1987 Big Bear 350 Rebuild - ATVConnection.com ATV Enthusiast Community

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Old 01-01-2017, 06:56 PM
Weekend Warrior
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Join Date: Aug 2016
Posts: 9
Default 1987 Big Bear 350 Rebuild

It's winter so I'm working on rebuilding some parts on my 1987 Big Bear 350. Got it from my uncle this past summer for nothing. Sat around for a while then I began to play with it. I don't have any pics of it prior to tearing it down except this one.

First I experienced a small, occasional clunk noise. Quickly found out that gas was entering the crankcase and flooding the engine- pretty much turned my oil into gas. Carburetor rebuild is on my list. Worse problems were soon to come, with an oil leak at the transfer gear and middle gear drive. At first it smelled like gas, which led me to believe that it ruined the seal on the transfer gear.

I found it a whole lot easier to remove the entire engine. Getting the middle gear and transfer gear out was impossible with the engine still in; the drive shaft splines are rusted into the transfer gear yoke. I'm not gonna be rebuilding the engine as it was running amazing prior to the tear down. The focus will be on the drive train, rear-end, and carburetor.

Of course when I removed the middle gear cover, I slipped and put a small hole through the casing. Was thinking about JB Welding it, but I believe I can pick one up for $30.

The S.O.B. causing me tons of problems.

Was able to open up the transfer gear case after removing the final drive u-joints and yoke. Found it particularly easier for being my first u-joint ever. It was a pain to remove the circlips as they were on the inside rather than the outside. The inside looks great.

U-joint, o-ring and shims (that of course split cause they were rotted) from the middle gear drive.

I was making good progress until I went to tackle the lower u-joint on the transfer gear. It will not budge. I use the hammer/socket method since I don't have access to a press. Any ideas how I can get this sob to break loose? I'm thinking heating it up...

Looking forward to some input and advice from you guys as I progress with my rebuild!
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Old 01-03-2017, 10:05 PM
Weekend Warrior
Join Date: Jan 2017
Posts: 17

I would avoid hearing it up if possible. Don't be afraid to get rough with those u joints. I heated one up once and ended up having to replace the whole thing. Try spraying with a engine degreaser and rust buster (wd-40 or Thrust) and then wait a minute or two. Then lock into vice if possible and really get after it. U-joints above an S.O.B quite often. Don't let it frustrate you though. If you think heating it would help try heating it as little as possible.

Hope this helps!
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