Left Side Crankcase Oil Leak 1974 Honda CL125

[Sammysofa]

Hello I have a 1974 Honda CL125s1. The left side crankcase cover is leaking oil from it. I have replaced the gasket and still get the oil leaking.

Is the left side supposed to have oil behind the cover for the Alternator?
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Sam Stella
1974 Honda CL125S1

[Nobby the Bastard]

[Sammysofa]

[Teflon-Mike]

There shuldn't be ol in the magneto housing; there should only be chain 'throw' behind the front sprocket cover.
If you have il i the mag-housng, that points to a faled crank seal.
If you have engine oil in the sprocket cover, you likey have an out-put shaft seal.
If oil is drippng through the casing onto the shift lever, then you probably have a failed selector shaft seal.

Leaks from the out-put shaft seal, usually indicate a routinly over tightened drive chain, and likely buggered bearings, rather than simply just age hardened seal (likely on what a 35 year old bike?)

A small 'weap' from output shaft seal, can be tolerated... call it an auto-oiler for teh drve chain! JUST make sure you check the egine oil level every time you ride!

A weal into the mag-chamber is probably not so easy to ignore, and does hint that the motor probably needs a complete tear down.

All three seals are in the LH crank case, so top end has to come off to slit the crank-cases, and the bottom end come apart to get the case free to swap seals.... and with that amount of work, the expense of buying three £5 seals is peanuts compared to a complete gasket set, and anyhing else you likely find that begs attension in the doing, like crank bearings, out-put shaft bearings, rebores and slappy cam-chains.

Your call how to progress; but buying the Haynes manual would probably be a good start.
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Sammysofa]

[Teflon-Mike]

The two O-rigs you have changed seal the magneto cover to the crabk case and the inspectio cover to the mag cover, to stop rain & road water from getting i and shorting electrics,

The Mag rotor is on the end of the crank-shaft, that s sittig in he crank-case, that aught bee full of oil.. there HAS to be a dynamic seal, outboard of the main bearing supporting the crank in the crank case t stop the engine oil leaking t of the crank case.

Replacing that, I'm sorry, but does beg stripping the engine to the bare cases so you can fit the new crank seal to them and then put the crank through it.

Ignoring it? Well, now you have replaced the casing O-rings, any engine oil wont seep away... at some point it will fill to the same level as the oil in the crank case, I don't expect that will enhance performance any, as the magneto rotor acts like very big hydraulic damper stirring it as it goes around... hot oil might cook the electrics there, if enough hot oil gets in there, but oil in the magneto rather than in the engine is't going to do much for engine lubrication as it should....

Your engine, your call! BUT oil shouldn't be leaking into there....

An as aluded, it MAY just be an almost 40 year old seal sayng 'enough', but likely thats ot the only 'problem' in the engine, to be tackled on tear-down.

Fact that you are runig a near 40 year old bike; suggests that ts either a scrap-heap survivor that has been tickled back into life, and new use will put strain on all bits that weren't worn out whilst bike was still young, or rotted in twixt time, and his is just the frst hint of all the possible "Resuscitation Failures" possible ad likely to come before the bikes de-niggled and ruining reasonably reliably; OR its bee restored, and this is symptom of something like an engine tear-down that's never been done, or done properly, and you are again, looking at possible resus-fails, or de-niggling bad work on top of real over-haul processes.

Welcome to the wonderful world of classic bikes.

If you want a relatively reliable everyday rider you don't have to lift too many spanners at, go buy a Yamaha YBR or something; If you want all the joys of Classics and the fun of spannering them, grab the book, read the instructions and dive into the fun of wrenches and pliers, gaskets, worn bores, oval bushes and rusty bearings.. That's what its all about.
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'