ATC 110 - idles, won't rev

[WFOWS6_IL]

I'm new to the site and looking for help. I bought a VERY nice looking 83 ATC 110, but of course it has issues. :)

The bike idles great, but won't rev out.

Here's what I've diagnosed so far.
- Compression: 100 psi
- brand new carb...same issue with old carb.
- new air filter
- no intake leaks...sprayed everything with starting fluid and no RPM increase whatsoever.
- exhaust is not plugged
- fuel flows well from gas tank and has new gas
- new plug

Here's some observations:
- If I turn the choke on, the bike will rev great for about 5 seconds and then will bog
- Taking the air box lid off and/or the air filter off doesn't make a change in the way it revs.
- Tried adjusting the needle up and down, but no changes
- Adjusted air screw, but still bogs. Did affect idle like it's supposed to though.
- With air filter off...I can block carb inlet with my hand completely and it will do the same thing as if I use the choke...revs for about 5 seconds and falls on it's face.
- It doesn't sound like the valves are loose and don't hear any timing chain slap.


I'm going to check the valves and timing marks later this evening, but was curious if there was a common problem with these. This might just be a compression problem, which I don't mind rebuilding the top end. Going to also perform a leak down test later this week.

Also, I was researching and some sites said people checked timing with a timing light? Wasn't certain on that cause I've only used timing marks. Thought that was interesting since it's CDI I believe.

Any help or suggestions is appreciated!