Gearbox removal

[Frasier]

Dear experts, I have to take out the gearbox, it seems. The question is: if I take the engine out of the frame, is it possible to remove the lower half of the engine, and take out the gears WITHOUT removing the cylinders, pistons, cyl.head etc.? Thank you in advance.

[Gnasher]

Dear experts, I have to take out the gearbox, it seems. The question is: if I take the engine out of the frame, is it possible to remove the lower half of the engine, and take out the gears WITHOUT removing the cylinders, pistons, cyl.head etc.? Thank you in advance.

No.   The bike doesn't have just a gear box, the gear cluster is within the engine casing and there's 2 bolts that sit under the barrel block.  These are either side of the cam chain void and cylinders 2 & 3.


Why do you need to remove the gear cluster?       

[Frasier]

English is not my first language - I mean the gears. The reason is the usual: I have to examine the gears, and shifter forks, it randomly jumps out of gears under load.Sooo, a complete engine disassembly waits for me, it seems....

[unfazed]

To dismantle the gearbox of the FZS600 you have to do a full engine strip.
The reason: Yamaha put two crankcase bolts under the cylinder barrels and you cannot remove the bottom half of the crankcase without removing those two bolts 

[Frasier]

Thank you all.

[Frasier]

Disassembled the engine, removed the gears. TBH the gear dogs didn't seem too terrible, but if it jumps out of gear what can I do...I was lucky to find a low mileage gearbox from a '94 FZR600R, and combined the best gears into a working unit. The 2nd gear pinion is a b**** to remove and install... Now I wait for some Loctite sealant, then I'll reassemble the engine.Just for my own entertainement, added the costs of necessary parts together, if everything was new. Wow. Good thing that almost everything's available new, but a complete transmission overhaul, some crankshaft bearings, a complete gasket set adds up to the value of my bike, even if every work is done by me.

[Gnasher]

Disassembled the engine, removed the gears. TBH the gear dogs didn't seem too terrible, but if it jumps out of gear what can I do...I was lucky to find a low mileage gearbox from a '94 FZR600R, and combined the best gears into a working unit. The 2nd gear pinion is a b**** to remove and install... Now I wait for some Loctite sealant, then I'll reassemble the engine.Just for my own entertainement, added the costs of necessary parts together, if everything was new. Wow. Good thing that almost everything's available new, but a complete transmission overhaul, some crankshaft bearings, a complete gasket set adds up to the value of my bike, even if every work is done by me.

Jumping out of gear isn't always the gear box it can be a clutch issue.  The gear selectors don't wear as such (accept in the extreme) they bend and it doesn't take much, to stop the gear fully engaging and getting jumping out of gear.  Also be aware 2nd and 6th gear ratios are different on the FZR600, which will mess up how it accelerates, so make sure you use the FZS600s pinons and gears.     

[Frasier]

Thanks. FYI I didn't use the FZR600 transmission, but the '94-95 FZR600R, which is identical to FZS600 and YZF600R Thundercat. I cheched all the parts, the shift forks look good, measured to be square, no bend. Shift drum is like new, the bike has 36 000 kms in it. Clutch is ok.Some gear dogs were rounded off unfortunately, but I was able to replace them with donor parts.

[Gnasher]

Thanks. FYI I didn't use the FZR600 transmission, but the '94-95 FZR600R, which is identical to FZS600 and YZF600R Thundercat

 

I cheched all the parts, the shift forks look good, measured to be square, no bend. Shift drum is like new, the bike has 36 000 kms in it. Clutch is ok.Some gear dogs were rounded off unfortunately, but I was able to replace them with donor parts.

Often it's nothing more than bad adjustment, push rod and cable play. The possibility is the clutch push lever assembly and/or ball screw housing are worn.  If there's not enough push (it's only mm) the clutch wont disengage properly, the gear will not fully engage and drop out.     

[unfazed]

Disassembled the engine, removed the gears. TBH the gear dogs didn't seem too terrible, but if it jumps out of gear what can I do...I was lucky to find a low mileage gearbox from a '94 FZR600R, and combined the best gears into a working unit. The 2nd gear pinion is a b**** to remove and install... Now I wait for some Loctite sealant, then I'll reassemble the engine.Just for my own entertainement, added the costs of necessary parts together, if everything was new. Wow. Good thing that almost everything's available new, but a complete transmission overhaul, some crankshaft bearings, a complete gasket set adds up to the value of my bike, even if every work is done by me.

Jumping out of gear can be caused by broken spring on the Shift Drum or Shift Shaft or both. I remember someone on here a long time ago and he had a bend on the drum rotating mechanism on the shift shaft which was causing his gear lever not to full rotate the drum to the next gear