9 replies to this topic

[Mxrab]

Can someone confirm which way around the thrust washer is supposed to go. It came off with the chamfer towards the crank but I’m not sure if that’s correct, logically it looks to fit better the other way around.

[GraemeC]

Internal diameter chamfer towards the crank/away from the primary. The chamfer is to allow the thrust washer to clear the fillet where the crank steps up in size for the main bearing.

Usually it won’t fit the other way.

[Mxrab]

Internal diameter chamfer towards the crank/away from the primary. The chamfer is to allow the thrust washer to clear the fillet where the crank steps up in size for the main bearing.
Usually it won’t fit the other way.

That’s the problem, it fits either way. I just don’t understand what the chamfer is for. The step in the shaft where it locates is 90 degrees, there is no fillet. I’ll get some pictures tonight.

[Spider]

That's a worry if there's no fillet !

Try fitting it the other way, it shouldn't be able to go flat against the thrust face on the crank, there'll be about a 1 - 2 mm gap. If there isn't, something's seriously wrong here.

[Mxrab]

That's a worry if there's no fillet !

Try fitting it the other way, it shouldn't be able to go flat against the thrust face on the crank, there'll be about a 1 - 2 mm gap. If there isn't, something's seriously wrong here.

The fillet is there but the washer sits behind it on the shoulder. Hence it can fit either way around. As per attached sketch.

[Mxrab]

Sketch

Attached Files

•  BC7DA9CB-8BE2-49C6-90D0-79AB5DBFE2A5.jpeg   52.22K   1 downloads

[Mxrab]

Not a great photo but you get the gist

Attached Files

•  9DC08A0A-6FF2-4360-82FE-678EBCE473B7.jpeg   41.87K   9 downloads

Edited by Mxrab, 03 August 2021 - 09:18 AM.

[Spider]

There should be a 2nd fillet on the step that the Thrust Washer locates on. It's not as big as that first one.

I'll see if I have a file photo

[Mxrab]

There should be a 2nd fillet on the step that the Thrust Washer locates on. It's not as big as that first one.

I'll see if I have a file photo

It doesn’t appear to be there at all, as I can fit it either way round snuggly. Crank doesn’t appear to have been reground either. It’s a 1275 A+ 12hd24 from a mid 80s metro if that makes any difference. Tbf there would be no harm in fitting it as you’ve said even if the 2nd fillet isn’t there. Just seems odd

[Spider]

All these radius's and fillets are there to give these parts fatigue strength from cracking. That would be my worry, especially on a crank.

I guess there'd be little risk in running it, as long as you don't want to rev it hard, the worst that would happen here is the tail with the flywheel will detach.

I'd suggest taking it to a decent machine shop or crankshaft repairer for an opinion.