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Brilliant, cheers, there is a good spark so it sounds like I have either a broken/poor live or a dodgy earth so hunting for that will be tomorrow's task 👍

The fan gets switched on when the oil temperature gets high. The fuel pump gets turned on when you first turn the key but then switches off unless it's getting a pulse from the cdi. The pulse from the cdi is the same pulse that fires the ignition coil, so if you have spark, you have the required pulse to operate the fuel pump relay, you just need to ensure it's getting to the pump control relay. When wires have no continuity, or have high resistance, it's almost right at the end of the wire where it crimps into the metal terminal, it either corrodes or breaks the wires inside the insulation. Wires do sometimes break if they have been chafing for a long time on something and worn right through the electrical tape, insulation, and then the copper wire, but that's easy to spot by the frayed insulation.

On the contrary, you and everyone who have replied have been very helpful, I really appreciate it. That's really good advice, thank you. I will pay particular attention to the earthing and post any findings.👍

Thanks for sharing, looks like a fun time. Im getting a little old for that kind of riding but like watching it. 👍

As i recall the motor controller, a very expensive part and no aftermarkets available, is activated by the CDI, and it absolutly has to have a good ground to operaate correctly, including the fan, the controller itsself may be grounded through the CDI, not sure, i am having trouble relating what i know to yours because the one im more familar with didnt have a fuel pump. I think what you are doing stripping the wiring loom and checking is the best way to find it, you can throw expensive parts at it all day long and still may not get it. You have worked hard at it i havent been much help, but good luck.

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What you say makes perfect sense but I think I must still have enough fuel in the tank to allow it to gravity feed as I tried removing the pressure line and blew into it...still nothing!! I gave up yesterday after stripping the whole top end and the wiring loom. Fuel relay working on rpm makes sense but I don't know what activates the fan as I can't find a thermostat!! Will have another go later today......

Thanks, no, I haven't noticed any other problems. I have now stripped out the complete wiring loom and will now test each of the wires!!

Yeah it does sound like a bad switch, you can take them apart and clean them up, but for this level of inconsistency i would just replace it . Aftermarket ones are fairly cheap and i havent had any problems with them.

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.

That's brilliant, I will have another go at it this morning!! Thank you!!

Cdi coils should have almost no resistance on their primary windings. 0.6 Ohm would be about right. Coils for switched 12v have resistance.

I just inherited a 2001 550 from a friend have a friend and have no idea maintenance Pass there is no manual. It is running pretty good right now, definitely needs some attention and tlc. What basic things should be done to get it in good working order and where can I get a manual?

Photo has been removed, what part are you referring to.

Good work finding the pushed back pin.. Time after time it's the wires not the electronic bits.. or Switches.. That flickering could be a key switch, or perhaps the kill switch, with dirty contacts. I'm pretty sure the flickering will be because the voltage to the gauge is dropping below the about 5volts the internals of the gauge usually work on.

That sounds like piston ring blowby, how long since you did your top end job. If you are using synthetic oil it takes longer for the new rings to seat.