I don't have a dial gauge, and I saw the Deet method of using a straw and clothes pin. However, I just found the chisel mark and a timing tab. Are the points supposed to just start opening when those two align?

The bike is running pretty well, but I still get a little bit of pinging or knocking occasionally. I'm running 91 octane in it, and I've been thinking about getting a octane additive, but maybe the timing just needs to be dialed in better?

 Also, if I put a little bit of white chalk or something in that chisel mark, could I use a timing light to see if it's timed correctly? I remember doing that back in the old days, when I could rotate the distributor one way or another to zero it in. However with this bike all I can do is just keep adjusting the point gap.

 

 

Best practice is to verify tab and mark align at correct timing first.  Other than that a strobe timing light and those marks could be used to get you a lot closer than guessing. 

Thank you for the reply Mark, but at this point I don't know how to verify if they align at the correct time. It kind of seems like they align after TDC by the feel of turning the flywheel counterclockwise. I thought I had an old timing light around here, but I must have gotten rid of it.

At this point I have just been guessing on timing, just adjusting the gap. By closing it down from about .015 to .013 seemed to be running much better with less knock or pinging, but it still has a bit when I back off the throttle. It does not seem to knock or ping when I'm accelerating.

EDIT: I used a hot glue stick into one of the spark plug holes with a piece of masking tape around it. I put two marks about 2 mm apart. When I lay down and sight along the top mark, turn the flywheel counterclockwise until the two marks align, then go to top dead center it does move almost exactly 2 mm. So it looks like those two marks are at about 2 mm BTDC..

Somewhere there you said you feel the marks align after tdc so just wondering if you're getting your lefty & righty confused. The only way that could happen is if the crank key was broken & flywheel slipped. But probably not that if she's running pretty good, 1.8mm btdc & points 'just' moving 'then'. I have strobed mine & that's all good but can cause a worry also as can jump around a bit i guess due to points pivot slight wear or minute main bearing play. I used to lose sleep over it haha.

My thought is that it's likely not "pinging" when backing off the throttle...  backing off cause less load (obvious) and a momentary surge of "richness" (not so obvious).  Both conditions are likely to reduce "pinging". not create it. 

I believe, and it's just my belief, that the "pinging" sound sometimes heard on a two stroke might simply be unburned fuel igniting in the exhaust port/head pipe of the exhaust after conditions in the combustion chamber dump unburned mixture into the port. 

RT325, the reason I thought it might be after top dead center was just the reaction of the magnets in the flywheel. I should have known better because I had one of the spark plugs out, so it wouldn't be compressing anyway. Once I used the hot glue stick I'm absolutely sure that mark indicates 2 mm before top dead center  I spent a while trying to use a DMM, but it didn't work as expected. So I eventually got a big magnifying glass, and put it in a small portable vice so I could work hands-free. Then I stuck the handle of a channellock pliers between the flywheel and the case, to freeze the flywheel just a hair before the mark. Then I carefully opened the points, then slowly moved them until they just touched. Using bright lights and that big magnifying glass it was pretty easy to see. Then I checked it over and over, back and forth, and it just starts moving right when it hits the mark. I went for a ride and it's running the best that it has so far. Mark, I think you might be right about what's happening, it's not pinging, it's just what a two-stroke does. Again, on acceleration it doesn't happen, and that's where I think it would do damage if it was occurring. So I'm going to call that good for now. By the way, a couple pillows really helped so I could lay down and rest my head while I worked :0) 
   

Most DMMs suck.  Try a simple test light


(If you "eyeballed" the points opening, you're likely advanced a few degrees)

Sounds like you've got it sussed with some clever ideas. If its not running like it should shall we guess at another cause. Dare i mention exhaust--no i won't, not yet untill we've heard a video of how it performs acelerating hard to revs then cruising not necessarily at great speed. I just run mine on 91 octane unleaded. But our 91 might be calculated using a different method in NZ than in the US. Actualy i've got nothing to base that comment on.

I understand that eyeballing it isn't the best way, but this magnifying glass is pretty powerful, It's like an "Inspector Clouseau" magnifying glass. :0)

I was mainly just watching for any movement of the arm, and it's completely still until it hits the mark. I checked the max gap after I was done, and now it's about .012

If there is a way I could use the test light just to verify where it's at, that'd be great. I'm just not sure how to do it on this bike.

Here's about a four and a half minute test ride, I think it's running pretty good now. I took it down to Pacific Coast Highway for about a mile, then back up across the wetlands, and a huge white heron flew right over my head. At wide open throttle on PCH with no wind, it'll do just a hair over 60 mph with the 17 tooth front sprocket.