Oil leak - breather issues?

[ralpharama]

Earlier this year I rebuilt an XS650 motor for a customer that had undergone a whole heap of unkindness in it's long life.

I replaced all the oil seals, gaskets, 'o' rings etc with new and all gaskets were seals with Wellseal It's now out to fourth oversize and pulls really well with bags o torque

I built it into an early Uncle Bunts soft-tail framed chop as requested - see pic with client below -

I have fitted a catch tank which is fed from the breather, which you can see in the photo.

After less than thirty miles it has developed a bad oil leak from behind the ignition pickup. The bloke is supposed to be having some fun riding it around before the proper paint job and a chance to let stuff bed in. He tells me a lot of oil is coming out of the cover behind the pick ups (points replace with boyer branson electronics ignition). I'm wondering if this could be as a result of crankcase pressure building up and am wondering if I need to make some form of custom airbox for it, so that there is a negative pressure on the breather when the pistons go down, thereby reducing crank case pressure on the seals.

What made me question this is the copious oil flow past the seal and the fact that the engine had two large bore breather pipes going to the airbox when the bike was standard.

Has anyone had issues with crankcase pressure causing oil leaks from seals?

Many thanks

Ralph

 

[peanut]

only just seen this post . Looks like this is likely to be related to oil blowby on your cam seals as well (later thread)

I would recommend that you fit a late type breather which has a single spigot with reduced ID and then fit a non return valve feeding into your catch tank. Plenty of posts on here about this.

Regarding possible crankcase over-pressure , have you done a compression test yet ?
Its very common for the head gasket to fail between one cylinder and the central cam chain tunnel .
Its standard practice now to apply 3 Bond both sides of the head gasket around the central cam chain tunnel and cylinders particularly if the block and head haven't been skimmed.
Grab some of this while you can at £12 its difficult to find these days and you usually have to source it from Thialand at £23 a tube. http://www.ebay.co.uk/itm/3-BOND-THREE-BOND-1104-NEO-GASKET-CEMENT-SEALER-1-TUBE-free-P-P-/181456518553?pt=UK_Motorcycle_Parts&hash=item2a3fa6bd99

ps just remebered that there was a Technical Bulletin issued by Yamaha at some point ,recommending a lower max oil fill than listed in the manual and marked on the crankcase . I can't find a reference to it but there was a thread on here last year about it.

 

[XSLeo]

On the oil level change I posted the Bulletin from the Factory manual. It explains why it was changed and how to measure your dip stick to tell if it has been changed.
Leo

 

[peanut]

thanks leo

 

[ralpharama]

Thanks for your reply Peanut. I have now measured the guys dip stick and it appears to be the correct one. Whilst I haven't seen a later breather, I already binned the twin spigot bit in favour of a single spigot I machined myself, as the way the engine fitted in the frame there wasn't room for it. I guess the purpose of the non-return valve is to encourage a degree of vacuum in the crank case as the pistons go up which isn't lost when the return down completely?

Any idea where I could obtain such a non-return valve?

Thanks

 

[peanut]

Thanks for your reply Peanut. I have now measured the guys dip stick and it appears to be the correct one. Whilst I haven't seen a later breather, I already binned the twin spigot bit in favour of a single spigot I machined myself, as the way the engine fitted in the frame there wasn't room for it. I guess the purpose of the non-return valve is to encourage a degree of vacuum in the crank case as the pistons go up which isn't lost when the return down completely?

Any idea where I could obtain such a non-return valve?

Thanks

only sure way is to drain the oil into a 2lt kitchen measuring jug or to refill from scratch

I put 'non return valve' into ebay and came up with zillions . you could use anything that fits basically ,something like this perhaps
http://www.ebay.co.uk/itm/Valve-Non-Return-6mm-/281406591363?pt=UK_BOI_FarmingEquipment_RL&hash=item418523d183. If you buy something with a similar sized spigot it will be enormous. You'll need to coddle something together with plastic tubing and clamps.

The more I look at that chop the more I like it .. Looks fantastic.

Have you done a compression test yet ?

 

[ralpharama]

Hi,

I haven't done a compression test yet as it's with the owner currently, though when I fit the non-return valve (I found a nice stainless one on flea bay) I will do one. I'm hoping it's OK, but considering how well it pulled I doubt that is the problem. I did use Wellseal on the head gasket when I fitted it so it should be all right. If it is leaking I'll have to get it skimmed I suppose.

I've put a lot of work into this bike making a lot of bits from scratch, so it's a real custom, not just a bolt together job! Sadly the guy insisted on the horrid hardly goesalong front end which is too heavy and the nasty hardly back rest.

When it is finally finished he is going to have a really nice paint job. Firstly I have to stop it's incontinence

 

[peanut]

thats the problem with designing stuff for others ...they've got no taste The other problem is that you don't have the bike in your workshop to work on at your leisure.

