davefrombc

Rock it back and forth a bit as you try to shift it into neutral.

Likely all it needs is the idle air screw adjusted .. Turn it in until it just seats, the back off 1 1/2 to 2 turns . Adjust in or out 1/4 turn at a time to find where it idles. Adjust it until it starts to "lope" and then enrich it about 1/8 turn. \

Is it something a little cleanup and re-weld can't fix ?

I can't help directly , but there is a service manual in the forum's Download section . . Click Browse / Downloads then ATV Service manuals / (and 9 more) and look in the Yamaha section .

I've never tried it. Glad it worked for you; but I'd keep that new box handy. As long as you're riding with at least one buddy and not too far off the beaten path I'd leave the resurrected box in the machine. It may live on forever or it may die tomorrow, but that can be said about just about everything.

Try running a hose from the overflow to a small bottle to catch the water. . If the hose in the bottle stays below the water level in it , it will draw back as the engine cools . If it continues to push out it could be a very small leak on the head gasket .. One just enough to allow combustion gasses to push out , but not large enough yet to allow water to get into the cylinder. If it only does it for a short while after you fill the rad to the top , it might just be the excess water being pushed out past the pressure cap as the motor heats up. If that's the case, it will stop bubbling once the motor is fully up to temperature.. When the motor cools , water will be drawn back in. After it does that for a few cycles , you should not see any bubbles in the overflow bottle, only the level change a little as it heats and cools . Continued bubbles would indicate a head gasket going bad , or less likely , but possible , a small crack in the cylinder or head if the rad did not have antifreeze in it and froze. \

Check the radiator cap. The system is supposed to use a 13 pound rad cap.. If it is faulty, it will let rad fluid spill out as the motor heats up.

Is it just carbon fouled or is it oily ? Have you tried a hotter spark plug? If it is oily , check the oil level to be sure it is not too high. Have you cleaned the air filter? and made sure there is no restriction in the air ducts . . Did you try running it with the air cleaner disconnected from the carb?... Beyond repeating those places to look , I am at a loss to help more. It doesn't make sense that it only runs such a short time before fouling the plug.

Yes . The pilot jet is mainly for idle , but it also has some effect throughout the throttle range. The service manual spec is the starting point for the adjustment .. Where it will end up is usually within a half turn or so + /- from that initial setting.

Petcock wouldn't be the problem if it was getting too much fuel to the carb . The floats and float needle valve control the fuel height in the float bowl. Most likely the old carb doesn't need a rebuild kit , just a good cleaning. Check the setting on the long needle for the main jet. Try setting it down one notch ( move the circlip that hold it up one groove so it sits deeper in the jet, reducing fuel flow in the main jet )

Are there oil seals on the valves? or intake valve guide so badly worn it's letting letting a lot of oil be drawn in? Compression sounds decent , but what shape is the oil control ring in ? The only other thing beyond those items is easy to check... Is the crank case over filled with oil and oil being drawn through the carb from the crank case vent? Those are the only ways I can think of that it can get oil fouled. . If it is just carbon fouled it has to be running super rich, and I can't see it running well at all if it can foul the plug that fast. Is the plug the recommended one ? Have you tried one with a higher heat range?

One thing about being retired .. The pay may not be so good but I have lots of time to play on the pc and with my toys. Growing up on a hobby farm, then living in the north and working as a millwright, messing with mechanical and electrical / electronic things all my life I've learned a fair bit of how things work.. I can very seldom answer specific questions in the forum , but I can often offer clues on where to look. Being able to search things out on the net is a huge bonus in looking for solutions .

I'd double check all the jets and passages too. I did a search on your carb and see there is what appears to be a stiff rubber part between the block and carb. It could be cracked.. I saw in another forum that the floats actually have two tabs to adjust them . One sets the float height ( I believe it said 13 mm), and the other limits the amount it can drop controlling how fast the fuel can enter the bowl .. Since the high speed juts are fed from the bottom of the flaot bowl ,choking the carb the way you do could put vacuum pressure into the bowl and pulling fuel up from an inadequately filled one. I found a video on rebuilding the carb. I don't know it it will help you, but I'm posting the link. In similar carbs I've worked on, I have found some very small holes in the long jet that can be blocked and not easily noticed. Make sure you remove the jests and check closely for missed blockages . Welders "tip cleaners" have a variety of wire sizes that fit for cleaning pretty much every jet.

check for an air leak between the carb and the engine .. Double check the carb again.. Float height ? .. a passage or jet blocked that you missed ? ... Sounds to me it is not getting gas or it is extremely lean unless you manually choke it by blocking the intake. Try turning the idle air screw in until it just seats and then back out about 1 1/2 to 2 turns initially. Does it run if you only half to 3/4 block the intake? Completely blocked it can only run momentarily until it no longer is getting any air through the carb.

