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Rotating engine with shims removed?

8ball

8ball

Forum Mentor
OK, I am not a newb to building and working on motorcycle engines, but my GS is the first one that I have had with over the bucket shims.

I took my valve clearances today, and had 6 out of spec. I used the zip tie method to remove the shims so I could take them to my friends shop to exchange them. The thread that explains that method actually tells you to make two so you can remove two at a time.

Now I came back to the forum and read several posts warning to NEVER rotate an engine without shims, but no one seems to explain why. Now I am trying to figure out what could possibly get damaged by hand barring the motor with shims removed. It can't be valve/piston interference, 'cause the valves will actually open less. As I said, this is not the first time I have built an engine, but maybe there is something specific to 8 valve GS motors I don't know. What am I missing here?

I am a little concerned, as I did have to rotate the engine

Someone please explain.
 
Because the edges of the cam lobes get torn up and so do the edges of the buckets. If the edges of the buckets get thrashed the shims might not go back in. usually its just the very slag on the edges of the lobes that gets scraped off, but still why allow it to happen in the first place!!!
 
Many are gonna chime in and tell ya your F#$%ed and you gotta replace the cams and all kinds of bullchit. Yes take a good look at the lobes with some good magnification and be sure the actual lobe faces arent scratched or damaged.. but if its just the slag on the very very edges its not an issue.

I am gonna get flamed by that statement, but its just the simple truth. my dad worked at GM for 20 years and he heard hundreds of them hit the floor all day and they were put in engines and no problems. I know of 3 bikes right now ( not mine by the way ) that guys had done this and never and issue..AS LONG AS THE LOBE FACES show absoultely no damage.
 
And by NO DAMAGE I mean other than the " normal" wear in marks one would expect to see on the lobe faces.

And always install shims with the numbers FACING THE CYLINDERS. This is so under normal wearing conditions the lobes dont rub the numbers off them..youll want to be able to read them..as well as physically measure them with good calipers..next time you do a valve adjustment. make sense???
 
Yeah, I will look at the buckets and lobes tomorrow. I never rely on the # on the shim. I always measure. Worst case would be replace some buckets and polish the cams a bit. If you look at the edges of the cam lobes on some of the more modern engines you'd be surprised how jagged they are, so I am not too worried about that.

Most of the engines I have dealt with are either shim under bucket or rocker arm adjusted, so this was just something I was not aware of, and is not mentioned in the manual.
 
You're right..it's not mentioned in the manual. I rotated with a shim out and did shave a little off the edge, but was able to get the shim back in and, despite all my fears, I've never had an issue.

Still, I did it without realizing what the risk was. I sure wouldn't do it again.

Oh, I also made sure to get search for all the metal shavings and get them out.
 
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