Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: adriangsmith on July 03, 2018, 07:32:35 PM
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I have an oil leak from the bolt above the sprocket in the picture below. It coming up the bolt stem. Did i miss something when rebuilding the engine?(https://uploads.tapatalk-cdn.com/20180703/5423bdc6772eaf57bb2f2c0cbe021cfb.jpg)
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I have looked through all my old photos but, bloody typical, not 1 pic showing that area. But, I think it should be a blind hole, ie, goes nowhere, because a casing bolt goes in it. Has a too long bolt been put in there in the past and gone through too far maybe?
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Just looking at your pic again Adrian, what bolt hole are you referring to?. If its the one at the top, its an external fixing point so no oil will come out of there, am I looking at the wrong hole?
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Hi Julie. Yes the bolt at the top. It goes through the casing you can see the bolt shaft going back into the casing in between the cast ribs. Quite a long bolt at 80mm or so.
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The vertical bolt just to the left upper of the sprocket
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No oil leaks from the casing joins at all. It is leaking out of the bolt stem between the 2 ribs.
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Yes, i see which one you mean now. Not sure why you have oil coming up through there, unless you have put a too long casing bolt in and made a hole in the casing or as Oddjob says, maybe something not aligned properly. Is there much oil coming up?
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Quite a good seep once its revved up
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I know i had real issues with those casing bolts on my engine, trying to fit the correct length bolt to each hole was difficult. I measured all my bolt holes with the vernier in the end to make sure i put the right size in the right place. really, it can only be a slight misalignment or the bolt has gone through the casing. No other way oil could come up the thread, the bolt / thread shouldn't be anywhere near oil.
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Here is a pic with the sprocket off, I can see how if an over long stud had been put in, it could easily have caused a crack. The crack may not be visible as it could be internal not external[attachimg=1]
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Also, if you say it weeps when you rev the bike, the oil is under pressure. The bottom of that bolt hole is very close to the oilway junction from the oil pump that feeds the gearbox. You could try removing the oil pump, put an airline up the oilway and see if anything comes up the bolt hole, if it does, there is a crack there somewhere.
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Cheers Julie,
I will check tomorrow.
I'll take the sprocket off as well so i have a clear view.
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I thought of that Ken but it may have been done by a previous owner. If the engine had been apart before and the wrong length bolt fitted, then Adrian has put the correct length bolt in which is now leaving a space under the bottom of the bolt for the oil to get out. The wrong long length bolt may have caused the damage but also hidden the damage by putting pressure on the crack.
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Bolt measured the correct length.
Oil leak stopped with copious amounts of threebond liquid gasket on the threads and down the bolt shaft.
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That would suggest to me that there is either damage or crap on the crankcase joit
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I had this problem after an engine strip down. I used a piece of poly tubing slid over the bolt. It stopped the leak but then the leak moved elsewhere from the joints. To cut a long story short I stripped the engine down again. I used less jointing compound and was extra careful about the locating peg on the gearshaft. I think because the joint had too much jointing compound the oil got round the back of the bolt. It's fine now I hope that makes sense.
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That bolt holds the casing halves together so any extra long bolt would cause a break in the lower casing. The case halves are not correctly sealed (on the crankcase split line) around the bolt hole causing the oil to escape the only way it can upwards around the bolt.