912 Big Bore

[av8rps]

I have a question about these big bore kits? Do you need to utilize a rotax airbox that brings in cool air to make max power?

Also, for us guys that are still running the 912ul, does anyone know if we would see a horsepower increase like the 912ULS does of 5 hp when adding the airbox? I always thought it would stand to reason that the 912ul would benefit from that, but never found people as knowledgable as what I see on this thread to ask. So what do you think?

Paul

[moving2time]

First saw some of the discussion on these big bore engines a couple of weeks ago. I have been searching the web for other information and I cannot find anything other than coments from various forums regarding the Zipper modifications that have been refered to so frequently. The only real information I have come across is the EdgePerformance web site.

Are the Big Bore kits that Big John and Mr Bill installed manufactured by EdgePerformance? Are the other gentlemen mentioned US distributers of the EdgePerformance parts or are they manufacturing their own kits that they are refering to as the 1622 Zipper?

I am hooked on reading the work on the installation of these Big Bore modifications and I love the potential that they bring to the 921 engine. Confused because the EdgePerformance kits are 1484 and 1693cc mods and all the references here are saying 1622cc. Leads me to believe that the Sippers are not related.

Big John or Mr Bill, are you concerned at all about these mods ending any factory responsibility for your power plants? Would a 921 class help with the installation of these mods?

So much to learn. I need video and way more photos. Sounds like I need to start looking for a used 912UL engine. Joe B

[WWhunter]

JoeB.,
Reread through this entire thread and you will find that the Zipper kit is sold via a couple different sources. Jay, Hal, and ? (I forget). They are advertised on Barnstormers. I bought the kit and it is fairly easy to install. I only have about 5 hours on it so far and other issues have arose that have limitecd my time on the engine. I will say it definitely adds power over the stock configuration.
Mine is 'runnng rough' and I am going to tear into the carbs today and rebuild them.

[BigJohn]

Lots of questions but that's what happens when something becomes popular, in prior forum posts you can find contact info on where to obtain the BigBore Zipper kits from Hal, Jay or Wayne. these are not Edge kits I believe they are a much better quality conversion than Edge but I am not the expert just the test pilot for the 1622 Bigbore. I run this conversion without an Airfox but know individuals running the 1484's with and without airbox's, I just don't have it installed at this time, certainly would help having cooler air but my design allows a lot of outside air to flow over the air filters. I now have just over 100hrs on the 1622 and about 50hrs on the 1622 with the high performance Cam installed, a strong 120+hp probably more like 125. The 1484 105 hp and 1484 114hp are available for purchase and there are several already flying, I am sure that they will offer the 1622 in the future as all continues to go as expected and I get some more hrs on the test engine. We have opened it up 3 times now during the test and see no issues at all. The 1484 kits are bolt on, The 1622 will require machining of case and heads.

Contact info:
Jay 775-388-2046. Nevada
Hal 775-934-5714. Nevada
Wayne 951-255-9144. Southland Rotax. S. Ca

[moving2time]

BigJohn, Thank you for the reply. You answered the big question I had regarding the Zipper and the Edeg kit. The next biggest question I have has to do with the milling that is required for the bigger kit install. I assume that you are milling something on the block. What are you milling and is it a critical set up ie: exactly parallel to the face of the block or is it just the rough removal of something in the way? I don't understand the value of teh air box but perhaps as you write more about your experience with your engine mods I will learn. So much to learn! Joe B

[BigJohn]

BigJohn, Thank you for the reply. You answered the big question I had regarding the Zipper a Joe B

Joe B

On the 1622 BigBore (which is not yet available, Still being tested) does require the case to be split and the cylinder sleeve openings machined out to fit larger cylinders, As well as a change of the Cam, likewise the Heads have to be machined to fit the larger cylinders, This keeps thicker Cylinder Walls to handle the power increase. As far as an airbox is concerned in most cases it allows cooler air to the carbs, cooler air is richer and thus produces more power I believe the formula is for every 10 degrees of air temperature increase to the carbs you loose 1% Hp, engine heat can increase air temp to carbs by 40 degrees or more thus a decrease of 4+HP.

[BigJohn]

Bigbore running great, Only issue I have had related to it is my Prop has been to small 70" Warp, So just installed the new 75" Whirlwind, Wow, now I can use all that extra power, Innitial tests show a significant increase in Climb, Slightly slower cruise speed but heck I pitched it for Climb performance primarily and cruise second. Could still get greater climb but need some of the cruise.

[rdooley79]

I bought some extra kitfox parts from Jay a few months ago. He's a good guy. At the time he was installing the first of these kits. Talking with him (he's so excited about the zipper) and buying from him.
He's a straight shooter and honest.

[kananaskis]

What are the fuel requirements for the 1622 kit? Will it use regular MOGAS with alcohol?

If not, will there possibly be a lower compression version in the future? What do you estimate would be the power output for a regular MOGAS using version?

Also, is there any more news about the test engine's progress?

If converting a UL 80hp engine, is there a preferred serial number or manufacturing date range to look for, especially regarding the gearbox or case strength?

[KitfoxJ]

Hey Kyle
We can build you a 1622 9.7:1 for 87 oct producing 115 HP.
When you find an engine. Get me the serial number and I will research it. A 4400000 up will be good. With steel inserts instead of helicoils. Only worries with the ethanol is like with me and my Kitfox older fiberglass tanks but not with anything to do with the engine.
Latest ZIPPER customers are in OR, TX, OH, CANADA, South Africa, and Me on my Model 4 as of yesterday, two hours.
We sent out another complete rebuild w/1484 11:1 with our New Cam. Not yet installed but I'll keep everyone posted.
Thank you to all of you who have purchased the ZIPPER BIG BORE KIT.
Jay