Vev

Skyscooter, As mentioned in a previous post ... the push rod oil feed to rocker gear is already in production on current engine. In fact I retro fitted this system to my thick finned 2.2 head 2 weeks ago. Cheers Jack

Hi Phil, The sail cloth was self adhesive … it comes in a roll and has a paper backing over the glue side which you just peel off before you use it. Cheers Jack

Hi Phil, I have replaced mine twice … first time I used duct tape but it had short life. The second time I went to Whitworth Marine and bought some rip stop sail cloth in a 50mm x 5m roll .. very nice stuff and it’s UV stable too. Cheers Jack

I had a good conversation with the South African Jab distributor this evening who has been inserting K liners into Jabs for a couple of years with very good success. He said he has seen engines comfortably run out their 1000 hrs without problem. However, having said that, he believes that lean cruise burn is the root cause in terms of premature valve guide wear; despite the introduction of rich kit from Jab he says more fine tuning is required in most applications. He is of the view jetting can vary between aircraft owing to minor variations in set up and use… he said to target < 700 deg C EGT at 2750 rpm (being the transition phase on the needle) is good place to start to extend he life of valves and guides. Any thoughts about these comments are welcome? Cheers Jack

Here's a handy file from Jabiru that give you all you need to know about oil dip sticks and oil levels. Cheers Jack Dip%20Sticks%208A035A0D-1.pdf Dip%20Sticks%208A035A0D-1.pdf Dip%20Sticks%208A035A0D-1.pdf

Hi Tomo, Not sure of the a/c you hire have a EFIS fitted ... many of these have G meters as part of their fuction... this is not often known. Cheers Jack

Hi Nick, I can’t say I have seen anything that has excited me in terms of engine breather improvements. There have been a couple of attempts at fitting inline oil condensers before the oil/separator, but these in my view could create more problems in terms of back pressure and therefore higher crank case pressures. I think the only sure fire improvements to reduce crank case pressure in the 4 cylinder is the larger crank case sumps as fitted on the latest model engines.. However this will be an expensive retro fit upgrade. Others may know more??? Cheers Jack

For what it’s worth, I have decided to replace the exhaust valves owing to excessive seat wear and as a precaution … I’m concerned about how much fatigue the exhaust valves may have suffered with the amount of guide wear… the valve are as loose in the guides as Tiger Woods wedding band…. no need to measure the defection in this instance. I also need to measure and compare the new replacement oil fed rockers (they turned up in the mail today) with the old splash/mist oil rockers as they look to have a different geometry…. This may help reduce the side loading on the guides. ..I will let you all know if different once I measure them. Cheers Jack

What an interesting video clip … thanks for sending JR. My understanding … there is insufficient free air volume in the crank case (see Jabs Service Bulletin JSB 013 -1) which causes a positive pressure and is compounded by a low pressure in the rocker chest from the inlet value guides allowing air to be escape through to the inlet induction. Jabs fix was to get us to all to drill 3/23 holes through the heads to atmosphere to vent the rocker chest… the hole is on the pressure side of the ram air cooling side. Later model engines had deeper sumps which increased the free air volume in the crank case and reduce pressure build up… they also increased the drain back holes at the base of the push rod tubes to improve drain volume to the sump. I agree again with Nev’s comment … you really don’t need that much oil to lubricant the rockers. In my mind, it’s more about getting the lube into the right place and having it drain away quickly thereby taking away the heat without damaging the lubricant. A long dwell period of lubricant caught in the rocker box just exposes the oil to possible burning and oxidation as well as of loss of the lubrication characteristics. I don’t really think I’m telling anyone anything new as Jab have publicly documented this issue and make this point quite clear in their Service Bulletin. However I am concerned that their vent fix doesn’t keep up with the pressure differential when the guides wear, which in part starts a damaging cycle of wear on the valve train. Hence one of my initial questions if valve stem seals would have been a possible fix to allow the oil to drain and save the rocker gear despite valve guide wear. Cheers Jack

Hi Brian, Thanks for your feedback mate .... do you know what type of K liners you used? What made you decide to use them.. did anyone recomend them to you? Look forward to hearing how things go? Cheers Jack

