Hi guys, I have this 72 CT2. Cleanup work continues and making lots of headway. I just can't seem to figure out why it won't start. Pops with choke on and occasionally with it off but that's it

Carb - carb dip and ultrasonic clean twice, ran wire though passages. Air compressor seized so couldn't blow through but did with Carb cleaning spray. starter jet in bowl is clear

Has spark, it's a smaller spark than I'm used to but is regular
Pulled flywheel to check woodruff key which is in place. I don't have a timing gauge so rough set to crack open just before TDC.

Air cleaner is off. Tried it with baffle and silencer out and with pipe completely off

With carb off  lightly touched reeds to see if they're stuck. they seem to open

thumb over spark plug hole. It's pushing my thumb off but will get a compression tester this weekend.
Speedo says it has 1660 miles but who knows if that is accurate. 

What would you do next? I'm stumped.


 

Perhaps, now is a time to utilize an RT325 method... Put an impact wrench on the flywheel nut... pop the air filter hose off for a straight shot into the carb... Now I'm not sure what to spray into the carb as the wrench spins it CC... WD40?...  NO STARTING fluid...  
If that gets and keeps it running.. timing is close and then I'd suspect fuel delivery.. Realize, this is a left handed skand-ahoovian txt'ing..
Sneezles61

I may try that. But will try a few other things first. Seems like when I was a kid these bikes just ran with very little tinkering.  Then again they were Less than a decade old then. 

Yes my method [which was a reverse drill not an impact which would undo the nut] & it worked great & takes all the effort out of it. But that was on an LS3-100 in the vid & also did an RX125. 175 might resist too much for the drill--but i'd try it!!. Just cut a short piece off a 3/8 drive extension with a socket on the end. Think i had a deep socket by the looks, but changed to a short socket for more control.
If you have a regular spark & its happening a little before top [1.8-2mm by eye in your case] then is it just flooded & needs full song & a spin. First thought was flywheel key but you've covered that.

Yeah that was first startup after 20 years sitting outside & rusting away. Motor kept tightening to a complete stop, like seizing but not & would free immediately for another 10 second run.Was carbon blowby way down past the rings leaving zero clearance so a short run expanded it to go tight & Halt. Never had that happen before. Was a little rocket after a piston clean up.

I could see some minor carbon streaking on the piston through the exhaust Pipe manifold and some bubbling as the piston compressed on the upstroke. I was in ”screw these bikes” mode last night then got over that by morning. Plan is to pull the known good coil off my CT3 to test then replace points and condenser, drain oil and check wet side crank seal, go through carb for the fourth time. If all that fails and if the compression is low I’ll do a top end. I have a spray bottle with premixed fuel which has been sprayed into open carb with throttle open to no effect. I’m thinking the crank seal is the culprit 

I bought a DT100 used and not running from the original owner about 25 years ago. Owner sold it because he could no longer get it to start. I tried and tried with the same symptoms as yours. I took the head off and found a crack in the top of the piston. Replaced piston and ran great. 

Thanks PC! I’ll definitely look for that as this unfolds. Appreciate the advice. The PO is deceased but I’ve no doubt the bike had been sitting for many years before his family sold it. Now I know why it was such a steal. 

I'd clean the points and try a new spark plug or two because that's fast, easy and cheap to do.

Yes could be the right side crank seal as can be forced out when the bikes been parked for years & gets a belly full of twostroke oil from gravity feeding through the pump & i didn't think of that. Could be left side, but right side seems more common for some reason.

I would do what my big brother used to make me do when one of our 2 stroke bikes didn’t want to start even after checking everything you checked, we were around 10 & 13 years old at the time. And that was him putting the bike in second gear and making me push him while he popped the clutch and bounced hard once on the seat so the rear tire would not skid to a stop and he would hold the throttle open and after about 2 house lengths of pushing while in second gear it would roar to life and off he went, the rest of the day it would always start in a few kicks, we just knew the bike had been flooded with fuel and thought that was normal starting procedures for these old 2 strokes.