Gwbarm

I did see it i have just never seen a 4 stroke piston chewed up that bad it must have not been getting any oil at all.

Is that from 2 stroke or 4 stroke engine.

Yeah that must have happened when the gear broke. I dont think you went deep enough to screw anything up, but check to make sure your shifter mechanism is working properly.

There are specific tires for snow and sand but not very useful for anything else https://www.amazon.com/Maxxis-M910-4-Snow-Sport-22X10-8/dp/B0012TTCFM/ref=sr_1_1?dib=eyJ2IjoiMSJ9.QbylT1TqI4P04VEsMAoSetDfZcSXpaH-pwn30_gEbeFOrVNftNhhiEEJVvLcy-k2j8LXGKytygYCOpxG5ev3UcnxZxobwimjkjhK2R4ql2E5R6Ek9KqnHyNCZvEyIm6SuYyBrQThIKu7ihec2KgIse9woFTSAG3OHKMTjzTBCQ_C2bvI88VH25_nGXUZLUZvZd_LN0tUqjcBiQoWpWTFRe85aH_dGNe2gkVEMDnlAR-oSHTqxpasuTu7CDRh_3BJptxgXnEalWUSmZnieBDLdL6Kmz3EJ7E_x5V2nr_PMr8.np96b7cnA2Qv1YDvDgyY-h-YEbiqRfNCyHHUKwut7Og&dib_tag=se&keywords=maxxis+4+snow&linkCode=sl2&linkId=6f63b3096dd990efe72afd4ac3e12a53&qid=1733176103&s=automotive&sr=1-1 I generally just stick to a tire that will disperse the snow and be very useful for other terrains as well.

Never been to one but it sounds like a lot of fun.

Flaky shiny means metal debris i would check closely for wear.

I think i would go with the tractor tread so it will dispense the snow quickly.

Throttle position sensor would also be my guess, and maybe try cleaning the throttle body.

I would have the piston and rings in hand and take it with the cylinder to the machinist as a guide for the rebore. Depending on how bad the cylinder is you might have to upsize 2 sizes to get it right the machinist could tell you this before you order the kit.

I would put the rings one at a time in the cylinder and Mic the ring end gap to see how badly they are worn, should be around .019 i would also Mic the cylinder and piston to see if it is within specs if not get a new piston. If the cylinder has scratches the piston should have matching scratches unless they are from a previous rebuild job.

Good job finding that those little gremlins are always around

I am as cheap as they come, i have done what you are doing many times it works ok for my application i restore old 60s motorcycles that probably dont get 100 miles put on them in a year, but if i was doing what you are doing for a good running ATV that gets ridden like an ATV, very hard, i would go ahead and get a rebore since you are going to have to get new piston and rings anyway. You can make what you have usable but you will never get it exactly back round without a rebore.

Marvel Mystery Oil has been around for a while, a little history: its red like transmission fluid with a sweeter smell. I also use liquid wrench used to use it all the time and them PB Blaster hit the market, still not sure which one is better. Good luck with that Stihl makes great saws. It is composed primarily of petroleum distillates, including mineral oil (60–100%), mineral spirits (10–30%), tricresyl phosphate (an antiwear and extreme pressure additive in lubricants, 0.1–1.0%), ortho-dichlorobenzene(a softening and removing agent for carbon-based contamination on metal surfaces, 0.1–1.0%), and para-dichlorobenzene (a precursor used in the production of chemically and thermally resistant polymers, <0.1%). Origin The Marvel Oil Company (also known as Marvel Carburetor Company; Marvel-Schebler Carburetors since 1928) was founded by Burt Pierce in 1923.[2] Before World War I, the company produced carburetors for automobiles and aircraft. Some of these encountered problems with clogged jets, prompting Pierce to formulate a blend of chemicals and petroleum to clean and maintain them. Marvel claims the oil creates a top ring seal producing higher compression, preventing blow-by on power strokes, resulting in more power.[2] Supporting evidence is not provided. The Marvel Oil Company, initially based in Chicago, moved to New York in 1941; it was purchased by Turtle Wax Inc. in 1999, returning to Chicago.[2] According to the company, the name Mystery Oil comes from Pierce's answer to the question, "What kind of oil is this?" to which Pierce would respond, "It's a mystery!"[2]

