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Old 1 Oct 2008
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Location: Stockholm - Sweden
Posts: 316
Engine overhaul - what to do and not?

My R100RT, 1981, needs some service and overhaul.
It has run 160 000km and is leaking oil at the pushrod tubes/grommets and cam-chain cover.
The gearbox has been overhauled and is wating for the engine to get a similare attention. The final drive is overhauled to.

What would you do at 160 000km overhaul when the engine is opened this much ?
Of cause I have my ideas, but am all ears to yours to -

There is so much to drool over at the "candy-stores":
* http://www.motoren-israel.de
* http://www.wuedo.de
* http://www.siebenrock.com
* http://www.q-tech.de
* http://www.hpn.de
* http://www.fallert.com/index2.html
* http://www.wunderlich.de/
* http://www.rabenbauer.de/
Not to forget the neat gadgets CC and Luftmeister in California used to offer! -

My main usage is commuting, a mere 30-50km one-way; traffic jam, highway mainly. Speed limits 50, 70, 90 and 110km/h.
Using 33/11 finaldrive and HPN 5th (+5%), and 1st (-6%).
All weathers - none to bad to drive; if too chilly I switch to my Winter-bike with studded tires and skiis.

How would you optimize the engine ?
Drive Safely,

Last edited by dc lindberg; 7 Oct 2008 at 07:41.
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Old 2 Oct 2008
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The engine should not need over hauling at this mileage.
Just do a compression test and fix anything it shows.
For tuning, just do a major service, and include new needles and needle jets. Check teh diaphragms carefully, renew -BOTH- if in any doubt. ( otherwise you will have synchronisation/vibration issues)

given that you want to fix your oil eaks, and will be removing the heads anyway. Check the condition of the valves and seats, replace teh valve springs anyway. Also check the valve guides for wear.
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Old 3 Oct 2008
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I agree with Oldbmws tips, but for riding in Sweden I would suggest some heated grips.

The R100RT engine in original state is well suited for commuting and should last for a long time.

But if you are looking for something special, then the list can be endless. I’m interested I this one: Motoren-Israel - Silent-Hektik PowerBlock Zündkit 121878
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Old 4 Oct 2008
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Posts: 316
Thanks for the feed-back -
I would really like to have a fully electronic ignition, and it could be done, but... I need a machin-shop and some skilled support/help...:
A bit tricky to install a Silent Hektik, Omega Ignition or similar contraption with my "power-plant"... -

I have tested:
- high compression.
- high-flow valves
- larger valves than stock
- dual plugging
- throttle/slide carbs

What I think I will do is to raise the compression to 10.5:1 or there about. I will use high-flow inletvalves, maybe I will stick to 44mm or I might use 46mm BMW high-flow if I just could find-out which straight 6 it was that had them... 524 ?...
If I go up on inlet I will have to go down on exhaust... this is a tricky one. It should be ok with stock 38mm exhaust, but BMW did put in 40mm exhaust on the 1000cc... why?... better cooling ?...

I have a set of Venolia 10.5:1 pistons. I could use them, or I could shorten the barrels. Last time I lowered the heads - but that caused way too much extra work to fix the combustion chamber.

I have used dell'ortos PHM 40. Those are a little bit too larger for lower revs, but at cruzing speed on the freeways they are really nice - I will use them on this RT.

I have tested VW valvstem caps - that goes on all my valves ever since! -

There are two things I really wonder about:
* if I opt to use BMW pistons, should I use stock or light-weight Siebenrocks ?
* should I stay with stock 308' cam or change to assymetirc 320' or 324' ?

My aim is to have a powerfull cruizer with that little extra that we all want from time to time, but not trading off too much of the Beemers reliability.
Since we have high octane gas/petrol available all over, a rase in compression is not problem, especially if combined with dual-plugging.

Of cause have I though about compressor- and turbo-charging options since these gives a lot of power - but both options have too heavy down-sides on a commutor vehicle -

As for the strickt overhaul I will change the conrod bearings, probably new pistonrings, new valves, new valve-guides, dual-plugging, new cam-chain and follower, install an oil-pan spacer ring and an oil-cooler and a better generator (see links above) a Bosch 90A with internal fan (fits just inside the fairing) - all this due to the leaking pushrod-tubes grommets and the leaking cam-cover gasker; just as well to get all this done when the engine has been opened this much -

What's your views on this ?
Drive Safely,
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Old 4 Oct 2008
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Why dont you just run it on nitro when you need the extra oomph? That way you at least will have a tractable ride for when yo need to go somewhere.
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