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Discussion Starter #1
Hi All,
I had a service done at the weekend - it was a year 2 service at 9500miles. They carried out the smaller '6000mile' service and I'll get the 12k service done at year 3.
It was a basic oil change and check-around. I noticed the chain looked like it had been cleaned and on the ride home the bike was very smooth on gearchanges. Checking the chain tension though, they had tightened it much more than I'd like. The manual has the measurement 51 - 56mm from the bottom of the swingarm to the centre of the chain (with some weight on). I could only see 40 - 45mm. I decided to slacken it off a bit and got it to around 50mm. It will probably go a bit more clonky on gearchanges and on/off throttle, but I don't want to damage anything with an over-tight chain.
I may run it for a bit and re-check in a week or two.
Anyone else had experience of dealers over-tightening the chain? Maybe they think it should be tighter than the Yam manual?
Cheers .. Tony
 

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Personally I'd loosen it. As I've said more times than I can remember in various chain adjustment discussions for drive chains and cam chains, a bit loose is far better than a bit too tight. In fact fairly loose is better than a bit tight. Chains are not meant to run under any tension at any point in the run.

I broke the side plate on a chain running it too tight.
 

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Speaking of chains, can I use the PTFE spray from Lidl on it? Also I tightened my chain this morning as it had loosened in my opinion in the roughly 150 miles I've put on the bike in the last week from new. It's still within the limits but I would have preferred to adjust it on a centre stand when you can find the tight spot, this only having a side stand is a nuisance.
 

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I will say it again, don't get over concerned with chain adjustment. If you look at how loose dual sport and motocross bikes run chains you will understand. If the chain is good, there is not enough side play to have it come off. Don't overthink it. I only have two or three chain adjustments in 15,000 miles when I put new chain and sprockets on my dual sport, and it lives in a lot of dirt and crud with minimal cleaning. Plus mechanical engineering knowledge that chains are never meant to run under preload tension.

If you have to worry about where the tight spot is, that small fraction of an inch, you're over thinking it. Here's a bit of a Q&A article from Motorcycle, by John Burns

Dear MOby,
A few months ago my Sportster 48 started cohabitating with my boyfriend’s ’09 Yamaha R6. Among the many strange adjustments that interest me is why my BF seems to be so anal about his bike’s drive-chain slack, which he insists has to be 40 to 50mm. He checks it all the time. My Sportster’s belt slack is apparently supposed to be around 15mm. I never check it and don’t much care, and I feel like he sort of wants to shame me for my casual attitude. As a matter of fact, when we swap bikes I feel like his has way too much slack, sometimes feels kind of jerky, and I’m beginning to think this might extend to other parts of his personality. What gives?

Loose Cannon
Janesville, Wisconsin
Dear Cannon,

Your BF’s true jerkiness will only really reveal itself over a time period much longer than a few months. For now, let’s try to keep it to just differences in hardware and lifestyle. Your BF’s Yamaha R6 has a rear wheel that travels up and down nearly 5 inches, which makes the chain looser and tighter as the swingarm moves up and down quite a distance. In the photo above, as the bike’s rear axle moves upward those 4.7 inches, you can see the chain will get tighter because the front sprocket is some distance ahead of the big silver nut that marks the swingarm pivot. That 40-50mm of chain slack (what the Yamaha manual specifies!) is just enough to be sure the chain’s not too tight when the rear sprocket is at max distance from the front one. Too tight puts undue pressure on the countershaft (the one the front sprocket is attached to), which can lead to a host of nasty expensive internal engine problems. Too tight will also keep the suspension from being able to stroke through its full travel. It’s best, then, to err on the side of loose, but not too loose. If Yamaha says 40 to 50mm, there are very good reasons why – though closer to 40 does reduce driveline lash, and may make your boyfriend seem less jerky.


The chain could be significantly looser than 50mm in that case. All that would suffer is a bit more driveline snatch, which I'd personally much prefer to a steel chain yanking on the counter shaft or wheel/cush hub bearings when suspension compresses. I'll learn to ride smoother to make up for the snatch. I would be running more than the factory recommendation, making it 50-60mm slack.

Sometimes there are problems with manuals, not always quite right. The KLX250S manual says 35-45mm (1.4-1.8"). I actually lined up the counter shaft sprocket, swing arm pivot, and rear axle centerlines, adjusted about 12mm (.5") of slack. Let up on the rear wheel and the slack measured 50mm (2") slack! If I ran the recommended, it would be like a banjo string. The manual is too tight, I'm guessing, wasn't really tested, but rather is a generality like the 4000 rpm break in rpm thing. I run the KLX chain at 50-60mm (2-2.5"). My XSR will be a shade loose too.

The manual says 51-56mm (2-2.2"), which is a bit narrow range, but seems realistic. I haven't set up to see exactly what it should be yet, but I will be running to the loose side. The chain will not wear faster and will not cause possible expensive damage as too tight can. Just makes sense.
 

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Discussion Starter #5
Thanks for feedback, pretty conclusive -> keep it on the slack side. Since I loosened the chain tension, it's definitely less smooth on the transmission, but that's better than damaging the shaft.
Like KLX says - learn to ride smoother!
 
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