide in the front and a quarter inch or less in the back that is a sure sign that you need more ride height in the rear or less ride height in the front. Which you chose to move depends on a whole slew of variables and should be decided on a case by case basis.

 

[Guest]

Re: suspension

Re: suspension

Your very welcome Katman. Feel free to vary from my sugestions as they are more recomended starting points than one of the ten comandments, but I believe you will find them close and the results worth the effort. You have done an amazing job on that bike and have made an effort to cover all the bases. It gives one a real sense of accomplishment when you are able to make real improvements on a product that in its own right was quite a technilogical step forward. Im sure if you were to ride a stocker and your project back to back you would be speechless. Please keep us updated on how things work out. How is the weather up there these days?Went to a local bike hangout yesterday and there were about thirty bikes there. I left mine at home but hope to get a bike out next weekend, weather permiting. Steve

Thanks dude for your kind words. Weather here is very nice last week was sunny and in the 60's. This week the low 50's and rain. Next week we should be back to normal. It's a good week for pulling things apart.

 

[Guest]

Do either of you dudes have the stock numbers for a gs or a kat? Just to get a base ine.

 

[Anonymous]

Do either of you dudes have the stock numbers for a gs or a kat? Just to get a base ine.

Sorry Kman, I don't have any numbers for a Katana. I wish I would have taken some measurements on my stock GS1100E before I did the mods. There are lots of them in here though so it would be interesting if someone would make some measurements for us.

My first measurements were with the bike on it's suspension. I got closer to 10 degrees with it lifted properly. I was going by eyeball before and didn't do too bad.

I have the 954 triples purchased now. I can't wait until i get some more parts to sort this out some more. I know the rear spring rate is going to be a bear to sort out. It's off a 750 and it feels pretty stiff right now.

I've several dirt bikes and I know all about static sag and sag with the rider. It's very important. If that isn't right you can't possibly make adjustments work correctly. I need to look up the spring rate for a 750 to get a baseline.

I love this kind of stuff. You guys are teaching me a lot. I really appreciate it.

 

[Anonymous]

stock numbers for a base line

stock numbers for a base line

No Katman, I don't know what the stock numbers are on these bikes because they are so far from anything that works that I never paid any attention to them, even twenty years ago. Back then things like swing arm droop were only understood by a very small number of folks and they were not likely to share what they new. The Japanese had figured out how to make power but they were just scratching the surface on how to get them to handle.They tended to copy the British, who knew how to make low powered bikes handle but had no clue about how to make power, so many of their ideas did not transfer to the more powerful Japanese machines. Today there are ten thousand peaple in the US alone that understand more about chassis dynamics than even the most savy race tuners from the 80's. The british used to believe that a good handling bike should have the countershaft, swing arm pivot, and rear axel on the same plane. In other words, little or no swing arm droop, especially once sag was factored in. This works with 50 horsepower, it doesnt with a 100.

 

[Anonymous]

proper spring rate

proper spring rate

Hi Sammy. The proper spring rate may not be that bad to figure out, my guess is that the spring is way soft, but I have been wrong before. What year gsxr did you use on the back of your bike? How much do you weigh? Have you checked the sag yet? When you do what happens to your free sag or what I call static sag when your total sag is set at 35mm(aproaching the upper limit for the rear)? Some shocks can get away with less free sag than others(Penski) but none like less than 5mm in the rear, most require at least 10mm. With a spring that is too soft you usually can not get the total sag right without going below the bare minimun on the free sag.

 

[Anonymous]

Re: proper spring rate

Re: proper spring rate

Hi Sammy. The proper spring rate may not be that bad to figure out, my guess is that the spring is way soft, but I have been wrong before. What year gsxr did you use on the back of your bike? How much do you weigh? Have you checked the sag yet? When you do what happens to your free sag or what I call static sag when your total sag is set at 35mm(aproaching the upper limit for the rear)? Some shocks can get away with less free sag than others(Penski) but none like less than 5mm in the rear, most require at least 10mm. With a spring that is too soft you usually can not get the total sag right without going below the bare minimun on the free sag.

I'm using a 2002 GSXR750 swingarm. I haven't checked the sag yet since the bike isn't complete. I need a battery, tank, seat, etc. I tip the scales at around 220 in the summer.

I won't have a problem checking the sag. However, if I don't know what spring rate I have, how do I order another if it's not right? I'm doing some internet searches with no luck just yet.

 

[Anonymous]

I won't have a problem checking the sag. However, if I don't know what spring rate I have, how do I order another if it's not right? I'm doing some internet searches with no luck just yet.

Swanny, if you can measure some basic dimensions for the current spring, I can calculate the rate for you. Springs are one of the few things in this world that can be designed on paper and actually have the final result be the same as the calculated one.


