I have a 96 400 trail boss (i think) 4x4, bought it cheap but needed alot of work. I finally got it running good the other day, except it ran really rich, so I cleaned the carb and new plug adjusted everything, started it up, let it idle for a minute, then reved it up, and ya, somethin broke inside. How bad of a job is it to take that motor out/apart, I'm used to working on ski doo sleds, this atv thing is new to me. Any idea of what mite have broken? Took the reciol and starter off, and i can rotate the motor about 3/4 the way, and the piston goes up and down, but there is definatly a stop lol! Any help would be appreciated, btw I paid $800 bucks for it, is it even worth messin with?? thanks again

 

i would say the rod

 

do they have rev limiters? was is my bad that I put it in neutral and reved it up? I didn't hold it there just up and then clunk

 

not shure if it has a rev limiter on it no just a quick rev it shuold not hurt it thay are a good motor exept ite stock piston

 

thanks for the info, like i said, im new to the atv thing. ok another quick question, how do you take the motor out? im guessing it comes out one side or the other, do i have to take the fuel tank off? i think i can figure it out, just not as easy as my sled! thanks again

 

If it looks like it needs to come off do it. Because after 15 minutes you'll do it any ways. I have a 400 lower end I'll be getting rid of soon. Or maybe if the project is too much I'll buy the 4x4 let me know what you find. Good luck Doc

 

no you don't have to take the fule tank foo but it shure is easer if you do

 

thanks guys, Like I said, I bought it as a project, and ya it's more of a project than i expected now, but that's half the fun. Can't learn anything if ya don't tear into it, with a lil help from this site! It's looking like by tomorrow night this time I should be able to post what's wrong with the insides of the ole gal. Another ? where do I find the serial number, I'm not even sure what she is, it has grey fenders, red around the fuel tank n light, steel racks, 4 wheel drive all chain, n ya, im guessin it's a 400 cuz it said 400 on it, but that was it, no other stickers

 

Sounds like a 1994 400L 4x4. The model # will be on the right side frame pillar below the shifter. Good luck. Doc

 

sounds to me like you dropped your timing chain,you said you can turn the engine 3/4,piston goes up+down.you probably have a valve open+the pistons hitting it,preventing complete revolution.