Automatic Chain Tensioners

I had installed an RMA unit a while ago, but recently removed it due to concerns raised here (lack of support, over tensioning, outright failures). I found reference to Kelly Cork's Nissan Car mod (http://www.accessnorton.com/rma-automatic-cam-chain-tensioner-t10075.html?hilit=kelly cork) and was wondering exactly how this thing works. It looks like an hydraulic tensioner unit, so where/how does one get the oil pressure? Does anyone have a direct experience with this thing? and if so could you enlighten me as to how he modified the car tensioner. Or perhaps how to get a hold of him, if he's still around? Frankly it doesn't look all that difficult and I would be interested in taking on the project - if I can figure out what to do. Winter is coming and I'll a bit of time...

Thanks!!

The Kelly Cork ones don't use hydraulics to take up the tension, they have a small ratchet and a spring that allows the tensioner to go in only one direction unless you depress the ratchet mechanism by hand. I seem to remember that they were based on a standard Datsun or a Mitsubishi car unit, with some modifications to fit inside the Norton timing cover, easy to do yourself if you have access to a mill. I had one fitted to my 750 cafe racer with S4 cam and other trick bits and it worked fine without any problems, it was also quite easy to fit.

................."it worked fine without any problems, it was also quite easy to fit." ........good to know

So if I got this right, the spring that's internal to the tensioner pushes the shoe (slipper) outward. The small ratchet clicks about every 0.030" and doesn't allow the thing to retract. Every time the chain goes around the tensioner will extend until it's tight. This would mean that between the loose and tight points, there can't really be more than about .030" difference. Is this enough? If things are more than a bit out of being concentric, wouldn't that be a problem - i.e. put a lot of stress on the gear shafts? Just trying to puzzle it out...

I can't comment about the Kelly, but my spring loaded RGM tensioner over tensioned the intermediate gear and tore

an oblong hole in its securing "hole", thus a costly repair, and a vow to never ever use anything but the stock.

Dare I say it I have ridden and raced Commandos for 35+ years and never had a problem with timing chain tension. Just set it and, if and when I took the timing cover off (which is a fairly rare occurence), checked it. Can't for example remember when I last had the timing cover off our "family racer" Commando, or the 1970 Production Racer.

This, like many other "improvements" offered aftermarket for Nortons seems like another answer to no question.

Joe/Andover Norton

ZFD said:

This, like many other "improvements" offered aftermarket for Nortons seems like another answer to no question.

Click to expand...

agreed, and I feel especially true regarding the "necessity" of installing a spring loaded cam chain tensioner

there is no "problem" that needs fixing, and in fact myself a quite a few others have reported damage due to over tensioning

Here's an RMA on ebay I'll never install again after 2 of em failed horrifically in Peel.
http://www.ebay.com/itm/Norton-Commando ... 0521242544

Here's a past forum thread on this with other tensioners and photo's to guide ya.
rma-automatic-cam-chain-tensioner-t10075.html

Main reason for chain tension stablization is stabization of cam end ignition triggers and then valve control. On next Peel I'm calling Baxter's cycles with huge piles of worn out stuff to get the most chain link grooved Norton tensioner they can find, cryo temper and dry friction coat, every now and again.

I have been running one of Kelly Cork chain ajuster on my Norton for over 20 years now and over 50,000 miles and have never had any problems with it, when I frist mounted it I replaced the timing chain and it made the timing side a lot quiter when running, after the rebuild 2 years ago I seen no reason to not keep using this set up I am still running all my orginal timing parts in the timing cover, so I have been happy with this set up.

Ashley