Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: stoutgoose on October 31, 2023, 07:35:17 PM
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I'm wondering if I have a wet-sumping issue.
The bike emits a reasonable puff of oil smoke when revved reasonably hard (over 4000 rpm) on the stand. Friends also mention they can smell oil when trailing me, with a small puff visible, but no oil smoke on overrun.
I rebuilt the engine about 5000 miles ago, which included new valve guides, valves, and valve stem oil seals. The bores were in spec, as were the pistons and ring end gaps, so I honed the barrels but nothing more.
I did not replace the oil return stopper in the oil pump because I couldn't find a seal kit, and now I am beginning to wonder if it is this that could be contributing to the oil smoke.
The oil tank level doesn't deplete significantly, however when I drained the sump today, over 1.5 litres of oil came out from just the sump. I started and ran the bike and then measured the oil level which was now at the bottom of the dipstick, so I added another 1.5 litres and this brought it halfway up the dipstick.
I took the bike for a good blast with some hard acceleration and WOT at times. Back home, the oil level remained at halfway, and when I drained the sump again about 3 hours later, 1.5 litres of oil was again extracted.
Is this a normal amount to be expected to be contained in the sump of a '78 750?
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No, it's sounds like it's sumping, overhaul the oil pump, including the stopper valve and spring and hopefully it will be OK again.
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Many thanks. Any suggestions of stopper seal suppliers?
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Nurse Julie and Trigger.
Sent from my Pixel 7 Pro using Tapatalk
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Nurse Julie and Trigger.
Sent from my Pixel 7 Pro using Tapatalk
Thanks Roy, yes, we used to hold stock of the kits but the chap we bought them from in USA sold out to Cycle-X who now charge $199 + shipping etc.