Mech

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..

No offense, but it's been overlooked before... have you checked the bulb ? The wires run up near the top right frame rail I think, under the seat.. I'd test the switch, there at the connector.

Yup, I'd try a different tool, possibly a torx if one felt like it might tap in reasonably tight. Next would be as suggested, try to tap it around, You need a small chisel that's not too sharp, so it will dig in if hit straight down, but won't cut metal away when we lower the angle to get the bolt to move. If not a chisel, then an engineers punch that is ground off nice and square so it it sharp and will dig in.-Then a couple of sharp hits downwards to get the chisel or punch to bite in, then one light tap to try and move that side around, then go to the opposite side and repeat, two sharp hits to get the punch to bite, then lower the angle and give a tap or two, then go back to side one and give that a tap, then side two... and so on. If neither of those works then drill it out in stages, trying to loosen it by taking the center out first, and trying plan two above, then drilling it bigger and trying an easyout, then drilling it right out and re-tapping if necessary.

Ok, well since it's now going back and forwards, it must have been in gear before, and the sprag clutch was what prevented it going forwards. The sprag clutch is a one way clutch that provides engine braking when the engine revs get low enough for the centrifugal clutch to disengage. Normally the centrifugal clutch locks up and crank and gearbox shaft turn at the same speed, but if you are going down a hill with the throttle off and the engine gets slow enough, the centrifugal clutch disengages and the bike tries to run away down the hill. If the gearbox shaft is turning faster than the engine shaft after the centrifugal clutch has disengaged, the sprag drives the engine shaft forwards and provides engine braking. At idle, before the centrifugal clutch locks up, the engine is turning faster than the gearbox shaft and so the sprag slips. When the engine shaft isn't turning because the engine is stopped, then any rotation of the gearbox shaft is faster than the engine shaft and so the sprag tries to turn the engine, which in low gears seems like it's locked up. I suspect you still have the bike in between two gears, but not in the proper neutral place. Between third and forth perhaps.. I think you need to keep rocking the bike backwards and forwards, while pushing the shift lever down, and keep rocking and tapping the lever till eventually it will shift down one gear at a time to the proper neutral. It will probably take a lot of rocking..