Dural Pushrods and Iron Heads

[bassgreg]

I have spoken to a few engineers, guys who restore A10's for a living and a my dad, who rode them when they were just motorbikes.

Apart from the fact that BSA designed and built them with steel push rods, here is what I have been told.
The cast iron heads expand at a different rate from the alloy heads, and for that reason the Dural pushrods are not really appropriate. Some have said that they simply altered the gap to suit and have had no problems, but I am now running with steel and so far they are quieter and the bike seems happier.

I have done 100 miles or so on the steel now, and tomorrow will check to see if they are holding up, especially on the exhaust valve that ate the alloy rod. There are other problems which could cause wear, but I would expect them to show other symptoms too.

It really isn't much hassle to take off the rocker box and check, so if you are in any doubt it is well worth a look.

 

[coater87]

 Now you guys got me all worried. Just purchased new push-rods to replace the three rusty bent ones I had, and they are aluminum.

 Maybe I will save myself the trouble of these things and just modify some VW ones, looks pretty straight forward and has got to be better then running an engine with push-rods that slowly (or quickly) erase themselves.

 

[muskrat]

I wouldn't be that worried Clive. The alloy ones that are in my cafe lasted 9 years of racing and another 6 on the road. If the ends are polished and there's no issue with the cups the only thing that will accelerate wear is lack of oil.
Cheers

[duTch]

 Thought I mentioned it, but must've been in another concurrent thread Re: Dodgy parts, checked my clearances the other day, and had  in- 0.009 /ex- 0.012 closed em to in-8 and ex to 10....can't remember what I set'em at last time though, but wasn't much diffo - (either 8/10 or 10/12)
 
 Bottom line is; nothing to worry about