Got the brake shoes and cover out, brakes shoes good not stuck to the drum at all, linkage works fine. Its never been taken apart before and has been many years since the brake shoes have come close to touching the drum. The linkage ( Brake Rod Arm) that connects the foot brake and parking brake together is frozen solid got it soaking in PB Blaster but so far no amount of hammering has moved it. So now i know why the brakes dont work and it has nothing whatsoever to do with the transmission not working. Got to dig deeper. Bolts that havent been removed in 34 years. Look just like new. and they were tight.

Well i finally got the little culpret to move, its been soaking with PB Blaster for 2 weeks with no movement , added some Marvel Mystery oil came right loose with a few small taps. Still wont roll around so onto the brakes, not sure exactly how the brake system works on the hydostatic transmission it is somehow interlinked with the transmission but i will give it a try. Just looking back over the thread i have done a lot of work to this stupid thing, doesnt seem like it, cause im just doing a little at a time. Other projects taking priority.

Welcome, you have 2 of the greatest ATVs produced good luck getting them going. The Yamaha Moto 4 350 or YFM350ER eventually became the prototype of various Yamaha models such as Warrior, Raptor Big Bear, and other YFM designations. Fitted with a bigger 329-cc engine, this sport ATV was designed for strong midrange pulling capabilities and serious mudding and riding in shallow water.

All Moto-4 models have the VIN code marked on the frame near the left footpeg when seated on the ATV. However, this specific location may change from year to year. Other areas where you can find the VIN are between the engine and the A-arm, on the neck of the frame close to the triple-tree, or slightly forward on the front-left footpeg. Cleaning the frame with a wire brush will help make the VIN more visible.

Wix are good filters should do the job .

Looks great, love that green color you used, Tires are really beefy looking i do like them. Iv got to get a set i think i will get those. Your efforrts have really paid off it looks like new.

Ground the wire to the engine case and see if the light comes on, if so it might be the switch. Or it could be the bulb, but make sure its in neutral.

I have also had some of the same problems with aftermarket carbs, try adjusting the mixture screw located underneath the front of the carb, also check to make sure your throttle plate is closing all the way at idle, you may have to adjust the cable. if that doesent help compare the jetting with the original carb. If you still have the original carb clean it good and put it back on.

No compression i would be looking at the timing and valves

Looks really good

Yeah! I thought it might be these little typical lawn mower brake pads also, but on this one not the case. Got real little brake shoes. And i can see how they would get stuck if you leave the parking brake on too long especially if there are no pad left which im assuming is what im going to find. I was hoping i could get the other unstuck with PB Blaster but i may try tapping with a small hammer. I have a very small Ball Peen which would be perfect but i couldnt find it today.

I quit avoiding the inevitable and tore in to it today. Got the whole backend off and found two problems! The brake is stuck and also the lever that you push back and forth to take it out of gear so you can roll it around. The brake must be really stuck because i pulled it around with the John Deere so i could work on it and the wheels dragging the whole time and it still didnt break loose. Thr brake is housed under this cover attached to the transmission and is a bear to get to. The lever has been soaking in PB Blaster for the last couple of days hasnt helped yet. You can see in the middle left of photo it pulls up on the piece of flat metal which attaches to a valve to move it in and out of gear. . A whole lot more than i had planned on getting into, rathar spend my time on a quad. but these are gaining popularity a lot of lot of people are restoring them, so probably time well spent. Glad i pulled it off it was a mess under there. Things seemed a little slow today thought this may be a little entertainment.