Author Topic: Old Smallblock Misbehavior  (Read 654 times)

Offline Guido Valvole

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Old Smallblock Misbehavior
« on: December 09, 2018, 03:54:49 PM »
Among other Guzzis, I have a 1979 V50 II. For the most part, it’s been very reliable. Last summer (17) it puked a large quantity of oil on my left boot and the ground, traced to a jammed flapper valve in the loop-style breather box used in place of stock as it came to me with K&Ns. I replaced the old box with a new one, problem solved.

A couple of months ago it did it again. Maybe… it was fine when I stopped and went into the store. Large pool of oil on the left side when I got back. ?!?! Wasn’t running when the oil came out! Dipstick showed a little at the end, and I have a sump extender so there’s an extra quart. Figured I’d ride the 5 miles home with an eye on the oil light. Got home, no drama other than a slightly slippery rear tire. No more loss of oil.

Off with the tank. Check breather box and flapper valve. Ok. Check drain hose from the box to the sump. Oops, get plug for sump as the hose comes in below the oil level. Hard to tell but there *might* have been blockage in that return line, although from what I do not know. Straightened it out and looked through and it looked ok, maybe a little sludge on the inside. Maybe. Cleaned it out with compressed air.

Put it back together and check compression. Good, and nearly the same on both sides. Excuse to get a leakdown tester, just in case there was a ring problem with compression getting past and into the sump. No problem there either. Close on both sides and within the healthy zone.

So tighten everything up and ride. No problems. And since then, no problem. Starts and idles happily and with its lower gearing is much better around town and in traffic than my Monza.

I’ve heard stories about older smallblocks randomly puking oil. Anyone out there have suggestions as to possible causes? Other than “character”, lol.

Thanks! CR
V50 II
V50 Monza
Le Mans 1000 (IV)
Martinez, CA

Online pete roper

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Re: Old Smallblock Misbehavior
« Reply #1 on: December 09, 2018, 09:38:37 PM »
Are you certain that it's engine oil? Early smallblocks are notorious for puking gear oil out of the gearbox breather where it sits in a disgusting pool in the webbing on top of the box. If the angle at which the bike was parked was more extreme than usual maybe it was just overflow from the 'Gearbox Lake'?

Just a suggestion but nobody else seems to be willing to take a WAG!  :grin:

Pete

Offline Huzo

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Re: Old Smallblock Misbehavior
« Reply #2 on: December 09, 2018, 11:51:05 PM »
Are you certain that it's engine oil? Early smallblocks are notorious for puking gear oil out of the gearbox breather where it sits in a disgusting pool in the webbing on top of the box. If the angle at which the bike was parked was more extreme than usual maybe it was just overflow from the 'Gearbox Lake'?

Just a suggestion but nobody else seems to be willing to take a WAG!  :grin:

Pete
Ummm...
WAG..
Wild Arsed Guess..??
« Last Edit: December 09, 2018, 11:51:45 PM by Huzo »

Offline pat80flh

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Re: Old Smallblock Misbehavior
« Reply #3 on: December 10, 2018, 05:31:36 AM »
  I recently removed the airbox on my V65, as I was getting an intermittent  slug of oil passing to the ground from the stock setup. After I removed the box (no small task). I ended up not using a bresther box at all. Instead, I used a fuel line cross, which I tied to the top of the trans. Both lines from heads go downhill to the cross. One line return to oil pan. Last line is an open breather run straight up the frame leg, and ending in a loop, up high Has worked very well all this season, oil level stays up even after several hours on the road, and no leaks.
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Offline Guido Valvole

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Re: Old Smallblock Misbehavior
« Reply #4 on: December 10, 2018, 02:05:56 PM »
Thanks, all. It was definitely engine oil - Redline Shockproof in the gearbox, which it happily puked all over the top of the transmission until I replaced the stock breather setup. Gearbox Lake, indeed!  :grin: For whatever reason, Redline oozed through the gaskets and seals of the Monza but stays put in the older seals and gaskets in the V50.

Monza has the stock airbox as that's how it came and it works, so if it ain't broke... and yeah it's a major PITA for access to anything. But it works.

