Walker Fowler Returns to the Center of the Box at the FMF Steele Creek GNCC
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By marcosphoto
Hi folks, a little disparity brought me to this forum. To set the stage, I'm a 35 auto tech in the industry 37 years now. Licensed motorcycle tech also, 20+ years. I race superbike and motocross. Always done most of my own standard work (outside of specific race machine works) including building my own race bike engines. Now that skills are out of the way, onwards and upwards.
Helping a neighbor with his old quest 500, right front axle seal leak. Well, looks like everything else - right? Wrong! Initially I noticed the CV joint was lacking large lands to place prybars on to pop it out, rather a thin shield like ring very close to the diff seal. Knowing the ring appeared quite delicate, I only pried gently and the CV popped out. However this is where things get weird. Came out only around 7-9mm then hung up again, felt like the clip was catching inside the diff. So spun and pulled, spun and pulled until I was blue in the face but no success getting it out. Also while it was out, I could see that the delicate ring around the outer circumference of the joint was actually the sealing surface where the seal contacts, instead of the norm where the seal rubs inside the diff much deeper and stays cleaner. I've never seen a joint like this, also the service manuals photos which apply to 650 also reflected a standard joint I am accustomed to rather than this one I was fighting with. Rather than break something in the diff, I decided to stop while I was ahead and reassemble the machine before something broke. (The joint would pop in and out of place easy enough, just wouldn't slide out further than 7-9mm). While the joint was a little out and sealing surface exposed, I cleaned the seal and sealing surfaces clean as possible before putting back together. Seems to be holding for now, but eventually I'm sure the leak will come back. Any thoughts as to why that CV joint just refused to come all the way out?
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By 86ccord
Just picked up a 2008 Big Bear 250. It was sitting for about 1 year it's definitely a project. Currently chasing down a no spark issue. Imagine that lol
Tons of info around the forum. I look forward to learning!
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By psychodad
Just rebuilt a 2006 Yamaha Big Bear carb for a friend and would like to double check the float height before I give it back to him Anyone have a manual they could look it up in or a really good memory.
Thanks
Jim
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By VikingTrad3r
I have an 86 yfm250 (moto4 250) i picked up.
It bogs and pops a bit out the tailpipe if you can even get it higher up in the rpm. It is pretty gutless. I have other 250’s (timberwolves) and its ultra gutless compared to them.
It has an aftermarket carb on it that has a “W” on it Its not a mikuni but it looks close
i figured jetting was off at the high end.
i had a mimuni that was very crusty, swapped the main jet into the W carb, and the needle, which was set on low slot 4 so left it there.
it actually ran much better, and cured what i thought was a problem caused by a lean condition from the W carbs main jet being too restricted when i compared to the factory mikuni
I had it out and was enjoying the upper rpms that i couldnt reach before without bog. at wot it would fall on its face low top speed.
after getting it hot, it would actually refuse to start after dying.
back to the drawing board.
when i first got it i adjusted the valves. So i retraced my work and thought maybe id overtightened. double checked, nope all good. .005 exh , .003 intake, check.
So i checked the compression.
here is the trickyness. help me understand this. I am at 3500ft asl in calgary canada
- initiate test, it goes to 75psi right away. this is low. Even at my elevation im thinking 110psi minimum
but....this thing starts no problem. even -20c it starts. makes no sense to me. so i press the starter again and it goes to 85. Then i press it again and no change. Then i turn over again and it jumps to 95. Then again...no change. Then again and it goes to 115. finally finishes at 120 and i cannot get it to go any higher than this.
ive repeated this multiple times.
i press and hold the starter...it will max at 75. Then a series of maybe 10 more quick turnovers from the starter and compression inches up to 120psi.
So, i think the low compression explains the low top end, and even the backfiring out the exhaust when hot. The exhaust is rich enough (incomplete combustion in chamber) and to ignite in the muffler.
it gets worse when hotter.
makes me think i have a crack, or something that is low down on the cylinder wall. When the piston stops just above it on the upstroke, and i then turn it over again, it adds pressure to my tester reading.
thoughts?
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