Oil leaking from blow-by

Hello all!

Ive had my 2014 GRiSO 1200 8v SE for about a year now. I changed all of the fluids on the bike myself except the fork oil shortly after buying it. This is the first issue I've had with oil showing up in unwanted places.

I got back from work today and noticed a small drip beneath the exhaust. I traced it up the length and it seems to be originating at the blow by system, just beneath the front of the gas tank. The extent of my understanding ends about there, I don't have a manual and am mostly lost on how to troubleshoot and service this issue.

I've attached a few images I was able to take of what I believe is the offending part/area. I'm not sure if the small rubber breather piece and the clamp are prone to failure, or even if it's safe to remove them both and replace them without oil expelling everywhere.

Is there anything that might have motivated this leak that I can work to mitigate against in the future?

I'm sure I'm leaving out some necessary details to help diagnose this issue, so please ask away and I appreciate the help!

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Most likely the 'condom'. There's one unused port that's quite large compared to the others. It has a 'condom' type seal. It is prone to leaking more than the others. They can all ooze a bit, the condom tends to be the one that fails.


Item 17. Part # 978781

No idea if it's still available.


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Yeah, they're still available. If it isn't the condom then it's most likely the breather hose cracking and leaking, they're the parts #16 in Beetle's pic. They come off the cam cover plates on the back of the heads and loop up to the condensor box. They are stupidly expensive but while they are available we keep using them. Once they go NLA we'll work out some other alternative.

Oh, and of course the ritual warning not to fill the oil to the 'Full' mark on the dipstick. You want it no higher than half way between the 'Add' and 'Full' marks and don't add any more unless it drops off the bottom of the stick.

Hey Pete, thanks for the tip on the engine oil. I checked the oil level at cold and level and it was beyond the full line (measuring from the dipstick threads sitting against the engine threads).

I've read a bunch of conflicting things online regarding the proper way of measuring the engine oil for the 2014 GRiSO 1200 8V SE. Because its oil cooled, does it make more sense to check oil when the engine is hot, and wouldn't that mean that when checking cool the oil in the cooler has dripped back down to the resevoir? I had previously filled it to 3.6L when I changed the oil & filter last September and so far as I can tell its been running fine until this oil drip issue from the blow by.

I let it run for 5 minutes and checked the oil (while level) after removing about 500mL this morning and the dipstick read about 1/3 between add and full.

Is there anything in particular I should look/listen for to indicate the engine needs more or less oil?

I appreciate the help on this! I'm still very new to these bikes and trying to learn as much as I can.

People fret enormously about how much oil to put into their engines and the reality is you can run one almost dry and it'll still keep working! When we built the 1400 motor for Beetle's bike we hadn't yet learnt about the greatly exacerbated oil expulsion issues caused by the increase of swept volume of the motor and a couple of weeks after he'd got it home he started it ne day and the oil light came on! On checking the oil there was none visible on the stick and after we dragged it back to the workshop we drained out only a couple of hundred ml of pitch black tar! The rest of it had been pushed out of the breather system and burnt!

We dropped off the big end caps and there was some minor damage to the shells but, astoundingly, that was all. The truth of the matter is that as long as there is sufficient to cover the pick up, while it's not good for the engine, or the oil, with modern synthetics you can get away with an incredible amount of abuse! We just slipped in a new set of shells and Mark started buggering about with the blow-by and condenser/return system to prevent it happening again. Also over time he's been using progressively less oil and keeping the level lower and lower. I don't know where he's at exactly with that now, it's still a work in progress.

Things to remember are that with every revolution of the crank the volume of the crankcase under the pistons varies by about 2/3rds of the swept volume of the motor producing a 'Panting' action, then there is the inevitable blow-by past the rings that increases the pressure in the case which has to be allowed to vent somewhere and when it does it will take oil particulates with it. The idea of the condensor system is to allow those particulates to settle and re-combine to then drain back to the sump. The excess 'Gasses' expelled are then fed to the airbox and re-breathed through the motor where the remaining hydrocarbons are burnt.

Also contributing to this expulsion of oil will be things like the proximity of the spinning crank to the surface of the lubricant in the sump. When the engine is spinning at 6,000 RPM the gas in the case is already a maelstrom of oil particle being flung off the crank which is spinning a hundred times a second. The cyclonic forces it creates within the gas will also tend to whip up more oil from the surface of the foamy mass of oil in the sump and the closer that surface is to the spinning crank, the greater the load of oil being carried in the gas and the greater the strain on the condensor and return system.

As a further problem the actual volume of the crankcase itself hasn't really changed since 1984! Yet the swept volume has increased from 850cc to 1150cc so the pumping action experienced with the newer motors is much higher than it used to be!

By adding less oil you move it away from the crank and lessen the pumping action. All Guzzis since time immemorial have 'Found their own level' as far as engine oil is concerned and while several factors will govern where that will be on any individual machine speaking *generally* the 'Happy place' where they stop *using* oil tends to be somewhere between the half-way mark and the bottom of the stick.

