When did they go to lower CR

[Reddog74usa]

Anybody remember when they lowered the compression on the Shovels and did they do it by reducing the size of the piston dome or enlarging the combustion chambers or did they do a little of both to achieve the lower CR's? I have a late 82 that's never been into so it is at stock CR. This bike feels like it has one of those "S" cams in it for those late lower CR Shovels which I do like, as any late model Shovel I ever owned always ran great with nice low end mid range power with the "S". The lower CR didn't seem to hurt the performance at all and the bikes seem crisper and more responsive at the low end and midrange compared to the "H" cam Shovels I've run.

The bike runs great as is so I don't plan on tearing into it anytime soon but when I do I'll be going 9.5-1 cr with an original Tom Sifton 440 cam.

[Ohio HD]

If my memory is intact, all Shovels were 8.0:1 until '81, when they dropped to 7.4:1.

[Reddog74usa]

Thanks, do you know if it was just a piston change?

[Ohio HD]

Yes, they made a slightly smaller dome. And they could have introduced them in late '80 as well.

[76shuvlinoff]

If I may ask. What was the point of the lower CR?

[Ohio HD]

Poor quality unleaded fuel. It was really to reduce detonation as far as I know.

[kd]

I recently mentioned in another thread here that I remembered one year when some of the Lowriders were "soft dogs" and others were still snappy.  I can't remember the exact year but it was around that 198 0 vintage.  I think the year you could buy it in silver/grey?

[Ohio HD]

I recently mentioned in another thread here that I remembered one year when some of the Lowriders were "soft dogs" and others were still snappy.  I can't remember the exact year but it was around that 198 0 vintage.  I think the year you could buy it in silver/grey?

I think that is true as I remember it.

[JW113]

Yep, '81. But don't forget, the 1200cc FL models were 7.25:1. Cop bikes mostly.

-JW

[14Frisco]

Service bulletin M-0772, Low Compression Pistons / 1980 80 Cubic Inch Models, accessible from Service Bulletins, lists the pistons.

[waltcentral]

My 1980 Tour Glide was 8.0:1 and would ping like crazy after I got a few miles on it. The problem was stated "poor fuel quality".  They did not at the time figure out the additive package to stop the heads from up and raising compression. Problem occurred  after trying some unleaded AMOCO. That bike was stolen and my 1981 had the low compression and was fine.