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Ignition Timing

BoyToys

Well-known member
Super Patron
Hey kids, thought I would create a new post to differentiate from my most recent one on Solex jetting and my issue with poor bottom end performance.Zspryte got me thinking about timing and I had to dig back to earlier posts I'd made to refresh my memory...being old you know!

Back in January of '24, my first actual drive and plowing action at home, plowing my driveway. It ran fine, none of the bogging down off idle when feeding throttle.

Then around mid March '24 I started tuning the basics and noticed the timing was at 20°BTDC (spec is for 6°BTDC, vacuum hose disconnected at idle), so of course I reset timing to spec and adjusted idle sped and mix screw accordingly. Idled fine sitting in the driveway but I never took it for a spin down the road. It did have a substantial bog/cough if I punched the throttle too hard, which was not an issue during my earlier snow plowing a couple months prior and before I retarded the timing.

All this past winter I had to keep the rpms up in granny gears or she would bog down. I just lived with it....but it's not right!

Blah blah blah. Why was there so much (20°) timing initially from the previous owner? My vacuum advance canister seems functional....if I manually put vacuum to it, the timing advances. So the 20° I had with hose disconnected was all baseline at the distributor and theoretically would advance even more when on throttle and pulling vacuum from the carburetor port.

Next trip up to the cabin I'll be adding some advance to see what that does...not as much as 20° but more than the 6° I'm currently at. And I'll check the actual vacuum at the carb port.
More to come...comments always welcome.
 
All ears.

I do know what a bitch it is to see the timing marks. And remeber that spinny thing you timing off is the cam.
Thecrank doesnt come out of the motor on that end.
 
Yeah, you educated me on that 'spinny thing' back when I was adjusting my valves. Weird damn motors these, with the cam where the crank is supposed to be.
So, here's the deal. Spent yesterday and night at my cabin, with vacuum gauge and timing light in hand. Removed the right side of the dog house, taped the timing light trigger down, and stuffed said light beneath the alternator and secured with a bungie cord to keep it pointed at the timing marks. I have about a 1 inch gap behind the radiator that I can peer down from the top and see the timing marks.
Timing was at around TDC. Why I don't know, perhaps confusion on my part or too many Rainiers when I last set it. Did a little research (to find a picture on a Saab site) and I believe the farthest mark to the left is 3°ATDC, then TDC followed by 3° BTDC, 6°, 9°. I either set it wrong or didn't have the dizzy cinched down tight enough.
So crap, a twist of the dizzy up to about 12° advance made a boat load of difference. I have good ported vacuum off the carb when opening the throttle, and hooked up my MightyVac to the advance canister - pulled a vacuum - and the timing advanced as it should. Took a short spin down the dirt road, much improved. Now just need some snow to see how she'll do under load.
Happy camper so far. Actually able to run in all three tranny gears with the C4 in 2nd. Could not have done that before.
 
Great news. I have a low hour imp here and its motor is very fresh. That imp can pull all gears in all ranges. It moves very handily and is videoed drifting in my gravel drive during one of the summer clowders. That was likely old style induced behavior but yeah that little motor can make some power
 
Great news. I have a low hour imp here and its motor is very fresh. That imp can pull all gears in all ranges. It moves very handily and is videoed drifting in my gravel drive during one of the summer clowders. That was likely old style induced behavior but yeah that little motor can make some power
If going solely by the on-board hour meter, my motor has almost 2900 hours on it. I've done everything a guy can do tuneup wise but have never checked the compression (probably because I don't want to know).

Your Imp can pull all gears in all ranges: Does that mean you can take off from a dead stop in top - what I would call 12th - gear? Or maybe better put, what's the highest gear that you can pull from a dead stop? It seems shifting on the fly would be necessary at some point. I've never had mine out of 2nd in the back/3rd up front...and only now that I've fixed the timing running down a hard packed dirt road that I really don't want to be hauling ass on.
 
Given a few things :
So 3rd in the front is direct drive.

A model sprytes only have the oc4 and its ranges (in the rear). The engine is direct drive.

My imp operation is typically 2nd front and what ever range is needed in rear. I find this way i can go down to 1st front or up to 3rd front to find the correct ratio for whatever task was at hand.

But yes on a flat gravel driveway i can get going in fourth range. I ride clutch a bit in 2nd or make really quick 1-2-3 shifts
60 inches of fluffy snow? Forget those shenanigans range 2 gear 2 and let it wallow
 
Thanks buddy, that's helps me understand capabilities. I currently find that range 2 is probably where I'll leave it and select whatever gear is appropriate up front. Was not the case last winter when running with 0.0 ° advance (stupid me). I had to be in range 1 and usually 1st gear until I got going and could grab 2nd on the fly, and this on a measly couple feet of not-so-fluffy snow.
Looking forward to this coming winter.
 
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