RMA cam chain tensioner

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Apr 15, 2004
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Does anyone have a photo of an RMA tensioner installed in an engine? I put mine in the 850 motor and it doesn't look right. The shoe is pushed back almost as far as it will go and the chain feels very tight. I'm measuring less than 2 mm of slack. Maybe that's ok but it doesn't look good to me.

I'm thinking I didn't grind the case down enough. I'm reluctant to do any more grinding with the engine assembled so I'm thinking I might put the standard tensioner back in :(

Debby, I don't have a picture but someone may. Yes with the spring and the leverage of the wedge it does make the chain seem tight. Hundreds of these have been put on bikes with nothing but a timing cover removal so fear not. A little wax on the spinning carbide bur will make the cut fast and neat and keep the bur from loading. There is not that much to remove. Study lady you will pass right through.
I took another look at it this morning and the .060" the instructions said to remove isn't even close. I did find a photo over on britbike.com and that guy ground his down way more than I have so far. His was basically resting on the bottom of the case, which requires grinding the dowel pin boss down pretty much as far as you can without breaking through. I think the timing cover would need work too.

And where do you find these carbide bits? :? The local hw store doesn't have anything like that, and I don't know of any machine tool supply shops in this area. Denver is a financial services town. Not much industrial activity here any more. Maybe McMaster Carr or somebody like that would have them? I don't really know what to look for though, not being a machinist.

I don't know, seems like more trouble than it's worth...

I consider RMA or Corky's Nissan based one an absolute accessory. Must do mod. On Page 2546 of The catalog you find burrs with 1/4 shanks and 3/8 dia. cutting barrels . get there here: http://www.mcmaster.com/ We have about five industrial supply places here. Granger is easy to find but you need a company account. Corky's needs no carving what so ever and tensions from the inside not the outside.
Where can you find the Corky's tensioner? And at the risk of sounding obvious, can these also be installed on 750's?
I have fitted one in my 1970 750 and I simply removed the necessary material with a hand-file. If you put a dab of grease on the file it picks up most of the filings. The crankcase material is soft enough that you don't need any exotic cutters and using a hand-file enables you to control the amount of material removed. I have a Cork Engineering model fitted to another 1969 750 and have had no trouble with it although it was not a straightforward bolt-on excercise and I seem to remember having to fit custom bolts to get it mounted securely. I do agree that these automatic tensioners are a good modification to keep our bikes running consistently and reliably.
cam chain tensioner

Hi Debby, I just fitted one of these to my bike,I had to remove closer to .090" before the bracket was properly fitted, yes I agree the chain does seem to be a little tight, but after rotating the motor to different spots the chain does loosen up, watch to see that the brass wedge does not stick on a bur or rough edge.If you pre - assemble the unit you will see if there are any rough spots as you slide the brass wedge and plastic chain guide. Persevere with the file and you will be rewarded,clean the area REALLY well afterwards. Good luck, James.
I too am interested in knowing more about Cork Engineering's version - any links or photos on this one? I did a cursory Google on it and came up dry...
Bumping this up for those of us, me included, who would like more info on the Corky's unit.
Found 'em, and for anyone else interested, you ran reach RMA at 408 578 4032. They apparently don't have a website. - BrianK
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