This is a 954cc Ruggerini twin cylinder (23hp @3600 rpm) £250-£300 second hand, and gives my bike 136mpg. It revs to 3700rpm, but by fitting a turbo it will run at 4200 rpm (not that I have done it).

There was a little confusion about revs and over revving of this engine right up to the point where the engine had finished running in, the bike would only reach 73mph. I was not happy at all, thinking oh no, the bike will now have to be over revved to achieve a decent speed. But the confusion was cleared up when I fitted a Tiny Tach rev counter, she was revving to 3000rpm and not the 3600rpm as the seller of this engine stated. Seeing plenty of adjustment in the throttle stops I made the assumption that it could rev to 4200rpm if the stops were opened fully. My assumption was based on Dave Cummins turbo charged version of this engine reaching 4200rpm.

After opening the throttle stops (3600rpm), the top end is vastly improved and 90mph looks very likely. But this is achieved only by changing the gear box ratios (overdrive) and drive sprockets to suit.  I can't emphasize enough how important spot on gearing is, it really makes a world of difference.

The fuel curve (best fuel economy) is 2300rpm and with the current gearing the bike reaches this at 58mph.

Time to inspect the engine condition. Click on a pic to enlarge.

A spray down with wd40 cleared the loose dirt and crud and hence stopped contamination of the internals, and what was left stayed stuck until wiped with a cloth later on.

Removal of the rocker boxes gave better access to the banjo fixings of the pipe work on top of the engine.

There are two fuel lines (red / blue) which connect at the bottom of the barrels at the front of the engine, and attach to the injectors to the rear of each cylinder head. Also a black plastic pipe attached to both injectors via banjo bolts (copper washer each side of), this also runs from the front where the fuel goes in. This is the injector fuel / lube run off, and should be returned to the top of the fuel tank or spare tank, as it may contain air bubbles and hence needs to settle before returning to the engine as fuel. And finely a lube oil pipe (blue) that goes from the bottom of the right barrel, up to a clip, and on to two banjo bolts that feed the rockers. Looking at the front of the engine, half way down to the right of the middle picture bellow, we can see an oil pressure switch. This can be used for the oil warning light, or even removed if you don't want to use one.   

Now the cylinder head has been removed we can see the large pistons.

Checking the con rod for play up and down revealed that it was in very good condition, a tight slow roll back and forth. This means the big ends are ok. The main bearings seem ok no up and down movement of the crank shaft, and 1/2 mm end float. Taking a look past the con rod using a pen light, I could see the cam shaft, in perfect condition with no marks on the lobes at all. The cylinders had no signs of wear, still showing honing marks, and only a carbon ring at the top.        

   Replacing the worn rings is very important, not only will power drop off with worn rings, but air will pass down the piston and put a lot of pressure inside the crank air space. What happens now is engine oil will shoot up the engine breather tube, and as this is attached to the air inlet manifold you may not even know you are burning precious engine oil. Darker than usual or blue exhaust fumes when the engine is warm is an indication of this problem. 

I have now finished work on the cylinder heads I can safely say that this is an easy engine to work on. The valves can be taken out and replaced without the use of a valve spring compressor. Using my thumbs to push down the springs, the collets dropped out with some jiggling. The valve seats were in perfect condition and didn't need grinding in, other than using Auto sol polish to take away a few very minor black marks. The cylinder head gaskets are solid copper, so they can be heated cherry red with a blow lamp, this will make them soft and can then be reused. Don't be tempted to leaver them off the head with a knife tip you will just damage the soft alloy, rather use the wide part of a none pointed blade to ease it off bit by bit.

The crankshaft is a 6x6x25 keyway, 1:5  taper.

Compared to a chain, a belt saves energy, returns more mpg and lasts 3 times longer. The pulley lasts about 10 times longer than a sprocket. For pullies and belts: Gates http://www.gates.com/index.cfm Fenner http://www.fptgroup.com/

Click pic to enlarge.

The engine now rebuilt, and yes I did replace the piston rings (£70) as I found a lot of oil crud behind the air intake valves. This could of been from the air filter which had way too much oil in it to work properly.

Ruggerini make an 850cc outboard motor that revs to 4000rpm, it would be interesting to find out how they achieved this and if it is possible to use the parts on the RD211 engine.

Maintenance

Data sheet.

Workshop Manual