The pistons on my R80GS basic are worn and some of the cooling-fins have broken so it’s time for some work.

Siebenrock have a “power-kit” (new cylinders and pistons) which increases the power with 20% and torque with 30%.
Is there anybody who has tried it? Experiences on low-octane fuel? (Compression is increased to 9.5)

There is also an “enduro-camshaft”, 296°, any thoughts?

Hi AliBaba,

I have no personal experience with those parts, but my impression is that especially the power kit is quite popular in Germany.

Try http://www.boxer-forum.de/dc/dcboard...topics&forum=6

Although a german-speaking forum, I am quit confident that you will get advise if you post in english.

Regards

Lars

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I looked into this kit as well. The main advantage is that you don't have to change your carbs or heads, just bolt it together, get the jetting right, and away you go. I was told by one supplier that the high compression is a problem with low octane fuel. You would be looking at 93 or better octane, at least! This might be fine in Europe/ North America where such fuel is easy to find, but traveling abroad will be hampered.

My thought was to combine the 'power kit' with dual plugging of the heads (which spreads the flame better and reduces detonation). I was advised By Siebenrock that that would still not be adequate to run on 87 octane, and they would advise 91 minium even with the dual plugging.

A better option for travel is to get a proper 1000cc setup with heads and carbs to match. With dual plugging, lower octane fuel shouldn't be a problem.

Thank you for replies!
I’ve already checked the German forums, loads of info!

Running on low octane fuel with high compression (9.5:1) is an issue, and I hoped to find someone who has tried it. (Ted Simon had some kind of 1000-conversion).
Hmm, I just saw that the compression on KTM Adventure is 11.7:1, the new XT660 has 10:1. Maybe they both have dual plugging?
The R1100GS had 10.3:1 and it was not dual plugged, but I guess other factors also are important. (Timing ++)
Unfortunately less then half of the bikes mileage is in areas with low octane petrol so it might be an option to use octane-booster or to reduce compression temporarily.


To build a standard BMW 1000 is out of question. The price is high and IMHO the R80 runs better then the R100 (much smoother), but I think the engine with Siebenrock 1000 kit runs much better then a standard R80. (I haven’t tried the 1042 and 1070 but they are way to expensive anyway).

Hi AliBaba,

I've reworked my GS80 with dual plugging and balancing my pistons & conrods. It doesn't go faster, but much smoother. Should be positive for engine life.
What I refrained from was to lift the compression because of the above mentioned probs. If you stay in Europe, ok, but if you want to visit other countries I would prefer to genuine BMW parts. You will find spares everywhere. I'm not sure whether Siebenrock is well known outside Europe.

Good luck,
Hans

__________________
Only when we pause to wonder
do we go beyond the limits of our little lives.
(Rod McKuen)

I believe that Ted Simons bike was (is) an R80 GS basic (a 'parts bin special' combining G/S and GS pieces) with R100 barrels/ pistons/ heads added.

The Siebenrock claims smoother running then a standard R100 because the parts (pistons) are lighter = less reciprocating mass which reduces vibration, one of the reasons the R80 runs smoother.

I would say that sourcing a used R100 top end would not be that much more expensive then the Siebenrock kit. HPN has a reputation for very smooth running R100's in their rally and other special models. They balance the internals, which apparently makes a large difference, pointing to large manufacturing tolerances. Keep in mind that the this engine was designed in the late 60's and intended to be 600-750 cc's.

Thanks for interesting replies!

Balancing the pistons and conrods will have a positive effect on enginelife, I might consider it.
When it comes to dualplugging I’m not sure. I totally agree on the principle but I don’t like the way the plugs are placed underneath the cylinderhead. For me it looks fragile and I already have a lot of scratches in that area.

Yes Ted Simon has a Basic (like mine). I’m not sure how he made the conversion to 1000cc.
After what I have heard you should change the carbs if you use BMW 1000cc cylinders. With second hand prices from Motorworks this will be almost 50% more expensive then a new Siebenrock-kit. There will also be some additional costs to overhaul the used pats (carbs, new rings, gudgeon pins, top ends…). So in the end it will give me an expensive solution based on used parts.
But this is not only a matter of cost, I don’t like the way the R100 runs, and I have tried quite a few.
Siebenrock might claim smoother running then the R100, IMHO it also runs smoother then the R80.


It is a good point that the Siebenrock-kit is not genuine BMW-parts, and therefore harder to get outside Europe. If I come in a situation where I need new pistons, rings or cylinders I have to get them shipped. But is there a chance to find these parts in Africa or Asia if I go for the BMW-solution (standard R80 or R100)? I don’t think so; they have to be shipped anyway… Even in here in Norway BMW have to order parts like this from Germany.
Of course if the Siebenrock is more prone to failure that’s a very good argument to use standard BMW-parts.

When it comes to using HPN I don’t think that’s the right solution for me. They make wonderful engines and bikes but the last years I have tried to get in contact with them several times (mail and phone) without luck. That’s not the kind of people I will depend on. There are also other issues like cost (which I’m sure reflects quality) and it looks like their development have stopped or at least slowed down.

