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Hello all....new to quads in general, but been wrenching on old vehicles for close to 30 years now. I will be adding to this thread as I progress on this quad....I like to share my trials and tribulations with others in the community so others can learn, and assist as I go.

I picked up this quad a couple weeks ago, been looking for a second quad for a few months and never found anything that caught my eye locally. I came across this unit on-line a few hours drive from me, spoke with the fellow and looked at pics and decided to take a chance. I drove 1100km's round trip to go get it.

All bundled up for the winter drive back home....



 

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And unwrapped the next day....









Now what I got was a 1997 Big Bear 350 4wd, 5 spd semi auto with no hi/lo range. Bought from original owner who used it at a Lodge up in the North West Territories of Canada to basically haul luggage from the float plane to the lodge for 2.5 months of the year, then stored inside the rest. Quad is in amazing shape, still showing the original cadmium plating finish on most of the suspension parts etc.

A nice "Made in the USA" warn winch....

 

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Discussion Starter · #3 ·
The seller was up front about a possible motor/tranny issue. It locked up on him one day and would not spin over or move, after some rocking back and worth there was a noticeable noise and it would then move again. He only ran it long enough to get it to the garage area then never ran again until he was trying to sell it, then it was only once for about 2-3 seconds. I bought it on the assumption that it would need some motor work, but hoped it was only a minor fix to get it up and running.

Well last week I decided to fire it up myself for a few seconds, start would not turn it over so a couple pulls and it was running. Ran it for 5-10 seconds and could here a "ting, ting, ting " noise from the LH side cover area. Drained the oil and pulled the oil filter......not a good sign!





So I decided to pull the side covers to see what/if the problem could be found. Pulled the RH cover first....no visible carnage. Moved to the LH stator cover and when I pulled it apart from the motor several things fell out and I found the problem. :frown2:









 

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Discussion Starter · #4 ·
One of the starter gear assemblies broke free of the casting in the LH engine case, and stator cover, then fell into the motor and started eating the aluminum case! Not sure what caused this to happen, but regardless I have purchased another set of engine cases, and a new stator cover to repair things. Just waiting for those parts to arrive. Then tear the motor out, and swap everything over....should be a fun project for this winter.

I have never had a motorcycle or quad motor apart before, or even worked on one, but I have rebuilt motors, transmissions (auto and manuals) rear ends, suspensions, etc over the years, so the principles are the same. But I would appreciate any knowledge from members who have experience with these motors and units, tips, tricks, etc are always welcome.

I will continue to update as I progress on this project....stay tuned!
 

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Discussion Starter · #5 ·
Just received my Factory Yamaha service manual...got it off E-bay used for a great price. I am assuming it still has the price tag from when it was for sale at the Yamaha dealer...$322.20!! Got it for a tad less then that....:grin2: Should help with the re/re of the motor.





Also since the quad had a plow on it at some point in it's life the belly pan was missing. I looked for a used original metal OEM piece but couldn't find one, but I did manage to find a aftermarket (??) Yamaha HD aluminum unit NOS still in the factory packaging with instruction manual, bolts and rubber anti-rattle pads...should do the job. :wink2:



 

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Coming along nicely. Going to be a great little bike once it all running again.

The reason why you couldn't find a stock skid plate was because those 350 Big Bear's didn't have them. They only had a single metal bar under the engine. I remember doing the PDI on those before putting in the showroom. Couldn't believe they did not have a skid plate like the original Dual Range model that preceded it did. Although looking back on it I now know why. At that point in history when it was being designed, the 300 Fourtrax was still the best selling ATV on the market. Yamaha was trying to make it's own idea of the 300 Fourtrax, which had a formula of a bare bones, single range, lightweight but still very capable ATV....and have a cheap price. While this single range Big Bear did sell ok, it didn't match the popularity of the Honda 300. Additionally, by the late 90's the market had changed and sales of these kinds of ATV's dropped significantly. Even sales of the 300 were slowing, which it ended in 2001.

The skid plate you got in the pictures is not an aftermarket part. It is a factory Yamaha accessory. Nice find on that one as that's a rare piece.
 
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Discussion Starter · #7 ·
Great info Dezz....thank you for the history lesson, guess that was why I couldn't find an OEM skid plate....:wink2:
 

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Will be a nice little ride for sure , just wondering what will be the primary use for the bear?
 
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Discussion Starter · #9 ·
Will be a nice little ride for sure , just wondering what will be the primary use for the bear?
Just some lazy trail riding with wife or one of my daughters.....nothing too serious. I'll ride the bear, and they will use the bruin since it does not require any shifting. I'll also be using one of the quads around the acreage....hauling brush on the little trailer I have, and other yard related projects. ;)
 

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I bought a new Big Bear in 2001 I loved that ATV. I sold it to my brother and he used it for years. A manual is a great help, I work on ATVs on the side and have found they help.
 

