[JVS]

I think the 25mm slack needs to be on the upper run of the chain as per the service manual. Otherwise, as stevew has said, you need to have about 50mm on the lower run in the middle.

[Ducati Scotty]

+1, but every chain usually loosens up initially, so you be ok in 100 miles or so.  Why didn't you go with 102 and just set the snails to take up the slack.  With a quality chain it will take a while to run out of adjustment, and then you could cut it down to 100.

[sparklow]

Just for my slow pickup brain to wrap itself around, the stock chain length for my 2011 B5 is a 100 link with an extra half-link added?

[lemming]

Stock is 101....100 + the 1/2 link. I had a 102 on it prior, and even with the snails ALL the way out, it had too much slack and toasted my rear sprocket after 1000 miles.

85 mile run this morning, and good Lord is she a much happier machine. New bearing, chain and sprocket, and proper tension make for a much smoother ride.

[stevew]

I think the 25mm slack needs to be on the upper run of the chain as per the service manual. Otherwise, as stevew has said, you need to have about 50mm on the lower run in the middle.

Can't see how it makes any difference whether you measure the slack on the top or bottom run when on the centre stand.  Both run free from the engine sprocket to the rear and as the rear wheel is free to rotate the play will be the same on either run or the chain.

One again i'll say that 25mm on the centre stand is too tight. 

When static with one person on the bike the chain is, near enough,  in it's tightest position.  There should still be some play measurable then.  My estimate is that in it's tightest spot there should still be 15-20mm of play.  Set it to 50mm on the stand and all will be well.

I also realise that the chain is going to give a bit from new as the packaging grease gets re-distributed around the pins and rollers.  Setting it up to take this into account is not a good idea as the degree of 'settling down' is variable.  Better to set it right with 50mm play when fitting a new chain then adjusting after a couple of hundred miles.

Why not just get the right chain?  I find it hard to believe that in the whole of the USA there isn't a mail order supplier who can sort you out.  As i said earlier we have one in "tiny" England
http://www.the-chain-man.co.uk/index.html

[Ducati Scotty]

Ver few companies make half links for chains these days.

[JVS]

Can't see how it makes any difference whether you measure the slack on the top or bottom run when on the centre stand.  Both run free from the engine sprocket to the rear and as the rear wheel is free to rotate the play will be the same on either run or the chain.

Please correct me if I'm wrong: I think the chains on our Enfields kind of make a right-angled triangle with respect to the front and rear sprocket. The lower run of the chain is the 'hypotenuse' of the triangle and has a tad larger length as compared to the upper run, going towards the front sprocket. The upper run is supported by both the sprockets, but gravity acts more on the lower run, giving it more sag, hence more length. A 25-30mm slack on the top run equates to 44-53mm on the lower run. In all the service manuals, including the older real CI Bullet manuals, they all say 25-30mm on the 'upper' run. I guess this way, when the user adjusts it, he/she can see whether it will hit the primary case, if adjusted to be too loose on the top run. However, there must be a proper reason behind it lol.

Also, the standard Renolds 101 link chain is offered by Mr. H. It's a good quality unit.

[Richard230]

I assume that the recommendation for checking the chain slack at the upper run was to keep your hands away from the (potentially) hot muffler.  The slight difference in chain length between the upper and lower run would make no measurable difference in chain slack as long as the top or bottom run is tight when you check the slack on opposite run of the chain.  I get the same slack results when I check either the top or the bottom run of my chain.  Both give me a value of 1 inch.

[Arizoni]

Just hanging there, yes, the lower loop of the chain will dangle a bit more but if the rear wheel is off the ground or the transmission is in neutral (both will allow the sprockets to turn freely), moving the movement  up/down in the upper leg of the chain will be the same as the movement in the lower leg.

[lemming]

More than 30-35mm of slack on the upper run  on the center stand and my bike vibrates noticeably more, and has more lash in the drivetrain. When adjusted properly, between 20-30mm slack, it shifts, pulls and revs cleanly and vibes are pleasant, with no drivetrain lash. Also better mileage. Just saying what worked on my bike. With the variability in these, YMMV. I could acquire the 100 link chain in a day or less from my local shop, inexpensively. since my bike is transportation, not just recreation, I prefer not to be down for a week or two waiting for mail order parts I can source here. The 102 did not work. Could practically pull the chain completely off the sprocket with the snails all the way out. The 101 started life with the snails more than half the way out, so it seemed pretty likely the 100 would work. It did, and has settled in nicely over the 170 mile ride I did yesterday.

[ROVERMAN]

I have been watching this thread for awhile and just want to give my 2 cents worth. Just before the winter lay up i adjusted my B5 chain for the first time during routine maintenance. I tightened up one notch, looked good to me based on some experience from owning several bikes, including an 03' iron barrel. The last few rides in the fall i noticed a very harsh vibration that started through the foot pegs at approx 2,800 rpm. This was most noticeable at 53-58 mph in 5th. I did the good old loosen engine mounts and run it job to no avail and checked the usual suspects but kept coming back to that chain adjustment. So, last weekend i took it up one more notch. I ended up with about 40-45 mm on the centre stand and half that when mounted. This seems to have worked, just my opinion but the B5 at least seems very sensitive to chain adjustment. I have also noticed a large amount of side to side play in the chain on the sprockets. I have the stock chain in good shape.
Roverman.