RMA Automatic Cam Chain Tensioner?

Back in the mid nineties when I built my 1972 Norton from a running basket case, Norton News carried an ad for an Automatic Chain Tensioner by an outfit called RMA in San Jose CA. I ordered one of these things and instaled it as per the instructions which were very well written and illustrated with drawings. The kit fit well and I was pretty happy with things but for the tension which seemed high. As I recall, the tensioner did not ride on spring pressure alone but had a rachet in it so the spring would move the chain when the loose spot came up but allow no relaxing once it had passed. I called the folks at RMA and spoke with someone who did not feel there was anything to worry about. I went ahead and buttoned the timing case up with the Nortech oil pump & timing cover modification and ran the motor without trouble for 700 miles until the bike was laid up for the rear hub/brake issues detailed in an earlier thread.

Now the old Commando is being readied for riding again and I still am a bit nervous about the cam chain tension issue. Has anyone had any experience with these RMA chain tensioners? Is there anything to worry about?

Vintage Paul

hudson29 said:

Has anyone had any experience with these RMA chain tensioners? Is there anything to worry about?

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Paul, about a year ago I posted my experience with RMA tensioner.
I installed one about six years ago and when my motor was apart for a complete rebuild last spring I got a phone call from my master vintage bike mechanic. He was upset with the damage done by the RMA and told me he would not proceed with my rebuild unless I agreed to have him take it out and put back in the stock chain tensioner.
Basically, the RMA holds the chain dreadfully tight, too damn tight, so tight in fact that the tension caused the intermediate gear holder to wear an oblong hole in the inner timing cover. He had to carefully weld the hole to insure the intermediate gear was held properly.
I think the RMA tensioner is a good idea in theory, but in practice, at least in my own experience, it was a big mistake and I will never use one again. I have no problem checking the cam chain tension and moving the stock slider a little every 4-5000 miles as is specified in the manual.
The problem as I see it is that people are just not aware of what the RMA device is doing inside the timing cover.
This is often just forgotten about, my guess is people go well beyond the 5000 mile service interval and they assume that because it is spring loaded, well what could go wrong? Out of sight, out of mind.
I have no doubt people of this website will say hey, I installed on years ago and it is doing just fine. Is it?
How do they know without removing the intermediate gear that the extreme tension is not doing the same damage that was done to mine?
Please, don't let this happen to you, the damn thing keep the cam chain too tight. Remove it, and put the stock item back in, set your cam tension, and take the timing cover off every 4-5000 miles and reset it, presumably taking up a little chain stretch.
John

edit: I now see Paul has included above in his post the links, mine is the top link story.

HMmmm 1up3dn, you might just of solved why Ms Peel jerked oil pump nozzle off in her over over rev event. Likely racheted up till something had to give. This unwrapped the angle plate retaining the wedge and spring and freed them to be chewed up further in the chain/cogs. Silly me thought it was just tach needle disappearing that caused RMA to destruct, so was given a free replacement which did same thing within 2000 miles white never topping 5000 rpm. Too many strikes against the RMA so forgetaboutit. Go with a old deep grooved one or a rubber cushioned factory version.

Just bug Jim for the gear drive. :mrgreen:

Ummmmmmm, gear drive!

I've got this type, have no idea who makes it, Norvill did have one for sale on ebay a while ago, any info would be appreicated.

Josh, the chain-tensioner you have is I believe a modified Datsun car unit, it was modified and sold by an Aussie whose family name escapes me, although his first name was Kerry (this makes a change from 'Bruce'). Norvil used to sell them many years ago, but now sell the RMA ones at about double the original price. I had one of Kerry's in my cafe racer Commando for a few years without any problems whatsoever. I tracked him down quite a while ago, but it seems he was too busy trying to keep the roos from kicking down his dunny! I have an RMA one in a Roadster that I am building and when I started the engine for the first time it made an awful noise from around the cam area. It has everything new from the crank up, so I'm fairly confident it's not anything broken internally. I have yet to strip the bike, but the first thing I intend to do is to fit back the standard tensioner arrangement and try again.

Thanks Dave, much appreciated, the unit seems to be working fine, well for the 4.2 mile I did on it yesterday.

Love the profiling, eaten any cats lately ?, .

P.S. my mum was going to call be Bruce, my fathers name is Bruce, my uncles name is Bruce, suprisingly enough they are the same guy .

"I may be your Uncle, but I'm still yer Father".

