Mech

You should do a tune up first, clean and gap the spark-plug or replace it, clean the air-filter, check and/or adjust the valves, check and vacuum hoses for leaks, check the fuel supply getting to the carb is adequate by undoing the carb drain screw and checking the fuel keeps flowing even after the bowl has emptied, start and warm the engine up and adjust the idle mixture and speed as recommended in the service manual.

Sorry man but I had to laugh.. I know the feeling "oh I stuffed up.. I'm f***ed !".. The gasping too.. I know it well.. And that walking around in circles following the pain, hopeing that if you move towards it it will somehow stop dragging at your ribs.. haha.. Hope you get better soon.

Well the noise you are hearing may be the gears inside the gearbox banging together because the two gears are spinning at different revs. If you blip the throttle just enough to bring the engine gear up to the revs it's going to need to be at to engage the new lower gear you are changing down to, It may stop that noise. I think you need to try that and see if it lessens the noise. The noise could be in a diff, or an axle, or the gearbox. If we eliminate the gearbox gears clashing it would be a good first step to diagnosing the noise.. The exact procedure if you are slowing down is you let the throttle off till the speed gets low enough to shift down a gear, then give the throttle a small blip to raise the revs just at the instant you are moving the shift lever down, then let the throttle off to continue slowing down. If you are shifting down to tackle a hill then you have the throttle open as you approach the hill, then just as you are about to move the shift lever, but before you move it, you let the throttle off slightly to take the load off the gears you are in so they can slide apart easily, then just as you move the shift lever you give the throttle a blip so it raises the engine revs enough that it will be at the revs it should be for then new lower gear you are selecting. All these small throttlings on and off are done in milliseconds and it's critical they are timed right, and that the amount of throttle is just enough.. It's worth practicing though because in makes the bike last longer, increases your traction control and so riding skills and abilities. Bikes and quads are not like modern cars or trucks or even tractors. They use really simple old gears and need user input to get the best out of them.

Does the spark-plug have any sign of oil or burnt oil on it ? That will indicate whether the exhaust valve is leaking straight down the exhaust, or whether the oil is getting down the inlet valve or up past the rings.

Do you blip the throttle as you downshift ?

Most probably this.. https://www.partzilla.com/catalog/suzuki/atv/1997/quadrunner-lt-f4wd/carburetor Unless it looks like this... https://www.mickhone.com.au/partFinder/fiche/suzuki/1987/lt-f4wd/carburetor#next Those are suzuki part numbers they are quoting there, but if you tell us which one looks right, I can (hopefully) look up the exact mikuni model number for you.. You should really try to find a service manual to download for free. A manual will answer all of these questions.. There are some manuals on this site, or there are other places if you google.

Good one Martin. Thanks for that.

If the carb fits and is of the same venturi size then it should be usable. It may need a slight re-tune to suit the motor.

Try rotating the crank one full turn, back to the tdc mark, and then try it.

I go see the local wrecker every few years Gw and buy a wooden nail box or wooden box full of assorted bolts for twenty bucks.. or less. They are generally happy to get rid of a whole box full for more than scrap prices. I could sell you a box full of the real strange bolts that never get used.. real cheap..

Ok. Both the neutral light and the reverse light get power directly from the key switch, then, the switches(neutral and reverse) earth either bulb to make them glow when they need to be on They do that by being connected via the reverse switch, to the neutral switch. The reverse switch connects either the reverse or the neutral lights to the neutral switch, which then earths them if it's in neutral. Both the neutral light and the reverse light use the reverse switch on their way to the neutral light switch to be earthed. If you have a multi meter with an ohm gauge I think you should use that to test that the reverse switch is swapping the connection between the blue wire on the switch, and the blue and red wire, and blue and black wires.. The reverse switch should operate like a two way switch. The blue wire should get connected to either blue/red or blue/black depending on whether the bike is in reverse or not. Since the neutral light is working we know that set of contacts in the reverse switch are ok, and that the neutral switch;s contacts are ok, so you just need to check the blue/red wire is getting a good connection to the blue wire oh the switch when it's in reverse. If it isn't making contact, then either the switch is crook, or the reverse is not being fully engaged to operate the switch. output.pdf

Lol.. one nil to the hill. Lucky it wasn't worse. A stick try to take out your eye did it ? I've been caught out by the odd one poking out from the side of the track. Ya think you'll just sneak past, but it catches and swings and next second it's trying to stab a hole in you before you manage to stop the bike..

