need opinions on trans problem.

dannygraves · Post by **dannygraves** » December 26th, 2007, 11:43 am

So I tore into a friends yz250 motor this weekend and found the problem. He was having issues shifting into 1st. now I know for sure I'm going to replace the shift fork and shaft, but should I replace these 2 gears? Hes on a budget and only fixing this bike for his wife to ride, not going to hammer it. But I'm also a "do it once do it right" kind of guy and want to replace everything. here are the pics, tell me what you think I should do. the dogs are rounded, but not really that bad.

100hp honda · Post by **100hp honda** » December 26th, 2007, 12:27 pm

how much money he want to spend. gears are $75- $100 a pop typically. the rounding doesnt look bad, ive seen alot worse. put a new fork in there and slap it back together. if it only gets used 4-5 times a year and casualy riden by his wife then it wont ever see much need to have new parts. is that a brass insert in that gear?

britincali · Post by **britincali** » December 26th, 2007, 12:29 pm

I would replace the shift forks and the gears, it will only be a matter of time before they start jumping out.

100hp honda · Post by **100hp honda** » December 26th, 2007, 12:35 pm

i take back my first comment, sell the bike and buy HONDA (cr500 specifically).

. if thats what im thinking, that gear has a brass insert and spins directly on the counter or main shaft, with no steel collar? what were those yamaha engineers thinking

TJC510 · Post by **TJC510** » December 26th, 2007, 12:55 pm

i would replace the gears. there both preaty bad. the gears will end up putting pressure on the forks and cause it to grind it down again. just my .02

bigpower · Post by **bigpower** » December 26th, 2007, 2:07 pm

I'd try to get some different size thrust washers and shim the tranny. Thats a little trick I learned from a very experienced bike wrench. Those forks are toast(like, they either don't change the oil often enough, or they use shit lube), but you still got life left in those gears. I'm not seein any chips in the teeth, but my eyesight been suckin as of late. Take and clean up the edges of the dogs with a small file, and see what you can do to take up a little of the slop.
Ever grab the end of your countershaft and try and move it in and out? Most have a bit of end play, the older the machine, the more(usually, but not always)end play. Our KDX was real sloppy, but a combination of new bearings and tightening the shaft with some thicker thrust washers got it way down. It's the original trans, and it had some huge mileage on it. You can shim the gear over a bit so the dogs engage a little deeper, and still keep enough clearance when not engaged. That KDX is the best shifting bike I've ever ridden. I'm tearing down the 98 and am going to do the same thing to it. It's starting to get a bit sloppy.

What the hell, while you got it apart, at least talk him into spending the nut for bearings

dannygraves · Post by **dannygraves** » December 26th, 2007, 2:10 pm

thanks guys, just verified my thinking. I'm gonna tell him to buy 2 new gears, the shift fork, the shift fork shaft and circlips for the shaft. total w/o shipping from metric parts direct (formerly yamaha parts direct) is about $120. not too bad. Yeah, I'm not too impressed with the way this yamaha is designed, the shift forks are weak ,when the same happened to MFDBs bike, his fork turned blue because it put up such a fight, this yamaha shift fork has a more french mentality and is weak and gives up.
the bearings for the back sides of both shafts are rollers directly on the shafts, another thing I didn't like. The bearings don't press in all that tightly either, most of them came out of the cases when I split them, the crank one stayed on the crank.
one other question for you guys, how to you tell if a nicasil jug has to be bored and replated? this one had a lot of blowby showing on the piston above the pin on each side. I'd like to get away with a re-ring, because a bore and replate with get $$$.
it has a crosshatch showing a little on the sides, but only showing small amounts here and there.

bigpower · Post by **bigpower** » December 26th, 2007, 2:19 pm

dannygraves wrote: one other question for you guys, how to you tell if a nicasil jug has to be bored and replated? this one had a lot of blowby showing on the piston above the pin on each side. I'd like to get away with a re-ring, because a bore and replate with get $$$.
it has a crosshatch showing a little on the sides, but only showing small amounts here and there.

If its scared or you got aluminum showing thru the plating.

Otherwise, hit it with some oven cleaner, while its soaking in the oven cleaner, follow the crosshatch with a medium scotchbrite, rinse and run
Clean out the powervalve system real good

Post by **AlisoBob** » December 26th, 2007, 2:20 pm

dannygraves wrote:it has a crosshatch showing a little on the sides, but only showing small amounts here and there.

