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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.

Which one had no resistance, primary should have very little maybe.3 and secondary should be between 6 and 10.

Sounds like a bad relay did you replace it and still wont work.

You have been busy, sparlplug coil sounds weak, should be between 6 and 10 OHMs, what does the book say about that. . Do you get a good spark at the plug.

Update: Correction, I did check valve clearance it is 0.00. This Rotax 650 uses the shim type. So not as easy to adjust. After some the recommendations about testing electrical components I decided to just follow the service manual. I've now check the rectifier for voltage at 5500RPMs = 15Volts=OK. Manual states it should not to exceed 15volts. Checked and measure the resistance between the Stator wire leads AC-1 and AC-2 = 0.6 Ohms. Should be 0.3 Ohms. Checked continuity between Stator coils AC-1 to ground, AC-2 to ground. There was no continuity=OK. Measured voltage across 2 of the Stator coils while turning over the engine, they each measure with the 4-6 Voltage AC range=OK. Measured resistance on the Trigger Coil and it read 243 Ohms=OK. Measure Sparkplug coil and it measured 0.6 Ohms. Not sure if this ok? I hooked up separate gravity feed fuel tank and running it but still runs the same way. Tps out at 20MPH. Using an external tachometer, if it is set correctly, I only reached 5500 RPMs. FYI, I did make vides and load them to Youtube, so I know what I've done because my memory isn't the best. I have not yet checked for breather hoses for vacuum leaks or this below. I have it on blocks so once I get it off blocks I can try this.

I think these will be right.. The manual is for 86-89. If it's not right it probably means your bike is the previous model, up to 86. 86wiring.pdf 86 fuelpump.pdf

I had the battery charger set to 20amps , it seemed to crank over fine but the display still spazzed out . So just yesterday I found 2 potential reasons why there were no spark . A blue wire coming from the stator that connects to the CDI , one of the connector pins was pushed back . I fixed it with some needlenose plyers , and the next thing I did was check for resistance between the coil and the plug cap with multimeter. One didn't have any resistance and the other did have resistance, so I put it back together, and wait a go ! Spark . Put a small bit of fuel in the piston just to hear it start up . I now drained the gas as there was water in there ,next I'm gonna clean the carb up before I actually take it for a run !

You need a battery too. That dash display going screwy is because the voltage is dropping too low when you are using the starter. The charger isn't supplying enough power to run the starter. If it cranks too slow because of not enough battery power then it might not make spark, and if the cdi uses 12v it won't work at the very moment it needs to, just as the piston's coming up on compression stroke and the dash dies.

Good you got it going, rebuilding the original has always worked best for me, and yes, no ethynol gas, i dont use it in any of my small engines seems to destroy rubber partts and initiate rust on the steel parts.