Topic: My cb350f and it's little leaks

[574hondarider]

Hello All,

I purchased a '73 cb350f earlier this summer and have been working hard to make her great.  It was running decently when I got her, the PO had replaced all the seals and gaskets in the top end (4into1 kit  https://4into1.com/engine-gasket-set-honda-cb350f-1972-1974/) and put (cheap) carb kits in it but couldn't get it running as it should.  I figured out it was an intake leak and replaced the insulators, changed the oil (gn4 20w 50), plugs, and synced the carbs with a carbtune pro and it runs awesome...it feels like a bike that's 4 years old, not 47!!  (I also did other stuff like rebuilt rear wheel, bearings in front wheel too, final drive chain and sprockets, oem mirrors, grips, peg rubbers, and a bunch of misc. stuff)

The issue I am currently having is small seeping on most of the top end bolts, also some leaks from the shifter shaft, and maybe some from the stator bolts.  I have checked the oil when the bike is on the center stand and the cap is just resting on the threads (not screwed down) and it reads on the full line.  The breather hose is not binding.  With all the leaks, it has yet to produce 1 drop of oil on the ground, even after sever 100 mile rides (I have about 600-800 miles on her since owning).  Should I be concerned about the seeping....will it get worse, or should I just leave it alone?  I was considering draining a small amount of oil with a syringe, then maybe loosing and retightening to spec all the bolts, but I don't want to open a can of worms.  Any advice would be greatly appreciated!  I am not a mechanic, but have restored an old trail 70 a few years back and do all my own gunsmithing and stuff, so I am technically competent.  I have also printed off the entire manual and parts list.

[markreimer]

Personally I’d ride it till it becomes a smokey issue. The 350F is know for leaking oil along the outer left and right front corners where a high pressure oil cavity runs up the the head. Typically leaks between the cylinder block and head. If you’ve got oil leaking out the bolt heads up top, that is kinda weird. Checked the torque?


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[markreimer]

Oh also I just remembered. When I bought a cb750 I had oil leaking out the valve cover bolts and along some gasket edges. This was after a few thousand km. Turns out half the case bolts had become very loose! Snugged then up and leaks stopped. Don’t bother loosening them, just check the torque on each one


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[carnivorous chicken]

Great bike, dig the 350Fs.

For the shifter shaft, there is a seal under the cover that can develop a leak, but it's super easy to change at your next oil change.

If you're goign to check the torque of your engine bolts, be careful -- too much and they will strip pretty easily. In my experience if it's already seeping it likely won't do much to stop it. And once it starts weeping, it will get worse over time. I rode a seepy 350F for a couple years with a small rag tucked in between the tach and speedo and just gave it a quick wipe after a ride. Eventually it got bad enough to replace engine gaskets.

It is possible, however, to have a nice and oil tight 350F. Once it's tightened up it can stay that way.

[574hondarider]

Thanks guys!  Yeah I already have the shift shaft seal and will replace that before I put it away this fall.   I purchased an oil pressure sensor too as I hear they can start leaking.  I also plan to drop the oil pan gasket to inspect/clean the screen, and maybe replace the clutch then too (it slipped once on me but that was after a 100 mile ride and when I was approaching redline).  This will all give me a chance to polish the covers anyways.  I already have a couple hundred dollars in new oem parts that I have purchased and put neatly in a parts kit for when the time comes...buying new oem parts has become a new obsession of mine lol.

I will check the torque on them this weekend, hopefully just got loose from riding.  I don't like to have leaks, but I guess she is pretty old and I have been riding a lot.  Thanks again for the comments, it's great having experts who I can ask questions to!

[WhyNot2]

Man, that's a nice looking 350F.

Wish mine would run, so I can ride it..........