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Big Bore Kit to 1070cc - BMW R100 9/1980 on / Siebenrock
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Part #: PistonKit1100

NOTE: This is a special order item. Please allow 1-3 weeks for delivery.

Plug & Play 1070cc Displacement Big Bore Kit.

“Piston capacity can only be replaced by even more piston capacity” – this was the adopted motto during the Siebenrock's-internal development of the Big Bore Kit. The goal of this construction was to enhance the motor characteristics which were already outstanding thanks to the Power and Replacement Kits. They did it and the result for all BMW 1000 cc models from 1981 on-wards was the 1070 cc Big Bore Kit, which turned out to be the ultimate solution for sporty touring riders. After modification, an amazing 80 hp is available at an engine torque of 92Nm.
This performance boost was achieved using 151 millimeter long, high-stability connecting rods which, when weight-optimized and fitted with ARP screws, only put 450 grams on the scales. Quite apart from this, 98 millimeter, weight-optimized pistons are used which only weigh 428 grams including the rings, bolts and clips. Thanks to the well-designed piston form, it is not necessary to adapt the cylinder head to the big bore.
All of the parts required to mount the kit are included except the crankshaft bearings, see CSBearing460 if you need to replace them.
See preview of Siebenrock Expert Opinion on Modification and Installation Instructions here.

Vehicle Manufacturer: BMW
Application: BMW Airhead Models
Make/Model: BMW
R100 up to 84, R100CS, R100RS, R100RT Mono from 87, R100GS 87-96, R100R 91-95
Model Years: 09/1980 - 3/1994
Manufacturer #: 1101100 Siebenrock

Brand :
USD Price $3,200.00
BUY NOW $2,999.00

Quantity in Stock:2

Part #: PISTONKIT1100

Connecting Rod Bearing Shells:
Crank Shaft Bearing Shell Set - BMW Airhead; 11 24 1 258 460 / Glyco (4) [Add $49.99]


The following instructions require mechanical skills and knowledge of the relevant BMW
workshop manuals and installation instructions. Unless otherwise explicitly stipulated,
follow the official the BMW directions, sizes, weights, torsional moments, installation
manuals etc.

1. Disassembly
1.1 Remove cylinder heads and cylinder,
1.2 Remove both pistons and their connecting-rods.
1.3 Examine the condition of the cylinder heads especially valve guides.
1.4 Remove camshaft.

2. Assembly
2.1 install the enclosed camshaft.
Install on one side first and when complete, continue on the other side. Follow the BMW moments /torque /measures and all BMW installation requirements. Use only the enclosed SPECIAL 12-cornered 3/8" NUT for installing the ARP bolts into the connecting rods.
The connecting rod ARP bolts have to be "elongated". This can be achieved by a special device to 0.0054 to 0.0058 inches or via "multiple tighten down" and "multiple loosening" them as described below.
The thread and the surface under the bolts head are greased "from the factory" with molybdenum-grease because the friction during tightening is 20-30% less than when using normal engine oil.

2.2 Install new bearings in the first connecting rod, and insert one conrod in the engine according to BMW installation instructions. Please note the correct mounting location of our asymmetrical conrods.
WARNING: Pay attention to the clearance of the conrods and bolts. If you install the connecting rod the WRONG way, it will touch the crankshafts' balance weights when you turn the crankshaft half a revolution by hand.

2.3 Tighten the conrod-bolts to 36Nm.
2.4 Loosen both conrod-bolts a little.
2.5 Tighten again to 36Nm.
2.6 Loosen the bolts again.
2.7 Tighten the bolts a third and final time to 36Nm. Now the connecting rods bolts are elongated and assembled correctly.

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