Tank/Steering Stem Swap

[DevilsAdvoduck]

So the saying is that you learn through either trauma or repetition. It's been the former lately.

Here's the issue I'm trying to solve: My 81 GS1000GL came with a mismatched tank that came off a different year L and has twin mounting tabs on the rear that take a bolt running vertically instead of the single horizontal bolt mounting tab that my frame wants. I picked up an 81 GS1000G tank with the single horizontal tab, and I knew I would have to mod the front mounting point on the frame to match the further-forward grooves on the under side of the tank. What I didn't realize (but now know thanks to some great posts I came across on here) was that the GL has a triple tree that tips the forks forward a bit more to give the bike a more chopper-like appearance. The secondary effect though is that the forks will now bang into the new tank that I have once mounted.

Question: Would a GS1000G triple tree and steering stem fit onto the GL frame, and if so, would that then resolve the tank clearance issue? I came across a salvaged set off a G, but was hoping someone might have some experience with this before I make (yet another) uninformed purchase.

While I'm here, big thanks to the community on here. I've learned a lot scrolling through the forum!

[salty_monk]

I have a set of an 83 1100E that I would sell..... Not sure if that helps. As I remember it the GL frame is different from the G frame but a G tank or a 550 tank can be made to fit with enough work. Someone on here did it. Maybe Pianoman Dan from the Northwest?..

Edit ahh here you go: http://www.thegsresources.com/_forum...highlight=tank

This also might help : https://www.thegsresources.com/_foru...0+tank+on+850l

The Triple trees are definitely different, the trail is different between the two and they use the leading axle fork to compensate.

[DevilsAdvoduck]

Found out that a buddy of mine has the front end off a 1978 GS1000 that He might not need. Also sourced a 1980 1000G steering stem and triple tree for a couple bucks. With the differences in triple tree angles between the L and the G, I am worried that the L forks, with the axle leading the tube, will change handling too much if fit them to the G steering stem/triple tree. I'm going to take some measurements and bolt it up to see what the net effect is on the geometry. My notepad math makes me think that this will work out to give me my tank clearance without screwing up the geometry, but fitting it up will tell for certain one way or another. For $15, I won't be too upset if the whole thing doesn't work.

At the end of the day, I'm really just another guy who bought an L when he didn't want one. Now I just have to jump through my fourth point of contact to get the result I want. Live and learn.

[salty_monk]

It's been done before. There are some threads that go into a lot of detail about the changes in rake / trail but essentially the consensus seems to be that the bikes run stable no matter what combination you use... not much difference.

Use some Sonic or Progressive springs & 10W oil when you service them. If you really want to "pimp" them put some Racetech emulators in them. (You then adjust rebound with oil weight & compression damping is adjusted to suit using the emulators adjustments).

With those axle under 1978 forks you should run the twinpot brakes & CBR rotors....

[DevilsAdvoduck]

The Racetech emulators are on the long-term list for sure. Since that's a fairly easy swap (and since I have plenty of other things depleting the budget at the moment), they'll be on that list for a while...

The twinpot swap is back on the table!!! Once I make some headway on the build list, I'll definitely be in touch about that. Thanks!

[salty_monk]

Point to note... You have to completely take the forks apart to fit the emulators as you have to drill holes in the damper rods. It's not hard by any means but it's not simply "pull the caps off & drop them in" easy... you'll basically be doing a full fork service.

I suspect your new forks coming will need new oil & seals... with the 1000 forks you can blow the seals out (using the air spring valves) without taking the fork apart & re-install using black ABS sewer pipe as a drift. There is a thread around here somewhere. That makes it a much quicker job. If the seal hasn't moved in a while you'll need about 100 PSI to do it (I've done it with a bicycle track pump before). Make sure you put a rag over the top... oil can go everywhere when they "pop".

[DevilsAdvoduck]

Good to know I figured it’d be a bit of work to get the emulators, but not that much. Still, seems work the effort!

