Perplexing oil leak after replacing left cylinder (1200 Sport 8V)

The left cylinder on my 1200 Sport 8V (2010) was replaced when low compression was confirmed by a leak down test and the bore was found to be scored.  This was picked up after finding more oil than usual collecting in the airbox drain tube.

Ever since then the bike has been going great guns, BUT for a persistent oil weep, apparently from the base of the new cylinder.  It seems to emanate high up in the "V", then runs down the left side (never the right) and spreads across the engine.  It's not coming from the sensor mounted in front of the cylinder.  The 2nd image is after cleaning off, and riding just 25 miles.

The replacement cylinder was a different pattern to the original, in that the inner sleeve was thinner and so didn't make a snug fit into the engine block.  Piaggio said this didn't matter.

After they replaced the cylinder a further two times and still the leak, my dealer led me to believe the original cylinder would be repaired, as Piaggio couldn't come up with an original pattern one.  However, it seems I was given duff info, as these cylinders can't be rebored...?  What they actually did was fabricate a metal ring, to bring the new sleeve up to the original's outer diameter, to see if closing the gap would make a difference.  Sadly, it hasn't. They say the gasket faces have been thoroughly checked.

The dealer has committed to solve this, at their expense, since it didn't leak before the new cylinder; but this has been going on for many months.

Is anyone here aware of maybe an issue with newer cylinders on an older 8V engine?  Thanks.

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Dammit! Where's the popcorn emoji?!!

This should be good.....

I have no idea why the cylinder spigots were changed. The only reasons I can think of would be weight and materials cost or, maybe, to try to prevent people boring out the originals and replacing them for extra capacity but that hardly seems like a valid reason?

Some sort of casting porosity would seem like the obvious answer but I'm assuming by now that the *New* barrel has been replaced more than once?

I have seen porous cylinders before but not on a Guzzi. This was back last century when BSA (remember them?) put out a batch of porous cylinders on their unit singles - notably the 441 cc variant. These ended up all over the world and it just was painful in that didn't matter what you did, it would weep. Let's hope Piaggio didn't swoop to the same levels as BSA did.


Flat Tappeter, it might be worth visiting wreckers (breakers) to see if you can find an original in good condition. Cheap insurance maybe?

I've got spare barrels. Want me to dig one out for you? Left hand you say?

I'm assuming the barrel is plated, hence why no rebore.  Apparently they're onto the third new cylinder.  One of the staff said he did 100 test miles and not a drip, so they're puzzled why I seem to reproduce it every time the bike comes back "fixed".

Thanks for the offer, Pete.  Yes, left hand.  Would it also mean getting hold of another new piston and rings?  Let me first see what my dealer proposes to do next.  There was talk of trying a paper gasket... not sure if they were joking, but does it sound like a tried and tested idea?

Colin

Before we go any further I'm hoping your name is a joke? This bike has been rollerised, right? No point in looking for a solution if it's just destroying itself.

All barrels have been Nicasil plated since the mid 1980's. How badly scored was the original barrel? Was it beyond just being replated? I can send over a barrel and piston but I doubt it will fix it. You say it appears to be coming from the base of the cylinder inboard? It's not just a leaky oil pressure sender switch is it? A paper gasket will achieve nothing. If you want to eliminate the gasket as a problem just install the barrel with a thin smear of Threebond 1211 on the mating surface and no base gasket. You'll need to go up to the next thickness of head gasket for safety's sake.

If it is a porosity issue, which I find unlikely, perhaps it is the crankcase itself rather than the barrel that is the issue.

Correct ...the name used to be a truism, but not since rollerisation at 21K miles.

Personally I've not seen the leak with the fuel tank and airbox out of the way, so I could only peer up into that area with a torch and surmise the source to be inboard. An oil pressure switch happens to appear on an associated invoice (nil charge), so I'm guessing they already eliminated that possibility.

If barrels can be rebored and then Nikasil-replated (the dealer should have known this, right?) it's sad that they appear to have disposed of the original. And it was in my possession for a while, too! I wouldn't have said the scoring was very deep - could just about feel it with a fingernail - but then I'm not an engineer.

Thanks for the suggestion re. eliminating the gasket. Can I take it you've been fitting these cylinders having thinner liners and finding no such issues?

The changeover point was somewhere around late 2010-early 2011 I think. All later 1200's have the thinner spigots. The spigots themselves aren't an issue.

Right now I'd suggest pulling the tank and airbox and having a really good squizz down in the valley paying particular attention to that area around the switch. Apart from their general crappiness the early switches became NLA from Guzzi and they made a ridiculous Heath Robinson type spacer arrangement to allow fitment of the later, fine threaded but equally crappy, new type switch. If your bike has been fitted with a weird, 24(?)mm fitting with the newer type switch in it I'd piss that right off and go with an aftermarket switch, (Tridon PS029 from memory or there is a BMW x-reference as well.). I'd certainly be exploring all other possibilities before chasing further porosity or mating surface issues. The barrel, certainly the base of it, is far from a complex casting and the fact it has been swapped three times would point to it not being the source of the leak.

Thanks for the info, Pete. Right now the bike is back with my dealer, but I'll make sure to quiz them on the switch.

Just out of interest, on later 1200s was the crankcase made with smaller openings to match the thinner liners/spigots?

Nope.

I've not replaced a cyl on a Guzzi, but many on a P car. We use a thin layer of Curil T on the case, any base spacer/gasket and the cyl seat itself when putting new Cyls on a motor. Stands up to heat, is non curing, and seals against all leaks, even with some imperfections. I use it whenever I replace an oil pan or valve cover gasket. Worth a try?

I'm in the hands of my Guzzi service agent, but I'll certainly pop the idea over to them .

I had a weep like that and it was the little 2 bolt blanking cap - new O ring and Hylomar fixed it

It's a thought

Thanks for the tip, Brian.  I'm not exactly sure of the whereabouts of that blanking cap you mention, and is it something that could get disturbed by refitting the left-hand cylinder?

The dealer seems certain the leak is from the cylinder base gasket, inboard/front.  And it only started when they renewed the cylinder (three times!)  What's just as frustrating is the waiting ... this issue has been rattling around since June 2019.

Thinking on this further it's not dripping down from the breather hose where it connects to the condenser box is it? I can't believe it is cylinder related when it's been changed three times. Or the condensate return line dripping?

Is the cylinder seating correctly? Are both the locator dowels straight, undamaged and in place? Remember the lubricating oil for the top end travels up the studs that have dowels on. If they are damaged or deformed the barrel won't seat correctly and the oil won't be contained. That oil is under pressure, much higher than just the crankcase pressure.

Can you look over their shoulder next time they take the tank off (or take it off your self) ?. Like everyone says there are at least a handful of leak possibilities (I've had condom, cam cover, cam chain hydraulic tensioner bolt & oil pressure point leaking oil at various times) that can only be checked from 'inside'

Would anyone here have any objection if my Guzzi service agent sees this thread - not that they couldn't already, if they knew where to look?  I'm sure they know their stuff and are trying all possibilities, but they seem to be running out of ideas, so you never know if something here might present a new lead.

Don't see any problems ....it's not like it's secret sauce (and even if it was you could just copy & paste & nobody would be any wiser).

If you look at Pete R's post with the pic of Bowraboy, the bit I was talking about can be seen just above the main frame bolt position - squarish in shape with 2 bolts.

That is the cover for the former crankcase breather on the old 2V motors.

Hi mate. I had same leak after cylinder change and before started to blame them had a look in there and it was oil pressure sensor. And it was very persistent - Had to open it three times over and use different gaskets and thread locks. Hope it will stop it now.
Good luck with yours