won't start
 

just got a 125cc TaoTao and can't get it to start. Tore the carb apart and cleaned it. Jets are good, as is the float. Checked the drain valve at the bottom, carb is gettin gas. Checked spark plug, it is wet, so gas is gettin to the cylinder. Checked compression, seems good. Checked Spark plug for spark, and is gettin good spark. Tried spraying starter fluid in the carb to give it a jump start, but no dice. Checked the brake safety pin, and the pin on the back that has the cap over it. That one is good as well. Tries to start, sounds like it wants to, but just can't get goin. Any more ideas?

Adjust the valves. These small engines have valves that tighten with wear, and they're tighter still when cold. The classic symptoms of valves getting tighter over time is a quad that is progressively harder to start when cold (starts and runs fine when warm) - eventually with further neglect leading to a quad that won't start cold at all.

What are the valve specs? Or where do i find them? It is a 2008 Taotao 125cc. Should i do a real compression test? What should that read?

I use 0.004" inches on exhaust and intake with the engine cold.

But I wouldn't fret too much about doing it wrong. If the valves are too tight your quad will crank and crank without starting. If the valves are too loose the quad will start, but you'll notice valve clatter noise which will diminish as the quad warms up. Valve clatter won't harm anything over the short term.

Compare this with some automobile engines where the valves tighten when the engine warms up. Now if you set the valves too tight the engine could burn up the valves when the engine gets hot. In this case the valve clearances are set at engine operating temperature. It's messy and risky to anyone who does this wrong.

You, in comparison, have it easy. If you screw up you have a quad that won't start, or runs noisy (both benign) - instead of an engine possibly ending up with burnt up valves.