Jabiru 2200 (1st gen) spark plugs fouling - too much oil in rocker chamber @ idle RPM

[MarcoP]

THANK YOU ALL! It's nice to see i'm finally not alone looking at this.

11 hours ago, facthunter said:

I vaguely recall the need for a bleed hole at the top of the box. Check all SD's

yes, that's the JSB031-1 i've linked in my original post, but that bulletin is not for solid lifters engine, it's for hydraulic lifters one... still i am looking at this bulletin as an indication of a probable counter-pression issue which needs to be addressed as the bullettin says or in a similar way.
As example: there was an indication of changing the oil sump with a bigger one due to pressure issues. This indication was for hydraulic lifters engines too, but once more looking at the same direction of counter-pressure in sump or depression in rockerbox.

10 hours ago, Moneybox said:

Are your sparkplugs the correct heat range for the job?

yes, i used the correct ones as by manual (D9EA), then tried to switch to iridium in the same range: DR9EIX to fly to the mechanic. As the result of that flight was good, i tried to keep using them for some more hours, but same result.

9 hours ago, Siso said:

Can you just drill a small hole in the top of the perspex and see what happens.

that's going to be my next test, next saturday, I'll drill a hole of the same size of the JSB031-1 on the polycarbonate cover and try to see if the oil drains back when at idle. I suspect it gets worse rather than better. Another try i want to do is to run idle (with polycarbonate cover) and opening the oil refill tube and see if the pressure in the sump gets better and the oil in rockerbox flows back in the sump.

7 hours ago, kgwilson said:

The evidence shows the oil is getting in but not out

Exactly, but it happens only on cylinder #4 and #3 and only at idle.

7 hours ago, kgwilson said:

Most Jabs I know (Gen 1 to 4) run exclusively on Mogas

mine too, 100% of its life on MoGas (E5) 95 or 100 octanes.

7 hours ago, kgwilson said:

Find the oil return blockage and job done

100% agree, indeed the real problem is: what's causing the oil to not go back, only at idle and only on #3 and #4  (#4 more than #3)

6 hours ago, BrendAn said:

i wonder if he keeps the oil on the full mark on the dipstick.  

oil is always maintened at 75% (3/4) between the min and max.

2 hours ago, Thruster88 said:

he flew 25 hours since the rebuild but didn't say what if any oil consumption was.

the first 25 Hrs after overhaul i was running on aeroshell W100 and oil consumption has been 300 ml (100 of them into catch bottle).
Now i'm running Aeroshell W100 Plus after the run-in period and in about 15 hours i have added 250 milliliters of oil, 50 of them have gone in the catchbottle.

2 hours ago, Moneybox said:

if there are no valve seals and if that oil level in No.4 is abnormally high perhaps it can feed oil down the intake valve guide. I'd be looking for other reasons for the plug fouling, fuel, spark or sparkplug heat range. If its burning enough oil to foul the plugs in a short period of time then there'd be a lot of blue smoke.

level is extremely high at idle (only) in #4 and very high in #3.
Only #4 is getting spark plugs fouled. No blue smoke at all.

1 hour ago, Blueadventures said:

Send video to Jabiru at Bundaberg and ask them.

can you address me where to find the contect?

 

------

 

A friend of mine, nautical mechanic, gave me 3 "Occam's razor" ideas to think about, tell me what you think about:

1. are you sure the oil stick is the correct one? maybe it's a stupid thing, but if the previous owner replaced it, it may be not perfect and your oil level may result in being wrong.
2. why everything was good during the run-in period with aeroshell w100 (not "plus")?
3. it could be an idea to swap the heads and observe if the problem "follows" the head or not.

 

Here you are the video (if not working retry in 30 minutes, it's uploading right now) of the same test on the other side of the engine:

1. rockerbox of cyl #3 is getting full of oil when at idle too.. but if you compare to #4 the level is slightly lower. (please note that my polycarbonate cover have a bigger cavity than stock iron covers.. so the amount of volume available is wider, the same amount of oil you see in theese 2 videos is problbly filling the whole rockerbox when on stock covers.)
2. at the end of the video i do a mag test and here you can see the problem: a 200+ rpm drop and CHT of #4 going down when i keep the engine running with 1 mag only for some more seconds.. This is not the "full" failure (1 spark still working) like the one i've experienced in flight, but it's what i usually get after a long idle landing (mid downwind to touchdown) or after "gliding" 10 minutes.  

