I've a 1978 CB550K that has a leak at the tachometer cable, and I bought a new oil seal from BikeBandit. I removed the cylinder head cover to pull out the tach cap (I had a lot of trouble removing just the seal. I just moved and don't have half my tools). What I found when I removed the oil seal was this silicone like seal below it. Searching around, I haven't found anything like it on here. It's perfectly shaped (flat on the inside edge, with a nub that slides into the oil passage), so i don't think it's from the previous owner. It looks factory formed. Also, this cap isn't original to my engine, and I don't remember what year motorcycle it came from. it looks identical to the one I pulled off my engine, so I thought nothing of it until I developed an oil leak immediately after installation. I just assumed the oil seal was bad, and kicked myself for not replacing it preemptively.
1. Is this supposed to be there? Anyone see this before? Should I reuse it or not? Seems odd to me that it's designed to plug the oil galley, and didn't work that well at stopping the oil from getting past...lol.
2. Is the new oil seal supposed to be like plastic? The seal has almost no pliability. The center feels a bit soft, but everything else is hard. At a quick glance, it's difficult to tell the old and new seals apart.
3. Does the DOHC seal work on my motorcycle (91256-425-003)? Should I just save a step and use this? I didn't know of it before i bought the replacement seal. With the old seal, my tach cable could rock in the cap, and I read that this movement might instigate a leak.
Thanks all! Pictures are attached of the silicone piece. It fits into the grooved side of the oil seal, and the nub goes into the oil galley that runs alongside the cap.
Picture 1Picture 2
