Kitfox 7 Apex Build Episode 66 Yamaha APEX Skytrax Gear Box Clutch Replacement

This episode covers how to replace the clutch on a Yamaha APEX Skytrax Gearbox.
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[@Mike-01234]

That looks like a GM 34 element sprag it's not OEM for the TH400 which used the 17 element sprag. The 34 is installed in most performance upgrade for the TH400's. I believe it's OEM for the TH 4L80E which is modern version of the TH400. There are aftermarket sprags that don't have that clip.

[@ThatGuy-cw8gb]

You sir are the reason I want to build a Kitfox! Just starting my flying lessons so if I order the kit now it should be here by the time I complete training! Now for the money part… Precision transmission is another you tuber that dude knows transmissions inside and out. Hit him up about the TH400 clutch he’ll be able to tell you all about it.

[@HeeHawHighlander]

Good stuff Bryan. I was looking through my engine log while watching this and I also changed my sprag element at 135 hours. Mine still appeared to be ok but I wanted to play it safe. I had previously removed the clips from my original element and had reinstalled it since it looked fine. And of course removed them from the new element. I’m at 151.3 hours on my SkyTrax and she’s purring along nicely.

[@AlexZaboroski]

I'm approaching 150hrs, last gearbox oil change was clean about 20hrs ago, but this really makes me want to open it up now and have a better look. Thanks for sharing Bryan!!

[@foesfly3047]

I appreciate your ‘matter of fact’ way of looking at everything. You would make an excellent helicopter pilot and/or representative for a premium aircraft wheel and brake manufacturer 😉

[@whitetrashgarage8110]

Thanks for content like this. I've started my build with the intention of the apex for power. Seeing how simple the box is to work on really puts my mind at ease

[@russellsmith3825]

International harvester tractors had a planetary gear reduction unit between the engine and transmission they called a torque amplifier, from the factory the sprag clutches were a failure point. One upgrade that became an option is something called a "mechanical diode"which has 10 spring loaded pawls which allow the shaft to overrun in one direction but have a positive mechanical lock in the other, basically a super sized ratchet. If the sprags become a problem here, then this could be the solution.

[@russellsmith3825]

I posted a link in a follow-up comment, but the spam filters snagged it

[@oneninerniner3427]

@@russellsmith3825 yup, I've run into that too! Spam bots that is, Dang it! I was thinking mechanical diode as well.

[@challenger2ultralightadventure]

I would be interested to see how long that replaced clutch lasts. The only thing I may have done differently in your replacement, is to do a full wash down of the bearing and parts with solvent or brake cleaner. Just to be sure all the tiny particles are removed. Those could cause premature wear to the bearings and surfaces. Thanks for posting, I do like your willingness to make holes in your work bench to do a job. I do the same, and have had some people look at me funny, but hey, it's a work bench. Might as well make it "work". Cheers from Winnipeg.

[@BowenAero]

When putting out a KZbin video, editing is necessary and sometimes not everything is shown or explained in a video. The gearbox was thoroughly cleaned and flushed before assembly.

[@oneninerniner3427]

I thought that sprag looked familiar, th400 trans intermediate sprag clutch I believe. I've worked on quite a few of those trans. I think the failure could be from from impact. But the dogs should not fall out either, but did because the cages & little springs that hold tension on them are worn out & broken. But those other clips should remain as well I think. They keep a little tension on the spag cages so they stay more evenly spaced in between the inner & outer races so they won't chatter & float around I think. Also I wonder why they leave those other two races completely out? I'm not a big fan of that either. Is it so lube can get into the sprag easier? Idk? So how does the gearbox get lubed, is it from the engine oil, or is it a separate sump? If so what lube are you using? The sprag was intended for ATF of course. But the gears and bearings could use a little more viscosity. A good premium 100% synthetic ATF like AMSOIL or similar should be good I think. Or a low vis premium 100% synthetic synchromesh manual trans lube if it's a separate reservoir. Premium synthetics have better shear, wear resistance, better lube for gears & bearings too.

[@BowenAero]

We run ATF and it is self lubing splash system in the gearbox. A lot of design went into the lubrication flow inside the gear box.

[@oneninerniner3427]

@@BowenAero yup, ok

[@KeithPatterson369D]

As usual great video! 👍

[@MJPPoland]

Teal reccomends grease to hold that o ring. You would not have to waste a tube of silicone.

[@BowenAero]

Funny, cause Teal told me about the silicone.

[@williamgreen4757]

Buddy you have to clean out all the drive bearings. Always mark everything you have torqued, also use antisabatoge compound.

[@NimblyJimbly]

This may be a silly question, but is there a reason you didn't use compressed air during the cleaning process to ensure that there were no small bits left over?

[@brendanhayes2752]

I’m surprised you are allowed to use any aerosol products in California! I’m sure Governor Gruesome will be calling any day! Great content. Thanks

[@BowenAero]

Don’t tell him about my MEK supply.

[@mikep60]

Lmao would be funny if it werent true. That dude is a waste of time

[@ronmac1832]

Sounds like someone is living rent free in Brendan’s brain.

[@Mike-01234]

They also banned denatured alcohol which has .00001% effect on climate change. CARB's excuse was well no one will complain much about it we are banning the easy things have very little pushback. Which means common man who can't fight them because they don't have the money to do it.

[@gfackrell]

I found that once those small pieces of metal show up in the oil change, it's not much longer before a lock up. I think I had 4 lock ups, and replaced the sprag 10 or so times using two different gearboxes over 650 total hours. I'd recommend a new clutch element every 100 hours, or as soon as you find metal pieces. Once it locks up the first time, it locks up sooner the next time. I never got more than 50 hours on a new clutch after it had previously locked up.

[@tamiamibusch]

Man that sounds like a design problem.

[@BrianGochnauer]

I would more be worried about the clip particles getting between the gear teeth and damaging the teeth causing a failure in a few hundred hours; even if you remove the particles the damage has been done. I hope you checked the teeth for damage.

[@tonta332]

hi .. i want to buy that engine from you, i'm in vietnam, do you sell it please reply me

[@rsrguy]

If this is the same gb Henry is running... is he dealing with this too?

[@BowenAero]

It is the same gearbox, but currently he is running a solid gear with no clutch. It creates a lot of vibration, but he only does very short flights.

[@thompsonjerry3412]

I would bet that those are anti rattle clips.

[@oneninerniner3427]

Yes

[@irongoatrocky2343]

I can see you dont wear gloves either (Bitch Mittens as another KZbinr calls them!).... that brake cleaner will sure make your liver quiver eventually!

[@Mike-01234]

Been using break cleaner for 40 years liver in perfect condition. You know what is killing livers is fatty liver #1 liver condition now in the US why because obesity.

[@tamiamibusch]

130 hrs till failure that's not great.

[@BowenAero]

And that is why Skytrax has made an upgrade, see video here kzbin.info/www/bejne/jH3CfKR9gZaImKc

[@tamiamibusch]

@@BowenAero good on them for an upgrade but I think this shows the product was never tested properly for reliability. I doubt the upgrade was tested properly either.

[@BowenAero]

@@tamiamibusch I am one of 4 that are testing the new design. We are all very happy with the results. Maybe you don’t understand the experimental part of an experimental airplane.

[@tamiamibusch]

@@BowenAero I guess not even though I have built experimental aircraft for my own personal use. So what is the current mtbf then for the gearbox predicted and guaranteed?