I would like to get some opinions from the group as to the REAL benefit of fitting an auto. cam chain tensioner,anyone got one on their bike?, any noticeable change?.Thanks in advance. Ride safely. James.
Never heard of one braking well there was one guy with a locked throttle who did 10,000 rpms .LOL Taking Dyno Dave's advice wouldn't even think of running a Norton without one. It seems that the uneven loads on the cam as it travels through it's rotation couldn't help but make the timing a bit jumpy.
RMA Engineering in San Jose, CA Makes them some vender's now carry them in stock for a mark up. Kelly Cork in Australia makes one out of a Nissan car part that works well and is cheaper.
The RMA pushes from underneath and outside the chain and requires slight case mods. Kelly corks runs inside the chain and pushes down no case mods needed. RMA's provides constant spring tension were as Kelly's has an internal ratchet device that indexes about every .030 of chain slackening. Sorry no shopping baskets for these products unless you pay a mark up from a big house. maybe you could get them up some web sites and make it easier for all of us.
I have an RMA in one bike and a Cork Engineering model in another. I have not had trouble with either although the 'Cork' model needed modification to the mounting arrangement to get it to fit an early Commando with the cam-shaft breather. The RMA model states in the fitting literature that you may have to file a slight flat on one of the inner bosses where the timing cover screws fit into - a 3-minute job done in-situ for even the most mechanically insensitive amongst us.
Oscilating timing caused by loose chains allied to the mechanical points system on the first Combat motors were supposedly a large factor in the legendary unreliability of these models. I would not run a Norton without one. To adjust the cam-chain correctly is time consuming and requires the use of a new oil pump end seal and probably a new timimg cover gasket as well as some kind of special tool arrangement to support the intermediate gear shaft.
On balance I would fit another RMA unit because the Cork ones are not easy to get hold of. Norvil sells the RMA unit but the company is based in the USA so may be available from other sources.
I asked Pete Lovell (a Norton engineer in the UK) about these last year, and although he didn't say to me don't get one, he expressed an opinion that they possibly ran the cam chain a bit tight, and that he was not totally convinced in their worth. Having said that I have never heard of any catastrophes with one.
The near maintainence free aspect is appealing though.
I have installed one in my '71 Commando. The instructions detail a hydraulic lock method of holding things in place while the left hand thread oil pump nut is being undone. I stuffed a long piece of nylon rope into the combustion chamber of one piston on the compression stroke, with both valves closed, which worked fine.
Ten years ago I installed the spring loaded cam chain tensioner from RMA, and I regret very much doing so.
ADVANTAGE: you don't have to take off your timing cover and re position the stock sliding tensioner, this is rightfully perceived as an inconvenience every 5000 miles as specified in the workshop manaul
DISADVANTAGE: The spring loaded tensioner, in my opinion, puts too much pressure on the cam chain, in fact it over tightens it SO MUCH that, in my case, it created an oblong hole out of my intermediate gear spindle locating hole which necessitated an expensive welding repair and reconstruction.
Jim Mosher, of Performance Indian, and builder of the Bonneville Norton unfaired record holder, rebuilt my motor three years ago and called me when he had it torn apart to report the damage the RMA cam tensioner had done.
He insisted that he would not continue my rebuild unless i agreed to allow him to put the stock sliding tensioner back in in place after he finished rebuilding the damage done.
Here is the "other" problem: You cannot know IF any damage is being done from the very tight cam chain unless you take the timing cover off AND remove the chain in order to inspect the intermediate gear locating spindle hole to check for elongation. You CAN ride your Norton in blissful uncertainty for quite a while figuring everything in there is just hunky dory.
Just my own experience, but no way would I ever use anything but the stock slider, I learned my lesson.
there is absolutely no way I would use one. the customer service is non existent and it is extremely hard on the cam bushings, timing chain, sprockets and idler gear pin. here is the remains of one he refused to warranty.
Oh Dear : NOW , ' we ' all know not to play Tarzan on the spanners in the timing case , unless the cam spindle support cover is on ( see below )
Heres a gnatty ford ' kent ' pushrod 59 - 75 cam chain tensioner , light hairpin type spring , single row chain . unlikely itll go in there though . :?: :?
" The timing chain tensioner pad is a wear item and should be replaced at every engine rebuild. The tensioner spring can also weaken with age, making the tensioner ineffective and upsetting cam and ignition timing. " http://images.google.com.au/imgres?imgu ... oQrQMwADgU
The chainplate links should wear trenches in the buffer pad , so as the rollers roll on the pad surface . then its ' run in ' . 8) if its down to the metal , its ' run out ' . :cry:
NOW , EVERYONEs got one of THESE or Those hanging on the workshop wall . Havnt They .
Btw 10 grand will only get needle to bounce a bit off backside of needle stop, takes sickening more to bounce it so fast its invisible. Crank shaft end wobble can jerk the snort out of cam chain tension at some rpm jump rope threshold. Test this yourself please and get back to us.
I had a Kelly Cork one in my 500 Dominator race bike for about 10 years.
The bike went well and maybe this can in part be attributed to cam control aided by the tensioner.
However recently I took the timing cover off and found the whole thing moving about and it had partly ground itself into the cam sprocket.
So on the good side
- it worked for 10 years on a race bike regularly ridden at 7200 rpm.
- I cannot see any problems with over tightening of the chain. No worn spindle mounting holes etc.
On the not good side
-it is a bit of a fiddle to fit and needed grinding of the backing plate and from memory machining part of the sprocket on a lath ??? to get enough clearance. (It was 10 years ago)
-The mounting plate eventualy fretted loose. There is not much space in there and its all held together with one nut on a thin (1/4" but dont quote me?) stud. (See the photo in one of the referenced links above)
My view is the concept is good but it kind of feels like an after market comprimise squashed into too small a space for the whole thing to be really robust.
For a race bike with regular inspection worth it - probably yes.
For a street bike - probably no. I dont intend to fit one in my street Mk 11 Commando.