So I was eating breakfast a week ago Friday morning and doing a little market place surfing when an ATV showed up half hour from my house . It was a Yamaha, it had papers, it supposedly ran when parked but smoked...what could possibly go wrong for a 3 digit price ?
I present to you the 99 Yamaha Big Bear. It's 2wd and came with what I thought was compression when I pulled the pull cord over . Boy was I wrong.
When I got it home Friday night I popped the plug out, threw some mixed gas in the cylinder and tried to get it to fire ...my first sign should have been the heavily oil encrusted spark plug end. My second sign was that it wouldn't even pop. My third was it felt the same loose/tight cycle when I pulled it over without the plug in (but it did have great fire).
So apart it came. Thankfully you can do a top end job in the bike on these and within an hour and a half I had found culprit.
The bear bears bad news.
The cylinder probably could be cleaned up but people seem to have great luck with the Chinese cylinders for this bike, so against my better judgment I put the order in to Bezos power sports and got a jug and top end kit coming.
I'll be watching this one. I have a 99 grizzly 600 4x4 basketcase. My cousin bought it thinking(hoping) it just needed a tune up, but the cam was snapped in half. He bought all the parts to fix it and lost interest, now its my pile of parts.
In reply to TJL (Forum Supporter) :
I really enjoy doing engine work, so this was a fun quick one.
Parts arrived Thursday but I wasn't able to do much other than check the rings and do a quick mock up.
I was going to run the head as is but since the bike obviously got really hot I figured I'd get a proper gasket kit (I'm sure the head gasket that came with the kit would have been fine...but it felt kind of cheap).
I went down the road and borrowed this fantastic homemade valve spring compressor from a neighbour. Lapped the valves and installed new valve seals, which was a first for me.
With the head done it was time for assembly. Check those rings, fight with that forward timing guide . And slide all 3 rings into the bottom of the cylinder . It almost looks like a motor again.
You can see the hg I didn't use in the picture. It wasn't flat and I just didn't like the feel of it so I used the gasket out of the winderosa gasket set.
No picture of the head install, but it all went quite smooth. Got the timing right on the first go having set the valves on the bench (will re check after some heat cycles).
With everything back together I poured a little gas down the carb feed line and it started first pull!
After running 30 seconds I shut it down and dropped the oil. As you can imagine it was glitter city even after having flushed the case and oil cooler . So fresh oil again and a new filter then I was able to let it run a little longer .
Pushed it out of the garage and let it idle for 10 minutes to get some proper heat in it.
A little test ride around the yard shows that I need to clean the carb. Won't rev up under load without a little bit of choke.
Now, let the record show I dislike carbs quite a lot. This seems to be some sort of Kehin cvk type deal. While I did pull the bowl and blow out the primary and secondary jets I didn't really clean the carb properly so I wasn't too surprised when it wouldn't run quite right.
So instead of fixing that I tackled the lack of brakes. This bike had disk up front and a single drum in the rear. I like disk so I started there. The sight glass in the master cylinder was indicating either over full or empty. That's when I noticed the two screws that hold the cap on were mangled and stripped. Out came the angle grinder and I cut a notch in each, a flat head screw driver was then able to turn them out. There was some scaring on the cap but once the reservoir was filled and the front brakes bled I had functional front brakes. I think someone may have swapped the lh caliper and never bled it...but that's just a theory.
I then proceeded to adjust the rears but they are out of adjustment room so I'll have to get a set of shoes and tear into it.
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