And I’m all over the seals/gaskets. They should be here on Tuesday. With the shape of the bike when I got it, every scrap of rubber that I come across is getting replaced. Bit by bit, she’ll get there eventually. I tried getting the seals out of my current forks using the compressor, but even above 100 psi, they weren’t budging. Used the threaded rod and nuts home made tool to pull the lowers off and couldn’t even pry the seals out manually. Used some heat but no luck with that. Ended up having to chip them away bit by bit. Suckers must have been originally and just didn’t want to say goodbye.

[Steve]

With the differences in triple tree angles between the L and the G, I am worried that the L forks, with the axle leading the tube, will change handling too much if fit them to the G steering stem/triple tree.

There is no difference in the steering stem angle in the frame.

The only difference is in the triple trees. The G (and E) triples have more of an angle, keeping the fork tubes farther forward. The G triples have less of an angle, which pulls the fork tubes back. The front wheel remains in the same place, only the fork tubes got moved.

That difference was made to allow the fork tubes to be moved behind the axle. By doing that, they could extend them a couple inches, enhancing the "chopper" look that was strangely poplular at the time. Steering angle, rake and trail all remained the same, along with wheelbase, so handling is the same. As long as you replace EVERYTHING from the steering stem forward, you will be fine. By the way, 'everything' includes brake calipers, fender and speedo drive.

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[DevilsAdvoduck]

There is no difference in the steering stem angle in the frame.

The only difference is in the triple trees. The G (and E) triples have more of an angle, keeping the fork tubes farther forward. The G triples have less of an angle, which pulls the fork tubes back. The front wheel remains in the same place, only the fork tubes got moved.

That difference was made to allow the fork tubes to be moved behind the axle. By doing that, they could extend them a couple inches, enhancing the "chopper" look that was strangely poplular at the time. Steering angle, rake and trail all remained the same, along with wheelbase, so handling is the same. As long as you replace EVERYTHING from the steering stem forward, you will be fine. By the way, 'everything' includes brake calipers, fender and speedo drive.

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I was probably clear as mud with my description (it's a known deficiency). I knew the angle was the same on the stem, just wasn't sure if there was any variation in the length due to possibly a different bearing set or some other detail that I wasn't thinking of.

Forks on down are getting replaced thanks to a buddy's donor bike. The leading axle, even if it weren't a slight geometry shift with the new triples, aren't really my cup of tea (feel free to insert a joke about being the guy who bought an L who didn't want one, I deserve it). The good news is that I'm opening up the opportunity to eventually do a twinpot upgrade with a set of Salty_Monk's brackets.

Thanks for the input!

[Steve]

Just to toss a little bit of light in a different direction, the '80/'81 750E and 1100E also had leading-axle forks.

I'm not sure exactly why, but that's the way they were set up.

As mentioned previously, the front wheel on the 1000GL is in exactly the same place, relative to the rest of the bike, as on the 1000G. The stylists who designed the bike wanted to give the L the look of extended forks. The only way they saw to do that without messing up its decent handling was to move the forks behind the axle by straightening the angle in the triples. This allowed the fork tubes to go below the axle, sort of giving it the look of a chopper. A creative solution, but it required other compromises, like the smaller tank, but they gave that a peanut shape to further enhance the illusion of a chopper. Then there were the higher (VERY uncomfortable) handlebars and the stepped seat and chrome fenders to complete the look.

Good luck with your project.

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[DevilsAdvoduck]

Just to toss a little bit of light in a different direction, the '80/'81 750E and 1100E also had leading-axle forks.

I'm not sure exactly why, but that's the way they were set up.

As mentioned previously, the front wheel on the 1000GL is in exactly the same place, relative to the rest of the bike, as on the 1000G. The stylists who designed the bike wanted to give the L the look of extended forks. The only way they saw to do that without messing up its decent handling was to move the forks behind the axle by straightening the angle in the triples. This allowed the fork tubes to go below the axle, sort of giving it the look of a chopper. A creative solution, but it required other compromises, like the smaller tank, but they gave that a peanut shape to further enhance the illusion of a chopper. Then there were the higher (VERY uncomfortable) handlebars and the stepped seat and chrome fenders to complete the look.

Good luck with your project.

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Its definitely an interesting design solution to change the look of the L model. I appreciate the creativity even as I’m actively working to undo all of it!