Define "Jack Up Kit"

[Sven]

Whenever I browse ebay or Bandit accessory mechandise (or for other bikes as well), I see jack up kits, dog bones, etc.  I kinda have the idea that they raise bike up off the rear shocks, and that somehow improves handling but that's about all I can glean from the sites/auctions I've looked at.

I'm not really in the market, but I would like to understand why/how they work, and where/how they are installed.  Why does hiking the back end help?  Seems like that would be helpful only in going over speed bumps!

Someone wanna give me the light once-over?

[Sven]

PS:  The dog bones look like they are the tie-rods, so maybe they are just longer tie-rods?  If so, I understand where they go, but not how they are better.

[2005B12S]

It is any kit that raises rear ride height , usually 35mm, by altering the rear linkage. By raising the rear you can quicken the steering due to the reduction in trail. Personally, I don't see the need to raise the rear, it just makes the bike look goofy with the a$$ end hanging up in the air.

A slight drop in the triples, 10mm is ideal, will also quicken the steering without raising the rear. So will going with a slightly shorter profile front tire, a 120/65 for example.

Raising the rear to gain ground clearance on the B12 should not be an issue on the street, if you are dragging suspension/chasis parts on street tires you should probably be riding a GSXR 750 instead.

Ride On, Ed.

[Sven]

By raising the rear you can quicken the steering due to the reduction in trail.

OK, that's the essential piece of information that I was trying to get.

Not that I'm doing anything anyway, but a lot of people apparently are.

[stormi]

OK, that's the essential piece of information that I was trying to get.

Not that I'm doing anything anyway, but a lot of people apparently are.

Some people also use a longer dogbone to lower a bike so it's closer to the ground.  Good for us height challenged people.  A shorter dogbone will of course do the opposite.   Of course, as mentioned before, it does change the geometry of the bike, which should be compensated for with the forks if it's a significant change.

[smooth operator]

I just had my brother-in -law cut me out a new set of bones for my bike out of stainless. Has a welding/fab shop with a cnc machine.)The stock ride hight is fine on the road ways,but the Bandit is limited for ground clearance on the track.(and maybe I should get a GSX-R) I still have to drill the holes,I'm going to try 3.5mm shorter and measure befor and after . It should be between 1 -1 1/2 " rise.

[Sven]

Some people also use a longer dogbone to lower a bike so it's closer to the ground...A shorter dogbone will of course do the opposite.

This seems backward.  The tierod/dogbone is a vertical piece, so longer would push the tail up, right?

[stormi]

Some people also use a longer dogbone to lower a bike so it's closer to the ground...A shorter dogbone will of course do the opposite.

This seems backward.  The tierod/dogbone is a vertical piece, so longer would push the tail up, right?

Nope.    The shock is vertical.  The dogbone is linkage under the shock (usually bolted to the bottom mount of the shock), and is a pivot piece.  By lengthening the dogbone, the angle of the swingarm is changed, it's pushed lower.  Effectively lowering the tail end.  

I'll run out to the shed and grab you a picture of the way all of this works together.  As "luck" would have it, we have a dirtbike torn down in the shed right now, so this stuff is all easily exposed.

Dita also has the ability to take a dog bone.  If I can wiggle in between the two bikes. I'll see if I can get you a "bandit" shot too.  The 919 on the other hand, is not built to take a dogbone.

[Sven]

The shock is vertical.  The dogbone is linkage under the shock (usually bolted to the bottom mount of the shock), and is a pivot piece.  By lengthening the dogbone, the angle of the swingarm is changed, it's pushed lower.  Effectively lowering the tail end.

ON my B12, what I'm assuming is the "dogbone" is called the "cushion lever rod" in the service manual.  So, first, am I looking at the right part?

The shock absorber is vertical, and the two cushion rods are too; the shock and the rods are sort of an 45 degree angles from each other.

A shorter rod would seem to draw the bottom of the shock down closer to the ground and thus lower the back of the bike, while a longer rod would do the opposite, unless I am not following what's connected to what correctly.

I'd like to see the pix...one day this info will be helpful to SOMEBODY!

[stormi]

ON my B12, what I'm assuming is the "dogbone" is called the "cushion lever rod" in the service manual.  So, first, am I looking at the right part?

The shock absorber is vertical, and the two cushion rods are too; the shock and the rods are sort of an 45 degree angles from each other.

A shorter rod would seem to draw the bottom of the shock down closer to the ground and thus lower the back of the bike, while a longer rod would do the opposite, unless I am not following what's connected to what correctly.

I'd like to see the pix...one day this info will be helpful to SOMEBODY!

Ok,.. this is tough.  It's easier in person, because you can make the funny motions that show what things do.    But let's see if I can describe this.  

You have 3 main pieces here that are responsible for changing the height of the rear on a linkage style of suspension.  (there are linkage-less bikes that can't do this.)

1.  The shock.  Of course you can set the pre-load and stiffness of the shock and that will change the height of the bike.  Now,.. one important piece of information here, is that the shock never moves, no matter which dogbone you put on it, it does not lengthen or shorten.

