Zipper Installation Rotax 912UL


23 posts in this topic

Posted

Here is the installation of my Big Bore Zipper kit.

 

I am starting with a 200 hour Rotax 912 UL, 80 hp engine.  It is about a 1997 vintage engine.  The engine has not run since 2009 when I bought the airplane.  It was in good running order then.  

 

I hope to document the installation of the kit as well as the condition of the engine.

 

Here is the engine fully assembled to start with the mount still attached.

 

post-36-0-96043800-1443492988_thumb.jpg

 

Here is the beginning of the teardown starting with the engine mount and rocker covers (for painting).

 

post-36-0-36152200-1443493079_thumb.jpg

 

I have scanned in the instructions given with the kit and have posted them here.

 

Zipper.pdf

 

 

 

 

I will attempt to document as much as possible.  Please try and keep this thread on topic for future reference...

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Posted

Excellent!

 

"Now go out and feel the Zip!"

 

Love that! :BC:

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Posted

My friend Jeromie just did the 104 HP zipper in his 912 Avid MK IV. What a difference. Performance is incredible...beyond incredible and it still burns 87 octane! All I can say is Holly Shit! Very similar overall performance to my 150HP Magnum. His plane is 640LB 104 HP. He is getting 1500FPM @60 full of fuel 28 gal + his 235LB body in it. I can't wait to fly it myself (150LB) with half a tank of fuel. I bet it will match the magnum.

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Posted

I did the tear down and reassembly today on the engine.

 

After pulling down the motor it was obvious that this engine ran 100LL.  And ran it improperly.  Here's the heads before I cleaned them:

 

post-36-0-70463300-1443753144_thumb.jpg

 

The assembly of the engine kit is very easy and just as the instructions detailed.  The first part of the teardown was probably the hardest:  Getting the cir-clips out of the old pistons.

 

post-36-0-60615900-1443753374_thumb.jpg

 

Once the clip is out you can tap out the wrist pin from the piston and remove the old piston-cyinder assembly.  Here's the engine with the jugs all removed.

 

post-36-0-07363800-1443753634_thumb.jpg

 

Once torn town I cleaned up the heads and got most of the carbon and lead deposits off them.  One of the heads, #3, had a sticky valve.  A little Crysoil penetrating oil allowed to soak in, then worked the valve until it moved freely.  The rest of the valves appeared to work fine and didn't require any additional attention.

 

post-36-0-77658800-1443753172_thumb.jpg

 

Assembling the cylinders to the cases was pretty straight forward per the instructions.  Getting the cir-clips in place was a little challenging, but having two people (I was working with Dave on this project) helped.  The Honda sealant supplied with the kit was good stuff, if not a little messy.  It's a very thin and stringy liquid gasket material.  The OEM cylinders have an O-ring on the base to case surface.  These do not use an O-ring, just the liquid gasket material.

 

post-36-0-65765500-1443753191_thumb.jpg

 

The heads are a metal to metal fit to the cylinders.  The instructions suggest to use a skim of the Honda sealant if the mating surfaces of the heads isn't perfect.  As you can see above the heads aren't perfect, but would probably be okay.  I used the sealant anyway.  Again the stuff is very messy to apply.  I took great care not to get any in the cylinders or case.

 

Putting the heads onto the cylinders is not too hard.  As you can see the heads have a counterbore to locate on the cylinder.  The alignment of the head is critical.  There is virtually no lead on the cylinder to align the head so care must be taken.  The kit also came with new seals for the pushrod tubes (Yellow shown above).  These needed a little help to get started straight.  Again two people made easy work of this.

 

Here's the long block reassembled.

 

post-36-0-93155100-1443753241_thumb.jpg

 

Ready to "Feel the Zip".

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Posted

Nice work and write up so far...thanks for sharing.

Ron

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Posted (edited)

Maybe I missed some of the Zipper info while being gone for a week or so - Is it bigger bore? Are the rpms the same? - Did you start with 80hp 912? Same gas, so compression is same? 104hp? Same carbs/exhausts?

