gunthn, no, my nuvinci stays put so far. If your chainline is not quite right it will pull and force things to flex leading to problems, a straight chainline is important imo..
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Update on RC bike, you know some days how any project you tackle just works out easily and successfully ?.. well today is not one of those days. :?
Recent problem has been motor/chainring stage rubbing the frame at the swingarm, after a few hard runs parts are bedding in ( cranks onto bottom bracket ) and the 1mm gap i had for the chain is not that wide anymore.. so i got a new slimmer chain, shimano, break the half link chain off, put shimano on and of course.. not a half link it's either one link too long and my tensioner won't work, or too short and can't be connected... grrrr..
Then i decide to swap the 18t ENO for a 16t to reduce the gearing even more, uhm, that aluminum adapter is really.. and i mean " REALLY " wedged in there... I 1st clamped it in a vice, and tried the pin and hammer method, i managed to mangle some metal pretty good..
Then i fabbed up a tool from a 30mm socket ( had to file it down some more, this was made to remove the swingarm on my Honda 250SX trike as the stock honda tool is like 300 $ ), used a big 3/8" bolt and cranked down the set screws, clamped the bolt in a vice..