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Chassis specs and setup : handling ?


Joseph

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Hello

I've got my Katana R tuner bike out cause I need to give the W a rest

Specs :

91 chassis 11R

K7 fork and wheels

Ohlins shock at 11R spec

89 11R swingarm

 

This is give or take, the same spec as my 7W : K7 forks and wheels and a nitron shock the correct length.

I know they are not the same bikes, but, the chassis are both however very similar in set up and dimensions, there are not major differences

However

sitting on the 7, my legs are flexed, feet flat on the ground

Sitting on the 11, my legs are totally straight if i put my feet flat

Riding the 11, it feels very very shaky when cornering, it really does not feel safe to turn in nicely, as if the rear end was much too high maybe ? Not that i have major knowledge of riding dynamics

Is the swingarm linkage at fault ? I need to measure seat heights, maybe all this is looking at the wrong points but something feels off

Edited by Joseph
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The use of the word "Katana" here is really confusing. Do you have a 91 GSXR1100 M frame, with 1000 K7 forks and a GSXR 1100 K swingarm? First, I would check the basics, especially from the symptoms described. Are the headraces correctly adjusted? Is there play in the swingarm pivot? Are the tyres at the correct pressure and are the wheels centred correctly and in line? Is everything tightened up as it should be? Is the frame straight? Check all the obvious first, then go from there.

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33 minutes ago, TonyGee said:

why is that bike called a katana ? 

Because :

A- the katana is just a dress up kit on a pre existing bike

B- more importantly, i built it so i can call it whatever i see fit

:banana:

xD

On a technical note, i put new bearings all over, and i think i did the stem setting properly

However now you have got me doubting about the wheel layout

Chain has been done, there wasn't even the seat on that picture 

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2 minutes ago, Joseph said:

Because :

A- the katana is just a dress up kit on a pre existing bike

B- more importantly, i built it so i can call it whatever i see fit

:banana:

xD

On a technical note, i put new bearings all over, and i think i did the stem setting properly

However now you have got me doubting about the wheel layout

Chain has been done, there wasn't even the seat on that picture 

fair enough 

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The angle of your swingarm looks greater than mine. I've got an 1100N, with gsxr750 k9 forks, 750L2 wheels and a Nitron race shock - I kept the std swingarm and linkage, so a few similar things. I've 12mm of static sag on the rear - the amount the shock compresses due to the bike's weight, if you have next to no static sag, ie the shock is near topped out all the time. Lift the rear of the bike at rest and there should be some movement until the shock is topped out. The shock has a 475lb spring on it now, the 500lb/inch spring only worked when I was really tramping on. The forks still have the std springs in them and have 30mm of sag, I think the 750k7 had .95kg springs in them, the 1100's were around .75kg, so plenty firm enough. My bike is 96lb lighter than it was and handles really well, feedback is great front and rear, they can handle really well. 

I expect it's just in the set-up :)

20200826_143828.thumb.jpg.fc9d0ee4b9a9d97adb6168c3c9b59c7b.jpg

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It does indeed when compared to others

I did have the shock rebuilt by the Ohlins affiliated specialist here.

Maybe something in its set up has modified something ?

But that said, is not swingarm angle down to static shock (spring) length coupled to the linkage length ?

Pff this is no good, its definitely not the type of technical challenge my brain is wired for :(xD

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"Static sag" is the amount the suspension compresses under the weight of the motorcycle itself.

"Dynamic/Rider sag is the amount the suspension compresses with the rider seated in the normal position.

I'll let others with similar "Katanas" give you figures based on experience rather than theory because real life conditions have an influence.

The key point is that you are looking for the suspension to be working in the mid area of its stroke in normal conditions, not starting at one extreme and moving towards the other.

Swingarm angle is normally between 5-10 degrees unladen and just below horizontal with the rider aboard.

Do not set your sag with the bike on a paddock stand ! It will affect your figures.  Looking at your picture I would check your preload and shock length because the "ride height" look very high.

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23 hours ago, Captain Chaos said:

translation of the last pic:

"if you don't understand, don't fuck with it" :D

That would wipe out a big percentage of modified bike builds in an instant. Most of the collective knowledge of mankind has been gained by "fucking about" with things we don't understand. It's called "learning" for those that do it.

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