Gearbox question (for the long-term owners)...

[pmcburney]

I've done a couple of long trips on my RE lately.


Approx 3000 km to Bathurst and back, and another 1000 km round trip over the weekend.

I've noticed that fifth gear, at low revs - say 2500 rpm, has (I think) developed a noticeable whine.

Much the same as my Katana 1100 (they are renowned for it), but the RE has many less km on it.

I dropped the oil and noticed some metal in it - not a crazy amount but a noticeable 'sheen' for sure.
I'm assuming the case-hardening is deteriorating as it does in the GSX engines.

Are RE gearbox's prone to the case-hardening failing and developing a fifth gear whine?
It's the same 'box as a GT750 - my GT has no such whine with many more km as well...

How difficult a job is it to change gears in the 'box if needs be?

[FC Zach]

I'm not sure of the whine. You think it could be something else like the chain and/or sprocket that's causing the noise?

If you do end up needing to remove the transmission to further inspect the gears, you will have to completely remove the engine and tranny to do so. Not fun at all

[kettle738]

I'm not aware of a whining box on my RE5M, but that could just be because it's obscured by the exhaust noise. I do have two GT750s though, a first year J model that has just had a total engine overhaul including the gearbox by one of the UKs most noted two stroke engine builders and that box whines in fifth dreadfully, (first and second were renewed, the rest were all good) and to a lesser extent in some of the lower gears.

I also have a last model GT750B with just 8,000m from new that I have owned since 3,000m. This bike has never had any work on the engine beyond setting the timing and fluid changes; that one also whines in fifth. I've probably had a dozen GT750s over the course of 30+ years and to the best of my recollection they were all whiners to some extent.

I'm on my fifth RE5, (one still not ridden yet) and I can't say I've ever noticed whining but that's probably because I'm too busy cursing the horrendous transmission grumble that afflicts them.

I do remember gearbox whine on my very first 'proper' bike, a Suzuki T250J and I've always thought it to be something of a 1970s Suzuki peculiarity and not necessarily something to be too concerned about.

Mick..................kettle738

[Tonny]

Mine had the same whine in 5. gear. I changed the ball bearing and both 5. gear sprockets.
I am not sure it was the sprockets, but I would not take the chance, not change them,
At home I have close up pictures of the sprockets. There were some marks on the sprockets and the tooths a bit darker and a bit rusty.
Sorry for my English and sorry for the size of the pictures





-Tonny

[gerryggg]

A lot of motorcycle gear boxes seem to develop this galling and the whining when run with standard motor oil rather than one specifically made for motorcycles. From what I understand from the late Bob Wehman of Spectro Oils, most multi-grade automotive oils use a polystyrene that is very prone to shearing. When used in a gearbox (something rarely if ever done in an automobile) they break down to their base stock, usually 10W (on 10W40 oils) and can lead to galling of the gear teeth and excessive cam lobe wear on overhead cam engine. That might explain your problem as well as the relatively short cam and rocker arm life on many of the CB350/360s and KZ400s in the 70s. I don't recall there being a lot of motorcycle rated oils back then. I know the JASO now has a MA (motorcycle application) classification. I know some Suzukis have a distinctive whine when new due to a rough surface, I believe from the sintered metal gears. This actually seems to decrease as mileage accumulates.