Josh, Having actually done an internet search (I could have saved time and simply looked at old posts on here!) I find that Norbsa has mentioned this chap, Kelly Cork from Brisbane, in an earlier post and identified the unit as being from a Nissan model.

I am a Pom so no cats on the menu today, but probably having fish-lips on toast for breakfast. You will be pleased to know that my Chinese nickname means 'Ugly crater-faced foreign son of a bitch', so it's not only you chaps down under who insult your mates by way of showing fondness.

Does your family by any chance hail from Tasmania and can you play the banjo?

Love the nick name.

http://www.youtube.com/watch?v=Pmn9cVDmNEg

I think the guy's name was Kelly Cork, but do a search, it's been discussed here before. IIRC he quit making them some years ago.

I bought one of those RMA tensioners back when I rebuilt my 750. At the time, it was said to be one of the best upgrades you could make to your Norton engine. I never fitted it though because I felt it made the chain tension too tight. It seems I made a good decision for once!

Debby

I fitted one and for 11,000 miles it was fine until a broken (new OE part) exh. valve adjuster tip fell off resulting 0.100" clearance. My feeling is that the hammering the valvetrain took may have damaged the tiny guide pin and circlip and then shocked the brass and Delrin? shoes out of the guide leading to total destruction a few hundred miles later. At the same time I had fitted a PW3 cam but can't think that was too much cam for the RMA. Certainly it worked well while all was well although the tension is a little on the high side. This is the broken tensioner (whats missing is the pile of brass swarf flushed out of the sump, timing case and filter)

It would be really interesting to know exactly how many RMA tensioners have been sold, presumably in service, and not caused a problem.

In a search from more HP I recently disassembled my engine that I built about 8 years ago. As part of the process, I had to pull the intermediate gear spindle and that required heating up the cases and driving it from the inside out.

For discussion, the bike has seen 1000 mile days and multiple 500-600 mile days, and I've taken it well past the suggested RPM level.

When the engine goes back together, there is zero doubt about reinstalling the RMA chain tensioner. The only reason I wouldn't reinstall it is if the timing gear modification was available.

I wonder if some of these units are tighter than others? If they were all as tight as the ones that have done harm & as I remember mine to be, it is hard to understand how some folks have gotten good service out of them. I'm sure no mechanic or engineer, but this thing just seemed wrong to me at the time and it is one of those small niggles that visit me late at night when I should be sleeping. Right now, I'm inclined to pull it out if for no other reason than piece of mind.

I seem to recall the Nortec modification to the case required a straightened out paper clip or something of that nature to hold a ball in place in the timing cover until something else was in place to hold it. What do I need to do when taking the timing cover off and replacing it outside of the things the manual says to do?

Vintage Paul

hudson29 said:

I seem to recall the Nortec modification to the case required a straightened out paper clip or something of that nature to hold a ball in place in the timing cover until something else was in place to hold it. What do I need to do when taking the timing cover off and replacing it outside of the things the manual says to do?

Vintage Paul

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Assuming you're just referring to the Nor-Tech mod. When you pull the cover off, the spring and ball will simply fall out, don't lose them. When you go to reinstall, you have to push the spring and ball in far enough so you can slip something like a drill bit through the cover to hold the ball in position, pull the bit after the cover is on. Also a good idea to replace the o-ring on the pump. O-ring size is #202 or 1/2" OD and 1/4" ID.

Don't know if the factory adjuster has some innate fault to be corrected, but seems to me if a longer chain fitted then a plunger or spring mounted under chain would work a treat. I've looked up the width of belts and cogs that interest me to evolve or my special.

I'vev got RMa's on both my race motors, never had a problem. BUT, before I installed, I tack welded the pin as I didn't trust the circlip. Also, I don't set it dead tight, but give a little slack so the spring can move....

builder said:

ssuming you're just referring to the Nor-Tech mod. When you pull the cover off, the spring and ball will simply fall out, don't lose them. When you go to reinstall, you have to push the spring and ball in far enough so you can slip something like a drill bit through the cover to hold the ball in position, pull the bit after the cover is on. Also a good idea to replace the o-ring on the pump. O-ring size is #202 or 1/2" OD and 1/4" ID.

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Yes, probably Nor-Tech, another find from Norton News. The mod they did to the oil pump & timing cover appears to work well. The bike sat 12 years and still had some oil in the tank! Thanks for the heads-up on the ball & spring, I'll see if I can corral them when the cover comes off.

Vintage Paul