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Discussion Starter · #11 ·
Finally received my major replacement parts....sure there will be more once I tear the motor down. :wink2:

Engine cases..LH and RH side from a 98 big bear.





And a the Stator cover.

 

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Discussion Starter · #12 ·
Started tearing the quad down for engine removal. Nothing too exciting except when I pulled the top off the air box....:icon_ nono2:

Think it might have had a bit of restriction in air flow....





Mice had been busy!

And almost ready to pull the rear suspension and get the motor out of the chassis.

 

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Discussion Starter · #13 ·
I am also working with a company to make up some spare decals for my Big bear. My decals are in great shape for their age so I thought it would be nice to use them as templates for some reproduction decals.

Here is one of my decals.....



Not sure how exact the reproductions will be, might not have the same metallic in the colors, but they should be close and if your missing them or they are beat up from age should be better then nothing.:wink2: I'm sure the company that makes them will offer them on their site once all the work is done.
 

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Awsome project! Keep up the good work. It's all coming together nicely.
 
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Thats a nice clean bike. I was thinking the first year for the single range transmission was the 97 though. The 97-99 single range was known for the cases cracking on the starter gears. I've had several over the years with that issue. It may be too late for you to consider it but the 400 and 350 big bear had the same cases. You can actually change the transmission out of the 400 to get the better gearing they had. For that matter you can put the whole bottom end or just the crankshaft and cylinder and move it up to a 400. Good luck
 

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Discussion Starter · #16 ·
Thats a nice clean bike. I was thinking the first year for the single range transmission was the 97 though. The 97-99 single range was known for the cases cracking on the starter gears. I've had several over the years with that issue. It may be too late for you to consider it but the 400 and 350 big bear had the same cases. You can actually change the transmission out of the 400 to get the better gearing they had. For that matter you can put the whole bottom end or just the crankshaft and cylinder and move it up to a 400. Good luck
You are correct the quad is actually a 97...produced 11/96...but I could not change the heading to the thread after the fact. :wink2:

Thanks for the information on the quads with the same issues I have had, and the info about the 400 vs 350. I did consider the 400 upgrade, but decided for now to just stay with the stock 350....but there is always the future....:grin2:
 

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Discussion Starter · #17 ·
Well I had some time to actually look at the cases I bought closely....turns out there are 3 M6 outer case bolts snapped off, and the threaded shaft the gear selector rides on is also snapped off in the LH side case. As well as it looks like they used screw drivers to split the cases. Most of the surfaces look OK, but near the rear engine mount they really jammed a screw driver in there to pry and the case matting surfaces are pretty chewed up.

Gonna see if I can get an extractor kit, or at least some left hand drill bits and see if I can get the bots out, but not sure I should waste my time if the cases are damaged from the screwdrivers. Can you just use a little RTV on the matting surfaces to help seal them up?
 

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I would see if the seller will take them back.
Used engine cases are available, try again and get a set with good sealing surfaces.
Silicon works for awhile, but it will eventually leak. If the bad spot is in the crank area, it will mostly likely blow out from pressure developed with piston movement.
The bolts, or screws may just unscrew with a vice grips, they usually get loose when the tops are removed.

Another thing, be sure and get a pair of cases, that were together from the factory. A left from one bike and a right from another may have a very small difference you don't notice or cannot see and you will have a leak.
 

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Discussion Starter · #19 ·
Thats a nice clean bike. I was thinking the first year for the single range transmission was the 97 though. The 97-99 single range was known for the cases cracking on the starter gears. I've had several over the years with that issue.
Do you know why the case cracked on these single range tranny units? Trying to start it in gear, or ????
 

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Well I had some time to actually look at the cases I bought closely....turns out there are 3 M6 outer case bolts snapped off, and the threaded shaft the gear selector rides on is also snapped off in the LH side case. As well as it looks like they used screw drivers to split the cases. Most of the surfaces look OK, but near the rear engine mount they really jammed a screw driver in there to pry and the case matting surfaces are pretty chewed up.

Gonna see if I can get an extractor kit, or at least some left hand drill bits and see if I can get the bots out, but not sure I should waste my time if the cases are damaged from the screwdrivers. Can you just use a little RTV on the matting surfaces to help seal them up?
You certainly could use some RTV to help seal the damaged areas.

You can also rebuild the damage areas with JB weld two part epoxy and block sand the them flat and true again.
 
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