Mech

It seems the symptoms, and what does and doesn't work to get the fan to work, have changed since the thread started..

There's a 2014 manual here... https://www.manualslib.com/h/hisun+400xl.html You should follow their testing and diagnostic process.

Is this meant to have an auto engage diff lock does it ? If it detects slip it engages ? Do you have a service manual ? I'd check the diff is working.. getting drive to the ground.. I'd jack one side of the bike at a time, put it in four wheel drive, and try turning the raised wheel. If the diff and front drive is working then I'd test the diff lock solenoid is getting power to it, and that it has a good earth, and I'd check the wheel rotation measuring devices if it has any.

Electronics have improved vehicles, both their performance and their reliability, and electronic gear is really very dependable. People's dependency on "things" though, is a bit surreal.. It's like nobody can walk a few miles any more.. or find their way if they were willing.

Errr.. that diode is on the earth wire.. When you put power into the fan switch straight from the battery the fan goes, but when you try to use the original power feed from the fuse it doesn't go. You don't need to supply a better earth to get it to go.. What does that tell you ? It tells me that the problem is in the power feed, and it tells me the problem isn't in the earth end of things..

I think most quad wheels these days are tubeless, and you really don't want to be trying to get the tyres off quad rims in the bush any way.. they are bastards. I've done tractor and truck tyres using hand levers and breaking the beads with hammer and punch, but quads really are the mongrels ! I was thinking a bottle of tyre slime and a pump. Then.. you could just put the slime in there before hand to prevent annoying slow leaks from getting prickles/thorns in the tyres.

You could fit the master, then put your finger over it's outlet while you pump the brake lever, using your finger as a one way valve to get fluid in and most of the air out. Then connect the pipes and bleed it at the back wheel in the usual way.

To my mind the chances of a breakdown are more concerning than getting the bike stuck.. Bits of wood found laying around, or a rope, will get bikes out of most predicaments. Spare gas, some tools, spare spark-plug, some way to fix a flat tyre.. Those would be my priority.

Well if it was fine till it got dirty, and it didn't come right after a clean, I'd have to suspect it needs to be stripped, cleaned, and reassembled again.. But.., are you sure that there isn't an air leak between the carb and engine ? That sometimes happens after a bit of carb work, and gets overlooked in the belief it's a carby problem still. As far as the rebuild goes, the jets are presumably the right sizes since it used to run, and so the problem now is either that there is still a jet or two with blockages, or the assembly was not done right.. Perhaps the float level needs adjusting, or the slide needle is not set right.

Almost any aftermarket carb you buy (chinese or otherwise), will need a bit of tuning to suit the bike, so why don't you just clean and adjust the carb you have ? Chinese carbies are no worse or better than any other.. Do you have a specific problem with the running of the bike ? Perhaps we can diagnose and suggest what to check/adjust.

You have two problems, one is a crook fan switch, and the other is a bad power supply to that switch. A gauge can read a voltage to that fan switch when there's no load on the wire, but if there's a bad resistance somewhere in the power wire. the voltage will drop to zero when a heavy load draws more than the resistance can let through. You need to back probe your gauge into the power wire connector to the fan switch. That means poke it's probe in on the wire side of the connector. Then with the key on, and the fan switch out of the circuit, there should be twelve volts or a little more showing on the gauge. Then if you plug in that stuck fan switch, the voltage will probably drop to zero, or near to, and the fan won't go. But if you then jump power direct to the fan switch as you have been doing, the fan will go. If it acts as I say, then you have a bad connection somewhere in the fan fuse or holder, or in the splice in the wires that's somewhere between the key and the two fuses it controls, which are the fan and the ignition fuses.

Are you sure the voltage you are reading at the switch's plug has some current to it. If there's a bad connection before that plug, it could show voltage there, but only be enough to run the meter, not a fan. I suppose you have a wiring diagram and have seen there's a fuse and a switch, and some wire connectors (inside the loom by the look of them) , Fuses can get bad connections, inside the fuse, or where they push in.

I'd test the temp sensor in a pot of water, with some load on it, like a headlight bulb.. Perhaps it... err... sticks ?

Diodes usually drop voltage about 0.4-0.5 of a volt.. Are you sure the fact the fan stays on once it's started, isn't because the motor is getting too hot ? And the fan isn't cooling it enough ?

Fuel might still get through the pump, if it's centrifugal say, and so a tap is still best. If it has a tap it's probably because it needs it. If it's got a prime position on the tap though, it suggests the tap is vacuum controlled. As long as it's left on run or reserve positions it will close off when the motor stops. The prime position is for after it's been dry of fuel. To save cranking a lot you put it on prime and it flows straight through.. If left on prime the engine could flood if left sitting. There's a manual for download I see..

Oh ok.. I'd heard of Penzoil, but Quaker State is a new one to me. Wealthy quakers.. That's an interesting idea..

Ask what they are going to do with the grass.. They might be keeping it for hay or grazing.. You might be able to earn some money hay making and get to ride after it's gone.

The oem is simpler because they have sourced a suitable oil for you. They don't produce the oil themselves. If you look in the manual it will say what the requirements are if you don't buy dealer oil. The oil you buy, could well come from the same refining/oil company as the dealer oil. In N.Z the old trusted brands are castrol and shell.. they have the track record. Over there will be the same thing.. best brands. Is Penzoil a trusted proven brand ?

Yeah.. A clever guy should be able to lure them in..

Simplify life.. Sell everything.

Cheers.

Oh... and to the original poster.. You could try a hotter plug.. An NGK plug.. In jap bikes, ngk seem to last when nothing else does.. Don't know why, but it can be quite a dramatic difference between ngk and any of the other makes..

For my customers.. it's castrol, shell, or mobil always, and the spec recommended.. But that's just because of the liabilities aspect..

Well.. it depends on the brand of oil and what sort it is, but I've found that in old motors, and two-strokes, that some oils foul plugs. High detergent oils seem quite bad for it. They don't get a big thick layer of solid carbon on them, just an oily look.. Just shiny or wet looking, but it really buggers the plugs, even a good clean doesn't always get the plug reusable.. heating them in a flame sometimes does though.. As far as the oil to use goes. These things aren't really super high stress, not like something with a turbo say, or even a modern high revving , fine tolerance motor in a small hot engine bay. The commonest objection I hear to using some fairly bland type of mineral oil is that they have a wet clutch.. well we've had wet clutches for a hundred and more years, and most of them have been just fine with mineral oil.. It's only having to heavy or too lighter oil that effects the clutch. I've been running all the bikes I've had on plain mineral oil for years, decades actually.... and between myself and my two sons, we've had dozens of them.. Two stroke, four stroke, quads, motorcross, street.. I deliberately buy the plainest mineral oil I can for my own use because then I can use it in everything, including the chainsaw etc.. There is a lot of hype, but when you actually check it out, and actually compare your quad to some machinery, you realise that they aren't really very special at all..

I agree about running the carby dry if it's going to sit for a while. In this case, draining the carby to let the float drop, then tapping the carby (or putting a bit of compressed air through) to make the needle drop, then turning the fuel back on, might do the trick.. It's worked before when just tapping the carb didn't..