frame extension

[Craiger]

I've got an '80 850G as well and was wanting to stretch it at one point and was told....well, basically the same information I regurgitated. I think I'll end up cafe'n it. It's a project I'll get to at some point in time....just not now.

[mighty13d]

why not make an extension that would bolt up between the driveshaft and the trans. So instead of having them bolt up to each other, you would have the extension in there instead? yes, if you did this, you would have to not lengthen the swingarm, but instead move the pivot point it's self backward. I would think that a cool 4-6 inches could be done this way pretty easily... Maybe I'll whip something up that I could use to show everyone what I mean.

[mighty13d]

or maybe even just ADD a whole additional set of bushings and everything the 6 inches back so it's less cutting and just more welding. then it would even be possible to go back to stock at some point too... oh the ideas.

[tone]

Ive cooled down now guys so heres what ive done & some of the problems ive faced....

You could make a spacer plate for between the uj & the output shaft & thats fine for a couple of inch stretch but the extra weight does put some more strain on the uj itself & you would need to extend the area the uj fits into on the arm

my way of extending the shaft is to cut it nearer the back & use an extension to join it back together, imo its stronger this way

The extension piece is made as an interfearance fit to the shaft & the shaft is pressed into it by 2" either end with the required stretch being the length in the middle of the two sockets, the wall should be thick enough to take a decent weld 4mm seems to work ok

once its together i weld it all up then drill & pin it both ends & weld the pins (probably a bit overboard but it works) the welds are dressed then its spun on the lathe to check alignment, the centre of the extension can be waisted down to an hour glass shape to keep weight down at this point but keep well away from the 2" sockets either end

if you are looking at something like a 6" stretch on a sprung bike you are getting close to the point where the uj will lock up so please check how far you can go BEFORE chopping anything up, i mock everything up by moving the arm back on blocks & checking the shaft run before making the first cut, remember to take suspension movement into account

thats enough for one night guys i'll post about the swingarm itself tomorrow if anyones still interested

[drhach]

I had to chime in om this. Shaft drive swing arms are commonly extended. They are just not commonly extended on Suzuki GS's because, well, I don't know. However, the BMW crowd does this quite often to their BMW dirt bikes. If you want pix, go to the links. HPN is the main company doing this and they do very nice looking work. It's not trivial to do it but it is not impossible either.

http://www.ukgser.com/forums/showthread.php?p=1371833

http://www.hpn.de/english/english.html

I'd be willing to bet that there is a company here in the U.S that you could send it to to get it done. The only question is how much money do you want to spend?

[PAULYBOY]

Sorry, Tone, I didn't even stop to think that a metal lathe would do the trick for the shaft part. Taht sounds awesome. Like others, I'd love to see pix cuz I own an850. Maybe we'll do a search on the WWW for pix of stretched shaft driven bikes of any brand. A shaft is a shaft after all.

[bigmacstang424]

Thanks Tone I appreciate the advice. I was thinking about around a 6 inch extension. A buddy of mine works in a machine shop and was gonna stretch the drive shaft. I was worried about the shaft not being straight after welding in the extension, so ill let him deal with it. I was planning on doing the swing arm myself, and might end up making a hardtail so I dont have to deal with suspension travel. I might even bring the shocks back with the swing arm. Gonna be a winter project of mine. If I screw it up I always have my doner frame in the shed.

[Craiger]

If you don't mind, can you document this for us? I'd love to see it.

[bigmacstang424]

Ill definetly take some pictures when I start cutting. Probably wont be till it starts snowing out.

[Roostabunny]

...so my arms are around shoulder length.

Don't know why you guys are debating about the shaft. The hard part's going to be changing the length of your arms.

