anyone have experience with Seibenrock 850cc kits?

[mrclubike]

Well I actually did buy a kit 9 months ago. Like a lot of my projects it is becoming time extended as I found something else to divert me, namely fitting a K100RS fuel tank, seat and fairing to the poor thing.
 
More recently I have been playing with the oilhead and the R100  awaits attention so it is a case of "watch this space" for fitting the big bore kit.

Any up date Tony

[Tony Smith]

Well yes, the kit is fitted, I've done about 1000km on it and I am just impressed to bits. The engine runs smoother than it ever used to, which mich have a lot to do with th emuch lighter and well balanced pistons.

What was interesting was running side by side tests againt the R65/80 that also lives here. Up to around 75mph the 860 is way quicker in acceleration. but at about 75mph and beyond the R80 engine nails it - I suspect due to better breathing.

I have not changed carb jets, in fact I have not even moved the needle clip position as I  had time booked on a dyno and was going to double check mixtures then. However a friend wanted to put his bike in the "Northern Nationals" drags so I gave up my slot on the dyno and have rebooked for July. I may even cancel this as I am satisfied that it is not running lean, there are no flat spots so I suspect that fiddling will most likely only go backwards.

BUT. If I were doing this again, I would do it differently. The limiting factor on the 860 kit is that the piston crowns are re-shaped to suit the R65 heads. Knowing what I know now I would start with the 7-rock cylinders but use R100 heads and 7-rock R100 pistons. The only unique fabrication would be to have a set of 40mm headers made up with R65 width to them. I suspect an engine built that way would deliver significantly more HP out of the box then using the R65 heads.

In the interim however, I am very happy.

[mrclubike]

Tony
What final drive ratios are you using in your  800 and 860 conversions
Do you think a 37/11 may be to conservative

My kit is still stuck in customs 

[wilcom]

Tony
What final drive ratios are you using in your   860 (

Did you change the rear drive on the R65 before you went 860? Would have liked a camparo of the two rear drives with that kit

[Tony Smith]

Both bikes still have standard R65 final drives at 32/9. I will be fitting a 32/10 to the 860 (think you Wilcom)

BUT, it was recently said to me that the dimensions of the "old" and "new" final drive housings is diffferent and that therefore a pre-81 and post 81 swingarm are different lengths. I've never head this before and my intiial thought was that it is rubbish. But, I did a quick measurement and there may in fact be a difference.

I'm not particularly stressed either way as I do have a second pre-81 swingarm I can use, but until I get time to accurately measure the old and new parts and convince myself that they are the same dimensions the (as yet unfinished anyway) R75 final drive stays wrapped in oiled rags.

[Tony Smith]

Sorry i should have mentioned - from a power availabe point of view I reckon that either the R65/80 or the R860 will happily pull a 32/10 and woudl probably pull any of the higher ratio final drives, at some cost to acceleration and flexibility.

[Barry]

BUT, it was recently said to me that the dimensions of the "old" and "new" final drive housings is diffferent and that therefore a pre-81 and post 81 swingarm are different lengths. I've never head this before and my intiial thought was that it is rubbish. But, I did a quick measurement and there may in fact be a difference.

BMW list the wheel base as different for pre and post 81 which I have always assumed was down to the swinging arm length as they are different part numbers. Never measured them though or thought the final drive housing were different other than the obvious oil capacity, brake spindle lube and brake shoe differences.

[mrclubike]

The smooth case final drives are supposed to be interchangeable with the ribbed FD as an assembly
I sure hope so because i just spent $300 USD on a good one off of eBay
Just waiting for the gaskets  and seals to but it back together and install it
It will be nice not having to deal with the brake shaft leaking

[tiggum]

There is an inmate (Solo Lobo) on the Adventure Rider site (Old's Cool/Airheads) who has a thread of many pages on his efforts recommissioning a R65LS originally owned and refined by another inmate named John Jen.  When Solo Lobo bought the bike, it already had a smooth case final drive with a 32/10 drive ratio.  Check out his thread; MANY pages and lots of good information dealing with several sophisticated improvements.  Good reading!

[mrclubike]

Here is a comparison of the bore sizes

[Tony Smith]

Here is a comparison of the bore sizes

Prepare to be very pleasantly surprised.

[mrclubike]

Here is a comparison of the bore sizes

Prepare to be very pleasantly surprised.
 

I have a feeling I will 

I test rode a Moto Guzzi V7 III
And was amazed with the torque it had
I come very close to buying it
But instead of spending $7000 on it I decides to upgrade the R65 instead

[mrclubike]

The smooth case fit just fine
Of course I disassembled it cleaned it out and resealed it

It is off of a 1971 R60/5  37-11 ratio

The older cases have some nice features that were deleted from the newer style   cases

[Tony Smith]

It is off of a 1971 R60/5  37-11 ratio

A couple of days ago I dragged out one each of my "old" and "new" final drives determined to set my mind at rest one way for the other.

It suddenly occurred to me that the only measurement I needed to make was from the forward gasket face to the axle centre.

They are, as you already know, absolutely identical. Myth busted!

Your R60 final drive is a nice find. It's 37/11 is a ratio of  3.36 which is a useful increase from standard R65 which was either 31/9 (3.44) or 32/9 (3.56).

The R75 ratio I am going to use - 32/10 (3.20) is a bigger step, but I expect the 860 to pull it effortlessly.


One day I will try the R100RS ratio 32/11 (2.91) I expect it will "notice" that, but if I ever go touring it would be the "bee's knees". The only spare 32/11 drive I have is for a disc brake rear end and it doesn't have the drillings or "furniture" to mount drum brake shoes. The one on my R100RS, being the old case, does have the drillings and could be converted to drum brakes, but I don't feel any immediate need to try it as the likelihood that I will want to maintain a 160kph cruising speed on a naked R65 is pretty small.

[mrclubike]

Got it back together and rode it 100 miles

Power is excellent 
It will easily run 70mph

But it definitely has more vibration 
Not sure if I  can live with it

I will sync the carbs and ride it 

I forgot to check the piston balance
You would think they would have check that at the factory