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BMW K100 with single 32mm Bing carburettor. Sun Oct 09, 2016 11:43 am
David Nimrod
Silver member
Link to Post on UKGSER.
NOT ME - JUST THOUGHT IT MAY BE OF INTEREST
'After two years of riding my K100 turbo, problems started to occur, namely due to more boost and harder use!
I discovered 2 spark plugs were wet and black, further investigation revealed the top rings on 2 pistons had cracked.
I needed to fit 4 new forged pistons with lower compression ratios and better quality rings but this would inevitably
mean the bike got used harder, already it was proving far to easy to exceed the speed limits, a few occasions had
seen 250kph on the speedometer, in France that's lose your licence and your bike time.
I decided to remove the turbo and, because I'd disposed of the injection system, to convert the bike to carbs.
Half the reason was to keep everything really simple, the other half because it was an interesting project.
Four carbs would be the best set-up, but to keep it really simple, I decided to use a single carb and a log-type inlet
manifold.
Yes, getting an even mixture balance between the cylinders would be harder plus I'd lose a few bhp at the top-end,
but this is a road bike not for competition use.
I decided to use a 32mm Bing, purely because I had a spare one along with a lot of Bing jets, etc.
There is no fuel pump, just an inline fuel tap.
I ended up having to make three inlet manifolds to find an acceptable diameter for the main 'log', plus on the final
version, vary the inside diameters of the stubs for cylinders 1 and 4 to balance the mixture distribution between the
inner and outer cylinders.
Finally, everything is finished and working really well. The bike starts instantly hot or cold and acceleration is
seamless. It's returning a constant 46-48mpg per tankful which is acceptable.
I've left the 'soft' cams fitted to the turbo engine in place, with those, (it's the 16V engine), it will drop to 25mph in
5th gear and accelerate cleanly without changing down, the engine is incredibly torquey.
The acceleration at higher rpm is still really good, I don't know how it would compare to an injected system with
'soft' cams as I've never seen one.
It's been an interesting project and I'm pleased with the outcome'
NOT ME - JUST THOUGHT IT MAY BE OF INTEREST
'After two years of riding my K100 turbo, problems started to occur, namely due to more boost and harder use!
I discovered 2 spark plugs were wet and black, further investigation revealed the top rings on 2 pistons had cracked.
I needed to fit 4 new forged pistons with lower compression ratios and better quality rings but this would inevitably
mean the bike got used harder, already it was proving far to easy to exceed the speed limits, a few occasions had
seen 250kph on the speedometer, in France that's lose your licence and your bike time.
I decided to remove the turbo and, because I'd disposed of the injection system, to convert the bike to carbs.
Half the reason was to keep everything really simple, the other half because it was an interesting project.
Four carbs would be the best set-up, but to keep it really simple, I decided to use a single carb and a log-type inlet
manifold.
Yes, getting an even mixture balance between the cylinders would be harder plus I'd lose a few bhp at the top-end,
but this is a road bike not for competition use.
I decided to use a 32mm Bing, purely because I had a spare one along with a lot of Bing jets, etc.
There is no fuel pump, just an inline fuel tap.
I ended up having to make three inlet manifolds to find an acceptable diameter for the main 'log', plus on the final
version, vary the inside diameters of the stubs for cylinders 1 and 4 to balance the mixture distribution between the
inner and outer cylinders.
Finally, everything is finished and working really well. The bike starts instantly hot or cold and acceleration is
seamless. It's returning a constant 46-48mpg per tankful which is acceptable.
I've left the 'soft' cams fitted to the turbo engine in place, with those, (it's the 16V engine), it will drop to 25mph in
5th gear and accelerate cleanly without changing down, the engine is incredibly torquey.
The acceleration at higher rpm is still really good, I don't know how it would compare to an injected system with
'soft' cams as I've never seen one.
It's been an interesting project and I'm pleased with the outcome'
Last edited by David Nimrod on Sun Oct 09, 2016 11:56 am; edited 1 time in total
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