Jack Atkins wrote:
> I recently bought a 1993 GG 320. I love the bike but there's always room for
> improvement, right ? How much did you retard the timing ? Does retarding
> cause firing farther before TDC or nearer to TDC (retarding and advancing
> always confuses me) ?

Retarding is making the spark fire later in the 2 (or 4) stroke cycle. Imagine the piston moving up on the firing stroke - most engines fire the spark a few degrees before top dead centre (TDC). Retarding makes the spark fire closer to TDC or even past TDC on the way back down. Near as I can figure out the relatively slow speed of the flame front is what requires firing in advance of TDC. The idea being to get the best gas expansion as the piston begins its downward stroke. Too much advance and a significent amount of the gas expansion occurs before TDC causing knocking and even disintegration of the piston crown. A fairly common thing racing back in the old days.

Your 320 may well be better for you with the ignition retarded. It's not difficult but you will need a puller to get the ignition flywheel off. After getting the flywheel off scribe a line across the movable ignition coil carrier and its backing plate (there may be a couple of marks done at the factory - there is on my '98). This is so you can go back to the old setting.

To retard the ignition move the plate anticlockwise (the same direction as engine rotation). Try 3/16 of an inch or so. One thing you will notice is that it will be easier to kick over with it retarded.

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Billy d
billyd "at" direct.ca
http://mypage.direct.ca/b/billyd