Hello everyone, Im new to this forum and new to owning an ATV. I have always worked on cars, engines, and so on, so Im pretty mechanically inclined. However, never an old 2 stroke ATV.

An uncle of mine was going to junk a 1995 250 Trail Boss that had a blown engine. I thought it would be a great project for me and my 9 year old son, so I took it. I rode it a few times a few years ago when it was running, and I loved it! It was loud, smokey, and fast. Just the way I like it.

When I brought it home I removed the engine and stripped it down. It looks like the bearing on the primary clutch side blew apart and send metal all inside of the case. The piston and cylinder look bad.

The crank, bearing, oil pump gear, and rod are all pressed together.

So thats what I got so far.

As far as the crank, bearings, oil pump gear, and rod goes, should I purchase a new assembly? Or, should I take it someplace to have all those above mentioned thing pressed off, replaced, and pressed back on?

Based on what I read, I can use a bearing separator and propane torch to remove the bearings and gear. Then do the cold crank and oven heated bearings trick to put it back together.

My issue is still the rod. I would like to know how to determine if the rod/rod bearings even need changing. If so, what would be the best way to go about doing it.

Thank you.

Also, please advise if this thread should be relocated to the Ask an Expert area.

 

Welcome to the forum! Best to just buy a rod kit (hot rods are what I used the most of) and have a machine shop or dealer install it. Unless you have a 20 ton press,a dial indicator and stand, and bearing separator for the oil pump gear as you mentioned. Then all you would have to do is install the two bearings on the clutch side(let the shop fit the new bearing and gear back on the stator side) Lot less hassle this way. I did quite a few for customers doing most of their own work. Best to have the bearings on the crank first (especially the two bearings together) and stick the whole assy in the freezer(Momma won't mind then heat the left case up(while it's up on wood blocks) and the crank assy will drop right in. Same on the right case half,just heat around the bearing cavity(use gloves) and drop it on the crank. This way you wont have to beat on the end of the crank (trying to force the crank through the bearings) which is the last thing you want to do. OPT

 

Great! Thank you polaristech. I cant seem to find any dealer around here that will do the above mentioned machine work. Now, maybe my crank, rod, and rod bearing are ok. How can i tell if the rod, shims, and or bearing need replacing? There is play from side to side but barely any up and down.

I can do the main bearings and oil pump gear on my own.

 

There should be NO play up and down!!! Side to side is ok. Even a small amount of up and down play will lead to a rod bearing failure pretty quick especially if you put a load on it with a new piston.I've seen this happen before. Don't waste your money since you've already got the crank out!! Best to do it right the first time. OPT

 

Ok, good to know. I was thinking of sending the crank and rod to Mrcrankshaft. I checked his website. seems reasonable. No one around here will touch this crank and rod. buying a new crank rod assembly runs about $350.00. Ouch!!