My grandfather gave me his 1970 CT1B that had been sitting since the eighties I belive. After rebuilding the carburetor I was able to get it up and running with him pretty easily, but in my efforts to make it actually rideable, it seems to be only getting worse. It would fire up and run with a bit of a struggle, and only run with the choke on. It wouldn't idle though, I had to keep it revved up to 3-4 thousand rpm minimum or it would die. After some research I figured it was probably the crank seals, so I dove into the engine to replace them. One of the seals was sitting crooked in its bore, and didn't look fully seated, so I believe that was the problem. While I had the engine out I pulled the jug and piston off to clean all the carbon and junk. Reassembled with new gaskets and such, and now I can't even get it to fire up. It also feels easier to kick then it did before, which makes me think there's a compression related issue. I get around 120 psi with a compression tester when kicking it, (which I know isn't the most accurate but it's something at least). I pulled the head to test that the compression release wasn't leaking, and it was fine. I tried annealing the original gasket and reusing it, but no difference there. To test if it was a fueling issue I sprayed some starting fluid in which didn't really make a difference. I've got it to barely fire a couple times, with or without the ether, but not enough to run. I'm kind of at a loss here. This is my first 2 stroke and I'm wondering of anyone has any ideas. Sorry for the long question, thanks. -Logan

 from the UK.
If you haven't done so yet download the manual from the tech library.
Not clear from your post, do you have a good spark?
Did you replace the carb o-ring (item 7)?
When you cleaned the carb did you remove the pilot jet and clean it and the passageway?
Lever down for choke on.
Sorry if I'm telling you how to suck eggs.
Probably gonna need a bit more detail of what's happening for the forum experts (not me) to help.
All the best
Pete

Welcome. First thought is the crank key fell out when you had the flywheel off--sorry but i had to ask. Without that timing could be anywhere but right. If that's not the issue i've run out of ideas unless its now flooded up & needs a good push or lots of kicking with the throttle open & fuel turned of or even drain the carb via the mainjet on the side. That's providing spark is ok. Getting back to the original very lean running it does sound like the carb is still obstructed in the pilot jet & choke jet. Both are small & choke jet can't be removed but poked & sprayed in both directions as sucks from the bowl--you'll see the hole leading under it. Jet is only about wire brush strand & same with the pilot jet. I guess your seals are still in tight because as belly full of fuel--if flooded--can push the right side seal out, or both sides really just from kicking. 120psi sounds good,. If it feels positive on the kickstart by coming up to compression & feeling it through, any reasonable comp will light it up. You mentioned compression release which isn't common or original on a 175 but doesn't sound like a problem. Can blank it off if you want or fit a plug in the hole. Hope to hear she runs again soon. You're obviously not afraid to get right into it. Flywheel needs to be tight too or they can shear off the crank key when running, more with 250 & 360's heavy flywheel.

Yeah the service manuals have been a big help, I was very glad to find those here. But yes, it does have a good bright, snappy spark, so unless it's timing related I don't think it's an ignition issue.

I rebuilt the carb when I first pulled the bike out from where it sat, but I'm considering going through it again. Some junk from the tank may have got past the filters. And yeah choke lever down. Surprisingly, I did get it to stumble over a bit with the choke off. It's just odd because it worked enough to run before, and now I can't get it to start at all. 

Thanks for the input Pete!

The crank key was pretty tight in its keyway so I didn't touch it. I know it was there when I put the flywheel back on, I had a flashlight in there to make sure the keyways were lined up. I haven't entirely ruled out timing, but I don't think it's the problem. 

I was kicking on it for a while, so it very well could've been flooded. I'll clear it out and try some more later. And yeah the compression release was aftermarket, my grandpa used it like a Jake brake on the trails, but it didn't seem to be leaking.

I'll keep you guys posted, thanks again. 

Yep won't be timing or not whats stopping it anyway. Points gap is how timing is set, but you'd have to be doing something very wrong with points for it 'Not' to run at all, so doubt that. Points just breaking at 1.8mm btdc to be perfect in time--.

As RT says the choke jet in the bottom of the bowl is fixed and tricky to clean as it's so small.
I wonder if it's flooded or the exhaust is blocked.
Might be worth removing the exhaust and giving it a go.
How does the air filter look?
When you went through the carb, did you clean and keep the original jets and as I said before is the o-ring item 7 ok?
 

Update! It's alive! I went through the carburetor again, cleaned it out, new seals and gaskets and such. That may have helped a little but It still wouldn't run. In all that time kicking it over, It still seemed to easy and that was still nagging me. So I got a new set of rings and did a quick hone with some glaze breaking stones to get some cross hatch back in the cylinder. And that did the trick, I got it to fire up and run. I'll come back to it tomorrow but I think I'm seeing the light at the end of the tunnel. 

Great that you have it running better. I would get rid of the compression release. It's not really needed on a 175. One less thing to go wrong.

I finally got to go for my first little test drive of the bike which was fun. One problem though... at one point it randomly decided to rev up to like 8 grand on its own. I hit the kill switch and shut the key off and it just kept running. Pulled the compression release and that killed it, but that was strange, can't say I liked that. Obviously air would have to be getting in somewhere for that right?I finally got to go for my first little test drive of the bike which was fun. One problem though... at one point it randomly decided to rev up to like 8 grand on its own. I hit the kill switch and shut the key off and it just kept running. Pulled the compression release and that killed it, but that was strange, can't say I liked that. Obviously air would have to be getting in somewhere for that right?