2012 primary chain tensioner question
Talked with a retired HD tech, he told me of constantly replacing transmission race bearings as well. Replaced the auto tensioner with a hayden, and eliminated a lot of vibration and noise. And shifts smoother now, too. Check out the article about the Hayden M6 here: http://www.hdopenroad.com/reviews/a-...uster-blues-2/
By the way, I dont sell anything, just ride!
By the way, I dont sell anything, just ride!
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,640
Likes: 6,446
From: Honah Lee
I installed 2 of these (b model with the relieved area) and sold the third on ebay. The ebay fellow said his got too tight and he paid to have it installed and then taken out. I installed one in mine and since I have the inspection port it appeared too tight also. It was just so quite and smooth you would swear it was whining and too tight. I pulled the primary cover and only then did I realize that unlike the manual adjuster that it's easy to fill and measure chain free play, the auto one is a little different in how it fills since it has the two heavy coil springs in the bottom of the tensioner pushing up quite hard but still spring loaded. This is what gives you the impression it's too tight. When you first push you will get about 1/4" free play but when you push harder you will tighten the springs till they bottom and get about 3/8" more. They are OK as long as you do not have a worn chain and sprockets (from abuse) that cause you to have a lot of run out. If so then it may ratchet up and get you down to 1/2" total. Then it's getting kinda iffy. I installed the third and the owner could not be happier. Note the relieved area in my 'B' mod one. The 'A' model did not get too tight either. It stuck from too much tension and did not ratchet forward. Once ratched forward, they do not ratchet back. With wear in the chain pins, the chain gets longer (lot of pins add up) or the shoe grooves in it will allow one tooth jump. Note in about 20K the outer links of the chain groove in and once the chain rolls I doubt it will ever ratchet anymore for life of bike. Just my opinion but Harley got this right. They actually have a thicker replacement shoe I guess for chain and sprocket wear. Must be for a police use million mile hard ridden Harley
Last edited by Jackie Paper; Sep 14, 2018 at 11:15 AM.
Elite HDF Member
Joined: Sep 2007
Posts: 4,928
Likes: 69
From: Near Myrtle Beach, SC
The stock primary tensioner seems to be the root cause a malady of issues. I have known folks with OEM adjusters that would not tighten at all, thus a loose chain and all of the noise and lash that comes with that....and I have heard just the opposite....the OEM tensioner rachets the chain tighter and tighter, causing eventual bearing failures, spline damage, etc.
It appears that the OEM tensioner is a tightening mechanism with no ability to loosen tension when the chain cools off and gets shorter. Not to mention its inability to compensate for chain wear, it just appears to be a pretty poorly designed part. Factor in the effects of an over-tight primary chain on various bearings and splines, then it's pretty apparent that there is a legitimate cause for concern for big twin owners.
I have decided to install a Hayden in my bike and get the OEM trouble-maker out of my world.
http://www.haydensm6.com/Quicktime/M6BT-07Installed.mov
It appears that the OEM tensioner is a tightening mechanism with no ability to loosen tension when the chain cools off and gets shorter. Not to mention its inability to compensate for chain wear, it just appears to be a pretty poorly designed part. Factor in the effects of an over-tight primary chain on various bearings and splines, then it's pretty apparent that there is a legitimate cause for concern for big twin owners.
I have decided to install a Hayden in my bike and get the OEM trouble-maker out of my world.
http://www.haydensm6.com/Quicktime/M6BT-07Installed.mov
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Seasoned HDF Member
Joined: Mar 2010
Posts: 38,640
Likes: 6,446
From: Honah Lee
Neither the old school manual adjusted tensioner that jumps in 3/16" steps or the new auto tensioner that jumps in 1/8" steps has the ability to actual loosen while in service. They both are designed to give the chain about 5/8-3/4 free play when cold to allow for primary case expansion when hot. The chain may grow slightly when hot but that would actually not hurt anything since the chain would not be too tight. (makes thing noise but that hurts nothing) What happens is the aluminum primary when hot grows and lengthens the distance from the front sprocket coming out of engine and rear sprocket going into transmission. This can take about 3/8 of chain slop out in my experience from setting a manual tensioner at 3/4 free play cold and on a 98 degree day here on the coast with the tensioner checked after a hard long run. Sure it would be more if you run in extreme conditions and why Harley calls out the 3/4. Normal less then 100 degree I believe you can drop it back to 5/8 easily. When I checked my manual tensioner after the run the oil temperature of the engine on my dip stick was 255. Of course with the manual adjuster the chain need to have almost 1/4" too much play to be able to manually raise the adjuster one notch. The auto one does it on it's own with about 3/16 too much play. Were the auto one shines is the two bottom springs allowing for a little loose chain and yet not make noise. Heat will easily override them. So in a way they do compensate for heat. You can see the tension springs on the bottom and the trigger for allowing another step if chain gets too loose. Also note it is the older 'A' model. The 'B" mod mainly allowed Harley to sell it for older bikes without the two spacers. Also older manual adjuster. Only moves in steps.
Last edited by Jackie Paper; Sep 14, 2018 at 11:15 AM.
