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Got a hand-me-down trail boss from my dad. It started right up and ran great in the summer of 2019. I guess in the fall, it wouldn't start any longer. My dad pulled the carb out and cleaned it up. Still wouldn't start. Also threw in a new spark plug and I confirmed it's gap. I made sure that gas is getting down into the carb. Finally, I adjusted the choke screw 1.5 turns out and tried different settings with the idle screw. It turns over like it could catch, so I know it's not the starter or anything. If I give it a little throttle while turning it over there is maybe the very faintest sound of an extra grunt but I could be imaging that.

I'm thinking about trying a new carb off of ebay. First, I had a couple questions to make sure I'm currently all hooked up correctly.

There are 3 inlets (not sure what they're called exactly but they're basically nipple inlets). 2 brass and 1 black. I know at least 2 of them had hoses on them - my dad thought they were just air inlets and could remain open without hoses. Can anyone confirm this. Here are some pictures showing one of the brass nipples on the left and black nipple dead center, just above the idle screw:

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The other nipple is located below the carb and I can't get a picture of that one while the carb is installed.

The other question I had is that there was another inlet nipple coming off near the chain sprocket (off the gear box??? Not sure what that is exactly). I believe my dad actually replaced the hose coming off of that and that is also currently open to the air. Is that correct? Should that be connected to one of the carb inlets? Here is a picture of that:

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Final question - depending on what you guys have to say about the above info. Anyone have any luck with specific sellers of aftermarket carbs on ebay or other places?

Thanks!

Tommy
 

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Welcome to the forum. Those hoses on the carb go somewhere. Is this a two stroke?
 

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Discussion Starter #3 (Edited)
Welcome to the forum. Those hoses on the carb go somewhere. Is this a two stroke?
Hey thanks for the welcome! After I posted this I did find a video showing a cleanup of the exact mikuni carb that I have. It looks like the hoses that were connected to the carb were open to the air but they were routed through those hoses. I could absolutely be mistaken with this though.

I also found the service manual and downloaded it. The one thing I'm still trying to figure out is where the hose that comes off the tranny goes (2nd pic).

I did ask my dad for sure if he knew if it was a 4 stroke or 2 stroke because there is a separate oil reservoir. He told me it's a 2 stroke but the oil is injected after the engine starts...
 

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I actually misspoke: the hose in the second pick is coming off near the tranny/gearbox; it's not near the sprocket. I was trying to post by memory it's actually sort of near the disc brake which is why I misspoke.
 

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Discussion Starter #5 (Edited)
Update for you guys. Spark plug had a good spark. Compression was low - about 90 PSI with throttle wide open. Since I was already in over my head and I figured I had nothing to lose, I removed the top of the engine. The piston was visibly rusty and did not move when I pushed on it. I sprayed PB blaster in it and pulled off the cover to see the belt/clutch/flywheel area. The PB blaster had settled in and when I rotated the clutch (?) the piston rotated nice and smoothly. I could then rotate it by pressing on the piston top.

At this point, what should my next steps be. I assume my biggest issue was the seized piston. The only gasket I really have access to right now is the head gasket. I will at the very least replace that.

EDIT: I believe I should be able to get the entire top end off at this point. After about 3 hours, I got the additional 4 bolts that attach the top end to the bottom end. From here, I assume it's cylinder and piston clean up and gasket changes? Can anyone confirm?

Also, since it was seized, do I need to dig into the oil aspect of this? as far as I can tell, oil is getting down to the bottom end of the engine - according to my dad, this is a 2-stroke in which the oil injects itself when the ATV is running. How do I know if something is not right since I can't run the engine. Did it seize up in that single winter season?
 
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