I went thorough 2 sprags on my 05/06. Both times the idler gears had broken teeth. The first sprag was the tiny one that came stock in 05. The second was the upgraded replacement one that became stock around 06 or 07. Same part number. In both cases the idler gears had broken. When the first one failed I was clueless. It would refuse to turn as if dead, or after a few tries start fine or start with some clanking, maybe grabbing and letting go. Eventually, it refused to turn over at all as if frozen. It had power to the starter. I jumped it from a truck. It turned very slowly but I felt the starter would overheat Took the plugs out. It turned over fine then. I felt the crank was ok. I took the cover off. The sprag had a kink in the retaining spring holding the cogs in place. It jammed and wouldn't spin free either way. I got new gears from a recycler for pennies.
Second failure, it made a big clank but started. It would start but every once in a while would catch and let go, clank, or just not turn over at all as if dead. Again. I'd move the wheel with it in gear. Kept trying using an car battery. It would suddenly start like before. Knew something was off. Assumed it was the sprag. That sprag (an upgraded one), proved to be Ok but the idler gears were broken again. I couldn't find any at recyclers. I looked at Hermys web page, they were listed as not available. Their site had nothing listed for the series. I called and was able to order a spares kit. It came with new side cover, starter, gears, sprag, gaskets, all parts being much bigger, hence the side covers.
I suggest you take the cover off and see what you have. There's nothing to lose. FYI no instructions are included. Therefore, when I put the new parts on I dry fitted things with no gaskets, nothing was tightened down. I tried using the old wave washers. They made it hard to turn the idler gears with my fingers, a lot of drag. Without them, it worked smoothly. So, I assembled it with the new parts provided, leaving them off. They aren't included in the kit. I figure they would be if needed. The kit is complete with everything.
Why not take the cover off and see what you have. There is nothing to lose. You can always make a new gasket or just be careful and use a skim of gasket cement if it isn't the problem. If you take the sprag off make careful note how the splines line up or it can take an hour of fiddling to line the key up with the slot. When sprags work, they spin free one way but not the other. Don't force anything. It all fits like a watch. It should only take a few hours if you've never done it before. You'll need to restrain the wheel with it in gear to get the bolt out of the sprag and to torque the new one. I did it with a strap, blocks, and tied the brake down. Others have written they put wood into the sproket; I don't know about that. You need a breaker bar and a torque wrech. Mine wasn't super tight. Good luck.
