Btw, does anyone reading this already have a modified or well performing SR250 that wants to try these brackets and report back to me? I'll offer free shipping
Just to re-cap the idea/purpose...
The SR250 was designed and developed to be a commuter bike basically and to function in all environments and in all countries - meaning large variances in fuel octane and quality. For this reason, the stock ignition timing is quite mild - reduced timing helps reduce engine knock with poorer grade fuels and keeps cylinder pressures slightly lower - also reducing the risk of pinging.
Spark timing is very important to get right for a single cylinder (or any engine) and should ignite the fuel at a point BTDC so that the mixture starts burning and peak cylinder pressure is reached at between 10 and 20 degrees ATDC. If you ignite the mixture too early, peak pressure will come too early and will result in power loss. The same goes for igniting the mixture too late - you will miss out on potential power.
Now with modern standard to premium fuels in most developed countries (especially in Europe) the octane rating or RON is around 95-98. In Sweden 95 is everywhere and you cannot get less, and 98 is available quite widely. With higher octane you get a slower more controlled burn of the mixture. So igniting it too late, you miss out on some potential power.
So what is the magic number for initial and peak advance? There isn't one really, there are too many variables. On the SR the timing curve is fixed and controlled form the CDI box - peak advance comes n by 3000rpm. On modern bikes they have several more inputs that control the timing - with the addition of MAP sensors and throttle position as well - all to get spark at the right time for that precise riding moment. So on the SR, there is only one adjustment to be made - the position of the pick up (which is fixed from the factory) and the CDI doesn't care what the throttle is doing or the intake pressure, it just measurers rpm and releases a spark based on that.
I have read and seen performance engines gaining considerable power (5-10%) with optimised ignition timing, so that is why I thought it would be worth trying the brackets. I hope they work two fold - more efficient (cleaner, more complete combustion, leaving less carbon buildup in the engine), and more power - getting peak cylinder pressure earlier. I need to do more testing on its effects with engine head temp and air fuel ratios from the exhaust/O2 sensor, but with all the parts I designed installed, including the brackets, that first test mule made good power, so I am feeling confident. The only risk is the potential too knock but more testing will reveal or negate this issue.
The last reason I am trying them is because many engines, especially these ones that many have had a hard life, will loose compression over time from worn cylinder walls and piston rings, even slightly leaky valves. I am talking a reduction from say 180psi (I doubt its that high but the manual says so...) from the factory to 130 or even 120psi after 20-30 years of use. This means much less cylinder pressure - requiring the mixture to be ignited earlier to make up for it. Btw, if you're getting compression readings below 120psi, its probably time for an inspection and rebuild - 110 is really deaths doorstep.
So I would not recommend these brackets for anyone using less that 95RON, or who is getting compression readings higher than 140psi
Again, any early adopters willing to try???