Vintage Dirt Bike Q & A

Hello,
I have a 1983 and 1984 yz125 I have restored and they are in great shape except the 1983 will not start. Followed same steps as 1984 which started first kick! I have good spark, fuel and cab was cleaned and rejetted with new parts and seals. If the timing was off should I expect some reaction such as back firing or would it be totally dead? I even placed fuel down the spark plug hole and it did not ignite. Tried it with air filter boot connected and disconnected, choke on and off but not even a cough. Spark is strong but could be mis timed I am thinking. Thoughts please?
Also, does anyone have a chain guard for this bike? This is the plastic piece that sits on front top right side of swingarm and protects the SW from the Chain. Two bolts on side of SW hold it in place.
Appreciate your thoughts.

Here is an easy way to check that it is firing. Put your timing light on the plug wire. Using a drill with a socket attached, spin the engine over and see if it is firing. You can also have someone kick it over instead of using a drill. Make sure to leave the spark plug in the head. If it is firing, the timing light will flash as it does when its running.
To check the timing without it running, do the same thing with the spark plug out but grounded. This makes it much easier to turn the engine over. Just because it fires with the spark plug out, doesn't mean that it is firing with it in.