anyone have experience with Seibenrock 850cc kits?

[Tony Smith]

Mrclubike

Sorry to hear that you have a vibration problem, mine was alread pretty good as I'd balanced the old pistons, but the 860 set were pretty much perfect out of the box.

You must have been very unlucky to get a set that are sufficiently out of balance to cause noticeable vibration.

It is a PITA, but you know how to fix that.

[mrclubike]

The vibration is still in the normal range between 60 and 70 MPH
But it is more harsh in that range
At 55mph  it is very smooth  and at 70 it is very smooth
The bike has never been real comfortable vibration wise in the 60 to 70 range but was tolerable if i put me feet up on the passenger pegs 
I forgot to check the piston balance when I was putting it together and like you said they may be just fine anyway
I am wonder if my rods could be out more than they should
When I get back from my trip in June I will pull it down and check every thing 

[Tony Smith]

Here is a thought.

Did BMW do any component balancing prior to assembly? To be quite honest I very much doubt that they did as they would have specified a weight range from the suppliers and left it at that. Certainly most BMW engines I've ever pulled down showed no signs of metal removal for balancing purposes (except those that had been apart before).

When I put my R65 engine back together I balanced the pistons and mass balanced the rods (they were out by a surprising amount). I didn't "end for end" balance as I don't think that is warranted on a low revving engine.

Anyway it has always been as smooth as silk. The 860 piston were so closely matched I didn't bother trying to do anything further with them and the engine remains smooth, including a significant way past redline (which was an accident).

I wonder if you have always had a bit of an imbalance in your rods which is now highlighted after fitting the much lighter pistons.

Anyway, I hope you get a result as any vibrations become very annoying after a while.

[mrclubike]

It is coming back apart tomorrow 
I hope I find something out of balance or the 860 kit will go back into its box and I will reinstall the 650 barrels
The 37/11 final drive will stay on regardless

I know when I replaced one of my pistons I didn't balance them and  It vibrated bad enough I had to pull it back down
I discovered they were off buy 7 grams
Let me tell you it isn't easy getting 7 grams out of one of those little pistons   

[Sejati]

I know when I replaced one of my pistons I didn't balance them and  It vibrated bad enough I had to pull it back down
I discovered they were off buy 7 grams
Let me tell you it isn't easy getting 7 grams out of one of those little pistons   

So you took off 7 gr from the other piston to balance them ? Btw how much is the weight you got previously from each piston ?

I have weird non dome piston in right side which I believe is not original piston for R65LS. And I have bad vibration and pretty low compression. I’m in process to open the other left cylinder to compare.

[mrclubike]

So 
The pistons were less than a .5 gram different  and the and the rods were less than a gram different in weight
The old jugs are going back on  and the 7Rock 860 jugs are for sale   

[mrclubike]

I know when I replaced one of my pistons I didn't balance them and  It vibrated bad enough I had to pull it back down
I discovered they were off buy 7 grams
Let me tell you it isn't easy getting 7 grams out of one of those little pistons   

So you took off 7 gr from the other piston to balance them ? Btw how much is the weight you got previously from each piston ?

I have weird non dome piston in right side which I believe is not original piston for R65LS. And I have bad vibration and pretty low compression. I’m in process to open the other left cylinder to compare.

The origanal pistons are about 340 grams
And the 7rock pistons are 420grams

[Sejati]

Thanks for your sharing.

[ged in oz]

So 
The pistons were less than a .5 gram different  and the and the rods were less than a gram different in weight
The old jugs are going back on  and the 7Rock 860 jugs are for sale   

Well, that’s a real shame.

If the pistons and rods are actually balanced, I’m wondering where the vibration is coming from. Crankshaft counterweight imbalance/mismatch?

[Bob_Roller]

Are there any markings on the piston crown, to show orientation ??
I just looked at my factory manual and the piston pins are not centered on the piston, they are offset .
I don't know if would make a difference or not .

[mrclubike]

Are there any markings on the piston crown, to show orientation ??
I just looked at my factory manual and the piston pins are not centered on the piston, they are offset .
I don't know if would make a difference or not .

Yes they have arrows pointing forward and they were installed correctly

[Tony Smith]

If the pistons and rods are actually balanced, I’m wondering where the vibration is coming from. Crankshaft counterweight imbalance/mismatch?

I know Mrclubbike to be a skilled and careful mechanic. If it was anyone else I'd be suggesting re-torqueing the engine mounts.