GS550 Front Fork swap

[Guest]

Hi new here I bought a GS550 1979 model and the front fork stanchions look like they had been in a vice at some time in there life and the lower fork legs looked like they had no idea how to remove the seals .
So i bought a set of GS750 the only difference I can see is the one lower leg does not have the C clamp for the wheel spindle . So is it a straight swap or do I need to do something or change something to make them fit ?

Stu.

[Baggyarse]

Can anyone help ?

I would have thought somebody could have answered my question but obviously nobody has ever done this swap before so I must be the first one to do it.

Stu.

[tkent02]

No, I've done a lot with 550 forks. Can't understand your question. C clamps?

What year 750 forks did you get? Are they leading axle forks?

The 750 fork tubes are longer too.

[gsrick]

If your talking about leading axle forks, there is only one side that clamps down on the axle. You will need to change the triple trees with those forks or your steering geometry will be messed up. There is a difference and as Tom mentioned the fork tubes of the 750 should be a larger diameter, meaning your going to be jamming the tubes into the trees. Get forks from the same bike or do a complete front end swap, trees and all. Your axle length and spacers will be different, that and your speedo cable might not be long enough to wrap under the axle to connect to the speedo drive. That happened with a swap on my 1000G, the L model uses a longer cable and it also used different brake caliper mounts. Check you measurements carefully before swapping.

[Baggyarse]

Ok I bought a set of 1979 GS750 forks they are 35mm and fitted my yokes no prblem the only issue I have is the spindle fits ok along with the speedo drive BUT! the castellated nut does not tighten up fully to get a split pin into the hole , its about half a hole out , I am using the GS550 spacers but I would have assumed they were the same ,but apart from that so far it seems ok.Brake calipers line up ok.

[steveb922]

Do you have a washer behind the castle nut?

[tkent02]

Something isn't right. The '79 750 forks have the axle cap on both sides just like the 550.

You are using the 550 triple camps, 550 axle and all of the spacers? I don't have a 750 here at the moment to check but I thought all of that stuff was the same, other than the length of the fork tubes.


Can you give us a picture of what you have?

[gsrick]

My bad on the tube diameter, Tom was referring to tube length.

I'm talking about the difference in the placement of the forks in relation to the steering head. If you look down on the triples of a leading axle and the triples of forks with axles that end at the bottom of the forks, you'll see that the clamps are in a different configuration. Just off the top of my head I think the L triples are nearly in line with the steering head, were the other standard forks are arranged in more of a V pattern. This offsets where the axle lands in relationship to the rear axle. Mixing fork types with different triples will change the placement of where the axle travels. Either lengthening or shortening your wheelbase and effecting your steering geometry, which may destroy the handling the engineers built into their design.

As far as the axle goes if you are using the 550 triple trees your going to need an axle for a 550 or rethread the axle, as the 750 is probably longer since the forks are spaced wider. Same thing happens if you use an axle from a 1000 on a 750. It is physically longer since everything is spaced wider.

[tkent02]

My bad on the tube diameter, Tom was referring to tube length.

I'm talking about the difference in the placement of the forks in relation to the steering head. If you look down on the triples of a leading axle and the triples of forks with axles that end at the bottom of the forks, you'll see that the clamps are in a different configuration. Just off the top of my head I think the L triples are nearly in line with the steering head, were the other standard forks are arranged in more of a V pattern. This offsets where the axle lands in relationship to the rear axle. Mixing fork types with different triples will change the placement of where the axle travels. Either lengthening or shortening your wheelbase and effecting your steering geometry, which may destroy the handling the engineers built into their design.

As far as the axle goes if you are using the 550 triple trees your going to need an axle for a 550 or rethread the axle, as the 750 is longer since the forks are spaced wider. Same thing happens if you use an axle from a 1000 on a 750. It is physically longer since everything is wider.

But if the forks are from a '79 750, they are not leading axle forks. Might be spaced a little bit wider, they probably are.

Still we could use some pictures.

[Baggyarse]

Ok here is the bike with them in .I added some picture in my profile so just click on my name and view there ,these forks have an air valve in the top of the forks .
I bought the complete front forks and yokes, they are 35mm (checked with Vernier gauge).

[Baggyarse]

Sorted now many thanks .


Stu

[tkent02]

Those look like 650G forks, they fit the 550 with no changes. Same length and everything.

[Baggyarse]

They are the same length and now I have seen a set they do look like GS650 type ones thanks for looking and your time .

Stu

[tkent02]

With 750 forks everything fits, tube length, tube spacing, axle, fender, all of it bolts on but you get two front brakes.
This is the most common way to improve the brakes on a 550.

What didn't fit?