Two engines in the R 80/7?

[jfduclos]

I'm considering buying a 1980 R80/7. In looking at the specs I see that there are two sets of engine specs. Evidently there were two different ones ie different compression ratios, horsepower, etc. Was there a standard and a higher performance model? If so how do you tell the difference. Any input on this topic, would be greatly appreciated, Thanks

[jdmetzger]

I believe pre-1981 R80's are 9.2:1, and the post-81's are 8.2:1. I have also read that SOME European R80's pre-81 had the lower compression ratio, as well.

The main difference is the lower compression ration bikes had a shim at the base of the cylinders, which lowered the compression ratio. I'm not sure if you can "see" the shim when it's in place or not. My 78 does NOT have any shims.

[28796]

I believe pre-1981 R80's are 9.2:1, and the post-81's are 8.2:1. I have also read that SOME European R80's pre-81 had the lower compression ratio, as well.

The main difference is the lower compression ration bikes had a shim at the base of the cylinders, which lowered the compression ratio. I'm not sure if you can "see" the shim when it's in place or not. My 78 does NOT have any shims.

I don't believe you'll find shims on the later bikes either. My 87 R80 certainly didn't have any. The piston design gives the 8.2:1 comp ratio with the Euro pistons being slightly higher. If you want to wake up a later R80 pop in a set of the Siebenrock 9.5:1 pistons.

[flash412]

Dang! You learn something new every day. This would explain why my white '81 R80G/S was so much faster than my Blue '81 R80G/S. (The white ones were made in '80 and early '81. The blue ones were made after.) Neither of them had any base gaskets. I rode those bikes for seventeen years and never knew that they had different parts.

[jfduclos]

Thanks, guys for the enlightenment. This 1980 was picked up by the original owner in Germany and shipped home, so I'm hoping that it's one of the peppyer ones. Any idea why they would have wanted to downgrade the performance in the later models? That kind of 'progress" just doesn't make sense to me.

[boofer]

That's when leaded gasoline was on its way out......and unleaded was not available in higher octane.

[Na Cl K9]

...premium 96 octain rated fuel would be at a disadvantage in places where such fuel grades are unknowen/unavailable. Mine ran on nearly anything I poured into the tank so long as it was filtered to remove dirt and water.

In the 80's I noticed that the output and compression figures were the same for all 1000 cc engines except the early CS which there are very few of in reality (by engine number). The 800 cc engines were the same except for the first production R80GS...far as I know anyway.

My GS was from the first production numbers and purchased new in late 1980. It came with a bad clutch disc (soft splines), bad chrome on both fork tubes and activating the rear brake produced a pronounced up and down movement in the brake pedal. BMW fixed all the problems...It became my most favorite BMW. Still is.