Originally Posted by jackone
Made some adjustments today and here is what happened. Connected vacuum from engine to carb with a barbed fitting. Ran fuel line direct to carb. Bypassed diaphragm unit totally. Very difficult to start cold. Had to feather throttle and crank it a lot. Once started idled well and ran well. Any way to aid cold starts? Does electric choke need to be checked or replaced? Not really sure that replacement would aid starting. ANy thing better carb wise?
The idea behind the vacuum operated fuel shutoff is a good one. When the quad is not running the fuel is shut off. Without this automatic shutoff it is very common for the needle valve in the carburetor to sometimes stick open and the gravity fed fuel system empties the entire fuel tank onto the garage floor through the carburetor overflow hose when you're not around. My garage (and many others) have a natural gas fired water heater and furnace that can ignite those fumes.
That said, those vacuum operated shutoff valves are really failure prone, and generally a real pain in the butt. I have a manual fuel shutoff valve which I bought on eBay for about $5.00, and I use it religiously. The point is, though, you really should have a fuel shutoff valve of some sort and get used to using it if you store the quad inside a building.
On the cold starting issue: Have you checked your valve clearance? These need to be adjusted periodically. Valves tighten with wear, and they tighten more when the engine is cold. So the first symptom of valves needing adjustment is hard starting when cold, eventually leading to no starting at all.
Somewhere I've seen a link on how to test the bystarter valve (what you call an electric choke). I'll try to dig that link up and post it by tomorrow evening. Maybe others have it at their ready and can post it sooner.