Noisy 5th gear...

[pmcburney]

Hi all,


Having finally gotten the Kat registered (no thanks to Team Moto... tools ), I've been riding it around a fair bit shaking it out.

All looks good apart from a leaky cam-chain tensioner (easy fix) and 5th gear is pretty noisy.
I'm thinking it's simply age related with the gradual degredation of the case-hardening, I've had it on previous bikes as well...

My question is, is it possible to split the cases without removing the barrels - i.e. how hard is it to pull the bottom case off only and then put it back together?

If it's not too difficult, this would be the quickest way to replace both 5th gears without doing a complete teardown with new gaskets and rings and valve guides and cam chains and such.


Any info about similar experiences greatly appreciated
Thanks
Paul

 

[Suzuki_Don]

I have not done this particular task myself although I have split the cases on my own motor in a complete teardown.

But it is the way to go. Drain all the fluids, turn the motor upside down on the workbench, remove the sidecovers (clutch, Generator, etc) and any other parts that connect to both of the cases. Gear selector, clutch plates, etc will need to come out. But the cylinders, head, cam cover, etc can all stay in place. The generator rotor can stay in place. Just make sure the crankshaft stays in the upper case as you withdraw the bottom half.

Undo all the crankcase bolts after removing the sump and the bottom crankcase half should come off. Make sure you have not missed any bolts (there are 6mm & 8mm ones) some can be obscurred by grime, others are just hard to find, then there are the two on either side of the output sprocket. On my motor there were 31 bolts to be removed. I am assuming this bike is chain drive.

Then the two transmission shafts will lift out of the upper case.

The noise could be worn teeth on the gears or worn bearings holding the shaft, only a visual will tell you that.

There will be something that I have forgotten to mention, but it will become obvious when you are doing the job. If I have made any incorrect statements others will correct me.

Good luck, it should only take a couple of days to complete the job.

P.S. A pic of my 6th gear is attached for reference. I only found this on reassemblying the transmission shafts in the motor. On my initial inspection of the transmission I did not see the damage as it was only on one side of the tooth and I was rotating the gear in my fingers and only viewed the tooth from the other side. Make sure you do a better inspection than I did initially.

 

[Nessism]

P.S. A pic of my 6th gear is attached for reference. I only found this on reassemblying the transmission shafts in the motor. On my initial inspection of the transmission I did not see the damage as it was only on one side of the tooth and I was rotating the gear in my fingers and only viewed the tooth from the other side. Make sure you do a better inspection than I did initially.

I've seen this kind of damage before and think it's at least partly due to lubrication film breakdown. Not trying to start yet another oil thread but the transmission really chews up oil so it's important to use a high quality diesel or motorcycle specific oil in our bikes. Some people claim auto oils "never let me down" or similar such claims, but damage like this gear show hidden damage that some people never see until it shows up as gear noise or similar - one of those ignorance is bliss things I suppose.

 

[trippivot]

the picture of that gear is ugly

 

[Suzuki_Don]

I've seen this kind of damage before and think it's at least partly due to lubrication film breakdown. Not trying to start yet another oil thread but the transmission really chews up oil so it's important to use a high quality diesel or motorcycle specific oil in our bikes. Some people claim auto oils "never let me down" or similar such claims, but damage like this gear show hidden damage that some people never see until it shows up as gear noise or similar - one of those ignorance is bliss things I suppose.

The funny thing is that there were no indications that I had any gear problems before I pulled the motor down. No noises of any kind. The wear happens on the 6th gear in my case and on 5th gear on the larger GSs because that is the gear that is used the most. A lot of time spent in top gear compared to the other gears.

Ed is the diesel oil better as far as property breakdown goes with the transmission compared to normal oil (I use MOTUL mineral). Does synthetic oil give better protection to the gears?

On another issue any advice on which oil to use and how long to use it for before changing over to synthetic on my new motor when I get it going. The motor has been completely stripped and cleaned out. No sludge or such stuff in the bottom end. Barrels honed, new rings, etc. Do I run it for a couple of oil changes on mineral oil and then switch to synthetic. How long before the first oil change.

Thanks for any info. I am going to have another go at fitting the cylinders to the pistons today, hope I don't break any rings this time.

 

[Nessism]

Regular 15W-40 diesel oil would be good for your first fill after a rebuild. That Motul oil is fine too but kind of a waste of money in my opinion. You can go to synthetic right off the bat if you want but I'd hold off and change the first oil out after about 500 miles or so, mostly to get all the dust and dirt out of the engine that always seems to accumulate no matter how clean you are during the build. Synthetic oil is not more slippery and shouldn't effect how the rings seat contrary to what some people claim but still, I'd wait for one oil change.

When installing the cylinder it helps to have some blocks under the cylinder and then rotate the pistons up into the sleeves. If you try to drop the cylinder down over the pistons it's easy for the cylinder to fall and pinch a ring.

Good luck

 

[pmcburney]

Thanks for all the info...


The only thing that bothers me about this is how difficult it's going to be to slot the selector forks back into the gears on the input and output shafts.

If a GSX bottom-end is anything like a GT bottom-end, the selector drum and forks reside in the bottom case - the gear shafts and crankshaft can sit in either the top or the bottom.

Thoughts?


Cheers
Paul

 

[Nessism]

Thanks for all the info...


The only thing that bothers me about this is how difficult it's going to be to slot the selector forks back into the gears on the input and output shafts.

If a GSX bottom-end is anything like a GT bottom-end, the selector drum and forks reside in the bottom case - the gear shafts and crankshaft can sit in either the top or the bottom.

Thoughts?


Cheers
Paul

I can't remember which half goes on last but the shift forks were not really a problem so don't worry.

 

[waterman]

I have to agree with Ed, the shift forks are not too bad to reinstall. Not nearly as tough as fitting cylinder over pistons and rings.

Not sure which Kat you have, but on the 650, I put all of the gears on the upside down top half of case and then fit bottom case. The shift forks are a little tricky but pretty much only go in one way, otherwise it won't fit tightly together. I used a pick to help guide it into position as I lowered bottom half.

Once assembled, I also spin input and output shafts to make sure nothing is binding. I will do a "dry" fit without case sealant to get some practice before final assembly.

Pay particular attention to any pinned bearings, the pins need to fit in their recesses.