Mark

 

[Anonymous]

spring rate for 2002 gsxr 750

spring rate for 2002 gsxr 750

Hi Sammy. i am not sure what came on the 2002 gsxr 750 but the most common spring for guys roadracing them is 425 so i imagine stock is pretty close to that. Spring rates vary dramatically on these things due to the different linkage ratio's that are used. For example the 99-2002 sv650's often use a 650 lb spring, while the 2003 version of the same bike uses a spring that is 150lbs lighter and as I mentioned the 2002 gsxr 750 uses one that is 225lbs lighter. Did you keep the stock geometry in the rear suspension linkage? One last thing. do you have a front suspension on your bike yet? the reason i ask is that I heard you mention that you just bought 954 yokes. You can not check swing arm droop untill you have a front suspension on the bike and it is set at an approximate height. this is becasue lowering the front reduces swing arm drop and raising the front does the opposite. Even going to a taller profile rear tire reduces swing arm angle. The 12.5 is just a base line setting. It is not carvbed in stone, but I wouldn't spend a lot of efort acheiving it, untill you have an approximate front ride height figured out. Steve

 

[Anonymous]

Re: spring rate for 2002 gsxr 750

Re: spring rate for 2002 gsxr 750

Hi Sammy. i am not sure what came on the 2002 gsxr 750 but the most common spring for guys roadracing them is 425 so i imagine stock is pretty close to that. Spring rates vary dramatically on these things due to the different linkage ratio's that are used. For example the 99-2002 sv650's often use a 650 lb spring, while the 2003 version of the same bike uses a spring that is 150lbs lighter and as I mentioned the 2002 gsxr 750 uses one that is 225lbs lighter. Did you keep the stock geometry in the rear suspension linkage? One last thing. do you have a front suspension on your bike yet? the reason i ask is that I heard you mention that you just bought 954 yokes. You can not check swing arm droop untill you have a front suspension on the bike and it is set at an approximate height. this is becasue lowering the front reduces swing arm drop and raising the front does the opposite. Even going to a taller profile rear tire reduces swing arm angle. The 12.5 is just a base line setting. It is not carvbed in stone, but I wouldn't spend a lot of efort acheiving it, untill you have an approximate front ride height figured out. Steve

Steve, Here's a link to the last few pages of my project. I don't want to hijack Katman's thread. Yes, the front suspension is on, but as you say, the geometry will change with the 954 troples. I tried to keep the geometry the same on the swingarm also. That was trickey - the frame was modified quite a bit for that.

http://www.thegsresources.com/_forum/viewtopic.php?t=4486&start=60

 

[Guest]

No worries you guys this is great info. MIght be an idea to start a suspention tuning tread for ease of searching later though. I don't mind at all it being discussed here either.

Could one of you guys post the formula for the droop? eg: D=P(pivot)-A(axle)/S(pivot to axle length) and so on?

That way us gear heads could just plug in our numbers and get the answers we need......

 

[Anonymous]

thread hijacking

thread hijacking

Hi Katman. I am new to computers, this one belongs to my stepson, but anyway I am not up on forum etiquit so if I did anything improper I wil apologize in advance. I am going to look at Sammy's project but I will be back. If either of you guys want to start a suspension tuning thread, i'll be happy to contribute. Steve

 

[Anonymous]

No worries you guys this is great info. MIght be an idea to start a suspention tuning tread for ease of searching later though. I don't mind at all it being discussed here either.

Could one of you guys post the formula for the droop? eg: D=P(pivot)-A(axle)/S(pivot to axle length) and so on?

That way us gear heads could just plug in our numbers and get the answers we need......

Ok,

cosine = Drop(pivot - axle)/Length(pivot to axle)

Once you have the cosine use a calculator or table to find the associated angle.

 

[Guest]

oh my....

I sorted out the issues today.....

put on a rejetted set of 33 smoothies for a comparison to see if it was carbs or ignition.....welll this thing lit up like a rocket. stood straight up in 1st and 2nd and ripped to redline. My baby has woken up.

my flatslides were way to jetted. took off the 135's and put on 125's and it was 60% better. going for 120mains tomorrow and I think that will do it.

the 33's has 125 mains and I couldn't keep the front end down or the tire from spinning.

My bandit arm is ready tomorrow so will post pics of it in a couple of days when I install it.

 

[Hoomgar]

Just leave the smoothies on it man

Sounds like it is rockin!

 

[Guest]

Good to hear that you got your problems sorted.

Just waiting to hear about the bandit arm.

 

[Anonymous]

smoothbores

smoothbores

Sounds like the smoothbores are working great! Im not sure that the flatslides make anymore power but they may hit a little harder when you first turn the grip. Flatslides are also more prone to vacume sticking. i don't think you can go wrong with either set. Sounds like the front tires are going to last a long time!

 

[Guest]

IS ANYBODY DIGGIN THIS?????

2002 bandit 1200 swingarm is on with a 93 gixxer armless caliper......