Advice ons plitting the cases on a 450

[maparker]

I sourced a box full of transmission parts for the 450...I think its just a bent shift fork, but won't know for sure. I've got the engine out and upside down on my work bench (not very light for a twin when you are picking it up yourself!)

I am trying to get to the tranny with an absolute minimum of dissassembly. I have loosed all the bolts on the bottom and am trying to figure out how to get the cases apart. My manual is telling me I have to pull but the starter clutch and the other clutch off the crank. I don't really want to do this as I just want access to the tranny and the shift forks etc. Anyone ever split the cases on a 450 and know if i really need to do all this or can I get to the tranny without pulling the clutches?

Thanks!
Parker

[Dave8338]

You can likely get to the trans with just pulling the clutch basket and its' assorted pieces/parts. I've never worked on a 450 GS but if the manual is like most others, it usually has a few extra steps that are not needed to do a specific repair. Much like the first line in most all repairs to a car states: begin by removing the positive battery cable from the battery...yeah right!

[GregT]

Just went & checked my memory against a disassembled 450 bottom end...
Right. To access the trans, start at the top. Take the cams out - quick & easy - the front camchain guide locates in the lower case & you won't get it back together with the guide sticking down & the chain under tension.
Remove the buckets & shims while you're in there - before they fall out. Mark where they came from of course.
Flip the motor. I don't think you need remove the clutch to split the cases but ensure all the pieces that cross the joint face are removed - covers, seal retainers etc. Look for any hidden bolts.
Pry gently & it should come apart.

Greg T

[maparker]

Thanks for the replies guys but, Uh oh, one for removing the clutch, one against... Crap.

Anyone else?

Other opinions on pulling the cams?

[maparker]

Pulled the clutch and there was little bracket that bridge the cases, pulled all that and they came right apart. Nothing obvious wrong in the tranny.

Little re-cap, I was riding about 65 mph and heard a bang and the bike didn't want to shift right. Nothing appeared wrong with the engine, starts fine idles, etc. Just wouldn't shift right, up could change to every gear, but you had to move the shifter up and down to get it to shift through all the gears. I hoped to see something obvious like a bent shift fork, etc. I cant see anything. I've pullled the gears and they look fine. I'm puzzled because I can't seem to get the shift forks to move smoothly through the shift cam. They seem to bind at the turns, I don't know if they are bent the shaft is bent etc.

Any suggestions would be greatly appreciated. I can post specific pictures of anything if that would help too!

Thanks,
Parker

[gearhead13]

Well, It will be hard to tell how well it shifts until the cases are back together. I would suggest replacing the shift drum, forks etc with the stuff you have, throw the other half on with a few bolts and see if it improves.

[GregT]

You can dummy up the complete gearbox in the bottom case & run through the gears.
Have a look at the dogs for rounded corners - if it's jumped under load it may have bent more than just a shift fork.
The rails for the forks pull out & can be checked for straight. With them out rotate the shift drum by hand - if it's bent (most unlikely) you'll see it.
Turning the shafts in the bearings will tell you if they're straight

Greg T

[bwringer]

A bent shift fork is a very subtle thing -- difficult to detect by eye.

I'd say replace the old stuff with the other stuff and try it out.

[maparker]

Hey thanks for all the input everyone. I think that I'll put the new stuff in and see how it seems to work with the cases bolted back together. If it seems good then I'll button it back up and give it a rip I guess.

Thanks,
Parker

[maparker]

Anyone out there got any advice on putting the cases back together?! There was no gasket when I split them...are they machined to such tight tolerances that you don't need a gasket? Should I use RTV or something similar? Please advise!

[bwringer]

Soooo... sounds like you're doing this without a manual, huh?


Anyway, the case sealer you need is sold under a couple of different names. Do NOT use RTV silicone or anything you find at an auto parts store.

I like ThreeBond Semi Drying Liquid Gasket:

http://www.z1enterprises.com/detail.aspx?ID=178

YamaBond 4 is the same general stuff and may be easier to find -- poke around the local motorcycle/dirtbike/ATV shops. Don't let them sell you RTV.

[maparker]

Thanks for the quick reply!

Yeah, I just pulled the motor and kept taking things off until I could get the cases apart. I do have a Chilton's or other generic manual, but in most cases it is not the most useful as it covers 400, 425 and 450s. Still I often prefer the advice of others who have been there done that as it is usually more useful!