Oil leak and crankcase bolt torque question...

[JimF]

I have been adding a small bit of oil to my 250 bitsa every week owing to a drip at the crankcase seam along the bottom of the engine. The oil does not appear to be coming from anywhere above. I look and look and can find no trickle of oil from higher up on the engine going down to form the drip at the bottom. It simply appears to be the seam at the bottom is the origin of the leak.

The drip is exacerbated by engine temperature; When I park the bike I will invariably find a teaspoon or two of oil on the ground underneath it after several hours, I can see the drips form and fall immediately after parking it when the engine is at its hottest, but overnight the oil pool does not proportionately grow in size with the drip rate experienced at the onset of turning the engine off. So it seems to me that when the engine cools either a) the engine seam closes up or b) the engine oil gets thicker so as not to pass or c) a perhaps a combination of a and b.

I am running straight 40-weight oil.

I have no clue how much oil I am losing when in motion, but suffice it to say I have to add several ounces of oil at a time depending on the interval and I am concerned about this because I would like to use the 250 for a six-hour trip this fall and I don't want to find the crankcase dry at the end of the ride or seize the engine en-route.

I have a motor-head friend whose advice for any small oil leak is "oil is cheap" but perhaps it's different (in my own mind anyway) when I'm not packing fur quarts of the stuff in the engine.

So I am wondering if I should just tighten up the crankcase bolts, and if so how much torque I can reasonably apply without risk of stripping the bolts? If tightening is the correct course of action, is there any reason given what I am trying to solve to tighten the bolts when the engine is either hot or cold?

Thanks everyone.

[Jordan]

I'd be wary of tightening it beyond reasonably snug. If it's going to seal, then it will with just that. The risk with overtightening is warping of castings and stripped threads.
A suggestion from a Ducati mechanic/racer is to assemble with no solid gasket - just a "3Bond" type sealant. That would involve a lot of re-shimming though. Then again, a new gasket might also need a reshim job.

Jordan

[JimF]

Hi Jordan,

Thanks for the reply. I don't want to take the engine down, split the cases and reassemble it, at least not now in the middle of our too short riding season. I'll probably just live with the leak and monitor the oil level religiously.

[graeme]

Think of it as it's marking its territory, rather than leaking.
You can say that you have special homing oil.
graeme

[kmev]

I have the same problem with my motor, which I assembled with NOS paper gaskets without any sealant. At first only the timing cover leaked so I got a new gasket and installed it with Hylomar - no more leaking there. Soon after my center case gasket started leaking, and now my clutch cover gasket is leaking too. I checked the torque on all the fasteners and none have loosened.

I'm still working the bugs out of the rebuild, but as soon as that happens I'm going to tear the motor down and regasket everything with Hylomar. That will give me a chance to polish all the engine covers with my new buffer, too.

My gaskets came from Syds. I guess I don't feel too bad because when I was there a narrowcase Mark 3 had been returned to reseal a leaking clutch cover that Malcom had sealed. The NOS paper gaskets are not great, but I'm going to use them again in hopes that they will seal with Hylomar and I won't have to reshim the motor.

What does everyone else do to get gaskets to seal? I guess I fell for Mick Walkers "these motors are so perfect they don't leak" and didn't use any sealer on assembly.

Jim - are you running synthetic oil? I put synthetic in my '72 Harley and the thing started leaking from every gasket imaginable.

[DewCatTea-Bob]

By: JimF...
" I have been adding a small bit of oil to my 250 bitsa every week owing to a drip at the crankcase seam along the bottom of the engine.
It simply appears to be the seam at the bottom is the origin of the leak.
When I park the bike I will invariably find a teaspoon or two of oil on the ground underneath it after several hours, I can see the drips form and fall immediately after parking it when the engine is at its hottest, but overnight the oil pool does not proportionately grow in size with the drip rate experienced at the onset of turning the engine off.
but perhaps it's different when I'm not packing fur quarts of the stuff in the engine. "

