I now have two big lumps on my workbench…
One shiny (and now blast-media free) 1976 R90S crankcase
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One crank with rods, Camshaft, timing sprockets etc in a 1980 R100RS crankcase (PO thought engine milage around 35K, 4K miles ago)
Alongside them are the R90S barrels, pistons, heads, started motor and a charging system.
These will form the basis of my new motor, but I need to decide on direction for my engine (and how to spend limited funds).
The chassis will be going back to fairly standard R90S, (perhaps different rear shocks and fork springs) but I'm thinking while the engine is out I should replace all the consumables that are normally difficult to access, replace any thing badly worn and make some sensible upgrades.
The fairly certain plan is:
1 - The crank and rods are going into the late R90S cases (and part numbers would be the same anyway according to the MaxBMW fiches) with new bearings.
2- The R90S heads and starter motor will be used.
3 - I have new R90S front cover and rocker covers to go on.
4 - I still need a late R90S style timing cover (Oct 75 to 78 I think) to look right from the outside (but I don't know from where).
5 - The heavy flywheel off the RS engine will be used.
6 - Boyer microdigital ignition and Boyer coils (if they can survive a bonnie!).
7 - It will get (but I don't know from where) R90S style starter cover and RHS air box (I have a LHS one).
My Motobins/Motorworks shopping lists so far have:
New clutch friction plate (while I'm in there…)
New clutch spring diaphragm (while I'm in there…)
New unstretched flywheel, conrod and clutch bolts
New woodruff keys
New bearings/shells for crank/rods
New oil pressure spring
New Oil pressure switch
New gaskets and seals
New timing chain kit (but…. which one?)
There are two areas of dilemma:
1 - Camshaft/timing chain/tacho drive/timing sprockets type (79 type, which I have, or 76 spec which I don't and will need many bits)
2 - Siebenrock high comp 1000cc kit (while I'm in there) which would let me keep the R90S bits wrapped up.
On Camshaft type: I have the orig white numbers R90S speedo, but a later electronic tacho is fitted as the RS engine had no mechanical tacho drive. While the perfect option is to get the correct tacho and correct 76 camshaft I'll need at least:
-76/77 style 308 degree camshaft with tacho drive.
-double row cam sprocket
-Double row crank sprocket
-tacho drive bits in the timing case
-Tacho cable
-tacho
Which at new prices will be a small fortune and realistically only have the advantage of being able to use an original mechanical tacho. However, I don't know if I can use the later 79 Camshaft with a correct looking timing cover and still use the early points replacement boyer (or bean tine points replacement one)?
On the Siebenrock Nikasil Barrel/new 9.5:1 Pistons kit, the consensus of my searches is that it make a useful performance benefit on an R80, but would it do so against a standard R90S barrel/piston combo?
One shiny (and now blast-media free) 1976 R90S crankcase
<iframe src="https://www.flickr.com/photos/106793933@N05/13745029605/in/photostream/player/" width="500" height="281" frameborder="0" allowfullscreen webkitallowfullscreen mozallowfullscreen oallowfullscreen msallowfullscreen></iframe>
One crank with rods, Camshaft, timing sprockets etc in a 1980 R100RS crankcase (PO thought engine milage around 35K, 4K miles ago)
Alongside them are the R90S barrels, pistons, heads, started motor and a charging system.
These will form the basis of my new motor, but I need to decide on direction for my engine (and how to spend limited funds).
The chassis will be going back to fairly standard R90S, (perhaps different rear shocks and fork springs) but I'm thinking while the engine is out I should replace all the consumables that are normally difficult to access, replace any thing badly worn and make some sensible upgrades.
The fairly certain plan is:
1 - The crank and rods are going into the late R90S cases (and part numbers would be the same anyway according to the MaxBMW fiches) with new bearings.
2- The R90S heads and starter motor will be used.
3 - I have new R90S front cover and rocker covers to go on.
4 - I still need a late R90S style timing cover (Oct 75 to 78 I think) to look right from the outside (but I don't know from where).
5 - The heavy flywheel off the RS engine will be used.
6 - Boyer microdigital ignition and Boyer coils (if they can survive a bonnie!).
7 - It will get (but I don't know from where) R90S style starter cover and RHS air box (I have a LHS one).
My Motobins/Motorworks shopping lists so far have:
New clutch friction plate (while I'm in there…)
New clutch spring diaphragm (while I'm in there…)
New unstretched flywheel, conrod and clutch bolts
New woodruff keys
New bearings/shells for crank/rods
New oil pressure spring
New Oil pressure switch
New gaskets and seals
New timing chain kit (but…. which one?)
There are two areas of dilemma:
1 - Camshaft/timing chain/tacho drive/timing sprockets type (79 type, which I have, or 76 spec which I don't and will need many bits)
2 - Siebenrock high comp 1000cc kit (while I'm in there) which would let me keep the R90S bits wrapped up.
On Camshaft type: I have the orig white numbers R90S speedo, but a later electronic tacho is fitted as the RS engine had no mechanical tacho drive. While the perfect option is to get the correct tacho and correct 76 camshaft I'll need at least:
-76/77 style 308 degree camshaft with tacho drive.
-double row cam sprocket
-Double row crank sprocket
-tacho drive bits in the timing case
-Tacho cable
-tacho
Which at new prices will be a small fortune and realistically only have the advantage of being able to use an original mechanical tacho. However, I don't know if I can use the later 79 Camshaft with a correct looking timing cover and still use the early points replacement boyer (or bean tine points replacement one)?
On the Siebenrock Nikasil Barrel/new 9.5:1 Pistons kit, the consensus of my searches is that it make a useful performance benefit on an R80, but would it do so against a standard R90S barrel/piston combo?