Hello.
Interesting thread, thought i might add my 2 cents. I dual-plugged my R100 heads along with polished and flow-tested the ports last year.The result, imho, is 100 percent better. Better fuel economy, smoother running, faster punch! As far as the exposed spark-plug goes, even if you break it, you still have i left to run on until you can make repairs. I also burn reg. gas exclusively.
The compression problem... i read somewhere that you can shim the cylinders to reduce compression in problem fuel areas. Simply done in a few hours max. I've never tried this though, any comments?


Good luck!

Lowering the compression through shims is possible, and your right is shouldn't be that difficult. However, you would loss at least some of the advantages of the Siebenrock kit in doing this. Part of how they increase the power with the stock valves/ carbs is by raising the compression.

Back to the previous comment on Ted Simon's bike. I recall the 1000cc modification being done by a shop in Britain (I'm sure the info is on his web site). The R100GS was sold in the US with the smaller valves (and carbs, if I am correct - Grant?) this may have been what they did, just swap the parts over.

Hello.
The US model R100GS (mine ) came equiped with 32mm carbs, although i don't know if the valves are also smaller or the same as the 40mm Canadian and European models.

The US R100's (later series, e.g. GS) all came with 32mm carbs. Everyone else that I know of got the 40mm carbs and bigger ports. I don't know if there was a valve difference or not.

But we can find out - give me the engine and frame number of both a US bike and a Canadian and / or European, and we can look up the part numbers and see if there is a difference.

Post em here!

The easiest R80 to R100 is just add the COMPLETE topend of an R100, pistons out.

Note that it is a bad idea to use R80 heads, even though they'll fit, with R100 pistons/cylinders - you will probably LOSE power. A few people have reported success, but the consensus seems to be that it's not good.

A used R100 topend is reasonably priced generally, and if it's a US topend, then you can use the original R80 carbs easily. DO change the jetting of course!

You can also use the R80 32 mm carbs with the Euro topend, but jetting will have to be sorted the hard way. Start with the R100 settings and check it carefully.

That's all I can think of at the moment!


------------------
Grant Johnson

Seek, and ye shall find.
------------------------

One world, Two wheels.
www.HorizonsUnlimited.com

__________________
Grant Johnson
Seek, and ye shall find.
------------------------
Inspiring, Informing and Connecting travellers since 1997!
www.HorizonsUnlimited.com

Hello Grant. Here's some #'s:
Frame:wb1047805k6153181
Engine:kbm0980425a
This is an '89R100GS/PD US model.

Thanks for an interesting discussion!

Okay I see that most of you would prefer to use genuine BMW-parts.
The compression might be a problem with low octane petrol (but no one has tried it). It’s easy to come around the problem when/if it happens by reducing the compression temporarily or use octane booster. (I’m not sure if it will be a problem because other bikes run much higher compression without problems)

I can’t see why it would be easier to use a complete R100 top end, for me the job looks the same and it will cost more money. If I even have to use an US topend (or change carbs), this doesn’t look like an easier way to me. The Siebenrock-kit also runs much smoother and has more power then the R100. So for me it looks like:

Siebenrock:
+Cheap
+Runs smoother then R100 (and R80), esp on low RPM
-High compression might be a problem with low octane petrol (fixable)

R100
+Genuine BMW-parts
-Expensive
-Based on used parts

AliBaba,

I agree with your assessment of the advantages of the Siebenrock kit over stock parts. However, I personally don't see an easy way to fix the compression/ fuel problem for traveling. Lowering the compression involves pulling the top end (replacing all gaskets/ o-rings = $), shimming, and rejetting the carbs. hardly something I would want to do more then once. If you do this, you will then lose much of the power advantage you gained going to 1000cc.
I don't think there is any question that the Siebenrock kit is not a great mod....for a bike that can be assured a steady diet of 94 octane fuel. Perhaps carrying octane booster would do the trick?
However, like you say, if the Siebenrock does indeed run smoother, perhaps it is worth the hassle in the long run.
On another note, it was once suggested to me that if I wanted to up the power of my R80, I should install the high compression pistons from the European road models (9.5 to 1 I think) and dual plug/ polish the heads. This should deliver at least a 10% boost in HP and torque, and will run on 87 octane as the bore is still narrow, and the dual plugging reduces detonation. So this Modification would:
*Increase power,
*keep the smooth running nature of the R80
*increase fuel economy
*stay with stock parts
*known setup = easy to rejet carbs.
*be economical
Worth condidering; price wise, I suspect it would end up similar to the Siebenrock kit if you could get some used parts (cylinders/ pistons).
Great discussion BTW,

Quite interesting point re carbs. I suppose most people tend to use the bigger carb when changin to 1000 cc.
The 32 mm carbs fitted on the 1000 cc engine will offer you a better and smoother performance in lower revvs due to better flow, but naturally the performance will be lower than in higher revvs with the 40 mm carb.
Another + for the 32mm carb is a lower fuel consumption, which is an important issue when travelling in areas with few petrol stations.

__________________
Only when we pause to wonder
do we go beyond the limits of our little lives.
(Rod McKuen)