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Old 10-31-2012, 12:31 PM   #1
cbi OP
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Question Siebenrock 1070 big bore touring kit

Dear all,

Been absent from extensive touring for a while & want to fix up my R100GS/PD sometime in the future. Aim- just reliable smooth good tourer

As a point of interest anybody got experience of an engine rebuild with the Siebenrock 1070 touring kit? the search engine on a couple of sights are a bit sparse..

Regards

Chris

cbi screwed with this post 10-31-2012 at 12:31 PM Reason: icon
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Old 10-31-2012, 03:12 PM   #2
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I've built 2 and they were wonderful..the pieces were works of art from the manufacturer and the bike ran strong and smooth..I also had the entire top end balanced to a .1 of a gram so that helped.

Make sure to install new lifters, upgrade the exhaust system, have dual plugged heads, and consider a K&N.

That's a compete package that works very well for grunt work or cross country.
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Old 11-01-2012, 12:31 AM   #3
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With all that extra grunt, a 5% higher top gear would be a good thing, and while you`re in there, a 5% lower first gear as well.
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Old 11-01-2012, 02:49 AM   #4
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Yep got a Seibenrock, 1070cc 1996 R100GSPD, twin plugged, early model large valve RS heads, Large diameter headers & Y peice to standard rear muffler, Red Centre full electronic ignition system, 450 watt alternator, high output Diode board, 14.6 volt voltage regulator, Nippondenso Starter, 5% lower first gear, 5% higher top gear, oil proof Seibenrock clutch, R1100 clutch spring. Fully rebuildable Drive Shaft, 4 piston front brake.

Very sweet bike, very fast.
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Old 11-01-2012, 03:07 AM   #5
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Dear all,

Thanks for the feedback.

Getting there..so far ( over many years):

Twin plugged & gas flowed
Moto Israel two into one exhaust with HPN baja ($$$!)
Longer 5th
450W Alternator

Thinking of getting sachs or siebenrock cluch

Other mods include:

Marzocchi fork inserts & Ohlns rear
Four calliper front brake

Local mechanic thinks I may have a bit of piston slap & valve wear but getting second opinion.

Bottom line, love the bike doubt going modern so considering rebuild for smooth use till I go grey..

Regards

Chris

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Old 11-01-2012, 12:12 PM   #6
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I have no expereince with nikisil big bore kits. I do have experience with iron lined big bore kits. They run great for a while. Then they start leaking oil for not enough gasket area at both the head and the case. It's miracle they don't blow a head gasket at their super then area between the cylinder stud hole and the bore. Then by around 20k miles the cylinder walls become very distorted for not being thick enough. Oil usage goes up and performance goes down. You can run a Sunnen hone done the cylinder and see that the bore is corrugated right in sync with the cylinder fins. It gets pretty ugly pretty fast. Our engines aren't the only ones that have had the bores taken out too far for their own good. Some people go there with about everything. BMW stopped at 94mm for a lot of good reasons IMO. They actually thought 94mm was too far and that is one of the reasons why they quit making 1000's for a while. I don't know from experience but I would think that super thin nikisil plated aluminum would distort a lot more that super thin iron or steel but . . . .

Better performance? I am all for more displacement. Consider your 980cc bike a hogged out 750 and look elsewhere for more performance. At 980cc's your engine is already a super short stroke engine for a two vavle hemi head at 1.33:1 bore to stroke ratio. 1.33:1 was THE limit for over squared engines for years mostly because you get to point of diminishing returns with a wide included valve angle and a super short stroke. They stopped there with their 450cc engine too. R65's have the exact same bore to stroke ratio as a R100.

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Old 11-01-2012, 12:23 PM   #7
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Quote:
Originally Posted by supershaft View Post
I have no expereince with nikisil big bore kits. I do have experience with iron lined big bore kits. They run great for a while. Then they start leaking oil for not enough gasket area at both the head and the case. It's miracle they don't blow a head gasket at their super then area between the cylinder stud hole and the bore. Then by around 20k miles the cylinder walls become very distorted for not being thick enough. Oil usage goes up and performance goes down. You can run a Sunnen hone done the cylinder and see that the bore is corrugated right in sync with the cylinder fins. It gets pretty ugly pretty fast. Our engines aren't the only ones that have had the bores taken out too far for their own good. Some people go there with about everything. BMW stopped at 94mm for a lot of good reasons IMO. They actually thought 94mm was too far and that is one of the reasons why they quit making 1000's for a while. I don't know from experience but I would think that super thin nikisil plated aluminum would distort a lot more that super thin iron or steel but . . . .