Its possible that the oil seal spring might simply have failed or just be a poor quality jobby but its easily replaced without a tear down. You can buy oil seals with different strength springs and of course they don't have to be Yamaha seals .



I personally use Neo 3 Bond Its the same formulae as the original Yamabond . Its like red Hermatite , non silicon based so you never get bits of silicon floating around the oilways.

If it is a crankcase pressure problem it wouldn't take more than a tiny head gasket leak into the camchain tunnel to build up excessive crankcase pressure over a few minutes or so of running. You might only see a drop of 10psi or less but it would be enough.

I've probably asked before but whereabouts in Somerset are you ?

 

[ralpharama]

Hi

I'm in Pensford, just south of Bristol.

I did hook the seal out, but there was nothing wrong with the seal which was genuine Yamaha. The ground section of the camshaft where it runs was pretty rough. My guess is that sometime in the past it was starved of oil or didn't have good oil or didn't have it changed often enough or all three.... Most likely! The engine had some horrendous bodges!

 

[peanut]

Merriott near Crewkerne .call in anytime you're down this way.
ouch that sounds bad.

Same thing happened to my crankshaft journal. the oil seal had actually trapped moisture which severly rusted the journal. it hasn't leaked yet but I haven't put any miles on it yet.

I guess the only permanent solution is likely to be a replacement camshaft, seals and bearings but the good news is you can remove the shaft and replace it without breaking the camchain though its damn fiddly.

 

[retiredgentleman]

Its very important that the camshaft is centred when its installed. When its centred, there is still barely enough camshaft surface protruding, to allow for the oil seal lips to make a good seal. If the camshaft is not centred, then one end is likely to leak oil.

Also, when installing the oil seal into the housing, it must be installed fully inboard in the housing. I think that is clear in my picture. If the seal is not far enough inboard, then it has little chance to make a leak proof seal.

Of course, the surface of the camshaft, where the seal lips ride, must be surgically clean, with no rust, corrosion, bumps etc.

 

[racerdave]

Looking at RG's pic above, too thick of a gasket, will also give you less seal purchase.

RG, have you or anyone ever looked into a different seal that has taller side flanges, and would stick into the cam more, if there is room?

 

[retiredgentleman]

Looking at RG's pic above, too thick of a gasket, will also give you less seal purchase.

RG, have you or anyone ever looked into a different seal that has taller side flanges, and would stick into the cam more, if there is room?

That's the thing...................there is only just enough room, certainly no extra space. The stock type oil seal that Mikesxs sells works just fine, as long as the cam is centred and the oil seal is installed correctly in the housing.

I've never had any reason to search for a different oil seal.

 

[XSLeo]

I run the housings with just the O-ring, no gasket. The housing seals to the head ok with just the O-rings. This let the housing be closer to the head, this puts the seal farther on the cam.
Leo

 

[Tyrella]

I have recently completed a cafe racer project and all is oil tight but for these seals. I haven't had this as a problem before so I guess that I have just been lucky.
I will double check the location of the seals based on the great tips on this thread. Bloody annoying having a sparklingly clean engine with oil on it.

 

[5twins]

If you haven't done so, clean the ends of the cam where the seal lips ride. Buff them clean and shiny with a Scotchbrite pad.

 

[Tyrella]

Thanks. It was a total rebuild but I will double check this.

 

[XSLeo]

For a valve that helps keep a negative pressure in the crank case A lot of us use a power brake valve. It goes in the Vacuum brake booster on a car, A hose from the intake Manifold plugs onto the valve. It lets manifold vacuum draw air out of the vacuum booster and not let air back in. It has a rubber flapper that acts fast enough to work on our XS650 engines and doesn't cost much. Here state side they are in most big chain auto parts stores, right on the rack.
Here the valve is marked HELP Item #80190, on the back of the package is a web address, www.DormanProducts.com
The big end is just the right size to plug into the stock breather hose. I cut the breather hose to about 2 inches long, plug in the hose and the valve has a 90 Degree fitting that is 3/8 inch diameter, use some 3/8 inch hose and run down below the engine off to one side, just incase some oil get out, Don't want the hose to dump oil in front of the tire.
Leo

 

[5twins]

If you run oiled pods, you can just position the valves over the tops of them. If any oil does drip out, it will get recycled through the motor. Basically, this is how the original set-up worked (hose connected to airbox) .....

 

[scabber]

The new style breather 80 to 83 is what you need the body is 17.5 MM. From the mounting surface to the end of the single outlet approximate 36.5 MM. The outlet can be shortened some. If the rings are seated you won't need the catch can other than aesthetics. A leak down test is better than a compression test. Nice build did you make the frame?