Grinding/Polishing Rocker Arms

AltaNorton · Mar 22, 2011

I know some people do it, what do you guys thing about grinding and polishing rockers? And maybe a quick how to, im thinking about doing it to mine.

Thanks,
Matt

Hobot · Mar 22, 2011

Besides lightening and looking cool the removal of the very end material allows very easy push rod placing and removing, makes head changing just an unscrewing and lifting, ahhhhhh. Dunstal's Tech notes has photo of his, so I did mine, just short of his extreme, though did cut into oil passage on one arm so I had to buy another to risk. Most benefit is removal toward the ends. I did not remove the balls, though I think one feel out to reseat. Arms are tapered profile only sharpened at edges.
Ran them to over 11,000 w/o valve float or any detectable damage, DAMITT as rest of the engine couldn't stand it. Light valves and heavy springs too of course.

If the Indians had arrowheads like this, we'd not be here : )

AltaNorton · Mar 22, 2011

Thanks Hobot. That is my only fear, grinding too far. I will just have to be careful and take my time. Yours look great though. I'll read the Dunstal article to familiarize myself.

PS
Sorry about the double post, I double clicked on submit.

AltaNorton · Mar 23, 2011

And of course after searching, I can't find Dunstall's rockers anywhere. Do you have a link to the website by any chance hobot?

domiracer66 · Mar 23, 2011

http://atlanticgreen.com/dunstall.htm

Carbonfibre · Mar 23, 2011

mattthomas4444 said:
I know some people do it, what do you guys thing about grinding and polishing rockers? And maybe a quick how to, im thinking about doing it to mine.

Thanks,
Matt

Its really a complete waste of time, unless you are building a full spec race motor, and trying to get higher rpm reliably.

dynodave · Mar 23, 2011

Carbonfibre said:
mattthomas4444 said:

I know some people do it, what do you guys thing about grinding and polishing rockers? And maybe a quick how to, im thinking about doing it to mine.

Thanks,
Matt

Click to expand...

Its really a complete waste of time, unless you are building a full spec race motor, and trying to get higher rpm reliably.

Very much agree-waste of time...
Even on my Dunstall Atlas which is one of the real/legal (65?) homologated 1968 dunstalls. That engine has a cam that is only 1/2 way between the 06-1084 and a combat cam.
It seems as though it was fully race prepped, then shipped out the door with a street cam. Floating valves are not a concern...

Dave
Atlantic Green Technical Services
http://www.atlanticgreen.com

Hobot · Mar 23, 2011

Hehe, motorcycles above 250cc are a complete wasteful luxury, let alone our excessive time expense on fancy paint and polished covers. The photo in DynoDave's site - are not nearly as sleek sexy as the b/w photo in Paul Dunstall's "Norton Tuning" booklet. Logic does not enter the equation unless some contest to attempt, the rest is just pure lust to satisfy. Will try a photo form book to show that Ms Peel are rather conservative compared. It made me feel like a real race modifier to grind and polish mine to feel like less valve train strain riding with the wind now and then.

What is Not a Waste of time is removing material off the very end of push rod side of rocker as allows push rod plenty of clearance to remove that hassle.

Could not get rotation to work here, R click image, click view image then click again to expand and turn head to match : )

swooshdave · Mar 23, 2011

hobot said:
Hehe, motorcycles above 250cc are a complete wasteful luxury, let alone our excessive time expense on fancy paint and polished covers.

This is perhaps the most wise and succinct words ever uttered by our dear hobot. Bravo to you, good sir, bravo I say. :mrgreen:

Lighten away! Besides, you can always point to them when the wife asks what you are wasting your time on and you can say, "Shiny". To which most women will just knowingly nod their heads. :mrgreen:

xbacksideslider · Mar 23, 2011

Hobot -

Thanks for the pics.

In your post of the 22nd, the standard rocker arm is clunky and crude while in your post of the 23rd, the Dunstall pic, the standard rocker is a better piece, more precisely manufactured.

Maybe Dunstall started with better parts or maybe the tooling deteriorated over time.

