out damn crankshaft... but how?

[groily]

When I said 'wear' above, that should really have been 'clearance' . Ie, pretty much nil wear if 1.5 thou clearance is about right? Which I think I have read hereabouts in the past.
Haven't 'done' many A series full engine jobs myself (mine doesn't go wrong much luckily), but beezermacc's must be the right approach. Don't want to take anything more than the absolute bare minimum off a journal.
Oh, and PS, I fitted hex-head sludge trap screws after cleaning out the crank - no noticeable difference in vibes. Probably less weight lost there (where it hardly matters anyway) than by cleaning crud off the pistons.
Cheers, Bill

[bikerbob]

 I think it is important that if you go down the route of buying a new bush that has the steel outer and a bronze inner that they are pinned. A previous owner of my A7 fitted a bush that was not pinned and the inner turned causing real damage. I remember when I restored my A65 the bush I bought was not pinned so I pinned it myself before fitting. it pays to check these things out before buying. A solid bush would be preferable if possible.

[Greybeard]

When inspected a while back in course of redoing the drive side shimming, wear was at one and a half thou and no problems, so it went back as it was and is still going strong. Not a highly-tuned engine, but still, not bad I reckon. No wear on the crank journals either, so I just fitted new shells while I was in there, and put new rings in (which it did need). Oil changes every 1000 miles, 20/50 oil, no external filter, bike mostly ridden medium-gently (to 35mph in 2nd, 50mph in third and cruised at 60-ish mph).
I think a bush can last well, on that basis.

Pretty much the same story as my rebuild except I'm using straight 40 oil with a filter.

[Topdad]

Mike it comes down to personal preference and how deep the pockets are ! I've had a plunger and 3 s/arm models all on original bush ,only blow one the plunger but I was 16 and stupid ,the others withstood anything I could throw at 'em. On the other hand after a long layoff from bikes I rebuilt the engine with the conversion ends and crank bal by SRM . Simply due to being able to cover cost easily and not wanting any hasle for as long as poss . That's was 2001 and the engine ,touchwood is still great. cheers Bob.

[morris]

I was going to mention how it would be good to find out why it has failed to ensure there is no reoccurence.......goo in the oil ways maybe?..as it does look like oil starvation has occurred?

I'm thinking along the same lines. This kind of damage definitely looks like insufficient lubrication.
A bearing conversion also wouldn't last long if not well lubricated, so you'll need that cleared first.

[orabanda]

Before fitting a bush to the crankcase, get a machinist to measure the bore in the crankcase for concentricity.

I have always found them to be out of round, usually 0.010"- 0.014".

This is probably the result of a 28 pound flexing flywheel which has done millions of rpm.

Anyway, I always have the bore machined true, and then make an oversized bush, with the appropriate interference fit.

This ensures you won't lose oil supply to the crankshaft, around the outside of the bushing.

I twigged to this potential issue after blowing compressed air into the oil delivery (pressure) port of an assembled engine on my plunger bike, and air rushed out from between the bush and the crankshaft, in several places!

This is a simple test to perform, BTW.

A friend who has been overhauling A65 / A50 engines for decades says he always checks the crankcase bore for out of round, and they invariably need to be machined before bushing.

Hopefully, the bore in your crankcase is not out of round, but at least check it!

Richard

[KiwiGF]

i have read quite a few threads on this already, but other than rivet counting and pain in the pocket is there any reason to NOT do the roller conversion? what convinced you to stay with a bush KiwiGF?

Ref above....my machinist convinced me that there was no advantage to be had from the roller conversion if the plain bearing was done properly, he would have done the job either way albeit he does not do grinding so I got that done by Hutt city engineers. He is very low cost so it was not the cost that swayed me, although I think the bearing itself is not cheap. The work he did on the bottom end cost $250 and included making mis matched cases fit etc....one of the cheapest items of my resto!


A guy in the bsa club runs an a65 hornet with roller conversion many years old, and which he rides hard, it has done over 95k miles without serious work.

The only Reason not to do the conversion maybe that you may find if difficult to find someone with good recent experience of doing the roller conversion in NZ?

[mikeb]

thanks for all the helpful comments on this. time for me to research local engineering shops and ponder my options.

[Rocket Racer]

That bush certainly wins the "worst I've ever seen in a  motor that hadn't gone bang" category.
Am not looking forward to seeing the main bearing shells if the bush was that knackered.
Given the bush runs in an oil bath that's a shocker. You are lucky you pulled it down before it pulled itself apart in a hand grenade type moment
I can only surmise that the bush inner has moved relative to the bush housing so that the oil holes were no longer aligned, cutting off oil feed to the bush... either way nasty nasty

[bikerboy]

One disadvantage with the SRM roller conversion is that you cannot run the bike with the timing case off. I know its not something you would do regularly but if you have dynamo or mag problems its double handy to be able to start the bike without putting the timing case back on every time you want to test it..

[mikeb]

bikerboy - can you explain why after the roller conversion you can't run with the timing case off? i know the crank is end drill for the oilway but can't see the consequences of this.
thanks

[Topdad]

Mike , part of the SRM conversion is to reroute the oil feed to the crank , the oil gets into the crank via a quill in the cranks end which inserts into a seal in the outer timing case and you get improved flow to the crank however take it off and no oil gets to the crank it just ends up on the floor/wall cheers Bob.

[Butch (cb)]

Mike , part of the SRM conversion is to reroute the oil feed to the crank , the oil gets into the crank via a quill in the cranks end which inserts into a seal in the outer timing case and you get improved flow to the crank however take it off and no oil gets to the crank it just ends up on the floor/wall cheers Bob.

Does this not suggest that it should also be accompanied by a modified timing chest cover with access windows? (But would that look 'orrible?)

[chaterlea25]

Hi
You only need a window to admire the shiney blue SRM oil pump if you have one fitted   LOL

John

[Greybeard]

Hi
You only need a window to admire the shiney blue SRM oil pump if you have one fitted   LOL

John

You need to take out a mortgage to afford the pump!