GS 850L engine transplant

[Deesel]

I just picked up a 1980 GS 1000G engine and carbs that Im going to put in my 1982 GS 850L. So far the externals of the engine look to be identical.
What changes if any will I encounter?
What is the difference between ignition systems? Are they interchangeable?
Are the starters interchangeable?
How much difference is there with the transmission ratios? I plan on using the 850 rear end.

Thankyou in advance for any knowledge and enlightenment anyone can share.
ECR

[Grandpa]

The swingarms on these bikes are not the same. It's possible the middle gear plates won't align.

Starters are interchangeable. Ignitions are not.

A GS1100G (standard, GL, or GK) engine would interchange with the 82 GS850 much better. You may have to get a bit creative, but it is possible.

[Deesel]

Thankyou Grampa for your input!

I have my original 850 engine and the 1000 motor sitting side by side and to the closest I can tell the length, width and height are identical. The only difference in physical appearance is the intake ports are slightly longer and bigger in diameter on the 1000 engine.
Checking with a tape measure and dial calipers- mounting holes are the same.
The drive shaft flange and its location is the same.

Does the 80 1000g engine have points and mechanical advance mounted on the engine? I thought my 82 850 has an electronic ignition and can I put this on the 1000 engine? Or what ignition should I use on the 1000 engine?
All the wires coming from the engine (magneto, shift indicator,etc.) have the same color coding and plugs.

It seems like it is going to be almost a direct bolt in. Is it going to be this easy or am I missing something?

Any comments and advice is appreciated
Thanks
ECR

The 1000 engine should be worth few more HPs and I cant wait!!!

[Grandpa]

The GS1000G does not have points. Only the 79 GS850G had points. In 1980 the 850 came out with electronic ignition with mechanical advance, and I believe the GS1000G has the same kind.

The 82 shaft models 850's and 1100's have electronic ignition with electronic advance. The ignitors are different. I'm sure you'll find a solution to this problem.

Yes, most parts will interchange. I'm glad the middle gear output flange seems to be compatible.

Best wishes to you. Yes, the 1000 has a bit more punch. I had 4 850's before getting my 1100 shaft, and there's a substantial difference in power and "long-leggedness".

[Deesel]

Do you think the timing curve will be different between the 2. Both engines have the same connectors on the engines, I wonder what would happen if I just plug er in? It dont want to cook anything. (igniters or pistons)

Thanks Grandpa (sorry about Grampa on previous post- accident)

[Guy]

The GS1000g and GS850g have the same ignition systems: mechanical advance and igniter, so the ignition curve should be the same. though the GS1000g has a similar bore but much longer stroke. The bigger engine has lots more torque, overall higher gearing and fuel consumption will probably be lower than the standard 850. Are you certain the output flange will match up? Grandpa isn't the first person to mention this.

[Deesel]

I bought the 1000g drive shaft because I heard that the flange was different. The shaft maybe longer to accommodate a different length swing arm but the 1000g flange bolts right on my original engine(so the 850 driveshaft which matches my chassis should work). I double checked- its the same. Both the flange and the layout and location of the output on the case.

Guy, you think the ignition systems are the same from an 80 1000g to an 82 850L? It really seems like they are because the wires and connectors are identical.

Thanks for the comments.
ECR

[SqDancerLynn1]

The drive shaft is the same length The bolt spacing is different You need the GS1000 drive shaft. The swing arm & the rear differential are the Same.You will have to modify the rear motor mount Might need spacers for the front Easy to deal with. The GS 1000 will cruse about 500-600 RPM less than the 850. The gearing in the secondary gear set is different

[Deesel]

Ok, went and triple checked and both have a four bolt pattern and it is 1.837" from center to center of each hole on both engines- they are the same within .002".
The number on the 1000 case is GS100G-10388 (thats 1000 engine right?) I was told this engine come out of a 1980 GS1000G.
The 850 reads GS850-154085.
I would say the cases were made with the same pattern (external atleast). All mounting points are identical.

SqDancerLynn would you say it is a worth while upgrade? I got the motor for $150.00. Its supposed to run good- Ill find out.
Thanks
ECR