090 dwell, point gap

[mackie]

what is the proper dwell angle and ignition point gap for an 090?

 

[artie__bc]

Point gap 0.35 - 0.45 mm, no spec in my book for dwell. Timing is set by dial indicator in spark plug hole at 2.9 - 3.1 mm BTC.

 

[mackie]

thanks for the info. i have a dial indicator so that should be no problem, but i dont know what position to set the ignition backing plate when the piston = 3 mm btdc

 

[artie__bc]

That's when the points just start to open, I believe. I'll check my book tonight to confirm it. Another thing, check your flywheel, there should be a timing mark - you have to take the fan off to see it - that should line up with a mark on the housing at 3mm + or - a bit. The Stihl book shows a test light of some sort hooked into the ignition system, then ou line up the timing marks & adjust the coil on its screws till light indicates timing is correct. I'm at the same place as you with my 090s, and I'm going to try using a coninuity tester or something to check my timing. I'll let you know if it works.

 

[mackie]

thanks alot, artie. that makes sense, the test light would come on when the capacitor releases the charge thru the points, i think. up till now i've adjusted the point gap with a match book and guessed on the timing, but i want to get it right this time.

 

[mackie]

update

i didnt have a test light so i used my finger on the plug and rotated the flywheel by hand. watch the small dial on the dial indicator because you have to spin the flywheel fast enough to get a spark. its not the most accurate way, but i think i'm real close to .12 inches btdc (3mm) when i feel the spark. seems to run ok, gonna mill some few spruce today, see how it goes.