No question in my mind Tomo that the oil is come via the giudes ... also seeing way too much carbon build up on the piston crown and ring lands too. Nev, I have found wear on the rockers shafts and valve stem contact points. Jab has sent me an upgrade with new hollow push rods and oil gal rockers to improve lubrication around these components. I think the geomertry looks NQR and agree with your thinking that this could be one of the reasons for a short guide life. I'm also concerned about heat as well as this may place too much thermal load for the lubricant. I dont think it is draining back fast enough to the sump from the rocker chest, despite the factory upgrade to drill a vent hole. I think the warn valve guides are causing a pressure drop in the rocker chest via the inlet guides as it sucks the oil through??? Cheers Jack

Thanks guys. The originals guides are aluminium / bronze but seem to have a very short life 300 – 400 hrs … not sure if they are too soft, get too hot or bad geometry of the rockers??? Despite still having a good compression test and leak down result the valve defection is beyond serviceable limits. You can see the amount of carbon build up on the back of the inlet valves owing to oil bypass, which to me suggests that valve stem seals would have been a good idea in the design. I’m at a point in time I need to replace my guides and I’m looking at the alternatives to improve durability as well as manage oil bypass (may be with valve stem seals). I’m not keen to play pioneer or test pilot but I hear there are engines out there with this mod and would really like to hear how things are going? Cheers Jack

At one of the engine forums at Temora I heard about an L2 from WA talk about using K Liner inserts in Jab value guides. I presume this is the same process used on taxis when converting engines to LPG to make the guides more durable? The L2 at Temora said it has fixed the valve guide wear issues and reduced oil burn to very low levels. By the way ... why doesn't Jab run valve stem seals? Anyone out there tried K Liner guides replacements or have a view? Cheers Jack

Completely agree Brian I fitted an MRX in my Jab 14 months ago ... had a small problem with the plug in power and sent it back. The Zaon guys gave it an upgrade free of charge and sent it back from the US in under 2 weeks... great service. Fantastic unit .. it doesn't replace your eyes to look and avoid but it does help fill in some of the gaps on the ones you miss if they have a transponder turned on. Cheers Jack

The new engine feeds the oil up through the push rods and then through the rocker arm to the rocker shafts and valve stem. Cheers Jack

Ian, Thanks for this, hopefully you did get it right .... good to see some common sense prevail in the interest of safety. Cheers Jack

Ian B, Can you speak with Mick and provide some substance to this cryptic reference about air space access? Cheers Jack

Ian, How simple is that ... great idea! Cheers Jack

nice one Bob ... thanks Jack

Found the problem ... it is the rocker box breather vent hole. It is misting a very small amount of oil out through the vent... oil when runs down through the water drain hole which goes though the head ... this allows the oil to make it's way to the bottom head bolt. I spoke with the guys from Jab at Temora who confirmed the source of the oil. All good and no issue .... Cheers Jack

Keith, Check the pedals and make sure they are free.... there was also an AD on the rudder pedals.... see jab site for details Quote from Jab; "When adjusted to the most rearward position (i.e. that suitable for shorter pilots) and pressed to full rudder deflection, the pilot can experience a situation equivalent to rudder pedal overcentering and locking. For example, when the pilot uses full left rudder to turn the aircraft at the end of the runway, then presses the right rudder pedal to straighten onto the runway heading it can feel as though the control has locked. This effect can be exaggerated by the pilot’s shoes – thick, heavy soled shoes with deep tread tend to snag on the pedal more than thin-soled runners. RA-Aus Airworthiness Notice AN161008-1-1 also refers. This Jabiru Bulletin has been prepared to provide additional information to owners and supersedes the RA-Aus Notice". Cheers jack

I've just completed a 50hr maintenance programme on my Jab 160. I noticed a very small amount of burnt oil around the bottom head bolt cap, not sure where this oil has come from ... any thoughts out there? By the way, leak down and comp test are all good, which I'm thinking it suggest there is no head leak... The engine is running fine and no noticable loss on power. Cheers Jack

I'll be there Tomo ... see you in the park Jab 160 19-4430 Cheers Jack

Ok ... So back to Big Pete question ... what's the difference? Cheers Jack

Sseeker, Interesting piece of info ... what makes you pretty sure? Cheers Jack