2.  Dogbones.  These are what I'm talking about geting shorter and longer ones.  The dogbones are #13 in the part fiche that I'm posting.  You have one on either side on this bike.  Some bikes have one in the centre, some have the set up you have.

3.  The rear cushion lever.  The dogbones work in conjunction with the rear cushion lever set.   In the fiche of your bike, that I'm posting, the cushion lever is #1( the weird sort of cross shaped piece.)            



The other half decided to get in on the fun, and mark up my pics for you.  

On the CR250R that you're seeing, the rear cushion lever is sort of backwards to the one that you have on your bandit.  But the theory is the same.

His bike (because my KTM dirtbike doesn't have linkage) shows the shock attached to the linkage ( same as your rear cushion lever ) and the left side dogbone ( his is a 2 dogbone setup like yours) attaches to both the frame and the rear cushion lever.  What you can't see well in this picture, is the 3rd bolt hole on the linkage.  It attaches to the swing arm.

Now,.. when you put a shorter dogbone (or set) onto the bike, the cushion lever is going to pivot (at the shock mount ), because the the shorter dogbone is forcing the the cushion lever to pivot toward the front of the bike.  This pulls the -front- of the swingarm toward the ground, which pushes the butt of the bike upward. (Again, it's a pivot action.)  

Think of the swingarm as a solid board.  Whatever you do to one end, the other end will do the opposite.



A longer dogbone will pivot the cushion lever toward the back, pushing it upward, drawing the backend downward.

[smooth operator]

Nice job Stormie, except, I think lowering the bike with the longer bones (I think) does shorten the stroke of the shock.Because I had a set made 4mm longer than stock for my gsx-r shock and I had too much sag.Put the stock bones on and I was able to dial in my sag w/ preload.BUT.. the gsx-r shock that was designed to fit another bike may have had more room to begin with. So maybe it doesn't change the throw of the shock. I'll take measurments using the Works Performance shock when I shorten the bones to get more hieght. I may only go 3mm shorter,I want to keep as much trail as I can to get the ground clearance I need.    Dan

[Sven]

OK, I *mostly* follow that.  It's hard because everything is indirectly connected so imagining what will move which direction is better with the pictures than with the exploded view (which is what I have in the service manual).

We both need to find something better to do on a Sunday, though!  We're back to 99 here today, so a ride to lunch was about all I could take.  Nice night ride for a couple hours last night though.  Got home around 11:30.

Anyway, thanks for the explanation.  At least I know understand the point of the adjustment and how it works.

[stormi]

Nice job Stormie, except, I think lowering the bike with the longer bones (I think) does shorten the stroke of the shock.Because I had a set made 4mm longer than stock for my gsx-r shock and I had too much sag.Put the stock bones on and I was able to dial in my sag w/ preload.BUT.. the gsx-r shock that was designed to fit another bike may have had more room to begin with. So maybe it doesn't change the throw of the shock. I'll take measurments using the Works Performance shock when I shorten the bones to get more hieght. I may only go 3mm shorter,I want to keep as much trail as I can to get the ground clearance I need.    Dan

I mentioned what you said to the other half, and he said that the shock doesn't get compressed or stretched out, but that the change did aftect the sag and preload.  I can't recall the specifics, but I'm sure he'll post if no one else can answer this better than I did.  

[stormi]

OK, I *mostly* follow that.  It's hard because everything is indirectly connected so imagining what will move which direction is better with the pictures than with the exploded view (which is what I have in the service manual).

We both need to find something better to do on a Sunday, though!  We're back to 99 here today, so a ride to lunch was about all I could take.  Nice night ride for a couple hours last night though.  Got home around 11:30.

Anyway, thanks for the explanation.  At least I know understand the point of the adjustment and how it works.

It would have been a much better explanation if you could see all the funny gestures I was making to illustrate it, while typing it.  

Pfft,.. I was doing tons in between messages.  I managed to install the windscreen on the 919, wall mount my enlarger, put feet on my darkroom cupboards, and generally reek havoc and chaos in the darkroom.  It's a real mess right now.  

It was raining most of the day here, so there wasn't much point in trying to take the bike out.  Had it been sunny, you would have been on your own to figure out the dogbones.  

No problem.  I'm glad to be able to make use of the info.  I spent a lot of time trying to figure that stuff out when I was looking into the "lowering" options for the 919.  Of course, as I mentioned, it doesn't have linkage, so I couldn't go the way we just discussed.

[Sven]

..wall mount my enlarger, put feet on my darkroom cupboards, and generally reek havoc and chaos in the darkroom....It was raining most of the day here, so there wasn't much point in trying to take the bike out.  Had it been sunny, you would have been on your own to figure out the dogbones.

Are you a professional photog or just a very able hobbyist?

You are the second Canadian to complain about rain this weekend.  Not a very compelling complaint as the lower 48 are either on fire or simply drying up and blowing away.