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front end swap question

  • Thread starter Thread starter 650cafe
  • Start date Start date
6

650cafe

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So I visited my local MC salvage yard today and found a gem. An 81 GS1100GZ carcass. Not much left of the old horse, but what is there is a very usable front end. This caught my attention because it is set up for dual-discs. The triple clamps, fork uppers and lowers, and both front calipers are there, all for the paltry sum of "about $75" says the man at the counter inside.
So....this setup would be totally sweet-assed on my GS650GL caferacer project. Anyone know the word on how easily it'll swap out? I have a feeling it'd be an unbolt-the-old-bolt-on-the-new deal, but I could be wrong. I'm thinking I'd need the GZ front master cylinder too, or a larger bore one at any rate. Not sure either about the front wheel....if I'd need one for a dual-disc bike or if my 650's wheel has tapped holes hiding underneath the little hub cover. Any advice here is very welcome. Thanks in advance.
 
Bearings are the same. Should bolt right up. Most triple tree stems are the same length. If your 650 (you didn't state what year it is) has the choke cable running thru the triple tree stem and you want it to continue to, then you would want to get one that is like that. Later year models of both have solid core stems. Your 650 wheel will work just fine, there are holes under that cover. I have a 650 wheel on the front of my '79 850 with an '83 1100 gk fork assy.
 
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Cool! Thanks for the info guys! My 650 is an 83, and glad to hear my suspicions were correct about that hub cover. My choke is bar-mounted, but that'll probably change to be located down by the carbs anyway. All I'd need then is that front end and a rotor. I'd considered trying to squeeze those tubes into my triples, but to heck with that...may as well go with the whole front end since it's a bolt-up deal. How about the MC? Did the twin-caliper bikes have a larger bore cylinder? I know with Harleys thats the case. Thanks alot for the help guys.
 
You would want to use the 1100 tree even if they were the same dia. because the 650 tree puts the fork legs at a steeper angle to compensate for the front side locaition of the axle.
 
Well I wouldnt mind a tad steeper rake...it is gonna be a cafe racer after all. But I'm good with the stock rake too. Do you know anything about the master cylinders? Sounds like silverbullet has one if I need it, but if the stock 650 M/C will work I'll stick with it. Thanks so much for this info...it's a huge help.
 
I've always used the master cylinder that came from whatever caliper (or calipers) setup that came with it (or them) from the factory.
 
Is your 650 an "L"? If so, you already have leading axle forks. Rake is the angle of the steering head to the ground, and is not affected by the offset of the trees and forks. The distance between where a line drawn through the center of the steering head to the ground, and the center of the tire contact patch is called "trail". It is very much affected by the offset of the fork crown and axle. I would not recommend "mix and match" between leading axle forks and non leading axle fork crowns and vice versa.
 
850 Combat said:
Is your 650 an "L"? If so, you already have leading axle forks. Rake is the angle of the steering head to the ground, and is not affected by the offset of the trees and forks. The distance between where a line drawn through the center of the steering head to the ground, and the center of the tire contact patch is called "trail". It is very much affected by the offset of the fork crown and axle. I would not recommend "mix and match" between leading axle forks and non leading axle fork crowns and vice versa.
Click to expand...

No, and I don't think I will Combat. If I get that front end I'll use the triple clamps and all from the 1100, so assuming the 650GL frame has the same neck rake as the 1100GZ frame, it will be as if it's still on the 1100 frame.
I'd like some triple clamps with some forward offset, but that will alter the trail too.
 
kingofvenus said:
You would want to use the 1100 tree even if they were the same dia. because the 650 tree puts the fork legs at a steeper angle to compensate for the front side locaition of the axle.
Click to expand...


Somewhat false info here..

The E style (straight leg) and leading axle (L G style) trees have 0? rake angle relative to the neck and all the GS bikes run the same neck angle.

The only difference is the offset from the stem..

leading axle trees have about 1" less offset to make up for the axle position..

In the end where the rubber meets the road both styles have the same rake/trail..

What you don't want to do is mix trees and legs from different styles unless you fully understand how it will impact trail. (IE add or subtracting about 3/4" to your trail )


I did this swap on my 79 GS1000L with a set off an 80 GS1100G. The G trees should drop in and bolt up without an issue.
 
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How is that wrong? I was refering to the difference in the tripple trees, NOT the steering head on the frame. Yes, i should have said offset, not angle. So that was what i had wrong.
 
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