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Old 04-15-2019, 10:35 PM
RFSchaller RFSchaller is offline
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,509

You’re probably right, Charlie. You saw how tentative I was about frequent oil changes helping.
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Old 04-16-2019, 03:57 PM
NinerBikes NinerBikes is online now
Join Date: Dec 2018
Location: Granada Hills
Posts: 186

Originally Posted by bobg56 View Post
Would the Mobil 1 be the type for motorcycles? This would be for the slip clutch that's for prop strikes?
Mobil 1 Racing 4T 10w-40 . Formulated with gearbox additive.
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Old 04-28-2019, 05:04 PM
Cammie Patch Cammie Patch is offline
Join Date: Oct 2018
Location: Boise, ID
Posts: 22
Default A little update

I just finished another 100 hour inspection on our RV12 (SLSA). We are putting about 70 hours a month on it.

About a month ago I ordered a new gear set and dog gear for the gearbox. If you remember, I couldn't idle much below 2500 rpm cold, due to vibration and gearbox chatter. I rebuilt the carbs, balanced them many times etc. But it didn't cure the problem. Aircraft only had about 120 real hours on it when we got it.

So, yesterday I cracked it open. I have to say that Sensenich is a bit barbaric in their prop/hub/bulkhead assembly on the -12. It's at least a two person job.
But, once I got it opened, I did see a lot of where on the dogs. Way too much wear for such a low time engine (about 400 hours now).

I wasn't happy to realize that CPS hadn't sent me the dog hub yet, just the gear set half. Since it's in a flight school, I had to put in what I had, and go with that for now.

But what a difference!! Now it runs smooth all the way down to 1600 RPM, with no chatter above 1800 rpm.

I'll open it up again when I get the other side of the dog gear and put that in.

The previous owner was very meticulous on how he operated it. He took Rotax and LSRI classes, and kept an incredibly well detailed report on each annual. He used AeroShell Sport 4 oil, and almost always used 91 octane fuel.

I have switched over to Mobile 1 4T oil. I have no other smoking gun than oil to blame for the early wear. I understand that Rotax has an obligation to promote the AeroShell oil, but I just don't think it's as good for the gearbox. I run about 95% mogas in the -12.

Another reference source: I just did an annual on a Tecnam SLSA, which has also been running the Aeroshell. It ran rough as well, with excess chatter.
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Old 04-28-2019, 07:47 PM
pilotyoung pilotyoung is offline
Join Date: Jan 2018
Location: Birmingham, AL
Posts: 124
Default Gearbox wear

That picture looks exactly like mine did after 450 hours. My engine has had Aeroshell Sport 4 Plus used in it since it was new.
John D. Young, RV-12 Owner
Serial Number 120022, N6812Y
Bought it as a flying airplane in Feb. 2018
Just passed 140 hours flight time in RV-12, and 10,000 hours mostly in corporate jets. I am a CFI; CFII; MEI; and a advancd Ground Instructor, CFIG; and hoping to be able to help new RV-12 owners by doing some transition training for new builders and owners in RV-12's.
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Old Yesterday, 08:32 PM
Cammie Patch Cammie Patch is offline
Join Date: Oct 2018
Location: Boise, ID
Posts: 22

I bought another SLSA RV12, and have seen the same wear in the gearbox, but the magnetic plug is pretty clean. I shimmed it up and switched oil. Still has some vibration, so I may crack it open again and replace the Bellville washers.
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Old Yesterday, 08:42 PM
NinerBikes NinerBikes is online now
Join Date: Dec 2018
Location: Granada Hills
Posts: 186

Tach time on the new to you S-LSA ? And new pics if you open it up inside. Good data base being formed.

Last edited by NinerBikes : Yesterday at 08:49 PM.
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