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gs850 gs1000 cylinder swap?

  • Thread starter Thread starter jandiel
  • Start date Start date
J

jandiel

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Anybody know if it is possible to upgrade a 1979 GS850 engine to a GS1000 with just a cylinder swap? I've read that the only difference between the 750 and the 850 is an overbore and that they run the same cams. There doesn't seem to be many aftermarket piston kits available for the 850 either, any suggestions?
 
I'd like to know if I can bore out my 82 GS850G to a 1000 or perhaps 1100? Where would I get it done and a rough estimate on the cost.

TIA.

Charles...
 
Well bother inlaw is a mechanic he says you can bore up 5 mm and thats it,but if it were me i would only do 3mm that would give 72mm bore and thats the bore of a 1100.you would also have make sure the piston skirts are the same hieght as the 850's so that they don't do any damage to the engine.
 
The 1000 engine has a longer stroke as well as a bigger bore than the 850.
I think the 1000 motor has about .400" more stroke and around .200" bigger bore- these are not exact figures. I dont think it would be easy to put the 1000 cylinders on the 850.
I bought a 1000 engine for $150 and a set of carbs for $51 off ebay. I have to fixup the carbs and rejet them for k&ns. Then it will be a direct bolt in for my 82 850L.
I will have around $300 by the time Im done (providing the motor is as good as I was told). I dont think that is too much to spend for a healthy gain in horsepower.
Now I gotta figure out what Im gonna do with my nice running 850. Gocart keeps popping into my head??!!!:-D
 
Deesel said:
The 1000 engine has a longer stroke as well as a bigger bore than the 850.
I think the 1000 motor has about .400" more stroke and around .200" bigger bore- these are not exact figures.
Click to expand...

Disregard this earlier post.
I double checked and the bore and stroke for an 850 is 2.7165 x 2.2205" and a 1000 is 2.7559 x 2.5512". So thats only .0394 (1 mm) bigger on the bore and .3307" bigger on the stroke for the 1000.
1mm bigger bore on your stock stroke 850 engine will only get you 868cc.
 
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