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Quote from: Gadge on March 26, 2015, 10:57:31 AMMany years ago I did try fitting a Rev counter to a BIS. It does work but it reads twice as fast because as Keith just pointed out the coil fires twice. So for instance it was ticking over at 750 rpm but showing 1500rpm and when I was on the move It was like I was driving a civic type R doing 8000 rpm down a motorway If that's the case if you buy a universal tachometer and set it to 4 cyl it should read correct
Many years ago I did try fitting a Rev counter to a BIS. It does work but it reads twice as fast because as Keith just pointed out the coil fires twice. So for instance it was ticking over at 750 rpm but showing 1500rpm and when I was on the move It was like I was driving a civic type R doing 8000 rpm down a motorway
Its not that easy to find an aftermarket rev counter for a 2 cylinder engine , so out with a soldering iron to modify one. The unit I used had a switch on the rear for 4, 6, or 8 cylinders. Each switch setting was fed from a resistor, that simply changed in direct value to the number of cylinders. The 4 cylinder value was twice that of the 8 cylinder ( and the 6 being 1.5 times ) , so I used a couple of resistors to make up twice the value of the 4 cylinder to make it work for 2. The value needs to be kept accurate to keep the calibration of the gauge . I have also fitted a motor cycle rev counter (MZ Scorpion 600cc single) that simply had an adjustment on the rear that can be tweeked to work on the twin cylinder engine. It should be possible to use rev counter from Twin cylinder 4 strokes or single cylinder 2 strokes for 1 spark per revolution.