HKS Install

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Posted

Getting ready to install the HKS in the model 2. Went back to the engine mount I got from TJay and a new plate and it should fit providing I move it forward 4". A lot of componets to shoehorn in around the mount. The long nose cowling I've got is the biggest drawback since it was made to house a Subaru. Want to avoid cutting it down at all cost if possible. Extend the plate, prop spacer, are possible options. Engineering begins!

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Posted

I’ve bought a proper extension of 2 inches from HKS, green sky, and I think the HKS distributor in New York State should be able to help you

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Posted

A prop extension is always an option and available. I will go to that once everything is in place and connected. Till then I'll work with moving it forward as much as possible and then use an extension if necessary.

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Posted

I'm sure you are considering where your CG will be, and if moving the engine forward to fit a cowl will negatively affect that.  I know lots of people use them, but the idea of a prop extension bothers me a little.  Any imperfection would be amplified by a prop extension, and the heavier the prop is that is used, the more that imperfection will show up in viberations and the like.   That is just my take on it, and like I said, lots of people use them, so maybe I'm just paranoid, (among other things)  :lmao:JImChuk

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Posted

CG will change and not for the best, but unavoidable unless I shorten the cowling and I HATE fiberglass work with a passion!  I'll tie cinderblocks to the tail before I'd cut the cowling. I don't care for prop extensions either but better than fiberglass work. If I had to build a cowling, I'd take up rattlesnake wrestling first!

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Posted


I think you'll be ok If I was to build a new engine mount for the Jabiru I would move it 2 inches forward.

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Posted


Maybe getting a cowling meant for the rotax would ease your install issues and not make it nose heavy.  4" is a long way to move it forwards.

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Posted (edited)

I had the Hirth mounted 4" forward of the position of a Rotax. Only this time I am using the mount I got from TJay instead of making a new mount, only making a new plate this time. CG on the Hirth was a little rearward of center CG so a tad forward shouldn't be a big issue. I can always move the battery to behind the seat instead of under the inst. panel. The battery is usually the last thing to install, depending on where you need the weight after initial CG numbers. BTW, the HKS dealer in the North East is extremely helpful in manuals and parts if needed. I was surprised that he was that cooperative on an engine that was bought used from somebody else, even though he probably sold it originally. If it runs and flys as good as it looks, then I will be pleased. Seems like a well thought out design. I never had a problem with Rotax two strokes but this engine might change my thinking. Time will tell.

Edited by Allen Sutphin
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Posted

Personally, I would try to determine the actual CG and weigh of the engine and prop combination.  Also the CG of the plane as it sits without the engine on it.  Then a tape measure, and a calculator will tell your pretty close where your CG for the whole plane is going to end up once the engine is installed in a specific location.  That may tend to eliminate some unfortunate surprises at the end,.  Being as how every thing else is finished on the plane, it should be pretty easy to get CG figures pretty close.  JImChuk

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Posted

Did weigh the plane the other day minus engine and prop and it was 370. My old engine mount (overbuilt) that I made was 15 lbs. The current mount is 7 lbs so dropped some weight there quick. Haven't weighed the engine yet, since I have it partially disassembled. Expecting to be close to same weight maybe a few lbs more. CG is going to move forward a tad per the numbers but generally stay in the middle range when loaded. And have 2- 6 gal wing tanks plus 3 gal rear header tank so a nose tank isn't in the picture. Bad as I hate to think about it, shortening the cowling is still a possibility.  Its about 8-9" longer than the standard cowling. even with all the negatives I prefer the engine out from the firewall.

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Posted

I'm not really a fan of doing fiberglass work, but every time I do it, I find it's actually kind of fun, and it turns out ok.  Last week, I did the lip on the Kitfox cowl as well as the bump out for the oil cooler.  JImChuk

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Posted

Hey Allen I have an Excel spreadsheet I designed for W/B which is setup for moving items around specifically engine changes but it works for batteries or anything for that matter.  You do need Excel on your computer or it might work with some of the Excel knock-offs.  If you are interested I can post it in the files section.  I wrote the program when changing engines in my Q2.

