Author Topic: strange oil weep  (Read 406 times)

Online Duncan R

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strange oil weep
« on: 10.07. 2019 15:02 »
I have had an ongoing issue with a top end oil leak, just changed the head gasket and rocker gasket so with a nice clean top end I could see where the oil is coming from, it appears that oil is weeping from the cylinder head bolt just to the rear of the spark plug (left and right) also the rear rocker box sleeve nut has oil fizzing out between the washer and the head,cylinder head bolts have the correct washers underneath and torqued to 35ft/lb . The rockerbox sleeve nut is as tight as I dare. Anyone had anything like this?
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Online A10 JWO

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Re: strange oil weep
« Reply #1 on: 10.07. 2019 16:19 »
Hi, sounds like there is a lot of pressure inside the engine, how old are the compression rings on the engine. Had this years ago on an old bike, I am wondering if some of the engine power is building up below the piston. Hope I am wrong  *eek*

Online Duncan R

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Re: strange oil weep
« Reply #2 on: 10.07. 2019 17:04 »
Hi,

Rings have done nearly 5K. No leaks from rockerbox gaskets. Bike runs great, really annoying as I would like to do longer runs but oil is getting everywhere including on the edge of the tyre.
Anglo - Indian A7SS (Actually is a 650)
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Online morris

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Re: strange oil weep
« Reply #3 on: 10.07. 2019 17:58 »
Oil on the edge of the tyre usually comes from the gearbox sprocket. Had the issue on the SA but installing an SRM oil seal sprocket nut cured that
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Online Duncan R

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Re: strange oil weep
« Reply #4 on: 10.07. 2019 19:20 »
Hi Morris,

No gearbox leaks its blow back from the top end leak - oil is pooling on the ski slope at the back of the carb. I checked the gearbox oil level and its the same as when I filled it after rebuild. I was thinking of trying some fibre washers under the offending head bolts and sleeve nut.
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Online muskrat

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Re: strange oil weep
« Reply #5 on: 10.07. 2019 21:15 »
G'day Duncan
The gaskets (or the mating surfaces) are compromised. Oil shouldn't be getting to those bolts/studs.
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Online morris

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Re: strange oil weep
« Reply #6 on: 10.07. 2019 22:39 »
No gearbox leaks its blow back from the top end leak - oil is pooling on the ski slope at the back of the carb.
No, I wasn’t saying that it must necessarily be the gearbox, but if that much oil is running down from the top end to land on your tyre, there definitely is a problem. After last top end overhaul I had some oil weeping, but running a spanner over the bolts cured that.
Could it be that there’s too much oil going to the rocker box? Plenty of discussions on this forum regarding rocker box oil feed and banjo bolt oil hole diameter.
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Online Duncan R

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Re: strange oil weep
« Reply #7 on: 10.07. 2019 22:40 »
Hi Muskrat,

That's what I was thinking along those lines. The cylinder surface is nigh on perfect and the head was tested for flatness last time it was off after lapping it on plate glass. , engine is running Head gasket deffo not blowing, engine is running spot on. I suppose it will all have to come off again.
Anglo - Indian A7SS (Actually is a 650)
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Online Duncan R

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Re: strange oil weep
« Reply #8 on: 10.07. 2019 22:44 »
Hi Morris,

Thanks I will check that out. I did replace one banjo bolt due to a dodgy thread, I got it from Draganfly
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Offline berger

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Re: strange oil weep
« Reply #9 on: 11.07. 2019 00:12 »
Duncan R not saying your leaks are not what you say they are  *conf2* *dunno* but a long time ago I thought mine was weeping from exactly the same places,  the rocker box sleeve nut weep was cured by stuffing thread tape round the nut and squashing it up to the head with the thick washer and carefully-[nightmare] feeding tape onto the stud, then the fun started - although it wasn't obvious the head bolt leaks were rocker box banjo and rocker gasket. copious amounts of cleaning and then rubbing fingers on cleaned rocker box found this out, good luck with your cure.

Offline Swarfcut

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Re: strange oil weep
« Reply #10 on: 11.07. 2019 08:33 »
Duncan, Musky's right. No oil should emerge from those head bolts, so the head gasket is not sealing completely. A copper/ asbestos gasket has "fire rings" designed to crush as the head is tightened down, ensuring a gas tight seal, but as these areas are slightly thicker, you can have oil leaks yet still have no sign of gas leakage. A solid copper gasket doesn't have this characteristic, but must be annealed and softened before use.

 So if you are sure the mating surfaces and gasket are good, then the lack of clamping force is the reason. Don't know if it is an Alloy Head, but with an iron head the bolts will stand a good deal more, so a bit more torque is worth a try.

 False torque readings ...make sure the head bolts are not bottoming on accumulated crap and oil at the bottom of the blind holes, the threads are nice and free and just lightly lubricated. With your bikes pedigree, are they the right bolts anyway?
 The rocker boxes have very narrow gaskets, but here again tightened down, no oil should emerge from the nuts.  Make sure the retaining stud threads are below the face so the nuts don't bottom before clamping the gasket tightly. Replacement parts from whatever source are always suspect, and even stuff from reputable suppliers can start in the same low tech environment halfway around the world. Sometimes the thread lengths require a bit of adjustment.

 Take berger's thoughts, make sure the leak is actually from where it appears to be, as the head bolt leak is a bit of a rare one. If the breather system is at fault, there will be lots of oil emerging from around the exit, above the gearbox sprocket, and onto the tyre.

 Swarfy.

 

Online Duncan R

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Re: strange oil weep
« Reply #11 on: 11.07. 2019 19:26 »
Thanks all for your expert info. I will start investigating and check all your suggestions

Thanks again
Anglo - Indian A7SS (Actually is a 650)
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Online Duncan R

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Re: strange oil weep -UPDATE
« Reply #12 on: 17.07. 2019 14:46 »
So off with the rockerbox and discovered oil in the centre well of the cylinder head and obvious oil flow tracks up to the top of the head and the rear bolts. Pretty sure this would give an impression that the oil was travelling up the rear bolts. I think possibly the rear rocker gasket on the front inner face and goo was displaced by the pushrod comb on fitting, hence oil pooling in the centre well than getting blown to the rear of the bike.

Discovered a suspect thread in the rockerbox for one of the rear studs , can anyone confirm the thread size/type as I repaired the other one ages ago , can't remember the helicoil size - Thanks
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Offline Swarfcut

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Re: strange oil weep
« Reply #13 on: 17.07. 2019 19:37 »
Duncan, The threads into alloy are all Whitworth, with most fastening nuts amd bolts  CEI (Cycle Thread).  The rocker box studs are part no 67 1245, and thanks to Musky posting a link in the Literature, Scans, Documents section of the Forum, the very first entry is a very useful table of fixing nut bolt and stud part numbers and their corresponding thread sizes," Nut and bolt part chart".

  67-1245 is a 5/16" stud, one end threaded 18TPI into the alloy rockerbox, and threaded 26TPI on the other end for the retaining nut.  If you do not have a parts book to hand, Draganfly have a good website with exploded parts diagrams and part numbers.

 Thanks Musky, this table has saved me from ruining a good number of threads by choosing the wrong tap or die. No need to guess, most common fixings are included, but as always there are some exceptions.

 Swarfy.

 Admin. Please include a link to Draganfly. Thanks.

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Re: strange oil weep
« Reply #14 on: 17.07. 2019 21:09 »
G'day swarfy.
Your wish is my command.
https://www.a7a10.net/forum/index.php?board=46.0
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
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