by Bill Jurgenson » Wed Dec 27, 2006 12:15 pm
hard to give a definite measurement. If you are light in weight, never have a passenger and still have the stiff original strut mounted, then the 25mm noted on the swing arm whould be OK.
I have around 40mm as you guessed but have a Wilbers (Technoflex) strut.
The only way to test is to push the tail down as far as it will go: 2-3 guys, best not lightweights, packed onto the seat should do the trick. The chain can then be almost taught. Once you've got this setting, you can measure the slack on the unweighted bike and note it.
Better too slack than not enuf, as long as the chain won't come off like a bike derailleur, it's not too slack. Just a little too taught will pull the chain tight when going over a big bump for instance and this really gets at the shaft bearing behind the sproket. It will also pop of the rollers from the chain in no time.
Couple of other points, too: inexpensive (elcheapo!) stamped chainwheels are very often not round, so you have to turn the wheel full circle to be sure. Only high quality machined aluminum cahinwheels are really round. They are worth the money and usually last just as long as steel ones.
I already noted that anything but the best chain is money thrown out. A really good chain lasts longer and runs more freely; the difference can amount to over a PS.
Don't use the white, sticky so-called lubricant garbage. All that does is bind the dust from the road to make a super grinding paste and wear out the sproket and chain in short order. Unfriendly people go as far as to maintain thet the stuff os pushed by the dealers exactly because it ruins everything so fast. And it positively is an absolute mess.
Clean the new chain first and just oil it with bicycle oil. Do it often. Only takes a minute or two.
The various Teflon dry lubricants are apparently pretty good, too. I have no experience with them, so I cannot say for sure, but they at least do not create grinding paste.
Personally, I ride unsealed chains with a clip lock, as a rule DID ERT2, and oil it weekly, even daily if I am riding an awful lot. On the track, each time out of the pits.