Turns over but wont start

You have to start with some good old fashioned troubleshooting. Is the engine turning over (cranking)? If Yes, the battery and starter are good. Does it have spark? Pull a plug wire and test. If not, you have an ignition system problem. Does it have fuel? Starting fluid is the easiest way to check (remove air filter and spray a bit in to see if it starts). Does it have timing or compression?

Everything seems ok it may have to do with the timing the compression seems weak but not sure how to troubleshoot timing

Use a timing light. A belt should not affect the ignition timing. Look for damaged wires/ vacuum lines near the front of the engine.