April 7, 20188 yr This was an air cooled Rotax, had the squish altered. Check timing also (electronic should be ok) also carburation.
April 7, 20188 yr You would have thought that the engine designers had already allowed for squish band design, but probably not for the lousy fuel that’s now being served up everywhere. Using extra base gaskets will raise all the ports and possibly have an affect upon performance. Not knocking (sorry about that) anyone’s suggested cures but is it a cure or just moving the problem. Removing material from the combustion chamber will lower compression and affect performance, even though the pinking might have gone. Pinking is really detonation and the cause is usually something causing the fuel and air mix to start burning before the correct ignition point. Potentially petrol/oil mix not as the manufacturer specified could create the fault. Carbon on the piston crown becoming to hot and glowing will cause the fault and air leaking in to the combustion process via crankcase/shaft seals. Exhaust systems leaking together with poor back pressure will allow fuel/air mix to escape leaning the mixture and creating ‘pinking’ or more correctly detonation.?? Edited April 7, 20188 yr by section swept
April 7, 20188 yr 3 hours ago, section swept said: You would have thought that the engine designers had already allowed for squish band design, but probably not for the lousy fuel that’s now being served up everywhere. Using extra base gaskets will raise all the ports and possibly have an affect upon performance. Not knocking (sorry about that) anyone’s suggested cures but is it a cure or just moving the problem. Removing material from the combustion chamber will lower compression and affect performance, even though the pinking might have gone. Pinking is really detonation and the cause is usually something causing the fuel and air mix to start burning before the correct ignition point. Potentially petrol/oil mix not as the manufacturer specified could create the fault. Carbon on the piston crown becoming to hot and glowing will cause the fault and air leaking in to the combustion process via crankcase/shaft seals. Exhaust systems leaking together with poor back pressure will allow fuel/air mix to escape leaning the mixture and creating ‘pinking’ or more correctly detonation.?? Another counter synopsis !!!!
April 7, 20188 yr Octane booster is a bandage for a broken leg IMO,section swept supplied a good technical response to this question,carbon build up is a very likely cause,I would suggest checking the fuel system for a lean condition,checking the plug heat range and however you can establish ignition system/timing is correct. Good luck.
April 8, 20188 yr Author Increase base gasket size cleaned all carbon from head piston and exhaust carb is jetted to spec in manual running out of things to do
April 8, 20188 yr 20 hours ago, Andyb1987 said: Increase base gasket size cleaned all carbon from head piston and exhaust carb is jetted to spec in manual running out of things to do Check crankshaft oil seals, timing, fuel mix ratio, buy your fuel from somewhere else as a test. Check for piston/cylinder bore wear. Experiment with altering ignition timing a couple of degrees retarded. Has this bike always pinked or started to do it recently? I assume that it is actually the engine pinking and not some other mechanical wear or fault misleading you, like chain rattling on frame etc.?
April 9, 20188 yr Author Ok thank you for your input I wouldn't know how ir where to start to get a head spacer made I did how ever put an additional base gasket of 1mm on the bike to no avail.
April 10, 20188 yr I have seen pinging on a lean running bike fixed with a combination of premium fuel and re-jetting... Might not be the issue but worked on at lest one bike. Good luck. Edited April 10, 20188 yr by jonnyc21
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