Here's what you need.. output.pdf

Was the engine running or were you rocking the bike back and forwards, as you tried shifting with the manual shifter ? They generally won't change gear manually if the engines turned off unless you rock them. To diagnose what's wrong with the electric shift you need to download the service manual and have a read, and then start following the diagnostic process they lay out. An early check is to see if the dash is flashing at you, and then to read the stored trouble codes which give an indication of which bit isn't operating correctly. Then you check the indicated bit, and it's wiring, and all and any bit's indicated as not operating correctly, before deciding which bit is the cause and which are not operating correctly as a result.

No trouble. Glad to hear it's a good one.

That is the momentary voltage to the coil when the cdi discharges.. The description of how to do the resistance readings is down a bit in the text. You need a meter with a peak hold feature to catch the very short voltage spike..

Well thanks Gw.. and right back at you.. Between the two of us, we do a pretty good job. haha.

I have the service manual you need. I'd upload it except my connection is too crap, especially with the weather today. I can try to upload the sections you need though.. This is from the genuine honda service manual for the 2004-2007 TRX400FA fourtrax rancher AT, TRX400FGA fourtrax rancher AT PGScape. output.pdf

The trick to welding up or patching over holes in thin rusty steel is to go right around the hole laying down a light weld far enough back from the edge that it doesn't eat it away, then either spiral in laying weld into the edges of the weld till it's fill to the center, or, make a patch to fit that weld. Welding slightly back from the edge lets you get a heat dissipating bead down closer to the edge that you would manage if you gradually follow a melting edge back and back.. It also lets you assess the extent and viability of the repair before you get a patch half attached and then finding out it's not going to be big enough.

There are various different types of ignition in use on various makes and models.. In your case they say to test the cdi charge and trigger coils for resistance, and out-put, then check the wiring, and if it's all good assume it's the cdi.. Ha.. not the best diagnostic help. To test the stator windings and trigger you need to check their resistance stationary, and that they put out some small voltage when the engine is cranked over. You need to check those voltages are getting all the way to the cdi unit. I assume you have the manual and are following it's recommendations and process. I don't have a wiring diagram but there should be one somewhere for free.. it should show you where the kill and ignition switches connect to the ignition, it would be a good idea to disconnect or test those. If you can't find anything, and you are sure all the wires are connected and have continuity, and aren't shorted to the frame anywhere, then it seems it will be the cdi unit.. Do you have a buddy that could let you try your cdi on his bike, or his cdi on your bike > output.pdf

If you find the reverse switche's connector, disconnect it, and then either test the operation of the switch with an ohm gauge, or, use a wire to short the wiring connector on the loom which should make the light come on.. That's how to confirm or eliminate the switch as the culprit. You should check the reverse lever is traveling full travel down on the case, perhaps disconnecting the cable and moving the lever by hand.

You'd better tell people what make and model it is..

Yup, need the box and filter before passing judgment on the new carb.

Good one.. I've got a set of builder's screwdriver bits in my toolbox. It has torx, allen, philips, flat, and square.. They are expendable and handy for bashing into rounded allens.. The slightly tapered squares are quite good in drilled out bolts.

Grease all those bolts Gw.. Looking good mate.. nice tidy job. I'd be a bit watchful when it's going that that rubber hose isn't a bit restrictive.. Might pay to check the carb first without that hose on there..