 

Thank you all!

Edited Tuesday at 10:54 AM by MarcoP

[Red]

I wouldnt take the applicability to Hydraulic lifter engines only as a always true case, if only because I dont understand what difference that makes to the rocker box oil delivery and return system

[Red]

Have you checked tappet clearances BTW?

[MarcoP]

 

>> tappet clearances >> 

but i'm not sure i've measured it in the proper way: starting from the point both valve are "up" and the tappet can "jiggle" a bit by hand... i've found the "looser" point of a valve is when the other one starts going down, more or less half way down. This is the point where i measured it. Given value is the max. I was actively looking for the max, don't know if its how its supposed to be done.

The used instrument is pretty cheap and coming from temu online sore for less than 2 €, highly probable it is not accurate.

 

Clearance seems to be too wide, but i am not capable to fix them, or i'm simply worried to try: not having ever seen how to do this properly.

 

Cylinder #4 

right valve: 0,38 mm goes through and 0,4 mm doesn't

left valve: 0.38 yes, 0.4 no
 

Cylinder #2

right valve: 0.30 yes, 0.33  no

left valve: 0.30 yes, 0.33 no

 

Cylinder #1
right valve: 0.35 yes  0.38 no
left valve: 0.30 yes 0.33 no

Cylinder #3
right valve: 0.35 yes 0.38 no
left valve: 0.4 yes 0.43 no

 

 

 

>> Oil Temps and pressure in the past months (taking from some gopro videos i've made) >>
 

31 October (coming home after 25 Hrs check - end of run-in period, first flight with W100 Plus oil again.)
   > downwind - 1600 rpm - 2,5 bars - 70° C
   > final - 1000 rpm - 1,5 bars - 70° C

 

1 December
   > park - 1200 rpm - 3,5 bars - 50° C
   > mag_test - 2000 rpm - 3,5 bars - 55° C
   > Full throttle on brakes test - 2800 rpm - 3 bars - 60° C
   > idle test - 830 rpm - 2,5 bars - 60° C
   > takeoff - 2950 rpm - 3 bars - 60° C
   > level flight - 2700 rpm - 3 bars - 70° C
   > descending - 2000 rpm - 2,5 bars - 70° C
   > climb - 3000 rpm - 3 bars - 75° C
   > final - 1000 rpm - 2 bars - 70° C
   
7 Dicembre (experiencing the problem during mag test, on ground)
   > taxi - 1500 rpm - 3 b - 50°
   > both mag ON - 600 rpm !! - 1,5 b - 50° (CHT 102/110/130/60  EGT 410/450/440/170)
   > Full throttle on brakes test - 2550 rpm - 3,5 b - 60°
   > mag_test oat 2000 rpm --> 400 rpm drop ! - 3,5 b - 60°
 

7 Dicembre (after spark plug replacement)
   > park - 850 rpm - 3 b - 50°
   > taxi - 1450 rpm - 3,2 b - 50°
   > mag test - 2000 rpm - 3,5 b - 50°
   > Full throttle on brakes test - 2850 rpm - 2,9 b - 50°
   > 2° mag_test - 2000 rpm - 3,5 b - 55°
   > takeoff - 2900 rpm - 3 b - 60°
   > level flight - 2700 rpm - 3 bar - 70°
   > base - 1300 rpm - 2,5 b - 70°
   > final - 1000 rpm - 1,5 b - 70°
   
21 december (today i experienced the full #4 shutdown during flight time)
   > waiting for takeoff - 1200 rpm - 2,5 b - 60°
   > takeoff - 2900 rpm - 3 b - 60°
   > level filght - 2700 rpm - 3 b - 70°
   > level filght - 2500 rpm - 3,5 b - 70°
   > descending from 6000 ft - 2500 rpm - 3,5 b - 70° (15 minutes before fail)
   > descending from 6000 ft - 2500 rpm - 3,5 b - 60° (10 minutes before fail)
   > sadly i've shutted down the camera before flying at idle and experiencing the problem.. but i can tell i flew the last 10 minutes at idle and then the engine started to be rough and CHT and EGT of #4 went down fast as hell.

