The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: snowbeard on 07.05. 2009 08:15

Title: interesting rocker mod
Post by: snowbeard on 07.05. 2009 08:15
so I am finally getting the head back on, and while cleaning up the rocker box I noticed that the arms have been ground, nearly polished, but not to a mirror shine.   they even stamped a new number on the housing?

I've had the rocker off before, but had only seen my own, and now that I've been looking into more bits for the super rocket, I know they are rough and heavy!  so I wonder, was this a racing mod done back in the day?  I've a good idea that someone who owned this bike in the past really knew what they were about...

http://img.photobucket.com/albums/v632/snowbeard/my%20bikes/spitfire/rocker3.jpg

http://img.photobucket.com/albums/v632/snowbeard/my%20bikes/spitfire/rocker1.jpg

http://img.photobucket.com/albums/v632/snowbeard/my%20bikes/spitfire/rocker2.jpg

I just wanted to share and maybe learn something new, I actually don't have a pressing question for once!!  ;)
Title: Re: interesting rocker mod
Post by: MikeN on 07.05. 2009 12:09
They have also been lightened around the adjuster bosses
Title: Re: interesting rocker mod
Post by: beezalex on 07.05. 2009 15:24
Snowbeard, that's a common racing modification.  The saved weight allows higher revs before the valves start to float or crash and the polish prevents the onset of cracks that could cause the arms to break.
Title: Re: interesting rocker mod
Post by: RichardL on 07.05. 2009 16:27
Snowbeard,

I'm curious about the aluminum colored gasket. Was that there, or did you buy it?

Richard L.
Title: Re: interesting rocker mod
Post by: snowbeard on 07.05. 2009 17:56
interesting, that's pretty much what I thought it was, good to know about the polishing reducing cracks tho! 

one of these days I'm going to meet the man (or woman) who owned this bike originally, at least I hope to. It has been in Colorado a long time as far as I can tell.

Richard, that is an aluminum gasket, got it from Domiracer.  it seems quite nice, but we'll see if it resealed on the second use (that was the intention, but good intentions only go so far!)
Title: Re: interesting rocker mod
Post by: dynodave on 10.05. 2009 01:38
Hi All
new poster,
been lurking for a while.
some may know me....
The original rocker box mod is for road/super rocket inlet valve spring/keeper diameter clearance.
Not sure exactically when it grew to the larger size. The books aren't so clear on that.
The iron head valve springs which are smaller in diameter, didn't need the mod to the rocker box. That rocker box has the original cast part number
The modified RR?/SR rocker box got over-stamped with the new number.
The exterior polishing is likely for cosmetic reasons.
Polished/lightened rockers are for hot rodding purposes.
cheers
dynodave
Dave Comeau

modified text for clarity....
Title: Re: interesting rocker mod
Post by: snowbeard on 10.05. 2009 05:45
Hey Dave, welcome aboard, glad I could pull you out of hiding!  ;)  thanks for the info

so when you say the "original mod" that makes it specific for the RR/SR, what is the difference from one still sporting the original casting number?  was it which rocker arms are used? or something else?

this is especially valuable info to me because the rocker box that came with my Super Rocket has a busted stud mount hole, and I have one to replace that rather than repair it (at least for now, I wouldn't dispose of it or anything)


and you're not the first to notice the outer polishing, for cosmetic reasons, I agree.   that was probably done once purchased, as well as the lightening of the rockers.

thanks!
Title: Re: interesting rocker mod
Post by: bsa-bill on 10.05. 2009 09:21
As I understand it, the Rocker Box for a Rocket is the same as one for a flash, the difference in the part number is down to the Rocket box's require longer studs for an Alloy head and fitted with such studs they warrant a different part number.
That said I have also heard about the different spring lengths, not sure about this as I have a rocket Rocker box ( well alledgedly came off a Rocket ) and can find no difference with it and a Flash one.
If anyone has definite experience of a difference between these box's other than stud length I love to know as I'm about to put a Flash box onto an alloy head and could possible do any modification before I fit it.

Off to Peebles show and autojumble in 1/2 an hour or so, any of you in the area should pop along it's a nice friendly show and you get to vote in each class - you are a judge  *dunno*

All the best - Bill