'84 gs850 parts swap to a '77 gs750 or '79 gs1000

[garyS-NJ]

I have a line on a '84 gs850 parts bike complete, cheap, says it needs carb work and no title... I'm looking at the CV carbs wondering if they might fit on my '77 or '79 (looks like below link says not without a head swap). and also looking at the header *(picture looks like a 4:1) and I'm guessing not.. And I'm thinking the electronic ignition will swap right into my '77 to replace points. Will the wheels swap right over to replace the rusty spoke wheels on my '77 and get me dual disks up front?? (is this desireable, or do people actually like the spoke wheels and paint rusty ones). Any other nifty parts on this '84 gs850 that would swap onto my '77 gs750 or '79 gs1000 (my gs1000 needs a seat cover and the stock seat is huge and hideous..). this is one link I found..

http://www.thegsresources.com/_forum/showthread.php?197298-GS850-vs-GS750-Parts-Swaps-Upgrades

 

[uk gs nut]

Shaft drive rear wheels won't fit chain drive bikes. Spokes ? We love them they are cool. Have them rebuilt with stainless Spokes. Fit the top end of 850 engine to your 77 gs750 for more grunt. Seats are not interchangeable very easy, but other bits and bobs will swap over. If it's cheap get it for spares stock. Also you could fit forks and just bolt on the rotors to your spoke front wheel the holes are under the plastic cover on right side of wheel, change master cylinder from 850 also.

 

[garyS-NJ]

Thanks UK nut! Any good sources on those stainless spokes here in the States? But then my rims are kinda rusty too.. I was thinking I take then smooth and follow with an etching primer and rustoleum wheel paint. Not sure if this is a shaft bike but if not, I think the mag wheel swap will be my path as I might be selling the gs750.. Oh, will the whole front end swap onto my '77 gs750? Fork tubes on the 77 have crazy rust.

 

[uk gs nut]

The fork legs should fit your triple mounts both 35mm I think.

 

[Grimly]

GS850 - 37mm and likely has longer legs than the GS750, so the legs and triples are needed (and assuming the donor isn't an 'L').
Otoh, the GS1000 had 37mm and the 850 legs will fit straight in to give the dual brakes (if the '79 1000 is a single-disc version) and the longer legs will not affect things adversely. 850 - 1000 is about 19mm difference in length.

 

[garyS-NJ]

Thanks grimly! My '79 gs 1000 has mags and dual discs up front... But you say I could swap the whole front with trees onto my '77 gs750? My '77 has rusty rims, rusty forks, and a warped rear rotor. So the '84 has longer lower legs or tubes or both and I should slide them up through the trees a little to maintain geometry?

 

[garyS-NJ]

Oh, and without a title, the frame and motor not worth anything to me.. If I could get the motor running, is it worth anything to anyone on here? I'm in north jersey.

 

[Grimly]

Thanks grimly! My '79 gs 1000 has mags and dual discs up front... But you say I could swap the whole front with trees onto my '77 gs750? My '77 has rusty rims, rusty forks, and a warped rear rotor. So the '84 has longer lower legs or tubes or both and I should slide them up through the trees a little to maintain geometry?

Here's a useful page of starting info....
http://www.dotheton.com/forum/index.php?topic=5669.0

Dotheton also has a list of triple sizes, stem sizes and bearings that swap over, just dig around the site, the lists aren't buried. I can't swear to it, but I think the 850 stem and triples will fit the 750 without much drama.
(all this is assuming the '84 850 wasn't fitted with L forks; as far as I can ascertain from uncertain sources, the non-L wasn't burdened with them, but some other models were fitted with the leading axle L forks, so if that's the case you will have to look at changing the tank too, as the L triples are shallower in offset and the legs will clank the tank)

 

[Chuck78]

The 850 is definitely a shaft drive, so the rear wheel won't work.
If you have the more common star type GS mag wheels, I have a rear on a 78 750E that I am parting out & getting ready to scrap out, needs cosmetically refinished and probably new bearings as most do, I would sell that to you for just a few bucks over shipping. Also, I would buy(&trade) the wire spoke wheel hubs off of you for spares if you were going to mags, but old beat-up rusty rims and seized spokes are of no use.
If you choose to re-spoke, you can get stainless steel spokes and nipples from Buchanan's. They already have the proper measurements in their database. They will cost you about $120. You'd probably want to treat the rust on the rims with naval jelly, have the rims sandblasted, & then powdercoated. New rims would run $190-250 each.

If the 850 is not a GS850L with leading axle forks, then the 37mm forks and 850 triples and the dual disc brake calipers will be a huge upgrade to the 750. A bike with rusted fork tube with rust or damage in the fork seal area is basically a useless bike that needs new forks, so go for this.
Just verify that the forks are a standard 850 and not leading axle (axle will be directly under bottom of fork, not up a few inches and mounted on the front of the forks).

 

[Chuck78]

Compression test the 850 engine, & then try to sell as whole, or tear down and swap the cylinders and pistons onto the 750 to make it 844cc. The head won't work with the 750 carbs but you can just swap the head and 850 cv bs32 carbs onto the 750. The 850 cans are just a bit more mild than the 750 cams, & produce slightly more bottom end power.
the 750 head and vm26 carbs also work on the 850 cylinders, but carbs will need re-jetted a bit. This would be the route I would go personally. An Athena complete engine gasket set is only about $80 or so, gets you all the top end gaskets.
Just need to check 850 cylinders for wear/damage, run a glaze breaker hone through it or have machine shop do this, & meticulously clean head gasket mating surfaces or have machine shop resurface them by taking a few thousandths of an inch off. 844cc with 4-1 exhaust and re-jetted vm26 750 carbs and 750 head/cams is a high rpm rocket 5500-11000rpm...
750 crankcase have to be very slightly clearances to fit the 850 cylinder sleeves, but well worth the upgrade if you are trying to sell/market this as a higher dollar bike.

good luck

 

[one_civic]

I milled my 850 cv head 0.020" and used our canadian slabbie gsxr 750 carbs with the larger cv port 850 heads, bolted right up to the stock cv intake manifold boots, check out the build thread in my signature for some more info.