919 chain slack measurement - Wrist Twisters
 
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post #1 of 14 Old 05-10-2015, 07:18 PM Thread Starter
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919 chain slack measurement

My manual is fairly useless on the subject as it doesn't tell me what state the bike needs to be in to take the measurement. On side stand, standing on its own, standing on its own with rider on, etc.
On my xr650, i basically got my base measurement and settings by bringing the swing arm up to put the front sprocket center, swing arm hinge center and rear axle center in horizontal line, and then checked tension and made myself a stick i could easily check for loose/tight.
I've seen people mention 30-40mm here for chain slack... but not how the bike was sitting to check it.
thanks

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post #2 of 14 Old 05-10-2015, 07:22 PM
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Service manual says to check it on the side stand...30-40 mm

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post #3 of 14 Old 05-10-2015, 07:28 PM Thread Starter
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thank you... i've actually found some posts now that mention it.

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post #4 of 14 Old 05-11-2015, 04:21 PM
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If the other posts haven't already mentioned it, a good post-adjustment check is to plonk yourself on the bike and get someone else to toe-test the amount of slack in the chain as the swing-arm levels out.

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post #5 of 14 Old 05-11-2015, 06:30 PM
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Quote:
Originally Posted by marylandmike View Post
Service manual says to check it on the side stand...30-40 mm
I always though that Honda's 30-40 mm is a little too much. Aprilia recommends 25mm. DID spec is 3/4" or 19mm
DID also says that the whiplash due to excessive slack will contribute to the wear. Don't know

DID spec
http://www.pinkmotors.hu/did/arlista...o_szerszam.pdf

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post #6 of 14 Old 05-12-2015, 02:22 AM
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Ok, so what would the measurement be if it were on a rear stand?

I put mine on the rear stand because it's easier to measure that way. I did notice that when it's running while on the stand, the chain does seem to bounce as if it's too loose.

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post #7 of 14 Old 05-12-2015, 02:58 AM
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Quote:
Originally Posted by KarlJay View Post
Ok, so what would the measurement be if it were on a rear stand?

I put mine on the rear stand because it's easier to measure that way. I did notice that when it's running while on the stand, the chain does seem to bounce as if it's too loose.
On a rear stand, there will need to be more slack in the chain than when there is weight on the rear wheel via the sidestand.

The key is how much the swingarm has dropped from level, or more correctly, moved away from a line drawn through the swingarm pivot and the centre of the countershaft sprocket.

The point of the slack in the chain is to provide enough freeplay that the chain isn't stretched to twanging point when the swingarm is flat, at which point simple geometry takes the rear sprocket to its furthest point away from the countershaft sprocket.

So if you can test the chain tension with the swingarm as flat as poss, ie with weight on the bike, then you can be assured that there is enough slack to accommodate the distancing effect of the swingarm geometry.

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post #8 of 14 Old 05-12-2015, 11:42 AM
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Quote:
Originally Posted by zaq123 View Post
I always though that Honda's 30-40 mm is a little too much. Aprilia recommends 25mm. DID spec is 3/4" or 19mm
DID also says that the whiplash due to excessive slack will contribute to the wear. Don't know

DID spec
http://www.pinkmotors.hu/did/arlista...o_szerszam.pdf
It's not a universal measurement. The specific value will vary based on the position of the bike and also the geometry/suspension of the bike, i would guess. like a bike that leans way over on the side stand might have a different value for chain slack than a bike that sits very straight up, or if there is a lot of static sag.

the 3/4" in the DID pamphlet appears to be with the swingarm level, which means it would be more than 3/4" on the sidestand. there's also an * after the 3/4" but i couldn't find where that * was explained at, so this might only apply to certain instances.

I just went through this last weekend, cleaning adjusting my chain, then questioning this, then re-doing, then doing it wrong... finally got it, bike feels really smooth. i'll have to check what it measures on the centerstand.

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post #9 of 14 Old 05-12-2015, 05:31 PM
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A possible remedy for those with serious concerns about excessive chain movement:

Powell Peralta Weld on Motorcycle Chain Tensioner | eBay

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post #10 of 14 Old 05-13-2015, 03:16 AM
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Quote:
Originally Posted by K1w1Boy View Post
On a rear stand, there will need to be more slack in the chain than when there is weight on the rear wheel via the sidestand.

The key is how much the swingarm has dropped from level, or more correctly, moved away from a line drawn through the swingarm pivot and the centre of the countershaft sprocket.

The point of the slack in the chain is to provide enough freeplay that the chain isn't stretched to twanging point when the swingarm is flat, at which point simple geometry takes the rear sprocket to its furthest point away from the countershaft sprocket.

So if you can test the chain tension with the swingarm as flat as poss, ie with weight on the bike, then you can be assured that there is enough slack to accommodate the distancing effect of the swingarm geometry.
Very nice, clearly written explanation of the reasoning behind proper chain adjustment. Such clarity and logic is a rare commodity these days and most welcome when it does appear.

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post #11 of 14 Old 05-13-2015, 11:47 AM
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Quote:
Originally Posted by K1w1Boy View Post
A possible remedy for those with serious concerns about excessive chain movement:

Powell Peralta Weld on Motorcycle Chain Tensioner | eBay
Makes me wonder why Honda didn't put these on at the factory. Cam chains have them, but drive chains don't.

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post #12 of 14 Old 05-14-2015, 01:19 AM
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They were a big deal on off-road bikes in the late 70's, when suspension travel suddenly went from 3" to 12" - I don't know if that's still the case.

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post #13 of 14 Old 05-19-2015, 06:30 PM Thread Starter
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Adjusted this last night when I put on new tires... was way tight before... now it's great. Really improved the riding experience.

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post #14 of 14 Old 05-19-2015, 09:27 PM
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It does make a big difference, to shifting and everything....good to have it right.

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