Hi all, happy new year. Posted here before about my sons pride and joy tat had a no charge issue that was solved with help from here. Hes been riding it and loving since last early last year. Last winter we did a full rebuild of motor,top end and bottom end and was running great for a while, a month or two then it stopped running and he was frustrated on left it. This is where the dad in me steps in and wants to fix it for him.Spark seemed erratic so a new coil was installed and it barley started but did. Convinced it was carb a cheap amazon was bought and crudely installed,it ran,kind of. He purchased some mikuni carb body's from e bay and have tried 3 different carbs all cleaned in ultrasonic and blown out. Case as been pressure tested with only a very very small leak on head gasket. Timing has been confirmed twice, 3mm BTDC, 
So today here's where were at, starts up cold first/second kick then sounds like it runs out of fuel and dies.Pull plug, wet, has spark, clean it and heat it, reinstall, fires up and sounds like it runs out of fuel. Do that procedure again and kick it forever and no fire BUT pops through the exhaust once and a while, hence why timing was confirmed again today. Im very suspect of the ngk br8s plug, even though its what the manual says to run, I feel plugs today are garbage.
Both him and I would love this sorted, he's at the point of paying big $ to have a shop look at it, I'd rather him save his money saying we can sort it but man is it frustrating.

 

First thing to do is to make sure that the pilot jet is a) not blocked and b) the correct size.

I would run it with a standard B8ES plug, not the one with R (for resistor) in it.

In addition to what Al mentioned, I would like to add a few other things to consider:

* verify fuel valve is clean. Just open the valve and let it flow in to a container.
* verify VENT on cap is VENTING. There is a small vent hole setup.
* set timing to 1.8mm, with yoke open. I believe 3mm is wrong. I have the A model. I thought they were the same bikes.
* verify floats set
* verify fuel valve clean/functional
* pull reed valves for inspection while carb off
* condenser check for 0.22uF
* compression. tighten head gasket around 15ft/lb