AltaNorton · Mar 23, 2011

I like your way of thinking Dave. For everyone else, I know it doesnt change much for a street bike performance wise, but its a cool mod. that can be done fairly easily by an inexperienced mechanic. To me its cool just to say i did it, and of course show people how shiny they are

john robert bould · Mar 23, 2011

swooshdave said:
hobot said:

Hehe, motorcycles above 250cc are a complete wasteful luxury, let alone our excessive time expense on fancy paint and polished covers.

Click to expand...

This is perhaps the most wise and succinct words ever uttered by our dear hobot. Bravo to you, good sir, bravo I say. :mrgreen:

Lighten away! Besides, you can always point to them when the wife asks what you are wasting your time on and you can say, "Shiny". To which most women will just knowingly nod their heads. :mrgreen:

Good old lathe turners phrase that " Fcuk the size, make im shine" I think the original concept of polishing rockers was to remove any "nicks" or casting defects that could develope into cracks and breakage... Generaly unlikly on a road machine. But be carefull not to over do it! Very high revs could "Flex" the over thinned arms..But they would be quite thin for this to happen.

Hobot · Mar 23, 2011

Naw, no one but no one has tested race level lightened rockers limits as me and I can assure you rockers are Not a weak leak in valve train. The main concern is not to nick the balls grinding or bother to torch em out and replace, Ugh there is an oil passage about 1/16" below surface along one side of rocker arm, but I forget which side it ran through that I ground through anymore. About all the stress is is plane of the knife edge of rocker so can thin them a lot but for the middle where most stress is handled and oil flows. Oh yeah a new rocker ran me about $80 from major vendor. It was the shorter rocker and did not uncover passage in 1st one I did, a longer one. You are plenty safe to grind off the very end pretty thin then tapper to taste the rest of the end and have at it on tops and bottoms and shaft area to pleasing profile, then sand and sand and huff and buff. Do it as I love to see more art deco and reflect on your grin inside riding along on hidden gemstones.

AltaNorton · Mar 23, 2011

Well once the rockers get back from the engine shop, I'll start. Maybe post some pictures after...if they turn out good.

AltaNorton · May 26, 2011

Well, I am about to head to the garage to get started on the grinding... Hopefully all goes well.
I also wanted to polish my con rods but unfortunately the bottom end came back assembled from the engine shop. Too bad.
Stay tuned for pictures of the finished product

Matt

Hobot · May 26, 2011

Did ya take off 0.06" or only 0.5", so ask yourself...

[video]http://www.youtube.com/watch?v=u0-oinyjsk0[/video]

AltaNorton · May 26, 2011

hobot said:
Did ya take off 0.06" or only 0.5", so ask yourself...

[video]http://www.youtube.com/watch?v=u0-oinyjsk0[/video]

Thanks hobot

My dad wasn't big on the idea of polishing the rocker arms so this thread may have been useless for me. Hopefully it helped someone else - I'll refer back to it eventually I'm sure, maybe just not for this bike.

I promised a picture of the arms, but i dont have one to give, Instead, here's the rocker covers I polished tonight.

AussieCombat · May 26, 2011

Have a go Matt, easy does it, don't get too excited with the grinding.
Better too thick than too thin. You don't want a box of scrap metal.
AC.

Hobot · May 26, 2011

Unless ya want to press limits of crank shaft whip the main reason to grind down a street bike rockers is to allow the push rod to slip in and out slick and can be first time every time and that means grind most right off the very tips of the push rod side of rockers. Its not hard nor dangerous, actually fun feeling like a real hot rodder. Keep going till they gleam like a new knife. If ya screw up only costs about a new tire worth to get another.

Impressive sheen on them covers, too bad it won't last in real life.

AltaNorton · May 26, 2011

We'll see if my dad will eventually approve of grinding the rockers...after all it's his bike so if he doesn't want it done, I understand. I think he just doesn't want to end up buying new rockers after I accidentally grind down to the oil lines.

Yes hobot, unfortunately the polishing pandemic has caught me too - but I like the look...it will have to be a regular chore from now on the keep everything looking nice.

Matt

PS. Now I'm on my way to hunt down Dirty Harry on Netfilx so I can watch the whole thing. It's one of the only westerns on there that I haven't watched. (for some reason they don't have The Good the bad and the ugly - what's up with that?)

Grinding/Polishing Rocker Arms

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