750 SF primary chain adjustment

TeddyG

TeddyG

Hero member
Location
Portland Oregon
Greetings,
I saw previous posts on the variety of ways this can/should be done, but I want to make sure that mine is adjusted properly since buying it last year. While riding it and accelerating to higher speeds, I've been hearing a sort of loose chain rattle from the lower left engine side, and I've been meaning to examine the adjuster. With a cold engine, I'm feeling @ 3/4 turn before the screw firmly seats in place. Following Paul Marx advice, I set it to 1.5 turns out, which so far, might've lessened the sound, but hard to tell with all the engine noise. The Green Book advises to turn the adjuster until a whine is heard and then back off, while the bike is in gear at 2-3K RPM (which I haven't done yet). So which is the preferred method? And what's worse- a too tight or too loose primary chain? I'm guessing too tight. Also, the Green Book advises changing the primary chain at 15K, although Wolfgang didn't think that was necessary when I asked him about mine at 16K miles.
Thank you all
 
My vote is follow Paul’s advice. And if you have sighted the chain recently and it’s undamaged then let it go another 15000 maybe …
 
On my triple I’ve done the “whine” method, as per the factory manual. Didn’t like it much, now use the “turns out” method. Much easier. Correct number of turns out depends on who you talk to, but the main thing is that you just take out the worst of the slack, without applying tension.
On Red’s advice I found that new cush rubbers is a bigger help regarding noise. My bike sounded like a chaff cutter before that.
 
Definitely NOT tight. As mentioned so many times on here before it's not a tensioner, it simply reduces the slack to avoid backlash on the loose side. Most are overtightened, evidenced by significant wear on the rubber slider. I just tighten mine until I feel a very slight resistance and then back off a tad. It helps if you practice this while the primary cover is off so you can feel the chain. IMO 1.5 turns out is way too much and will definitely produce slapping. And don't mistake rattling down there for chain slop - it's more than likely hardened clutch drive cush rubbers.
 
A useful description given by Keith years back is to use an oiled hand on the screwdriver. You need to take the chain movement or slack out. Definitely not a guitar string. The whine method doesn't work on the Murc dual chain, I guess still sold by Andy The Chain Man's son, I prefer that chain, it's much tougher, and it's a bit trickier finding their sweet spot. There by far the best replacement chain if you need one.
 
I agree too with Andy and Quinton, if by pulling in the clutch lever the clatter from the chaincase disapears it's definatley clutch drive rubbers at fault.
 
Well, it also could be the standard rattly Mikuni carb slides if you have them. I was pretty shocked at how noisy they are when my bike first got them.
 
It depends on what primary chain you have. Around 1 turn will do with a triplex more like 1.25 withe the duplex. As for the twin chains, you'll never get them silent.
Paul
 
Adjusting mine made a huge difference to quality of gear change . Mines got a roller tensioner ( not a blade) and I set it by ear, where it sounded happiest- you can also feel the tension through the adjuster . I think Keith’s oily screwdriver is a good analogy. You could always whip off the cover and set it by eye.
 
its probably time to check the key between the cam shaft halves, easy to do, plugs out, both end covers off, on stand, engage third gear and have someone turn the rear wheel by hand as you lay on the tank and feel the cam ends with your fingers, together, both left and right, they should both revolve in angelic harmony, if you detect a slip or a jolt/crack, the the key way is about to break.
CLEM
 
Thanks again guys for all your invaluable help- I'll stay w/ Paul's 1.5 turns out and see how it sounds/feels during higher speeds. The bike came to me with many things done incorrectly, so I've been wondering about the adjustment that was done to it. The manual's "whine" method seems a bit extreme, but what do I know. I realize these engines can be mechanically noisey, so hard to say if what I'm hearing is normal or not.
Clem- I will try your advice
 
Unless the cams have been separated several times annd refitted with the used flanges the cam-to-flange interface should hold firm. The knocking noise is very pronounced when they do go. It's a totally different racket from either a loose primary chain or worn clutch cush rubbers.
 
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