Thread: CT70 won't fire over, won't start

Help Please...Rebuilt 1975 ct70. Has spark and I think it is timed right.
However, the engine won't fire at all.
I cleaned the carb, still won't fire over.

If you are absolutely sure you are getting spark, it should be a nice bluish spark, then you have to see if you are getting gas. Turn your drain screw out on the carb and see if gas comes out.
You may just need a new plug. If the engine is getting gas and spark it has to run unless their is something majorly wrong inside the engine. You may have to clean the carb again thoroughly. You better double check the valve timing as well.

I just realized something different regarding the head I have on this that I got off e-bay.
It has a larger Spark Plug, a NGK B5hs vs C7hs that is standard and has a much smaller thread size.
Do yoiu think someone retapped the park plug hole, or is this head for a different model?

Different head? What are the size of the intake and exhaust valve for said bike?

All CT70's up to 1977 shared the same head, with large intake/exhaust valves; 1982 and later ones used a different combustion chamber design (and piston head) and with smaller valves. I don't think there are much differences outside of these two, but as you said someone might have retapped the head because they stripped the plug hole or something.