Spinning noise as revs build...

[Ruairidh Dunford]

One of my last jobs this year was to start up the newly build mag engine destined for the Cup Model.

All went as planned except for a spinning noise as the revs built up - nothing at all when turning over??

I removed the timing cover plate and could see nothing touching or moving, no witness marks. I thought maybe a dry bearing so oiled everything and reassembled. Still there!

On discussion with others we jointly concluded that the vernier drive felt seal retaining ring must be spinning. I started the frustrating task of disassembling, again!

As I started to take out the idler gear I noticed this:



It was the gear at fault, not the pin. It is now all replaced and back up together.

A new one to me.

[Charles P]

New to me as well. Better caught now

[Tony Betts]

Hi R,

Not seen that before.

Is the gear after market? Could have been made wrong.

If an original it looks in very good condition, for such a fail.

Tony.

[Ruairidh Dunford]

The gear is brand new and was a press fit on assembly...

[Charles P]

Mic up the shaft and see if that's too small.
If not you know the conclusion.

C

[Tony Betts]

I didn't realise anyone was making them.

I take it the supplier have been informed.

When you say press fit ?

Was you happy with the tightness of the gear? Or accepting what had been alowed by supplier.

I'm always sceptical of new gears, nothing to do with suppliers or even materials used.

It's just with the originals being different + and - sizes, and when fitting them to a different engine than they were made for. You risk them being tight or loose. 

So when made new. only one size is made, what standard size is worked to ???

Glad to here the problem is fixed though. Tony.

[Ruairidh Dunford]

The shaft is fine, the problem lies with the gear unfortunately.

[Charles P]

The shaft is fine, the problem lies with the gear unfortunately.

I assume that you have a spare original to hand.....

[Ruairidh Dunford]

I do thank you - the engine is back together, (see my comment below the film posted in my OP).

[Charles P]

I do thank you - the engine is back together, (see my comment below the film posted in my OP).

Ah yes. Good stuff. Do the idler gears wear much in your experience?