OHV Singles Rocker Gear

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Keith.owen
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OHV Singles Rocker Gear

Postby Keith.owen » Wed May 02, 2018 12:36 pm

All,
My rockers are a bit wobbly on their spindles and a time will come when perhaps I might need to do something about it. I guess it doesn't stop the bike running but is creating noise and is possibly affecting the valve timing. My question is, that since these do not seem to be amongst the available spares, is it possible to recondition them, by, perhaps turning down the spindle and then fitting phosphor bronze bushes into the arms. I would have to get it done by a machine shop but has anyone tried it? Also, are there alternative solutions?

Any input would be appreciated!!

Thanks and BR,

Keith
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Re: OHV Singles Rocker Gear

Postby nevhunter » Wed May 02, 2018 11:20 pm

Both the spindles and the arms are hardened on the wearing surfaces. This means they can generally only be ground to a new size. You might use a ceramic tip for the arms and perhaps temper them back a little to bore the holes bigger for the bushes. The "S" shaped rocker is hard to hold to remachine it. Keep the bushes fairly thin as you don't want to weaken them anymore than necessary. Since they are loaded a lot the bronze will have to be good quality or it will crush and move in the arm. Also don't undersize the shafts too much to maintain strength. You could grind the rockers out and make oversize shafts, Needs an accurate job to be done if you go that way as steel on steel is critical to lubricate and you are only running a very small clearance which you can obtain by honing (or lapping) for the final fit. Nev

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Re: OHV Singles Rocker Gear

Postby john.whiting » Thu May 03, 2018 1:20 am

The shafts are very likely case hardened,so undersizing more than about 020" will remove all hardening,and similarly with the rockers.Boring out rockers for bushes will very likely weaken the critical stress area where arm joins shaft and may cause failure.I would try lapping out the rocker bore somewhat,and harchroming and grinding the shaft,or making new O/S shafts......more likely I would put up with the noise,because shortly after you spend a fortune,you will find a good set of rockers and shafts at a swap,or on ebay.

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Keith.owen
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Re: OHV Singles Rocker Gear

Postby Keith.owen » Thu May 03, 2018 9:20 am

Hi,
Pretty much confirmed what I suspected.................

I'll just have to keep looking!!

Thanks and BR,

Keith
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Re: OHV Singles Rocker Gear

Postby Leejm » Thu May 03, 2018 1:09 pm

You could get the spindle hard chromed then ground down to fit the rockers. But the cost is high so you are better to look for replacement parts
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Re: OHV Singles Rocker Gear

Postby john.bryant » Sat May 05, 2018 11:01 am

To continue this thread on a similar theme.
A friend has asked me about case hardening.
Can powder be obtained in small enough quantities for
the DIY er and how easy is the process?
John

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Re: OHV Singles Rocker Gear

Postby john.whiting » Sat May 05, 2018 11:59 am

I think you are referring to "Casenit",which is a ferricyanide powder,and is available on ebay.Unfortunately this is a very superficial effect,only 002/003 .What you need for automotive parts is a max case,040 thick.The simplest way of obtaining effective carburized thickness is by using charred bone,with or without other additives,heat the part in bone char for four hours at 900 degC....If you take the bits to a pro heat treater,they will use vacuum carburizing ,producing negligible distortion in a suitable steel.And charge you a hundred quid min charge for a tiny bit.

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Re: OHV Singles Rocker Gear

Postby nevhunter » Sun May 06, 2018 1:26 am

Nitriding is better for bushed (plain bearing) situation. No good with rollers. Much less heat distortion and therefore doesn't require grinding . This is becoming common on valve stems. Chrome plating may cause breakage if not immediately treated for Hydrogen embrittlement. Nev

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Re: OHV Singles Rocker Gear

Postby cmfalco » Sun May 06, 2018 9:09 pm

Keith.owen wrote:My rockers are a bit wobbly on their spindles ...
Even the worst case where both the OD of the spindles and the ID of the rocker shafts are worn they probably can be dealt with relatively easily and relatively inexpensively. I only included the qualifier "probably" because I don't know if you've run your bike to the point where the rockers are flopping around horribly.

Assuming the wear is in the thousandths rather than multiples of tens of thousandths, the rocker shafts can be honed just enough to make them round again and if the steel is case hardened rather than just heat treated there still will be plenty of thickness left. If the hardness is from heat treating, you don't even have to worry about the thickness removed.

Once the shafts are honed the IDs can be measured (which can be any random size whatever, not simple fractions of an inch), the spindles would be hard chrome plated and ground to give the appropriate clearance for the shafts. As an example, both shafts may have left the factory at 0.500"-dia., but after custom fitting to the freshly honed rockers one shaft might need to be 0.493" and the other 0.495".

I'm better equipped than most, having a Sunnen hone in my garage and a toolpost grinder for my lathe. I mention this because I hard chrome plated the spindles on my 1928 Ariel's cam myself and then ground them back to the original size. The fact I was able to do this myself tells you the cost to have similar work done for you shouldn't be exorbitant. This would be my preferred solution since any bush thick enough to push into place would require removing quite a bit of material and thus significantly weakening the rocker arm.

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Re: OHV Singles Rocker Gear

Postby john.whiting » Mon May 07, 2018 12:40 am

The reason hardchrome is so expensive is EPA costs,which are horrendous for a commercial operator.If you get hardchrome done in a 3rd world country ,cost is peanuts.


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