I've been fighting a shift shaft seal on my FZR for awhile now, constantly wet/seeping. I'm on my third seal this season, doing everything I can think of to ensure a good install. Looking at the seal, it looks like the issue is the shaft itself has just enough play in the case to pull away from the seal lip at times. The shaft doesn't visibly appear to be worn, but I'm going to order a new one anyways. If the issue is the boss it goes through in the case being worn... I dunno how to fix that short of finding a new case? Are there oversized seals or seals designed to cope with more shaft movement I could substitute? Edit: To add to the disgrace, it puked oil overnight once the temps dropped in the garage, lovely.
You might be able to bore the case support and install a bronze bushing in there. Probably a couple of hundred bucks for a good machinist. If you can find a set of cases, they might already be pretty worn as well. Parts for those things can be tricky to find.
Are you talking about the seal where the sprocket is? Mine just started seeping recently. Are you getting OEM seals or measured seals from a bearings house?
Countershaft (Sprocket) seal is nice and dry. I originally pegged it as the culprit when I started finding oil on the pan, but inspection revealed it's fine. I've been using OEM seals, not sure I've got a decent bearings house near me? (Southern Maine) I like the idea of sleeving the boss, I don't like the thought of tearing that motor down... again... it was just refreshed this spring, it's only got 7.5 hours on it since. I really should inspect it I guess after my crash, needs the ignition cover recreated too, so... time to find a machinist, welder, someone to pull the dent on the tank... anyone want an FZR 3TJ in need of TLC?
So, crankcases have long since been 'NLA' up to and including YZF600R units. (I think those would require a custom seal to work with a 400 crank?) I've not split the cases on the 400 before, can I drain the motor, invert it and just pull the bottom case half for machine work or will it be more involved than that? And yes, the bike has 17s from the factory (3.5x17 front, 4.5x17 rear) I use for rains, for drys I've got a set of spacers that let me use an R6 front, and I've got a Dymag 3 spoke 4.5x17 magnesium rear currently. Still not sure I want to part with it, I love it when it's behaving, but I'm getting sick of being on a bike that I can't get parts for easily... especially after a crash. Of course, I want to build an even worse one off as it's stable mate so... my decision making ability is not the best.
On the 600 there are two bolts underneath the cylinder (font and center, you can see the little bulges in the exterior of the case) that requires you to completely dismantle the engine. Until you decide not to install the bolts when assembling the cases. However, Yamaha was nice enough to number each bolt location so you can easily put the bolts back in the right hole. Tip: Take a long or large piece of cardboard and number it 1 through 40. Poke a hole at each number. When you dismantle the cases, put each bolt in the corresponding hole in the cardboard. You can then take the lower half to a machinist (unless the shift shaft is at the split?) and go to town.
Maybe a Speedi Sleeve would work. They are typically used when the shaft is worn but may add enough diameter to work.
