Oil Leak, Gasket Advice

[WildGoose]

diagnosed...

https://www.bikechatforums.com/files/1_142.jpg

you can see here, my engine, and three gaskets in that area, one i have replaced with official honda (the clutch cover gasket) the other at the bottom of the engine, is the sump gasket, that is fine

the leak is coming from where the two engine halfs meet, from looking at the engine, it seems someone has used instant gasket (something i despise) to seal the two engine halves

now, it doesnt leak a lot, the level of oil never goes down, so i have no intention of sorting this until i have another bike, haynes manual says to split the engine, you have to drop it out of the frame, so its a major job

here is a page from the honda illustrated parts catalogue

https://www.bikechatforums.com/files/2_142.jpg

its the only page that deals with the two engine halves, and is it just me, or is there no gasket detailed there? i've gone through the entire book and there seems to be no gasket for between those two parts

my question is why? is it such a rarely replaced gasket that honda dont make one, and you just have to do it yourself with instant gasket (doesnt seem likely) would a gasket like this blow by itself?

and why would an engine like mine, with apparently such a low mileage (i bought it at 17 000 km's) ever have to be split? harsh life? HPI check indicates the mileage is rougly correct

the leak is fairly minor, it only causes my right boot to be constantly covered in oil, but i'd rather have an engine that didnt leak...

anyone ever split an engine before?
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So in other words, he stopped you for being flagrantly in posession of a motorcycle in direct contravention of the Hippies, Darkies and People Whose Face I Don't Like The Look of (Police Powers) Act. 1976

[Guest]

It's very rare (off the top of my head I can't think of one) to have a gasket between the two crankcase halves, and a very fine bead of sealant is all that is usually necessary. The makers use their own product (Yamabond, Sukibond etc.) but I always use a very thin film of blue Hylomar and then wipe it nearly all off if I've had an engine apart.

It's a pretty major job to split the engine if you're not used to it so if it's not causing problems I'd leave it alone. I'd have another look at the clutch cover gasket and the mating faces though, make sure they're absolutely clean and un-damaged.

But you say the level never goes down but your boot is constantly covered in oil - can't have it both ways

[WildGoose]

well, it would take a fairly major leak to let the oil go that far down between oil changes

but it doesnt take much to get a film of oil on your boot, especially if you never clean them cos i have no fairings, it leaks at the front of the engine, and gets blown round onto the peg area

so there you go...cheers for the advice tho, i hadnt planned on ever splitting an engine, unless totally bored
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So in other words, he stopped you for being flagrantly in posession of a motorcycle in direct contravention of the Hippies, Darkies and People Whose Face I Don't Like The Look of (Police Powers) Act. 1976

[stinkwheel]

I have my doubts as to your diagnosis.

The reason being, the level of oil in the engine is generally below the join in the crankcase halves and I have not seen a leak there before.

If it was an older bike with the crankcases split vertically I would have believed it, BSAs and Triumphs came with an oil leak here fitted as standard. On the plus side, they never seem to cause a problem provided you keep the oil topped up.

From experience, the most likley place for a leak is where the rowl-pin goes through the middle of the gasket (labelled 1). Although there looks to be quite a big drip of oil at the bolt below this (labelled 2).

What I would do is give that side of the engine a bloody good clean in soapy water so you have got rid of all the oil then keep a carefull eye on where it is coming from. A litle silicone RTV or blue hylomar applied to the clutch cover gasket in this area will do no harm providing you don't get loads of it squeezing out on the inside which would block oilways.

For future reference, you can make your own gasket for under the clutch cover by cutting it out of gasket paper or the side of a cardboard cereal box. Simply remove the cover, clean it up then 'stamp' the outline onto your gasket material using a thin smear of oil on the gasket facing as 'ink' then cutting round it. Make sure the two facings are perfectly clean before you fit the gasket and use a THIN smear of hylomar on both sides of the new gasket.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Robby]

Also a slightly different suggestion.

Is it definately oil?

If the design is anything like the NC24, thats right under the thermostat housing and a coolant hose. Decent strength coolant can look a bit like oil when its leaked like that, but isn't brown on your fingers, and tastes sweet.

Not a good idea to drink it, but many of us have had a mouthful when syphoning. Taste much better than petrol.

[pipnet11]

[mchaggis]

[Kickstart]

Hi

Although the oil level is below there, plenty of oil will be splashed on there and crankcase pressure will push some of it out.

I would also not expect to find a gasket between the 2 halves of the crankcase.

In the line drawing it looks almost like the locating dowel at that corner is seperate from the bolts holding the crankcase halves together. If that is true then it would not surprise me if that is the oil feed up to the top end of the engine.

All the best

Keith
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[pipnet11]