GSX1100 ET 5th Gear Whirring

[Russ750ET]

The 1980 GSX1100 has been slowly developing a whirring noise in 5th gear. Not horrendous but definitely there. Doesn't make the noise while coasting, only when on the throttle.

Shifts through the gears absolutely fine.

I'm thinking it's the 84,000 miles on the clock that may be the cause.

Obviously I need to open it up and investigate, but I was wondering if anyone else has encountered this and what is likely the be the cause?

Mainly so I can get an idea of what I'm getting into parts and price wise etc

 

[Duckndive]

 In top and under load "direct drive basically" 

So are you referring to "coasting" as on the over-run throttle closed in top gear ?  

[Russ750ET]

5 minutes ago, Duckndive said:

 In top and under load "direct drive basically" 

So are you referring to "coasting" as on the over-run throttle closed in top gear ?  

Yep. The noise only occurs when there's load on the engine when on the throttle, in top gear. 

[imago]

I haven't had it personally, so I'm going on the box design and symptoms rather than experience.

That said, they're a simple set up as transmissions go, mainshaft and a layshaft with a roller bearing at each end of both. So bearing noise under load in top is going to have both shafts rotating at their highest rpm. To me that means the most likely culprit would be the roller bearings at the sprocket end of either shaft as that end gets a bit more thump in terms of radial load. However, I'd say that if you're that far into the box with that amount of mileage you'll be replacing all four roller bearings anyway. 

[Russ750ET]

20 minutes ago, imago said:

I haven't had it personally, so I'm going on the box design and symptoms rather than experience.

That said, they're a simple set up as transmissions go, mainshaft and a layshaft with a roller bearing at each end of both. So bearing noise under load in top is going to have both shafts rotating at their highest rpm. To me that means the most likely culprit would be the roller bearings at the sprocket end of either shaft as that end gets a bit more thump in terms of radial load. However, I'd say that if you're that far into the box with that amount of mileage you'll be replacing all four roller bearings anyway. 

 

Awesome cheers. That certainly sounds like a likely cause.

I think I'll just go steady on her for the remainder of the summer and not do any excessive millage.

But it looks like an engine out and full strip is on the cards, something to keep me busy over winter!

[imago]

34 minutes ago, Russ750ET said:

 

Awesome cheers. That certainly sounds like a likely cause.

I think I'll just go steady on her for the remainder of the summer and not do any excessive millage.

But it looks like an engine out and full strip is on the cards, something to keep me busy over winter!

The good thing is it sounds like wear (whirring) and with roller bearings it'll just get louder as it wears more. If it was a rumble it'd be more of a concern.

It shouldn't be too bad to do though, the expensive bit is usually the gaskets now oddly enough. When you do it if you hit some weird/rare unobtanium give me a shout as I have a few engines on the rack and I'd be happy to help keep your dad's old bike rolling. 

[TonyGee]

I would say its more likely to be the teeth on the gears that are a bit rough.  

[imago]

6 minutes ago, TonyGee said:

I would say its more likely to be the teeth on the gears that are a bit rough.  

It could be, but the thing that's putting me off that is the mileage. Nothing's guaranteed until you have it open obviously, but usually if it's wear from high mileage you'll start to hear bearings first. If the mesh teeth pit or chip that's usually (again not always) down to poor oil, lack of oil, abuse, or something getting mashed in between them.

[TonyGee]

1 hour ago, imago said:

It could be, but the thing that's putting me off that is the mileage. Nothing's guaranteed until you have it open obviously, but usually if it's wear from high mileage you'll start to hear bearings first. If the mesh teeth pit or chip that's usually (again not always) down to poor oil, lack of oil, abuse, or something getting mashed in between them.

theirs only one way for Russ to find out though 

[Bubba1135]

18 hours ago, TonyGee said:

I would say its more likely to be the teeth on the gears that are a bit rough.  

I had my efe do this in 3rd under load, teeth were shagged when we pulled it apart.

[Russ750ET]

Could be either, or both bearing/gear wear then.

Just had a quick look on CMS and it looks as though gears are still available, which is good.

 

[fab]

have you checked for oil contamination? 

Edited June 28, 2023 by fab