The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: jonaf on 18.01. 2015 17:57

Title: Crankshaft bush service limit
Post by: jonaf on 18.01. 2015 17:57
What is the maximum allowed play between the rh side of the crankshaft and the bronze bush? Can't find it anywhere in the manuals....
Title: Re: Crankshaft bush service limit
Post by: bsa-bill on 18.01. 2015 18:16
3 thou when installing a new bush, measured at the drive side, shimmed between the crank web and the drive side bearing, that would seem to suggest not much more than that in use, most seem to achieve 1 - 1.5 thou
Title: Re: Crankshaft bush service limit
Post by: jonaf on 18.01. 2015 18:29
Thanks bsa-bill. Do you know the max. radial play between the shaft and the bush also?
Title: Re: Crankshaft bush service limit
Post by: bsa-bill on 18.01. 2015 22:06
0.0015 springs to mind, others might like to help me out here, critical it's line reamed with cases bolted together.
Do a search (the one top left of this page) for crankshaft grind or clearance and read through some of the articles, more than likely someone will give a better answer tho
Title: Re: Crankshaft bush service limit
Post by: jonaf on 19.01. 2015 19:28
0.0015 is the correct clearance when fitting a new bush.  The wear limit has to be more than that. But how much? 0.003? 0.004?
I am not able to find it anywhere neither in workshop manuals nor by searching the archive...
Title: Re: Crankshaft bush service limit
Post by: muskrat on 19.01. 2015 19:37
G'day Jonaf.
If it gets to 0.005" it's probably already blown up due to no/low oil pressure  *ex*  I don't like to see them with more than 0.003".
Cheers
Title: Re: Crankshaft bush service limit
Post by: jonaf on 19.01. 2015 21:56
Oil pump in good nick and not letting the engine work hard at low revs will probably help keeping the engine away from blowing up, I think. My A10 had more than 0.005" before I had it done.
But it would be very interesting to get an official figure on the service limit.

What raised the question is my mate's A65 Spitfire which has about 0.003 vertical play at the timing end. He thinks it OK but I don't quite agree...
Title: Re: Crankshaft bush service limit
Post by: Topdad on 20.01. 2015 11:34
I think your mate will find out soon, those spitfires had a reputation for self destruction unless you kept a close eye on the oil pressure. Tell him to get the end feed conversion that'll sort it ... for a while, regards Bob.