Working out where that 'Happy place' is is really very simple. When you do your oil and filter change pre-fill the filter before installation, (Making sure the old filter gasket has come off with the old filter before installing the new.) and then add oil to the engine. Two and a bit litres is all you need. Run the engine for twenty seconds or so to purge the air out of the oil galleries and then let it sit for a couple of minutes to allow oil to drain to the sump.

Hold the bike vertical and check the level by just resting the stick on the threads of the filler and add oil until it's a bit below the half way mark between *Add* and *Full*. Now just go ride it. Keep an eye on the level and keep checking it in the 'conventional' way with the bike upright and while it may use a little don't add any more unless it actually drops off the bottom of the stick. Somewhere in that bottom third of the range of the stick it will stop using any oil to speak of. That is your correct level and that is where you should always fill it to when doing an oil change, never higher as it will just get expelled. Also, once you know that 'Correct' point you can rest the bike on its sidestand and check where the oil sits on the stick. Do this on a level surface and from now on you can in future dispense with the whole 'Hold the bike upright' nonsense! The quantity of oil hasn't changed. Simply the way you measure it. If you know the level is correct it doesn't matter what position the bike is in. It'll still be correct!

I nowadays very rarely check my oil. I know where it's supposed to sit on the stick and I know that my bikes don't use oil. On longer trips in hot weather I'll probably give the level a casual glance every couple of days but as a day to day thing I may check it once between 10,000km oil changes. Really nothing to fret about once you know where your engine is happy!

One final thing is if the sump is constantly 'Topped Up' all that happens is the excess gets expelled into the airbox. When this happens it can clog the stepper motor and damage the throttlebodies. You don't want to 'Kill your engine with kindness' which is what you'll do if you keep filling it up with oil!

I have a 2014 and the first hoses that failed happened in the first couple of years and I bought it new. It seems like they are stretched on to the nipples of the blow by “box” in Beetles diagram and they crack there. I only changed the condom about a year ago because I was going in for a second time in the 9 years I’ve had the bike and I had one. This time I used larger hose from the auto parts store so it wasn’t stretched on to the nipples and I spliced it in the the other end with the “curve” that runs into the engine with a “connector”.
You’ll need to lift the tank up some to get to things. I didn’t remove mine completely as I think Beetle mentioned you could leave it connected and just lift it up and put something underneath to hold it while doing surgery.
Best of luck. Let us know if you run into a snag. There is certainly more info on this subject if you do a search.

So I ordered the replacement breather hoses and they've been delayed a few weeks... i'm considering going to home depot and getting some shrink tube to wrap around the cracked hose in the meantime.

Does anyone have any outstanding reasons why that wouldnt be a temporary solution? The tube I'm looking at is polyolefin and has an operating temp of up to 275 degrees... I'll link to it below.

I've read that the breather system isn't pressurized...can anyone talk me out of this idea?


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The breather system is very much pressurised. The term "blow-by" is a dead giveaway.

I'd try the heat-shrink fix.

When I bought replacement hoses in the past I had a very hard time trying to get them on the nipple of the blow by box. It was like they were too small. The rubber is hard but maybe heating it up would help. I also noticed one of the hoses I was sent (not from AF1) had a date of 2007 on it for my 2014 bike……in about 2016. Old already….
After a second issue with the replacement hoses years later, that’s where I went to the auto parts hose.
This isn’t a pressurized system. I’m sure there is more than one band aid solution running around on a GRiSO or two right now. Maybe even some kind of plumbing tape would work for now.
Good luck.

I purchased about one meter of 16mm (from memory) fuel/oil grade hose, two bayonet type plastic elbows (same as used in low pressure poly systems) and eight stainless hose clamps.
Cut a short piece from the head about seventy five mm or so to elbow, then elbow to condenser(#1 in the diagram) Following same basic path as original hose.
Been working fine for several months now. Cost in the order of $15 AU.

JohnA wrote:

This isn’t a pressurized system.

Au Contraire, mon ami.

Disconnect one of the hoses at the head, and see how much pressure is there, especially off idle.it's not much pressure, but it ain't ambient...


..oh, don't stand behind the open port. You may get covered in oil. Ask me how I know. [You must be registered and logged in to see this image.]

Follow up question for all you guys out there:

I'm awaiting the replacement rubber hoses in the mail. I'm planning on heating the tubes with boiling water/hair dryer to get them more elastic but I've also read online that applying dish soap to the nipples on the blow by box and engine over which the tubes mount can be super helpful. Considering how tight the access is, I'll take all the help I can get. How bad would it be for me to apply some dish soap to the tube & nipples, assuming it eventually circulated into the blow by system?

Once again thank you all! Ive temporarily solved my oil drip using shrink tubing and extra clamps as I previously mentioned.

Soap will work but so will rubber grease.