Am semi-seriously shopping (looking at) buying a used J250. he
I vaguely remember reading that Jabs require periodic valve clearance adjustments. Like maybe every 50 hours? And that versions of the engine don't require that? Maybe they have hydraulic valves?
Adjusting valves is something I can do. But being aware of importance of maintenance but not that enthused about doing it or paying others to do it for me(I own a plane because I like to fly... not because I like working on it, so all things being equal I'd prefer the version not requiring periodic valve adjustment.
One Jab I'm currently looking at has its 3000 engine described as follows:
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Any idea if that tells if it's one that needs the periodic valve adjustment? Any other comments about that description or things as a buyer I might want to know or check?
* (my Utopian aircraft engine would be like my four cylinder Toyota, which as long as a regularly change the oil and filter, plugs at 100,000 miles, will be solidly reliable for a decade with likely no further attention <g>)
Alex
P.S., In case it's not obvious, I'm in the USA.
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Hi Alex,
None of the hydraulic engines require valve clearance adjustment, no. The "Gen" labels can get a little murky on a grandad's-axe engine like that one, but it will have hydraulic lifters of some sort.
Personally, I tend to focus on the seller as much as the product in cases like that. You sound like you know your way around a tool box, so asking the usual leading questions like: How often do you change the oil? How often do you change the spark plugs and what colour are they when they come out? What fuel do you use, what's your oil consumption like, engine temps etc etc... If you get the feeling that he's interested in these things, knows the answers and still tells you how great the engine runs then that's a very good sign.
Incidentally, Toyota (and Porsche and a few others...) had a look at the small aircraft engine market many years ago and eventually ran away screaming (note: some poetic licence used). A piston engine running at 60 or 70 or more % power while being as light as humanly possible is, unfortunately, not going to live up to the standards set by automotive engines that normally live in the 10 - 20% output range.
Regards,
Doug.
Hi Doug.
Thanks for your thoughtful and useful reply.
As for your words “Incidentally, Toyota (and Porsche and a few others...) had a look at the small aircraft engine market many years ago and eventually ran away screaming (note: some poetic licence used). A piston engine running at 60 or 70 or more % power while being as light as humanly possible is, unfortunately, not going to live up to the standards set by automotive engines that normally live in the 10 - 20% output range”:
I don’t blame them for running. The liability risk, too, probably looked large to them.
But in one respect aircraft engine and aircraft makers have it way easier than auto engine and auto makers. In autos when even a trivial safety issue … and sometimes even a non-safety issue …. is discovered in their product the maker is forced to remedy it at their expense, and handle the logistics of doing so. At least in the USA.
In contrast when Rotax (I use them just as an example) discovers they’ve sold you an aircraft engine with a defect or a defective part, even one of serious risk, they not only take no financial or logistic responsibility to remedy it, but force the owner to do so, effectively grounding you if you don’t do so and do so exactly as they specify. (Grounding by issuing a revision to the operations and maintenance manuals…as the FAA requires compliance with the latest manuals to be airworthy.)
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