Won't start atc200s

[250rkyle]

I got a 1985 atc 200s it's got good spark its getting gas, timing is correct and I even put some gas in the cylinder and it won't act like it is even trying to fire and I just rebuilt the top end and had the cylinder bored.what could be wrong?

[ATC ADDICTED]

make sure the valves are opening and closing. make sure you tightened the cam gear to the cam.

[kb0nly]

I second that, check compression and the valves.

[250rkyle]

Ok thank you guys

[effort=results]

Triplecheck timing also. Good luck . Love those motors

[KFWA]

I would like to add to the question. I have an 84 200ES that I just bought from a guy who took it as payment for work received, so he knows nothing about it. The bike is pretty jerry rigged as far as wiring goes, but my problem is it will start with starting fluid but won't run past the starting fluid.

I've cleaned the original carb which was pretty nasty, and then ended up putting on a brand new carb - neither of which helped the problem. I can drain the fuel reservoir and have gas run out in a solid flow so I would assume its getting fuel (although I'm not sure). I replaced the spark plug.

As I've read many times, in order to run a bike needs spark, fuel and compression. I guess at this point my last option is compression so my question is - would my 200ES crank up and run (for only a couple of seconds off starter fluid) if it had bad compression - or should I continue focusing on the carb?

[GunsShooting]

After trying to crank it, pull the spark plug and see if it is wet with gas. If not, the fuel isn't getting in there where it should be.

If wet, try a new (or well-cleaned) spark plug. Sometimes that can make a world of difference. Super-clean the plug first, if that doesn't do it then try a new one. Even a plug that sparks fine outside the engine may produce a weak spark in the combustion chamber.

If that fails then it's probably time to check compression.

Russ

[my1423]

Timing advance unit backwards.
Happens all the time.

The magnet part pulls off the advancer and gets swapped 180.
Pull the 2 screws on the trigger advance plate then the cam bolt.
Pull off the advancer, pull the magnet off, swap 180, reinstall.