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Hi guys. I just bought a 1971 CB350 for a little fun project bike. The first thing i am going to tackle is a small oil leak on the riders left side of the engine. I have attached some pictures but they were taken at night with flashlights so its hard to tell whats going on. The pictures are from below the bike looking up, with all of the covers on, it was dark out so i wasnt going to start taking off covers by flashlight, i will do that next weekend.

But my question is if anyone has ideas of the cause of the oil leak, i will be doing forum searches as well. I know I am giving you very little information to work with, but more info will follow when i crack open the covers. The oil leak looks like it has been going on for a while based on the buildup on the frame and looks like it is coming from behind the cover where the chain sproket is located (transmition output shaft). but I dont think its a big leak because on short rides i do not see a spot on the driveway the next day. But i did go for a long ride and the next morning there was a stain the size of the diameter of a coffee mug, with a drop still on the frame. If it helps the oil drop still on the frame was much more black (dirty) than the oil on the dip stick when I checked the level (no change in level since before the long ride to the next morning after the ride).

thanks for the input guys. Pictures are attached to the topic.
 

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Those pictures could be from my 360 when I got it. Same type of leak and a very similar description. I changed the oil seals around the gear shift lever and the clutch rod and the problem was resolved. Not sure about the 350 but I think it is setup similar. To change the seals get a set of picks to get the old ones out. There are a few threads here about changing them. I put mine in the freezer for a little while to get it to contract a bit. It is so nice to be able to put the bike on the sidestand and not mark your territory every stop.
 

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Second the clutch rod and shifter seals as it looked the same on mine. One point of note, does your breather tube discharge right in that area?
 

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it was suggested,, and i found it helpful, to clean things up real well,, then dust suspected areas with baby powder... the source of the leak, no matter how slight, shows in a short time. You can kinda 'read' it. Worth a try before you go too far.
 

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No book needed:

Shifter seal, remove left foot peg, remove shifter arm (don't pull hard, spread the clamp to get it off if needed), remove side cover ,you can just prop it out of the way with the clutch cable attached or it just pop it off real easy, remove cirque clip and remove washer and then finally pull out old shifter seal using a hook, pliers or screw. Then I cleaned the area with brake cleaner, dried it, applied a little gasket maker around the outside of the seal and gently and evenly pressed it in with a deep well socket that slips over the shaft, note don't push the shifter shaft in! It's not made to go that way with out coming out the other side. Reinstall washer and clip. Note, they seal for me was flush or little below the case, if it is noticeable proud, probably not all the way in.

Clutch rod: I don't know if the rod can come just out so I just held it in. My seal just practically fell out.Clean and press in new seal with a socket, and done. That one is super easy!

Then I would clean the area while it's apart ( I would not pressure wash, IMO), put on the cover, the shifter (don't hammer it on!), the foot peg and done, no more embarrassing leaks in your drive way. Of note, my bike was over filled with oil and dumping a little oil out of the breather hose directly onto the center stand mine also still has the stupid chain oiler built into the shaft and who knows if that thing leaks.
 

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Dealer on ebay. http://www.disastermotors.com/. I got the set for $29 plus shipping. I called the guy as the kit did not list the seals by name. Super helpfull and new these old twins inside and out and gave some great advice on a little gasket seal maker and to watch for air leaks on the carbs/boots. He took the time to talk to me about and answer about 10 questions unrelated to the seals.

Not sure if he has your bike parts on ebay but check his website or just give him a call. Good luck!
 
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