Bought a brand new sparkplug coil. It measured 1.6 Ohms. It was harder to start, backfired more and ran same as old one.

You operated a switch.. There's a bad connection/contact somewhere.. You need to be doing what's called a "voltage drop test" on every suspect part and all the wiring. The test is to check for any voltage drop along a wire while it's got power in it and flowing to/at the wires's usual load. Look up voltage drop test and it will be explained and probably demonstrated online.

I cleaned up some plugs that had dirty and oil in them If I play with the light switch the starting relying clicks I walked away for a minute came back head and tail lights where on start button worked turned off the kill switch a few times came back on now I have nothing again what the hell is going on

I had a similar problem on my 350, but if it runs on choke the pump must be working, since the fueltank is lower than the carb. Maybe you have a clogged carburettor? When I crank the 350 for a split second the pump starts and build preassure then it stops. I do this everytime i start it to "prime" the fuel lines so i dont have to crank it so long. Inside the fuelpump is a preassure switch to that cuts the power to the pump when there is enought preassure in the line, The fuel relay somehow works with the rpm of the machine. I hate this setup, almost thought of putting a gastank from a 300 trx on it 😃

I thought you might have already done that, just thought i would mention it. This is a tough one. You may be right about the fan controller, i would check all the connections very carefully at the controller and CDI for good contact. Is there any other problems going on other than fuel pump?

Agreed! None of these problems should cause it to only run for a few seconds and quit.

I would change the oil , change the fuel filter, check the differential oil, if really black or milky looking change that. Also replace spark plug.

It had the problem before the overhaul, so it's probably not blow by or bad rings. You'd have to fit the wrong size rings, or break a top ring, to get enough blow-by to cause the filter housing to get oil in it. And, if it starts easily, it's got enough compression. So.. blow-by, by itself, shouldn't be a problem once/if you get the engine running. Neither blow-by, nor oil in the filter housing should cause the engine to stop after only a few seconds. If the air-filter was so full of oil that it choked the engine, then it probably wouldn't start easy, and it wouldn't start easily after the oily filter had flooded it of fouled the plug. If the oil in the filter housing, and the cutting out, are related, it will be fuel in the oil. There is a chance though that the two are not related. If you have a timing light you could connect that up and watch it to see if you are loosing spark. If you don't have a timing light you can fit a plug to the plug lead, and then rest that against the fitted spark plug so that the spark has to jump the first gap to fire the second plug. If the spark is good it will do that jump and the bike will run, and if the spark dies you can see it on the first/external plug.

Thank you for this info. The Quad is at my holiday home, so cannot check oil levels etc at the moment. It was not overfilled as the bike was not using oil and therefore had not been topped up in a while. However, it is possible that fuel got into the oil and I will check this. I have just done the top end so it is possible that the rings are not yet seated properly. If this is the case, I am not sure how to fix this as the bike will only run for a minute or two before dying. I will check the breather pipes for blockages etc.

Yeh, I have fitted a new relay and rectifier. If I cant find a wiring fault I can only think either the CDI or the fan actuator may be to blame.