[Agemax]

i dont own a shafty but i reckon extendng the swinging arm would be fairly simple if you had access to a machine shop, or a good mate who owns one!. extending the drive shaft is such a simple job as it is done all the time with trikes and even cars. a simple billet ally casing to space the shaft section and the final drive "hub" would be easy enough, then just extend the right hand side with a welded in extension to match the drive side.dont see any reason to alter the shocks as it defeats the object of extending the arm but if clearance is a problem then either move the shock mount on the arm, buy slightly longer shocks or make spacers to adjust the shock height

[tone]

Round two :-)

The reason for the sockets on the extension piece being a tight fit & so deep is to stop the shaft moving around during welding, i have them made tight enough that i usually need to heat the extension & cool the shafts to press them together, ive not had one move out of alignment .....yet

With a hardtail the shaft can be any length you desire as long as it runs parallel to the ground (12' gs 850 anyone ?)
on hardtails i usually run the shaft open & just use the back end of the arm where the diff mounts welded to the new framework

No machine shop or trick kit is needed to extend the arm itself just some carefull cutting, a tube bender & some decent welding :-) .....

For obvious reasons shaft drive arms are reasonably straight drive side, this makes it a simple matter to cut the thing in half weld in a joining slug to both halves then join them together with the correct dia tube, once linished back & coated most people wont see the joins

Another way is to cut the formed parts from both ends of the arm & replace the whole length of tube, the tricky part is keeping it all straight while you weld it up but a simple jig & some clamps holds it all fine as long as you are carefull

The other side can be a little more difficult as they often have a curve in them...
I there is a straight bit that wont either spread the arm (or narrow it) once the required stretch is put in then thats the place to cut & follow the steps perfected on the shaft side, alternitively you can remove the whole tube & make up another longer one to suit

hope it helps guys

[Craiger]

Round two :-)

The reason for the sockets on the extension piece being a tight fit & so deep is to stop the shaft moving around during welding, i have them made tight enough that i usually need to heat the extension & cool the shafts to press them together, ive not had one move out of alignment .....yet

With a hardtail the shaft can be any length you desire as long as it runs parallel to the ground (12' gs 850 anyone ?)
on hardtails i usually run the shaft open & just use the back end of the arm where the diff mounts welded to the new framework

No machine shop or trick kit is needed to extend the arm itself just some carefull cutting, a tube bender & some decent welding :-) .....

For obvious reasons shaft drive arms are reasonably straight drive side, this makes it a simple matter to cut the thing in half weld in a joining slug to both halves then join them together with the correct dia tube, once linished back & coated most people wont see the joins

Another way is to cut the formed parts from both ends of the arm & replace the whole length of tube, the tricky part is keeping it all straight while you weld it up but a simple jig & some clamps holds it all fine as long as you are carefull

The other side can be a little more difficult as they often have a curve in them...
I there is a straight bit that wont either spread the arm (or narrow it) once the required stretch is put in then thats the place to cut & follow the steps perfected on the shaft side, alternitively you can remove the whole tube & make up another longer one to suit

hope it helps guys

And you don't consider yourself a fabricator? LOL!

It does help. I don't have access to such tools, but understand exactly what you're explaining. Thanks.

Sounds more like extending a vehicle (read:Jeep) driveshaft more and more. That I'm familiar with....just have never done it myself.

[tone]

Lol @craiger
i'm just a back street bodger mate, but i will admit to being a determined one, theres nothing much thats clever about it tbh its just a case of siting down & working things out before you start, the biggest thing is carefull measuring BEFORE making the first cut

You're right its just like extending a car /jeep drive shaft or propshaft & i'm glad it makes sense to someone cos i find it more difficult to write than to do

on a slightly different note ive just shortened a gsx750 (chain drive) arm by 55mm .....now thats dead easy lol

[mighty13d]

I've shortened a driveshaft on a hotrod that has a 396 big block chevy with a cross-ram manifold and dual 500 4-barrel carbs on top.. it gets massive HP, but there is zero vibrations from it. and to think that all we did after cutting it was stick it together and spin it using a jack stand against it to see if it wobbled. with a couple tack welds and many more spins we got it so it doesn't wobble at all.

My point being that if you spend a little extra time doing something right instead of half-a$$ing something, it comes out well. So I would be that if someone spent a couple days figuring something out instead of a few min, this wouldn't be too hard. Heck, if my 80 gs850 wasn't a parts bike, I'd be tempted to do this myself just to see how difficult it would be.

I guess that my working at a naval shipyard as a structural fitter for a while probably helps me with metal work... Too bad I don't still work there.