Fork Spring Question : '77 gs750

[BigDaddyD]

I've recently rebuilt the front end of my '77 GS750 using forks off a '78 750 (I think) to run dual front disks and added progressive springs. In doing so, however, the new forks ended up being about 2 maybe 3 inches longer then the original single-disk forks. I'm assuming that the PO had used tubes or forks off of a different bike, or perhaps the '78 forks are just longer the the '77s.

In either case, I'm not thrilled about the extra ride height and would like to switch out the tubes from the old single-disk forks in order to lower my front end.

Here's the fun bit...

The original shorter forks have 2 different types of springs in them. One fork has a longer, what seems to be progressive wound looking spring, and the other tube had the regular, upper and lower spring combo. The combo spring is longer then the single spring and both springs are slightly shorter then the original springs that I took out of the '78 tubes when I put in the progressives.

I can only assume that the reason for the 2 different types of springs is because of the disk brake only being on the one fork. Either way...

My question is... Can I use the old combo-springs, or the new progressive springs from the longer '78 forks with the shorter tubes or am I going to have to find springs that'll work in the shorter tubes??

If that's the case... does anyone in the LA/Santa Monica/South Bay area have any springs that would work that they might want to sell or trade??

I understand that if I were to cram the longer springs into the shorter tubes it will more then likely stiffen the ride... but I tend to like the front suspension more on the tight side, plus I'm a heavier rider.

Also... all the internal parts on the forks are the same. So I know the upper tubes are interchangeable with the bottoms

Any ideas??

Thanks in advance!

D.

 

[BigDaddyD]

After reading a bunch of the write-ups here on the forum. I'm thinking I might just use the old longer '78 springs in the shorter tubes. Since new progressive springs will more then likely need spacers (from what I've read), and I like my suspension a little stiffer, compressing the longer springs into the shorter tube should compensate for any sagging that might occur, and would act the same as a spacer on a set of progressive springs.

Any thoughts?

 

[BigDaddyD]

Anyone?
Nothin?

 

[SqDancerLynn1]

As far as the length I would want the spring with or without spacer to stick up from the top about 3/4 to 1" when fully extended

 

[mike_of_bbg]

According to the fiche, the same split springs are called for on both fork legs of a 1977 GS750. I haven't looked at all of the GS parts fiches, but I can't really think of a situation where differing springs would be called for. Sounds like "creative engineering" to me, and probably a bad idea.

Ms. SqDancerLynn1 hit the nail on the head. If the longer progressive springs don't stick up more than about an inch in the shorter tubes, I'd use those with appropriate spacers to trim your ride.

 

[BigDaddyD]

awesome!

Yeah, I'm gonna tear into it today and if the progressives look like they'll fit I'll try them out.

 

[salty_monk]

Be surprised if they were that much longer... Sure you don't have a set off an 83 750 designed for a 16" wheel? From memory they are 32" from axle centre to top of the fork leg.

You could probably lose a little of the extra length by sling the legs up higher through the trees under the bars....

 

[BigDaddyD]

Yeah... they're a good few inches longer.
I tried pulling them as far through the trees as I could but they only had about 1/4" or so of room before they hit the bars.
Let me put it this way... when the bike was on the center stand the rear tire was almost touching the ground and the speedo-cable was stretching tight.

I ended up swapping out the longer bars for the shorter ones. Everything bolted right up, and the Progressive springs from the longer forks only stuck out of the tube about 1/2" or so so I think I'm good to go.

Rode down to San Diego last weekend and everything felt good. The shorter forks with the Progressive springs felt way more solid then when the springs were in the longer tubes.