Brass Clutch Bush's

[nsaints]

After taking off my side cover, to change my sprocket size I'm interested in everyone's views on this topic

Engine has done around 250 miles since rebuild, 5 plate clutch in an RT230, a brass clutch bush was fitted with the spiral oil groove
The chain was originally setup with 6mm of up and down movement using a push up tensioner

I was surprised to find a large wobble on the chain ring due to a heavily worn brass clutch bush - this has caused me to question if brass is the correct material in this application and ask what others think/have found?
Personally I'll strictly keep to bronze bushes from now on.

Brass versus Bronze using Google
"Brass, in general, has a poor wear resistance in comparison to bronze."

My clutch spider - you can see a kind off oil/brass grinding 'slurry' on the bearing surface that I found stripping out the clutch

[Warkton Tornado No.1]

Your Post is very interesting in qualifying the differences in plain bush materials.

Bronze ia an alloy that comprises materials with the desired properties for a given application & in the instance of bearing bushes, oil retention is what the OEM manufacturer will have wanted. It may not be obvious to the untrained eye, but the better bronze bushes will - upon close examination - appear porous. It is these pores that retain oil thus preventing premature wear.

Just for information, probably the best known plain bushes in engineering are Oilite which are produced by sintering & are actually oil rich so as to ‘hit the ground running’. The problem with them is that they require specialist fitting tools that ‘size’ them to the desired finished bore as they are pressed in. All too often, I have witnessed them being fitted then reamed to the desired finished bore which actually smears the surface & clogs the pores, totally defeating the reason for their use.

However, back to the clutch bushes available to buy these days, as we now expect, the World & His Wife jump on the bandwagon & produce inferior products & many Lambretta owners suffer the consequences……

[Storkfoot]

On my last rebuild, I ordered a bronze bush. On arrival, it had smashed into about ten different pieces. They are quite brittle. I ended up putting a brass one in but I have noticed that you do need to regularly replace them as, like you have seen, you get excessive play on the rear sprocket pretty quickly.

[nsaints]

To illustrate WT1's point regarding small holes in a bronze, or phosphor bronze bush. The small holes holding oil and aiding lubrication I found this image via a google image search which shows the small holes.
Click on the picture and it opens into a larger sized view.

Paul - to your point and a broken bush through the post
brittle = hard. Hard resisting wear as opposed to a soft brass bush?

[Storkfoot]

To illustrate WT1's point regarding small holes in a bronze, or phosphor bronze bush. The small holes holding oil and aiding lubrication I found this image via a google image search which shows the small holes.
Click on the picture and it opens into a larger sized view.

Paul - to your point and a broken bush through the post
brittle = hard. Hard resisting wear as opposed to a soft brass bush?

The wear factor on brass bushes was why I ordered a bronze one as I knew that original GP bushes were bronze. That said, I had no idea that the porous nature of the bronze was to hold oil, logical as it may seem now.

I have just looked on the internet at some well known dealers and it seems to me that some advertise the bushes as bronze but the picture depicts a brass bush.

Thanks for posting this thread, Andy. You have prompted me to try again with bronze bushes next time

[Fast n Furious]

I find that all these spiral grooved, shiney replacement bushes are made of brass and are just not upto the job. Maybe someone else knows different? They are often the only option available from some of our so called reputable suppliers.
The bush is a non standard size making options limited.
I use the proper sintered bronze ones from Scooter restorations. Never had an issue with them.

[nsaints]

Maybe someone else knows different?

All I know is my shiny spiral grooved brass one lasted 250 miles in a 20bhp engine and is already junk..

[Scooterslag]

Maybe someone else knows different?

All I know is my shiny spiral grooved brass one lasted 250 miles in a 20bhp engine and is already junk..

I recently put one of those groovy brass thingy's in my clutch- its only a standard 150 so maybe I will get 500 miles out of it? got a couple of bronzes types on order from Scooter Restorations so will swap over just for peace of mind. Cheers Paul

[gaz_powell]

I always have a stock of them in and generally change if im in the clutch or gearbox.

I just use the standard type from SR or AF.

I treat them as a consumable

Mind i have got one of those brass ones with a groove, but never fitted it.... Looks like i never will now