Forks swap info please?

[Classychick9]

Sorry in advance if this is in the wrong place it’s my first time posting, I have a gs 850 1979 trike and the forks are no good so I’m trying to source some others. My issue is I have no idea which I can use so my question is does anyone have the info on which others I could use please? Thanks in advance

[Grimly]

Sorry in advance if this is in the wrong place it’s my first time posting, I have a gs 850 1979 trike and the forks are no good so I’m trying to source some others. My issue is I have no idea which I can use so my question is does anyone have the info on which others I could use please? Thanks in advance

The GS850 used 37mm forks and so did nearly all the larger GSs from that era. The GS1000, GS1100 had 37mm, except the GS1100GK which had 44mm.
Beware, there are differences in layout - the L models and some of the 1100s used a leading axle design, which necessitates using their matching yokes to compensate for the offset. If you don't use the yokes, you'll bang your tank on full lock.
Then there's the annoyance of some models only had one disc instead of two, and the legs are not the same.

The Yamaha XJ900F also used 37mm forks and is a generation improved from the old GS mechanicals.

[Classychick9]

Thanks for the fast reply and the info I’ve really been struggling.

[Grimly]

Regarding the L yokes - I got that arse for elbow.
If you use the L forks, you have to use the yokes, but you'll bang your tank, so you have to use the L tank, as it's set slightly further back.
Pain in the arris altogether, but not insurmountable.
I fitted a pair of GS1000 forks to mine, but they turned out to be 19mm shorter, which is ok, as the slightly reduced trail compensated for the weight of the fairing and the steering quickened a little bit. This was accompanied by fitting v.slightly shorter rear shocks, so the ride height overall is about an inch lower than stock. The result is a nice-handling bike that belies the weight of it.