 

10 January (flying to the mechanic once more, with brand new iridium plugs, all good.)
   > level flight - 2600 - 3 b - 70°

 

.

Edited Tuesday at 11:38 AM by MarcoP
english fix, sorry for many typos, my english isn't that good.

[T510]

15 hours ago, Thruster88 said:

Oil consumption would have to be very high to cause plug fouling. A Rotax 582 can eat 400ml of oil per hour no problem. Perhaps the real problem is a weak ignition, just a thought. 

2 stroke oil is designed to burn, has a very low or zero ash content and usually has some detergents added to minimize the deposits in the combustion chamber.

 

Can't really compare it to a 4 stroke burning oil

[T510]

12 hours ago, MarcoP said:

 

 

A friend of mine, nautical mechanic, gave me 3 "Occam's razor" ideas to think about, tell me what you think about:

1. are you sure the oil stick is the correct one? maybe it's a stupid thing, but if the previous owner replaced it, it may be not perfect and your oil level may result in being wrong.
2. why everything was good during the run-in period with aeroshell w100 (not "plus")?
3. it could be an idea to swap the heads and observe if the problem "follows" the head or not.

1. If this is the case does it find a "happy" level where the oil level stays the same and the consumption is reduced

 

2. Have you tried going back to Aeroshell W100 - I know one of my cars burns more oil if I use one brand even though the oil specs are the same (both 5w30)

 

3. Are the heads identical so they can be swapped? If the oil drains back to the crankcase through the pushrod tubes do you change them with the heads?

 

 

[Moneybox]

My concern is that you are trying to resolve the high oil level in the rocker boxes. Are you sure that this is abnormal? How would anybody know how much oil is expected to be in the rocker box under normal operation? Nobody can see in there.

 

If you can be sure you are consuming copious amounts of oil you may be on the right track otherwise I'd be looking for other reasons for the sparkplugs failing.

[facthunter]

Oils for 4 strokes contain friction modifiers that will short out Plug insulators internally.. Just use conventional plugs and save your money. I'd check the Inlet valve guide fit on the valve stem. At idle the suction is greatest in the inlet ports.   The bleed may reduce the effect of the suction but not enough to stop excess oil getting there.   Nev

[MarcoP]

On 18/02/2025 at 11:48 AM, MarcoP said:

es, that's the JSB031-1 i've linked in my original post

sorry, my mistake, it's JSB013-1 not 031

15 hours ago, Moneybox said:

Are you sure that this is abnormal?

yes, look at picture below, it gives you the clear info it is abnormal (+ there is enough litterature in internet about the oil level in the rockerbox)

On 18/02/2025 at 11:59 AM, Red said:

I wouldnt take the applicability to Hydraulic lifter engines only as a always true case, if only because I dont understand what difference that makes to the rocker box oil delivery and return system

 

Ok, I've drilled a hole of 2,5 mm in the polycarbonate cover to simulate JSB013-1. HERE the new video of the test.
Results goes in the good direction but it's not 100% satisfying.

 

When not at idle (1200/1400 rpm is enough) all cylinders have oil level at green line, that said let's talk about when the engine is at idle, which is the common line in the problem.

• with NO holes (before "fake JSB013-1 test") cylinders #1 and #2 oil level is at green line
• with NO holes (before "fake JSB013-1 test") cylinder #3 sits at yellow line
• with NO holes (before "fake JSB013-1 test") cylinder #4 sits at red line ---> and spark plugs get fouled by oil travelling on the valve stem.
• Applying the hole on the cover ("fake JSB013-1 test") then cylinder #4 gets down to yellow line as #3.
• If i cover the hole with my fingers then the level goes up to red line, if I un-cover the hole the level goes down to yellow again.
• I have not tested cylinder #3
• While hole is open, if i oper the oil tube (refill/inspection) then the oil level gets up to red line again.