Then I would think its not plated.

Plated bores dont wear... period.

dannygraves · Post by **dannygraves** » December 26th, 2007, 2:21 pm

sweet, thanks!

bigpower · Post by **bigpower** » December 26th, 2007, 2:21 pm

AlisoBob wrote:
dannygraves wrote:it has a crosshatch showing a little on the sides, but only showing small amounts here and there.
Then I would think its not plated.

Plated bores dont wear... period.

The factory ones do.

dannygraves · Post by **dannygraves** » December 26th, 2007, 2:43 pm

AlisoBob wrote:
dannygraves wrote:it has a crosshatch showing a little on the sides, but only showing small amounts here and there.
Then I would think its not plated.

Plated bores dont wear... period.

nope, definitly plated, might just be carbon or something playing games with my eyes, I'm gonna clean it up and see what it looks like. I'm thinking a clean-up with some new rings will do it good

Post by **AlisoBob** » December 26th, 2007, 2:54 pm

It must be some shitty kind of plate job then.

I know a friend who flies a Harmon Rocket... Hard. 28" x 2800 rpm everywhere.

His Lycoming I.O. 540 ( nickel plated iron cylinder) looked friggin new, after about 1200 hours.

His nickel plating is done by Sentry Aircraft Cylinders in Texas.

bigpower · Post by **bigpower** » December 27th, 2007, 3:07 pm

AlisoBob wrote:It must be some shitty kind of plate job then.

I know a friend who flies a Harmon Rocket... Hard. 28" x 2800 rpm everywhere.

His Lycoming I.O. 540 ( nickel plated iron cylinder) looked friggin new, after about 1200 hours.

His nickel plating is done by Sentry Aircraft Cylinders in Texas.

Thats pourin the coals to it, but Lycomings are pretty tough( with the exception of some 540's manufactured in the 90's with the soft crank)

The bike manufacturers are like any other big biz, they get the cheapest plating possible. I thought that the repair and replate job Millennium Technologies did for our KDX was a steal at 250 bones shipped. The job was flawless, the material is top notch. For what a new bike costs, you'd think they could get similar quality, but unfortunately, they don't.

Nice bird there, Bob. Fast

Post by **AlisoBob** » December 27th, 2007, 3:54 pm

That isnt my buddies, just a stock photo to show what a Rocket looks like.

His is White / Green....

Friggin Irish...

ISBB · Post by **ISBB** » December 30th, 2007, 3:12 pm

i have spent many of hours in rv4's and 6's only hoping and wishing to get skinny enough to fly a rocket or even a radial rocket now that would be bad ass... but as it is.. im fat and dont make enough money to enjoy the sport anymore.. ugg

dannygraves · Post by **dannygraves** » December 30th, 2007, 6:21 pm

hey man, all I want is a little cesna 172... i'd be happy with that

britincali · Post by **britincali** » December 30th, 2007, 8:43 pm

dannygraves wrote:hey man, all I want is a little cesna 172... i'd be happy with that

I got 32 hrs training in one of those

dannygraves · Post by **dannygraves** » December 30th, 2007, 8:46 pm

I have my book somewhere, I've got a few hours in a 150, a few in a 152 and probably 9 or 10 in a 172. My dad always being drunk and late to take me to my lessons made me go through a few instructors

. too bad my mom put the brakes on all that, I could have a much more entertaining job now

dannygraves · Post by **dannygraves** » December 30th, 2007, 8:47 pm

oh yeah, and a couple in a 180 what a beast!

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » January 2nd, 2008, 1:48 pm

gears screwed the forks, bushings are oem

ISBB · Post by **ISBB** » January 2nd, 2008, 3:13 pm

dannygraves wrote:oh yeah, and a couple in a 180 what a beast!

RV4's RV6's, 150's 152's 172's 177's and the airforces version of a 172 with the back seats ripped out and a 180hp lycoming crammed in there... THAT was a fun plane to fly..

Only have about 80-100hrs logged would have to get my book and add them all up again.. Am going to however get back into it.. Found out a friend of mine has a 172 i might be able to make a deal with

BannedCR500Riders.com

need opinions on trans problem.

need opinions on trans problem.