Spinning noise as revs build...

[Ruairidh Dunford]

By virtue of their scarcity in good condition, I think that would be a fair assumption to make.

You will also know that Rob Beck has developed a neat extra oiler pipe that extends from the end oil gallery plug and into a hole above this gear to give it extra lubrication.

[Charles P]

Fortunately my mag engine experiences have all been with pressure fed cranks and perhaps there's more oil sloshing around the timing case in that case.

C

[Ruairidh Dunford]

That could well be the case but I have absolutely zero experience in that area and wouldn't like to guess for or against.

[Tony Press]

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.

This is the problem with 'aftermarket'  machined replacement parts unless made to the original works drawings with properly dimensioned sizes including machining tolerances.

If a part it made as a copy of an original and the machinist is estimating the tolerances they may well be wrong or different to the factory standard.

With gears (and pistons etcetera} the +and - sizes were the tolerances and selected from manufacture to give the best fit on assembly.

Cheers, Tony P.

[Nick Turley]

That could well be the case but I have absolutely zero experience in that area and wouldn't like to guess for or against.

I have a few really decent idler gears if you would like one.

[Ruairidh Dunford]

I am sorted now thank you Nick - much appreciated.

[David Witton]

Had exactly the same problem as Ruairidh. Aftermarket gears suspected.  Ended up bushing the gear for a tolerance fit on the shaft.  Didnt hear the sound of a spinning gear above the gear clatter!

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Had exactly the same problem as Ruairidh. Aftermarket gears suspected.  Ended up bushing the gear for a tolerance fit on the shaft.  Didnt hear the sound of a spinning gear above the gear clatter!

[Ruairidh Dunford]

Did yours press fit on initially as well David?

I can only assume a burr was holding it tight until engine load kicked in. The noise was very noticeable from first fire up once the revs picked up, rest of the engine is very quiet - so far!!

[David Witton]

Twas discovered on first engine stripdown so history unknown. The gears were in good condition and I was reluctant to otherwise discard them. Bushing the idler gear was all that was required. I do have other idlers where the gear is barely tolerance fit though