____ Huhh/what? - "packing fur quarts of the stuff in the engine" !? ...
Are you not in reference to a n-c.250-motor ? _ Cuz they are only meant to hold just 2 & 3/4th quarts !
__ Your symptoms (quoted above) are seeming to be the same as when the oil-sump capacity is overfilled...
But even so, when parked on the SIDE-stand, no further leakage then continues. However during riding (or whenever motor is upright), an overfilled oil-level will then leak-out past/through the right-end of the lay-shaft behind the sprocket, where the oil then moves-on to puddle-up in a bottom-cavity of the right-rear eng.cover, where much of the leaked-oil remains until leaned on the side-stand, when then the oil flows-out & runs-down & over underneath to a motor-case screw-boss and drips-off from there, (thus APPEARING to be coming from the split in the motor-case).
__ This occurrence is common, (usually from fuel draining-down into the sump), and is not easily determined to be the actual case when the oil is still fresh-colored -(rather clear).
So what needs to be done to eliminate this (rather likely) particular possibility for oil-dripping, is after a ride (that's been long enough to build-up such a deposited puddle of oil), don't park your Duke on it's side-stand, but instead let it's right handlebar-grip slightly lean against a wall, then take a rag and wipe-CLEAN the bottom/right-side of the motor-case (between the case-split & shifter-cover),, and THEN let your Duke lean on it's side-stand. _ Then soon after CLOSELY inspect for oil run-flowing from that eng.cover and run-down & over to the case-split underneath where it should later-then be seen in the process of dripping from a screw-boss (for the case-split).
__ When the oil is spread-out thinly underneath there, it's quite difficult to see where it actually came from ! _ That's why I indicated to wipe-off the case-bottom really clean in that area,, so that after being parked on the side-stand for a while, you can then use a new/fresh piece of tissue-paper to wipe the same (preciously well-cleaned) surface-area and then discover still MORE oil since redeposited there, (where it couldn't have come upward from the case-split).
__ It's my bet that such extra scrutiny will allow determination of where the ACTUAL source of the oil-drip really comes-from. _ Just as I've done before, many times, (which is why I so suspect this instance to also be the same-case, here as well.)


" So I am wondering if I should just tighten up the crankcase bolts, and if so how much torque I can reasonably apply without risk of stripping the bolts? "

____ You ought to just make sure that all those screws underneath there are hand tight,, cuz if any have loosened-up, then they ought turn about a half-turn (to resnug-down).


" If tightening is the correct course of action, is there any reason
to tighten the bolts when the engine is either hot or cold? "

____ That's good to have brought-up, as you may find that whichever condition (hot or cold) you first try, the opposite condition may also yield further tightening results.
So try it either way, both ways -(hot to cold & cold to hot).


Hopeful-Cheers,
-Bob

[Ventodue]

The drip is exacerbated by engine temperature

Well, that's just 'cos the oil gets thinner when hot ... (nat', Jim )

When I park the bike I will invariably find a teaspoon or two of oil on the ground underneath it after several hours

A couple teaspoons, Jim?! Nuttin' to worry about, IMO. (Look, most old old ladies tend to leak a bit, no?)

I would like to use the 250 for a six-hour trip this fall and I don't want to find the crankcase dry at the end of the ride or seize the engine en-route.

No chance. Just take a spare bottle with you, or simply buy what you need on route. And don't get too hung up on this, "Only use 40 weight" story - a regular multigrade, mineral or synthetic, will do.

I have a motor-head friend whose advice for any small oil leak is "oil is cheap"

And he's so right ...

So I am wondering if I should just tighten up the crankcase bolts and, if so, how much torque I can reasonably apply

Well, you can, if you like. Won't do any harm, but probably won't do much good, either! You see, it's not the tightest of the bolts that creates an oil seal. It's the gasket which does it, by compensating for minor deformities in the case faces. And that gasket is now feeling a little tired. As to torque, just use the conventional load for whatever size bolt they are, in 8.8 grade. (P.s M8x1.25, I think? In which case, 25-30Nm = 18-21 lb/ft.)

If tightening is the correct course of action, is there any reason given what I am trying to solve to tighten the bolts when the engine is either hot or cold?

Yes, you'll burn your hand if you do it hot!

Honestly, Jim, don't fret too much about it. Take some oil with you/buy some on the road (don't forget to take a funnel of some sort too), top up as necessary and keep monitoring. When the bike is leaving a big pool all over the place and the oil level drops like a stone, then it's 'engine out and replace the gasket' time! Until then, ride like you stole it!

Ciao

Craig

[Ventodue]

I have the same problem with my motor, which I assembled with NOS paper gaskets without any sealant.

Yeh, you can get problems with NOS gaskets 'cos they're all naturally pretty old now and have lost their ability to compress in the way intended. And some of the modern replacements aren't up to to the mark ...

IMO, best to buy new gaskets from a specialist supplier who knows what our old bikes need, gasket-wise - Nigel Lacey, for example. With good gaskets, you won't need Hylomar (whose use just raises certain other risks which, albeit small, I prefer to avoid in the first place ... )

Ciao

Craig

[Lonestar]

As I have several British bikes, and thus considerable leak experience, here are a couple of ways to locate an oil leak:

Add UV tracer dye to the oil, clean the bike, run the engine, look for glowing leaks under an ultraviolet light. (http://www.oreillyauto.com/site/c/detai ... &ppt=C0014)

Clean the bike, spray white powder (deodorant, foot powder, etc.) on all suspect joints. Run the engine, look for dark spots where escaping oil contacts the powder.

Cheers,

Dave

[Jordan]

The clutch pushrod seal, under the gear selector cover, can be a source of leaking.

Jordan