Cutting the swingarm?!?

Okay, I need some input as to why I can't cut the swingarm on my SECA for a larger tire/rim install? I have seen several shaft drive bikes over the years that have had the driveshaft cover removed or cut to accomodate a larger tire. Such as the Moto Guzzi 1000 from the early/mid '80s that had the cover removed and universal joints added to both ends of it to reduce/eliminate drive line lash in the twisties. What is the problem that lie ahead if I were to remove a chunk juts big enough to slide a larger rear tire in the swingarm? Is the whole drive shaft filled with 80W hypoid oil or is it just the pumpkin? My old Seca Turbo my dad put together in 1984 was sold to a guy in S.Carolina. He either removed or greatly modified the swingarm for a larger rear tire. I want to say it was a skeleton of a swingarm now that I think about it. Anyway, I need to know the answer to the question "WHY CAN'T IT BE DONE?!?"

 

I've heard of putting a dent in it but it wouldn't be too smart to cut a chunk out. Dirt and water would get in and shorten the life of the U joint and other parts. It would also be weakened so you would have to reinforce it in other ways. Besides, it doesn't need a larger tire.

 

Hello CPO:
SM3 Massey, here.

It's not filled.
There's Plenty of room ... provided the CURVED surface of the Swingarm you remove is reinforced with Billet and welded-up by some Ship-Fitter with the skills needed to patch the Hull of a Nukie-Boat.

The whole of the "Half Round" area where the wider tire would fit is hallow.
There is ... by my estimation ... more than an inch and three quarters of space surrounding the drive shaft.

You just have to be sure that the integrity of the suspension part is not compromised.

What you remove has to be replaced by Aluminum Billet and the weld made to insure that the replacement portion is stronger than what you removed to gain the space for the wider tire.

I've had the same idea simmering for awhile and actually made Magic Marker lines on the spare Swing Arm for what I need cut out and replaced.

The welding-up of it caused me to scrub the project along with other distractions ... but I'd like to see it done!

 

Well as far as the larger tire, it will need one once I put the Turbo 900 together. I realize cutting the shaft will intro dirt and water into the shaft cover and possibly shorten universal life. The universal is relatively easy and inexpensive repair. I also looked at reinforcing the area around the cut out section just to make sure it will hold up under the greater torque and hp the Turbo 900 will make. I feel the trade off of cutting out enough to fit a 150-160 series tire in the swingarm will be of great benefit putting the power to the pavement when the time comes. Any takers on this? Anyone ever even attempted this other than the guy that bought my 1st Turbo back In S. Carolina?

 

check out the picture of this guys bike... he modified it a bit.

http://www.xjbikes.com/Forums/viewtopic ... art=0.html

 

Okay, here is what is going to happen. I am going to cut the swingarm housing for the driveshaft. I am going to weld a piece of T-bar on top bottom and side to strengthen the area cut out or a c shaped section in the same area. I am going to fit the BIGGEST TIRE I can fit in to the new swingarm, because I know I WILL need it!!!!

 

whats the biggest tire you can fit without modifying? i too was looking into chopping the swinger, my friend wants me to put a 300 on the back but i think that would take too much effort!

 

You wouldnt be able to put a 300 on the back. stock is what a 110 and there is like 1/2 or 3/4 of an inch to the shaft. with the shaft casing out there is another 1 1/2 inch of room. So you really cant go to much bigger.

 

Just remember that there is a point where wider is not always better. There is a point where the wider contact patch will make it feel as though you are steering a barge. I had a buddy with a 90's sportbike and he went up in size and after a year went back to stock. With a 900 Turbo, you will need some meat under it though, so I can see the whole purpose of the operation.

 

Are you fitting a wider rear rim at the same time? is there a wider rim that fits on those? if not you're probaby wasting your time

 

I think the xj 900 wheel fits (?) but I am not 100% sure.

 

Oh yeah, my bad guys. I am swapping a wider Seca 900 rear rim onto the Turbo bike. The turbo came w/ super skinny 2.15 inch rims and the 900 came with 2.75 inchers. That is MORE than a half in wider. I know that it is not alot, but hey every little bit helps. BTW what is the major difference between a shaft rim and sprocket rim? Besides the obvious, I have taken apart a Radian rim and it looks very similar in design under the sprocket as it does under the drive adapter of a shaft wheel. Anyone have any feedback on this one? If they are relatively similar in design then a driveshaft adapter mated to sprocket rim would open a whole new avenue for a custom setup.

 

The Seca-900 has Rear Wheel Dampening wedges that will throw-off the spacing between the the Axle Mounting points.

You are likely to have a spacing issue using the 900 wheel.

I had my 900's Rear Wheel off to clean and lube the dampers. Thare are two spacers to deal with on the axle.

Plus: the 900's Rear Wheel comes with Disc Brakes. And the Brake Rotor for the Rear is specific to 900 as well -- I think? It's not a Flat Rotor ... its dished.
So you are going to have to find a 900 Ass-end to pull this off, I bet ... Chief ...

Hey, but what do I know. I only got a Crow with one chevron. You got more s**t on your sleeve and way more salt.

But if you decide you can't make that wheel fit without a whole 900 Rear End ... I'll sell you a whole 900 set-up and make you the happiest guy who ever ruled a Division in Uncle Sammy's Private Canoe Club.

If you are Golden Shellback ... you get 15% off.

 

Thanks for the input Shipmate! I already have a complete low mileage SECA 900 to do the swap. The rear end will go onto my Turbo. The rear is going to have some mods done first though. The driveshaft sleeve will be cut and re inforced and the shock mounts will be moved forward to raise the rear end up a little bit to accomodate the custom exhaust. I plan on an underseat exhaust from a Honda CBR 1000. Found one on Craigslist for a steal. I have gotten so many great ideas from this sight. Thanks!

 

You must have an Engineering Rate, Chief.
Cause you are getting-down and dirty with radical Mods.
You must have a little A-Gang going-on there.

Spent a little time in the engineer rates before handing-in my bilge-diving gear for sunglasses and sunblock.

When I sewed-on my Crow for Signalman Third ... I was so pressed and cleaned and spit and polished the guys in A-Gang used to heckle at me when I marched past them carrying the National Emblem for morning Colors.

 

Thanks for the input Shipmate! I already have a complete low mileage SECA 900 to do the swap. The rear end will go onto my Turbo. The rear is going to have some mods done first though. The driveshaft sleeve will be cut and re inforced and the shock mounts will be moved forward to raise the rear end up a little bit to accomodate the custom exhaust. I plan on an underseat exhaust from a Honda CBR 1000. Found one on Craigslist for a steal. I have gotten so many great ideas from this sight. Thanks!

 

No, NAVAIR! Structural Mechanic Primary NEC, Full Systems QA on two aircraft platforms, Ground Turn operator on P3 and S3, car junkie and just got back into the bike thing.

 

Outstanding.
And seven kids on top of all that?
You are quite a guy Chief. I wish you were close enough so that I could visit and hold the rag you wipe your forehead off with.

You got my admiration for all of that.
Way to go ... CPO!