The thing that #4 gets down to yellow line, which is the same level of #3, is very good, considering that #3 never had "too much" oil in the combustion chamber and never fouled the spark plugs!

 

 

So.. it's definetly an issue related to the "atmosferic pressure" in the oil circuit, the thing is: 

will we consider this just a rockerbox depression issue, or do we need to consider a probable oil sump counter-pression issue too?

 

There used to be a jabiru indication to change the oil sump with a bigger one to solve pression issues in the oil sump, but i can't recall if it was about a de-pression in the sump, or a counter-pression in the sump, or a depressionin the rockerbox or (at last) a counter-pression in the rockerbox.. anyone remembers this?
Anyway, they no longer sell that sump and i cannot find a used one, so.. 😞

 

I've received the suggestion to add an air/oil separator, not to bring separated oil in the sump again (absolutely not!), but to help stabilising the atmospheric pressure in the sump instead. Do you think it's needed / useful? 

 

In case this is still not enough It could be the step 1 needed to get to the desperate-final-weapon: connecting the clean air output of the oil separator to the carb air intake to help create a more consistent depression in the sump and help oil to flow back from rockerbox.

The idea is very similar to car engines, and very similar to what i've read in a post HERE (scroll down to 50% of the webpage to find the oil separator thing. Every chapter is translated to english a little lower than the french chapter)...but it seems a little hardcore to me and i'm worried to get oil in my intake air filter...

I'm attaching a pic of the oil separator too, carb should be connected on top instead of the air filter.

 

 

 

[johnm]

you must know the correct volume of oil (litres) to put in the engine ............. irrespective of what dipstick is used

 

.............. assuming you have started there ? (obvious simple advice thrown in) 

[MarcoP]

30 minutes ago, johnm said:

you must know the correct volume of oil (litres) to put in the engine ............. irrespective of what dipstick is used

 

.............. assuming you have started there ? (obvious simple advice thrown in) 

Never had the opportunity to perform an oil change. Overhauled after 20 hours from purchase. Then performed by certified Jab tech at the end of run-in. I presume it's the correct amount. Dipstick has been checked now, it's correct. But JSB013-1 is also saying "if you suffer of this stay with oil on lowe mark of dipstick". I've not done this, always at 75%.

[johnm]

........  step 1 ? .............. before you start the other steps - drop the oil and put in the correct litres amount ...................... and see if that ...................

[facthunter]

He's not filling it right up. It may have  a restricted crankcase volume which makes the "AIR" in the crankcase move around excessively and tend to POOL OIL a bit somewhere..  Check if there's excessive BLOWBY at the breather. That should be unlikely with The  servicing it's had. NEXT go back to the inlet valve guide running clearance. Thats where the suction originates.  Nev

[Moneybox]

1 hour ago, facthunter said:

He's not filling it right up. It may have  a restricted crankcase volume which makes the "AIR" in the crankcase move around excessively and tend to POOL OIL a bit somewhere..  Check if there's excessive BLOWBY at the breather. That should be unlikely with The  servicing it's had. NEXT go back to the inlet valve guide running clearance. Thats where the suction originates.  Nev

 

We used to have a service station with the quart and pint bottles on the driveway because it was common to check your oil whenever filling the tank. One day a lady came to the counter and asked for more oil. Her husband had asked her to fill the car with fuel and oil but there wasn't enough on the driveway.

[facthunter]

My brother filled Up his Fiat till it ran out the breather pipe. Nev

[liron]

I too had the same issue 4 years ago.

Turned out that the oil seperator bottle (very much like yours) was too restrictive and caused high crank case pressure, preventing the oil from draining back.

The oil is fed to the rocker cavity by pump and drains by gravity.

Run the test again with the dipstick off and check the results. 

I later on replaced the valve guides to accept a valve seal as well. Guide holes were too large and the valve would rock inside the guides

[facthunter]

The displaced air movement with that engine in the crankcase is from the front cylinders  to the rear ones  and back and those pistons oppose and displace more than one litre of air per revolution  THAT can move a lot of oil  with it if there's no baffling and not a lot of volume in the sump.   Nev