EdMO

Edited by Ed In Missouri

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Posted

The Zipper Kit consists of new cylinders and pistons (with rings and wrist pins).  You reuse the rest of the engine's parts without modification.

 

The kit uses forged pistons and billet cylinders.  The pistons are lighter and stronger than the original cast ones and the cylinders cool better with 14 instead of 9 cooling fins.  The design of the pistons make the engine smoother and lighter overall by something like 2 pounds.

 

Testing of the engine has shown smooth operation up to 6200 rpm.  Hal runs his at 6000 continuous for high cruise power.  The valves begin to float at 6400.

 

This version of the kit maintains the same 9.5:1 compression, meaning 87 octane auto gas is still fine to run.

 

There is a 11:1 compression version that makes 115 hp, but requires the use of a HD starter and slipper clutch in the gearbox.  (Standard parts on the ULS 100 hp motor)

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Posted (edited)

I will have to go back to the papers on my Soob, but I think the compression was raised from about 8.7 to about 9.1 or 9.2 and the prior owner told me to use at least 91 octane in it. But he was in Canada, if that makes any difference in gasoline grades.

Sort of surprised that you can run 87 with that high compression.

Sounds like a good conversion...

EdMO

Edited by Ed In Missouri

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Posted

This from my friend Jeromie regarding his Zipper install:

Just installed the torque kit. Took 2.6 hours to install, 1.5 to test fly and retorque .  (I own a European repair shop so doubtful customers will beat that time, figure a full day for the average guy)
Took it to sulphur creek Idaho and back over the weekend. I fly a lot in the Frank Church Wilderness area. So i have solid numbers for performance before the conversion.

The Aircraft is a avid mark 4 trigear heavy hauler. Empty weight is 641lbs and gross is 1200. Engine is a 1997 vintage 912ul 80hp with 545 hours. (Engine sat in wrecked plane from 98 till 2010 when i bought it with 2 hours on it)

Home base is KRLD elevation 400ft

So 1200 lb take off was 650 ft and averaged rate of climb at 65mph IAS to 4000ft was 525 fpm on a 700ft density altitude day.

After the zipper torque kit was installed and prop pitch adjusted 3 degrees to compensate, same conditions takeoff was 400ft, average rate of climb to 4000ft was 1010 fpm.

Staggering difference.

So flight to sulphur creek Idaho, make this flight a lot. I have good numbers on this trip.

With stock engine and a take off weight of 1120 (fuel burned getting their is 80 lbs) and density altitude of 6650 ft I have approx 900 ft take off run and rate of climb of 300 fpm at 65 mph IAS. I you have been their this means circling over Morgan Ranch 4 times and ridge soaring back to landmark.

After zipper install same conditions has a 500 ft take off and 650 fpm climb at 65mph and just fly out over the canyon turn around and out of their.

Cruise speeds, well this is the interesting part. Before the upgrade I cruised at 85-90 mph at 4.0 gph. After I cruise at 105 at 4.5 gph. If you do the math you will notice i actually have better economy at 105mph with the zipper than i did with the stock. About 1 mpg better economy and going 15-20 mph faster. Gets better.....

So the round trip from KRLD to Sulphur creek used to take 5.8 to 6.5 hours and i would have between 4.8 and 2.0 gallons left over upon return. In fact i always stopped in Joseph Oregon and got 5 gallons just for reserve. Remember, always crash with fuel, not without;)

This trip took 4.8 hours round trip and burned 21 gallons of fuel.

So lets talk money and time here. I actually use my plane for transportation not just a toy. So this upgrade was done mainly for financial reasons not performance. And it paid off big. I have a place in the San Juan Islands and travel for business to Salt Lake, Spokane, Portland, Seattle (yes i use an Avid flyer like a 172, I am that wierd)

My plane costs $31 per hour to operate minus hanger rent. $41 per hour if you include hanger rent at 100 flight hours per year. I budget $4100 per year for flying. If we use the Sulphur Creek trip as a verified number then redo the numbers we get an interesting result. The plane costs $1.75 more per hour to operate (.5 gph increase in fuel). I have always planned on a 1500 hr tbo on the motor. So if i keep the tbo the same then the cost goes to $42.75 per hour with hanger. So convert $4100 to miles. Pre Zipper it was 8700 miles. After zipper it is 10,070 miles on the same money. So if i travel the usual 8700 miles it takes 82.85 hours. At $42.75 per hour that is $3541.83 per year or $558.16 savings per year. Payback is 7.7 years for the zipper kit.