Better performance? I am all for more displacement. Consider your 980cc bike a hogged out 750 and look elsewhere for more performance. At 980cc's your engine is already a super short stroke engine for a two vavle hemi head at 1.33:1 bore to stroke ratio. 1.33:1 was THE limit for over squared engines for years mostly because you get to point of diminishing returns with a wide included valve angle and a super short stroke. They stopped there with their 450cc engine too. R65's have the exact same bore to stroke ratio as a R100.
You are comparing apples to oranges here. This is not a modified BMW cylinder etc.
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Old 11-01-2012, 12:36 PM   #8
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Quote:
Originally Posted by bmweuro View Post
You are comparing apples to oranges here. This is not a modified BMW cylinder etc.
Yes and no. Not the same casting, so the walls may be thicker, but that still doesn't change where the cylinder studs are and how thin the walls are at the studs. I'm not saying it's a problem, but the thickness (or lack thereof) of the cylinder walls at the holes for the studs definitely caught my eye.
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Old 11-01-2012, 12:53 PM   #9
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The cylinder stud holes are in the exact same spot. They kinda have to be. Certainly the cylinder walls are thicker and the fins are shorter I would hope but I have serious doubts about them being thick enough. I know the cylinder walls aren't any thicker at all four cylinder stud holes down through the length of the cylinder. They couldn't be unless you got a different case too. It's the same case. It's apples and apples.
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Old 11-01-2012, 01:01 PM   #10
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Quote:
Originally Posted by Airhead Wrangler View Post
Yes and no. Not the same casting, so the walls may be thicker, but that still doesn't change where the cylinder studs are and how thin the walls are at the studs. I'm not saying it's a problem, but the thickness (or lack thereof) of the cylinder walls at the holes for the studs definitely caught my eye.
I wonder if the cylinders 'walk ' more with no skirts? With even less gasket surface that could be a problem. I have my doubts but I still hope they work. Sure, I know they work right after you put them together but I expect my airhead setup to last! I still have my doubts about the clyinder walls' thickness keeping up with the bigger bore. Time will tell. I hope for the best. I will be pleasently surprised if they hold their own. Different cylinder casting or not, all of my concerns still come into play unless we get a new case AND heads too. We don't.

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Old 11-20-2012, 12:48 AM   #11
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My 1070 kit is fine after only 10000 miles or so, these kits have been around for many years now and I have never seen any chatter on the Internet that indicated that there is a problem. A new casting for the cylinders is very different than just fitting a liner to an existing cylinder as that used to be done with the old 1050 kits using venola pistons.

The Seibenrock kit in includes new longer conrods and a very nicer assymetrical cam and the components work very well together. It's not cheap though
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Old 11-20-2012, 05:53 AM   #12
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Quote:
Originally Posted by chasbmw View Post
My 1070 kit is fine after only 10000 miles or so, these kits have been around for many years now and I have never seen any chatter on the Internet that indicated that there is a problem. A new casting for the cylinders is very different than just fitting a liner to an existing cylinder as that used to be done with the old 1050 kits using venola pistons.

The Seibenrock kit in includes new longer conrods and a very nicer assymetrical cam and the components work very well together. It's not cheap though
I have started threads in two german forums asking for feedback regarding longevity of the 97mm (e.g. HPN) and 98mm (Siebenrock) kits.
Response was poor regarding the number of answers.
However, content of responses was positive through all posts.
Mileage varied between 10,000 miles (Siebenrock BBK) an 100,000 miles (HPN 97mm or others).
No problems reported.

I'm wondering why gasket surface should have decreased with bigger bore.
The head gaskets don't use the whole surface, just a small rim around the bore.
And at the cylinder base the surface is the same.
Or am I missing something?
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Old 11-20-2012, 06:18 AM   #13
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Quote:
Originally Posted by RGregor View Post
I'm wondering why gasket surface should have decreased with bigger bore.
The head gaskets don't use the whole surface, just a small rim around the bore.
That tiny ring is now VERY close to the holes for the cylinder studs. Not a problem, I guess though.

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Old 11-20-2012, 06:42 AM   #14
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Quote:
Originally Posted by Airhead Wrangler View Post
That tiny ring is now VERY close to the holes for the cylinder studs. Not a problem, I guess though.
If the ring seals perfectly it doesn't matter how much space there is on the outside

I've bought spare gaskets for my 1043, so far they are still not used

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Old 11-20-2012, 06:49 AM   #15
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The only downside to the Seibenrock kits is the cost of the gaskets around 40 each......I assume that the orange lines on the gaskets are a compound that help to seal the gaskets?

Charles
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