34 replies to this topic

[ACDodd]

Building an engine is about putting the clearances where you need them, not where they happen to be.

That's why engines cost, setting clearances takes time and that costs£££'s.

Ac

[minilee94]

Yeah I'm taking the gear back and he is guna give me a better one he didn't realise it was that bad

[Fast Ivan]

he didnt sell you a bad part, he sold you the basis for a part that will need machining to suit your build, the next one will require the same.

what you bought was a primary gear, forget the state of the bush_, if you want to build an engine that will work in terms of performace cost and reliablility then machining the primary gear bush is the first of many parts that require machining.

[Guess-Works.com]

New parts are machined to a tolerance, eg the bushes on new drop gears are machine to a tolerance which is appropriate for fitting onto a crank. It's up to the fitter to check the items for tolerance. ie the crank tail diameter.

 

To answer Matts question on how that damage occurs....

 

Over time a burr is created on the crank where the C clip is thrust outward on the slots... We all know about turning the C clip around to restore an 'in tolerance end float' but the burr will damage the bushes on the primary gear when it's taken off.. and in the case of this primary gear it's been twisted off back and forth. Simple answer is a file and take the burr off, before you withdraw the Backing ring and primary gear.

[The Matt]

Cheers GW! I could tell it wasn't running damage by the type of scratches. But couldn't get my head around how it's happened.