GT big block experiance : New GT crank info added

[Rich_T]

Static timing can be anywhere from 19 - 17 in most instances. You could go 16 degrees if you're going up the revs some more but by the time you're doing that you really should be using an advance retard ignition system in anycase

[1469leach]

Thanks,when you say going up the rev range a bit just how much do you mean?Lots of people get confused by this because they buy a cylinder kit which is ported to rev and deliver power at a certain point.They fit said kit set the ting as directed and think that's fine for the range of the kit.There are lots of threads on here at the minute about ignition retard/advance system,can you give your view on when they should be used and the benefits.

Cheers Jeff

[Rich_T]

If you intend your scooter engine to be for everyday use and not high power, for example max revs circa 7.5k rpm-ish with peak circa 6-7k rpm with stock heads relatively low compression and box type exhausts then static timing is fine. Once you increase compression, add pipes and start to dial into performance then you really need to increase the technology in the ignition system. For example, higher spark energy and an ignition that starts easily (retarded stage), advances to give the low to mid range power then backs off (progressively retards again) as the revs increase. What the curves are, how far they advance or retard and when they do it is entirely down to the individual engine and as there are SO many variations between Lambretta engines I wouldn't even hazard a guess as everyone will have their opinion.

[Timbo]

I'dont know if above is correct but it makes perfect sense, wish I'd seen it prior to getting an Augusto a few years back which caused me problems...

[dave wheeler]

yeah totally wreaked my piston using an augusta purely by riding very slow highland roads, heat just built and built

[eden]

thats why I didn't use an advance retard system before a fully programmable one came along. The curves are far too generic and as my engines are for from generic I feared one with set curves wouldn't match my engines characteristics.

Early days yet for my Kheper as its only done 3 or 4 hundred miles but so far its been good and its been fun messing around with different curves to see the difference in how the engine behaves.

[1469leach]

Been using an mtech on mine and have today I've never felt it's quite married up with the jetting especially in the lower to midrange.got a kehper ordered for my malossi 221,hope it works ok on that motor!

Cheers Jeff

[eden]

Little over nighter last weekend
GT was happy 2 up with luggage

[guygrrr]

Eden, what sort of cruising speed are you looking at? What speed/ rpm does yr set up like sitting at?

[eden]

in that video at the end where we are ridding in the rain we are traveling at 70 mph, it will sit at that all day. For rally use that's fast enough cruising speed, its got plenty left on tap when needed.

70 mph is a little under 7k rpm