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Posted

Thanks, but unfortunately I still do W&B the old way. That was the way I learned 40 yrs ago in A&P school and I guess I'll continue that way. Computers and I don't make good friends since my puter is almost as old as I am. I even still use the old whiz wheel for flight and fuel problems. The batteries in it haven't failed yet and its 40 yrs old. I appreciate the offer but I am too old school for the easier way. Besides the engine has to go where it will fit or I can make it fit. Not a lot of wiggle room to play with. I was a tad tail heavy to start with when I used the Hirth. Including my 18 lb engine mount.  Yea, I know! Overkill!

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Posted

Well since I wasn't able to sell it, time to start doing things. Room under the cowl is filling up quick.

HKS install 001.JPG

HKS install 002.JPG

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Posted

Looking good Allen.  Nice to see you back again.

paul

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Posted

Looking good. I think you need to get that bird in the air. Would hate for you to sell it and regret the sale later on.

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Posted

I removed it from barnstormers due to all the tire kickers calling. In 2 minutes you could tell they were not very serious at all. I thought 13K for a new Fox with everything new, completed, minus engine, with custom trailer was a good deal. But I guess I was mistaken, again. The HKS install is not a easy thing to do but I hope its worth it in the end.

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Posted

Finally got the throttles and choke cables installed. Had to make new choke cables to fit but they seem to work. Going to have to use a 'T' shaped throttle handle to avoid building a reversing quadrant. Similar to a twin engine setup and the temp mockup seems like its going to work. The 'T' handle fits my style better than the standard push/pull setup.

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Posted

This is what is usually used on 912s or HKS.  Probably the simplest option.   Like this one.  When I started this post, I was thinking I had an extra one, but now I don't think so.  JImChuk   CONTROL, Throttle Vernier-Assist, Dual, 4 ft

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Posted (edited)

The way the carbs are positioned it requires a reversing bellcrank. Same as a 582 setup. I'll still have one lever except it will be a 'T' type throttle. It will still be shoved forward to add throttle as normal. I think, if I remember correctly, Fred Stork has something similar mounted on the left side on his Avid.

Edited by Allen Sutphin

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Posted

You know your situation better then me Allen, but looking at your engine, the carbs sit the same way as the 912 carbs do.  And the springs on the carbs make the engine go to full throttle if no cable is connected or it came loose.  As your carbs sit, a pulling motion from the carb towards the firewall makes the engine go to idle.   JImChuk

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Posted (edited)

You got me puzzled now, Jim!  Maybe I am thinking backwards as comparing them to two stroke carbs. Maybe another look is required. Never dealt with a 912 type carb before. Thanks for the heads up!  If you are correct, and I have no doubt you are, I'll feel like an idiot. Pa always said "no sense in being stupid, if you can't prove it now and then".

Edited by Allen Sutphin

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Posted

Laying on the work bench, the 912 type 64 carb would be at full throttle because of the spring on the linkage.  That is just the opposite of how the 582 type 54 carb would be.  In this picture, the carb is at full throttle because of the spring on the bottom right side of the picture.  JImChuk

See the source image

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Posted

I'll go back to the shop in a little while and see if I am an idiot.

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Posted

No need to go to the shop to find that out Allen.  We constantly tinker with airplanes.   What other proof is needed?:lmao::lmao::lmao: On the serious side, it does seem kind of backwards to have a throttle positioned to be at full throttle.  Wonder if anyone ever said, I'll just see if I can fire it up and let it idle even though everything isn't hooked up.  Wonder how high a 912 can rev with no prop at full throttle, and for how long? But that's the way it's done on these carbs.  I'm guessing the BMW motorcycles  that use these same carbs are not rigged this way though.   JImChuk

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