New SR500 burnout recorded 13/02/2007
Click here to download the new video of the Yamaha SR500 prototype burnout filmed on the 13/02/2007
Click here to download the Head comparison video - standard head Vs Beare head!
Original SR500 Burnout
Click here to download the video of the Yamaha SR500 prototype.
The object of this burn-out is to demonstrate the amazing low rev torque that the sixstroke engine can produce. The front wheel of the bike is resting against a car bumper bar. I use between a quarter and half throttle in this demonstration. The gearing was unaltered from the standard settings and the carburettor was the standard 35mm Mikuni. The rear tire was a Dunlop ArrowMax 110/90-18 inflated to 20 PSI. I get started in first year and then roll off the throttle to nearly closed and allow the revs to drop to 500 with my full weight on the seat. I then change to second gear with the rear wheel coming to a momentary complete stop when I disengage clutch. The clutch is engaged, and, rather than stalling, the tyre once more commences to spin. Plenty of smoke, no mirrors!
The reasons for this high torque output are:
(1) The reed valves keep gas velocity high at low throttle openings and prevent spitback through the carburettor.
(2) There is a gain in mechanical efficiency because the cylinder head is returning power to the main crank, unlike a conventional fourstroke which suffers parasitic losses from the valve train.
(3) The compression pressure is maintained at low throttle settings because of the stratification of the intake charge keeping the fuel mixture swirling on the outside next to the spark plugs and retaining some exhaust towards the centre. The cranking compression pressure was the same as the standard bike, at 135 PSI.
(4) The effective change in volume of the expansion stroke is actually larger than either two- or four-strokes, which means that more energy is extracted during the combustion process.
Fuel economy at these rev levels is more than 35% better than the 4stroke.
Yes folks you can try this at home! In fact, I challenge anyone with a Yamaha SR500 (or anything other than a steam locomotive) to emulate this feat - I guarantee it will stall.
Note from the Editor:
I've seen the bike perform exactly as stated - quite impossible with any conventional engine. The bike was fitted with a 60's style hotdog muffler, which on a conventional SR500 would be very loud. When he started the bike, the decibel level was very modest, but the note! It sounded like a Manx on racing fuel, so much so that I swore I could smell methanol.
I've also seen the original video, and Malcolm does an excellent Gomer Pyle impression.