So here it is in a nutshell.
Takeoff distance reduced by 40%
Climb rate doubled
Cruise increased by 20%
Fuel economy increased by 1 mpg

Now the real benefit, travel time reduction. This will literally mean less stays in hotels or sleeping bags in FBO's. Thats a big money saver.

To sum it up,
It works better than advertised, way better:)

Jeromie Mead
Richland, Wa


 

 

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Posted

Jeromie,

Thats a great write up! Thanks Bro!!!

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Posted (edited)

Av8r3400.  I'm pleased to see that your castings have the same dirt brown color as mine.  I was worried about the color because I've only seen shiny new Rotax engines in shiny new airplanes I guess.  I thought they were supposed to be silvery new looking aluminum color.  

I was getting anxious about delivery on mine so I called Wayne (Hal's partner in the Zipper project) on Friday.  The engine is still at his hangar in Temecula.  They've run it and are now putting together a dynamometer so they can actually measure power output with the engine mounted on the airplane.  I'm thinking Kool prop at the moment but may eventually talk to Prince about a fixed pitch. 

 

Carry on

Dan

Edited by Emory Bored

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Posted

Does anyone know if the slipper clutch can be retrofitted to a 912ul if one wanted to install the 1484 High Power?

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Posted

Yes.  The slipper clutch and the high torque starter (also needed) can be retrofitted to a 912UL.  To me, it wasn't worth the extra cost for another 10 hp.

 

Slipper Clutch retrofit kit is Rotax pn 996-889 for $1298.71 (12-02-2015) but requires the wide (27mm) gear set.  If you have the narrow (22mm) gears you need to replace them also.

The high torque starter is available from Rotax (889-751 - $675.63) or aftermarket for about $400.  (link)

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Posted

Ouch, that's pricey.  I agree, probably not worth the extra 10hp. And I would be a little concerned about keeping the 11:1 cool and the chance of detonation if you got some bad or in mislabeled fuel.

Thanks for posting this conversion, very cool!

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Posted (edited)

This is reminescent of the "big bore" kits we use on dirt bikes.  I wonder is there is any advantages to be gained in the carb area of the engine?

Edited by Knuckledragger

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Posted

Since the same Bing 64 carbs are being used on the heavily modified 130+ hp engines, I doubt there is much to be gained.

IMO, I would think the exhaust side is where some hp may be found.  We would loose the nice quiet nature of the engine, but could gain hp. 

Just a thought. 

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Posted

Jabiru engines use a type 94 carb instead of the 64s.  I believe the bore on the 64 carb is 32 MM diameter, it's 40 MM on the 94.  Other than that, they are very similar.   Not saying it's a viable solution for more power, but it's a thought.   Jim Chuk

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Posted

Are you going to upgrade your mount to the "Heavy Duty for 912s" that Kitfox sells, or stick with the original?

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Posted

Great info. I am wondering what is the preferred coolant in the older vintage 912 80 hp?

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Posted

Dexcool or Evans NPG+ waterless coolant which is what I am running in mine which has several advantages.  Best to refer back to the Rotax service bulletins and get it from the "source".  That way you can make an informed choice that best suits your situation. 

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Posted (edited)

I have the upgraded Kitfox mount. All they did was to add a gusset in front of the oil tank.  Most of the cracking problems were with the 100 hp engine duty to the violence of the startup and shutdown.

Dexcool is the recommended coolant by Rotax for all of their engines.

Rotax has gone away from recommending Evans unless absolutely necessary.  It's much less efficient at cooling and is difficult to service if you are away from home.  Not to mention expensive. 

Edited by Av8r3400

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Posted

Dear Sirs , Is the the mount on this engine for an avid mark IV?

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Posted

The mount shown in the first photo is a Kitfox IV mount. 

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