What can we do with worn [out] rockers?

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julianharty
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What can we do with worn [out] rockers?

Post by julianharty »

With apologies to the "Drunken Sailor" https://en.wikipedia.org/wiki/Drunken_Sailor I'm seeking advice on how to deal with worn rocker arms where the faces are badly pitted. I've inherited at least one set (on the rear head) in the 1978 3 1/2 I've bought recently, perhaps the front set are similarly affected.

The pitting is quite severe, and seems to make the engine both much noisier at times and also sometimes the gaps change as I discovered when the rear set first widened and then (after I'd naively decided to adjust them) closed up so much that the rear cylinder didn't run properly, it ran significantly cooler and the bike was more of a single cylinder + a bit rather than a functioning V-twin... (anyway, back to my request)

I've read various posts on the forum and suggests range from using feeler wires viewtopic.php?f=4&t=1542&p=7353&hilit=worn+rocker#p7353 to reprofiling search.php?keywords=rocker+diamond

I've not seen anyone mention when to (try to) buy replacements or whether it's practical and cost-effective to get them refaced. I've already gone for fitting a replacement old set I bought online as a backup.

PS: I'd also be fine with buying another set (or so) of old rockers that have good quality faces.
pikl
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Re: What can we do with worn [out] rockers?

Post by pikl »

It's not too hard to resurface them. Need to make a pivoting rig to slide it in a certain radius across a grinder. And weld it up with TIG, with some very hard tig stick.

Resurfacing them and then hard-chroming them would give you a really hard face. I don't think it would wear the valve too much either (but that is always a concern). Either way, just tig welding and grinding it in an arc would definitely work for a long while, and it's not too hard to repeat it with an even harder welding stick if it does wear.
julianharty
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Re: What can we do with worn [out] rockers?

Post by julianharty »

Thank you for describing a practical way to restore them. I currently only have a MIG welder, I've wanted a TIG welder for a while so this adds to the reasons for obtaining one soon!

Can you recommend which welding rods to use please?

Also, I've spoken with NLM and they've had a large batch made (remanufactured) They have over 400 in stock currently. These are complete but need reaming to suit the shaft. They're not too expensive in my view (around £30 each + VAT of 20%). I may well try one or two of these soon. I've ordered an adjustable hand reamer & waiting for it to arrive.
pikl
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Re: What can we do with worn [out] rockers?

Post by pikl »

There are Stellite rods for hardfacing. It's likely Morini used this originally. If they did not, this procedure would make the rockers even more wear resistant.

Here's a nice topic about resurfacing Honda CB450 cam followers (very similar function, but these wear out much faster because they slide on the cams). Then he fit it on a rotary table/indexing head, on which you can grind it. He also contemplated using hard chrome, but concluded that it's far easier and faster to resurface followers, than to resurface the cams...


Truthfully, I think you might get away by grinding the welded lobe without a fixture. The Honda followers are long and touch the cam. The Morini rockers have a short lobe, and I guess the angles are not extremely important on a street engine. Not optimal, but would probably be good enough for me...
julianharty
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Re: What can we do with worn [out] rockers?

Post by julianharty »

Thank you again. I'm learning a lot about what's possible to do. In terms of immediate needs, I will either buy another old set of rockers online (my last set cost about $25 USD equivalent including shipping) or one or two of the ones NLM had manufactured. I'm not confident I've the skills or experience to start with the TIG welding and regrinding. That's something worth tackling when I've got more experience welding metals (something I'd like to practice and improve my skills in, but impractical for the next few months I expect).

Oh and the old Honda article is excellent. Really inspiring. I had a couple of the Honda 500T twins back in the 80's they were nice dependable bikes.
SupermotoDave
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Re: What can we do with worn [out] rockers?

Post by SupermotoDave »

A recent issue of Strega, no 120, had 4 pages on refacing rockers with something hard, not sure what as I have not had the inclination to type the entire article into babelfish.
SupermotoDave
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Re: What can we do with worn [out] rockers?

Post by SupermotoDave »

A recent issue of Strega, no 120, had 4 pages on refaceing rockers with something hard, not sure what as I have not had the inclination to type the entire article into babelfish.
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72degrees
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Re: What can we do with worn [out] rockers?

Post by 72degrees »

SupermotoDave wrote:A recent issue of Strega, no 120, had 4 pages on refacing rockers with something hard, not sure what as I have not had the inclination to type the entire article into babelfish.
Stellite was what was used to reface cam followers on AJS/Matchless twins. I think you can get it as rods suitable for TIG these days.
'It must be a .....'
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Re: What can we do with worn [out] rockers?

Post by 'It must be a .....' »

The Ace Cafe caters for worn out rockers.
julianharty
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Re: What can we do with worn [out] rockers?

Post by julianharty »

'It must be a .....' wrote:The Ace Cafe caters for worn out rockers.
Very Drôle, thank you :)
julianharty
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Re: What can we do with worn [out] rockers?

Post by julianharty »

SupermotoDave wrote:A recent issue of Strega, no 120, had 4 pages on refaceing rockers with something hard, not sure what as I have not had the inclination to type the entire article into babelfish.
Ich kann deutsch lesen. (I can read German) and live about 15 to 20 miles from Reading. Perhaps you'd either be able to email a scanned copy of the article or find a way I can read the original? If I can make enough sense of it I can add some notes here.
pikl
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Re: What can we do with worn [out] rockers?

Post by pikl »

If you buy replacement rockers, I just want to say it would be a waste to throw the old ones away. They are slowly becoming more and more rare...
julianharty
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Re: What can we do with worn [out] rockers?

Post by julianharty »

pikl wrote:If you buy replacement rockers, I just want to say it would be a waste to throw the old ones away. They are slowly becoming more and more rare...
Oh, I agree and plan to keep them and just about any old parts to hand. I've also been buying some bits and pieces I see for sale from time to time. I've had Morinis since 1981, have 2 currently, and hope & expect to have them in decades to come. Being able to keep them in good working order is vital for me. Also I buy parts from time to time to enable me to experiment with improvements where I won't destroy the working bikes if something goes horribly wrong. If I've got spare rocker arms then I can risk welding them (or getting someone to do so) knowing I can still ride the bike if the welding takes a long time or something goes wrong.
julianharty
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Re: What can we do with worn [out] rockers?

Post by julianharty »

And you've reminded me how disappointed I was to learn that the previous owner of my 3 1/2 had thrown away the old ignition system when he replaced it with the German Sachs one. He admitted he didn't know if it was faulty. What a waste and a pity to see them go to a landfill site :(
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