Author Topic: CB350F losing oil  (Read 1061 times)

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Offline nath180

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CB350F losing oil
« on: April 14, 2017, 02:15:40 AM »
Looking for some pointers, this has got me a little beat.

Bike smokes a little (hard to tell if oil or fuel, maybe both), after a 20 min ride you can wipe damp residue off the muffler tip, maybe a mix of oil and fuel - it's hard to tell.

Went for a 70km ride a few weekends ago, arrived home to a smoking breather pipe, checked dipstick and it was almost on the bottom line. Before the ride it was about 3/4 full.

A little oil on the fins and around #1&4 plugs. No other oil leaks around gaskets.

Plugs usually look really rich and damp, but after the long ride the plugs were dry and no build up. My guess is it was running abit warm and leaned up a little.

Did a compression check this arvo, bike has been sitting for a few weeks. 120, 110, 110, 115 cold.

I was expecting rings to be the issue, given the breather smoke.

Rebuild was apparently redone by PO, head/valves reconditioned (not sure what reconditioned included), new rings, primary drive and cam chains.

I was originally chasing a rich condition thinking the smoke was fuel, so carbs are spotless and balanced.

Next step from all research is probably a leak down test - unless anyone has other ideas?

Nath

« Last Edit: April 14, 2017, 02:22:50 AM by nath180 »

Offline rupaulpierce

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Re: CB350F losing oil
« Reply #1 on: April 14, 2017, 05:10:01 AM »
Mine absolutely pisses oil. Same story, PO rebuild top end, apparently did a #$%* job. Also a bit of smoke from one pipe, smoke from breather in traffic. Apparently this is par for the course with this engine. I'm going to try to re-torque this weekend and see if that helps at all.

Online carnivorous chicken

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Re: CB350F losing oil
« Reply #2 on: April 14, 2017, 09:18:34 AM »
Mine absolutely pisses oil. Same story, PO rebuild top end, apparently did a #$%* job. Also a bit of smoke from one pipe, smoke from breather in traffic. Apparently this is par for the course with this engine. I'm going to try to re-torque this weekend and see if that helps at all.

Par for the course with a bad rebuild maybe, but done properly 350Fs are smoke free, drip free.

Offline rupaulpierce

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Re: CB350F losing oil
« Reply #3 on: April 14, 2017, 09:27:50 AM »
Chicken, you recommend the Versah gasket set?

Offline nath180

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Re: CB350F losing oil
« Reply #4 on: April 14, 2017, 02:21:57 PM »
I have a 4 into 1 pipe, so it makes it difficul to tell if a specific cylinder is the cluprit.

After a ride you can wipe residue off the tip, thick like wet paint.

Offline nath180

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Re: CB350F losing oil
« Reply #5 on: April 14, 2017, 02:37:05 PM »
Vesrah kit for the 400F? Would the head gasket fit, or need to buy a seperate 350F head gasket?


Chicken, you recommend the Versah gasket set?

Offline Trevor from Warragul

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Re: CB350F losing oil
« Reply #6 on: April 14, 2017, 06:54:19 PM »
Smoke out of the breather is either rings or a worn out/overbored cylinder.  It's easy for a cylinder boring place to take out too much metal from a cylinder.  This happened to me.  I ended up buying a used block on standard bore, along with the used pistons.  New rings, and the smoke went away.
1971 Kawasaki H1A
1972 Honda CB350F
1976 Moto Morini 3 1/2 Sport
1978 Honda CBX
1997 Suzuki Bandit 1200
1999 Ducati Monster 750

Offline nath180

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Re: CB350F losing oil
« Reply #7 on: April 14, 2017, 11:49:31 PM »
Smoke out of the breather is either rings or a worn out/overbored cylinder.  It's easy for a cylinder boring place to take out too much metal from a cylinder.  This happened to me.  I ended up buying a used block on standard bore, along with the used pistons.  New rings, and the smoke went away.

True. From what I gather, the original pistons were re-used, but new rings were fitted. Whether or not it was re-bored I'm not sure.

Without starting from scratch again it will be very hard to tell. Rebore to oversize, fit oversized pistons and rings, and whilst open I guess valve guides worth doing as well, and re-seat the valves. At least I'd know its been done properly that way.

Thinking it will be pretty hard to come by a spare engine here in Australia. Parts for the rebuild would be hard enough.

Online carnivorous chicken

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Re: CB350F losing oil
« Reply #8 on: April 15, 2017, 02:30:50 PM »
Chicken, you recommend the Versah gasket set?

OEM if it's available, but it's been about 12 years for me on a CB350F...