If you will go back a few years the 5 year crank guarantee was not 5 years..
The old A&M engines which Brison bought/obtained/copied had the world's worst cranks..Brison HAD to guarantee their cranks in order to sell engines..If there had been no A&M crank problems there would have been no mention of a guarantee, would there? Does any other manufacturer have a guarantee on their crank in their advertising ?
.Hence the guarantee...They got it right, no crank problems...
The timing on the syncro spark depends on the rpm of the crank, there is no specific "curve"..
the timing is fixed at 28 degrees static..When the engine is first flipped the timing is retarded to about 2 degrees, then the timing is advanced according to the rpm change of the crank, so the tail is wagging the dog...If the low speed needle is set too rich the crank doesn't accelerate fast enough, the the timing lags, so the engine bogs a little until the rpm comes up..In practice the timing advances fast enough so that there is no lag...The syncro spark circuit can be set to full advance at either 4000 or 6000 rpm, and total advance can be either 20 or 26 degrees..Default unless otherwise set is 26 degrees and 4000 rpm, best for most engines...
AND the Brison 2.4 IS all a person could ask for in that size range