Unless you see any drips when it is sitting , I'd suspect possibly the pressure cap is faulty. It could be allowing water to escape out the overflow when the engine heats up . Can you fit a small container to the overflow to see it it catches coolant ? The only other check I can think of if it is a leak elsewhere that does not show up easily is to use a dye check and fluorescent light to find it. .

The only way I can think of would be to disconnect the line from the oil injector pump at the carb and temporarily plug the fitting so you wouldn't have a vacuum leak. . Fill the gas tank with 32/1 mix and run the engine .. See if oil comes out of the line from the pump to the carb. I suspect t is exactly because of an unreliability of that oil pump that so many eliminate it and go for premix. Your piston displays the classic scuff marks of an oil starved 2 stroke.

Since it is a 2 stroke it requires an oil /gas mix . My guess is either the oil injection pump has quit working or it was out of oil . A lot of LT 80 owners just premix the gas and oil and forget the injector. Here are instructions stolen from another forum on completely removing the injector pump. Most owners recommend a 32/1 oil mix although some say a 40 or 50/1 mix works for them . I'd go with the 32/1. LT 80 Oil injection/premix If you want to DC it, I would just pull everything off and keep it in the event you ever want to put it back on. Chances are you won't, but it would only take a minute to put it all back on if needed. To disconnect, pull the cover on the left side where you access the clutches. (not the small round one, but the whole side cover).. There will be a plastic piece on the front clutch that turns the oil pump, just pull that off. If you just want to DC it and leave everything intact, that should be all you need to do. You probably could plug the hose coming from the resevoir and then hook it back up, but not sure if that's necessary to prevent some minor draining into the carb. To completely take it all off........... Disconnect the hose coming from the oil resevoir. If you want to keep it attached, plug the end and roll it up and wire tie it out of sight. If you want to remove the pump itself, you can fabricate a cover that will bolt right on. Use the bottom of the pump as a template. Or you can order a block off kit I believe. Pull the tube from the carburetor and plug that hole.

Oil cooler systems are not usually high pressure so I'd suggest just taking one of the old lines to a shop and see if they can match up the fittings . If they have compatible ones they can easily fab up new lines for you. If you are going to an aftermarket cooler, you just need to be sure the fittings to the block are compatible. Use whatever hose you want, whether it be regular low pressure oil line hose or fancy steel braid covered. A shop that fabs hose can tell you whether high pressure hose is needed , but I doubt it .

Couldn't find a free service manual or wiring diagram . If you have no power to the lights or anything then the problem is in a mater relay if there is one , or in the ignition switch . Not turning over on the starter could be a safety switch or the transmission is not in neutral . Start at the battery positive and ground and trace the wires out . Check the neutral switch and safety kill switch. Check any and all relays . . Once you find out why the starter doesn't work with the start button you may also find why there is no spark. No spark could be the stator, pickup coil CDI box or coil. Most of those you have already replaced . Take it step by step from the battery out check connections for corrosion and wires for breaks . A wiring diagram helps a lot , but methodical elimination will do the job . You could try looking at the wiring diagrams of other arctic cat models for qa clue of how they are wired . Most likely they are all wired very similarly if not identically .

Use the chain to grip the sprocket to keep it from turning while you loosen the nut on the shaft.

All the manuals on the forum can be found by clicking Browse / Downloads . on the list on the right click "and 9 more" to bring up the rest of the service manuals in the list. Here is the direct link to the Honda 4trax one you want :

Yes, it's a 1990. I have a 1991. There is a pdf of the service manual for it in the downloads section of the forum. I bought mine used 5 years ago, and paid a lot more than $200.... LOL.. You got a great machine if it wasn't abused. They're solid full time 4x4's with all the power all but the extreme riders need. They'll top out around 45 Mph if you really want to push them. One thing you want to check is the splines on the rear axle hubs. They wear out over time, especially if the hub nut was not kept tight enough.. I had to replace the rear axle and hubs on mine. The splines were worn out to the point ther left hub spun freely on the axle.

Welcome to the forum. I'm sure you'll enjoy the Bruin once you get it running . Hopefully just a good carb cleaning and most likely a fuel tank cleaning if it was stored with gas left in it, and a new battery will be all it needs to fire it up.

Try some small adjustments towards lean on the air screws. It sounds like it may be running a little on the rich side .

You need to look for 14" rims that will accept those tire widths , the same bolt pattern and offsets as the rims you have now. Here is the source of a chart to help you choose . http://www.mud-throwers.com/atv_wheel_chart