Pat80flh, sounds like you're using something like I am, just without the breather box. Vent to outside (which was where the oil came from both times) requires the box to be full for anything to go out as its intake is at the top of the inside of the box. Which would be either from oil being pumped out from under the valve covers faster than it can drain or blockage of the drain tube. Or pressure in the crankcase forcing oil back up the drain line. Hmmm, is there any crankcase ventilation in those engines? Don't think so. But there shouldn't be any pressure in there when the engine is stopped. Both times the vent tube was full of oil, which then went out through the filter at the end. I'd install a catch bottle but there's not a lot of extra space in an old V50. Do have a photo of an Oilio Sasso can used for that purposes on a Ducati 750SS in my archives, poifect!

Sometime in the past I read/heard that older smallblocks sometimes puked oil on the ground, but that may have been gearbox oil.
cr
V50 II
V50 Monza
Le Mans 1000 (IV)
Martinez, CA

Online Chuck in Indiana

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Re: Old Smallblock Misbehavior
« Reply #5 on: December 10, 2018, 02:38:36 PM »
I'm betting the drainback tube to the crankcase was the culprit. There is a *lot* of oil vapor going through the heads due to (I understand) the pumping action of the case design. It wouldn't take long for the breather box to overflow if the line is pinched, (it's pretty soft) or blocked somehow.
Chuck in (Elwood) Indiana/sometimes SoCal

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The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt.' - Bertrand Russell

Offline Guido Valvole

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Re: Old Smallblock Misbehavior
« Reply #6 on: December 11, 2018, 12:22:18 PM »
Chuck, I think you're right. The line *shouldn't* have been pinched - but it's a tight fit between the engine and starter motor, so a little vibration could maybe cause a problem. Weird that it happened when stopped, though. Since I only use the centerstand I would have known if it had leaked while running. May have been just on the brink when I stopped. You're right about the amount of oil and oil vapor in the top end -- I forgot to completely tighten then valve cover bolts and was duly rewarded by oil everywhere. That's above and beyond what seeps through the original base gaskets and others.
V50 II
V50 Monza
Le Mans 1000 (IV)
Martinez, CA

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Re: Old Smallblock Misbehavior
« Reply #7 on: December 11, 2018, 10:00:21 PM »
Another possibility would be a blown gasket between the combustion chamber and pushrod tunnel pressurising the case but I can't see how that would come and go?

Online Chuck in Indiana

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Re: Old Smallblock Misbehavior
« Reply #8 on: December 12, 2018, 06:08:48 AM »
By the way.. I documented fixing the "old small block transmission breather problem" in the Monza inspection thread here: page 3
https://wildguzzi.com/forum/index.php?topic=89034.60
Chuck in (Elwood) Indiana/sometimes SoCal

02 Scura RC
87 AeroLario
79 G5
95 Skorpion tour
 
The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt.' - Bertrand Russell

Offline Diploman

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Re: Old Smallblock Misbehavior
« Reply #9 on: December 13, 2018, 07:59:37 AM »
I had a similar problem that started when I installed an breather oil return hose to the crankcase port, emulating the OE setup.

http://www.mgcycle.com/index.php?main_page=product_info&cPath=71&products_id=4434

My bike is fitted with K&N pod filters, and for years has been vented to atmosphere.  I thought it would be an improvement to capture the small amount of oil vapor that vents to air in this arrangement and return it to the crankcase, as is done in the OE breather system.  However, the first time I rode the bike with the new oil return line, it came home with a patina of oil spray over the engine and rear.  Puzzling over this, I discovered that the oil return line emptied into the crankcase below the level of engine oil, effectively blocking it.  (I run a sump extender, but keep the oil level relatively low to reduce pumping pressure.). I unfitted the new oil return hose and reverted to vent-to-atmosphere and the issue immediately disappeared.  Clearly, if the breather return line is below engine oil level, the breather system will be blocked and significant overspray will be the result.
1980 V50 II, lightly cafe'd, much modernized
1983 SP 1000 NT (Under Upgrade/Modification)
2015 KTM 390 Duke

 

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