HKS Install

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Posted (edited)

Just sent you a PM. My carbs are at idle with the cables unhooked.  The butterfly is fully closed held there by the springs, indicating idle condition. Pulling on the cables opens the butterfly against the spring tension. Scared me there for a minute! Different carb set ups for different engine configurations. All depends on which side the spring is hooked on. One side is full throttle and the other side is at idle.

Edited by Allen Sutphin

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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

My understanding is that if in flight you lose throttle linkage, the throttle goes to full power which allows you to keep flying vs forcing you to land.  Control the speed with mags.

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Posted (edited)

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

My understanding is that if in flight you lose throttle linkage, the throttle goes to full power which allows you to keep flying vs forcing you to land.  Control the speed with mags.

Yes, that is the idea I've heard as well.  It's just that it's opposite from what lots of light plane flyers dealt with on 2 stroke engines.  And for that mater on larger planes as well. No full throttle spring on our 85 HP continental on the Chief.  JImChuk

Allen, never did get any private message from you today...

Edited by 1avidflyer

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Posted

I think the bigger issue is to not let them deteriorate to the point that they would fail.  Chances of both cables failing at the same time is rare unless there is a splitter involved and a single cable running to the handle.  If one of the $1 springs fail, or something as simple as that, your done.  Besides my next machine, if there is one, will have a Lyco or Cont on the nose.

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Posted

'T' handle made and installed. Now to hook up cable. Since there is only about 2" throw on the carbs, I changed the leverage to allow for small adjustments.

Throttle 001.JPG

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Posted (edited)

I need some nerve medicine, just took a grinder to an$800 exhaust system that was on the HKS. Did get the muffler mounted where it will live. Now to make the pipes match the intakes and the exhaust flange. Had no takers on barnstormers so spent a couple hours engineering the exhaust. Hope the HKS is worth the aggravation of the installation.

Edited by Allen Sutphin
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Posted

Only way to know for sure is to:  Get er done!   JImChuk

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Posted

I am cuttin' an a slashin' like Edward Scissorhands! Cut it off twice and its still too short!

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Posted

This is interesting.

May I ask how much heavier the HKS engine is than a Rotax 2 smoke ?

I'm curious to know as I am building a Kitfox 2 with a KFM112 engine and that is deffo heavier than a Rotax.

Will you be putting your battery and header tank behind the seats to help with c of g ?

If so, how are you routing your fuel pipes and breather system ?

I have twin tanks also.

Cheers.

Skelly.

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Posted (edited)

The HKS is approx. the same weight as a 582. Maybe a tad less depending on the installation.But it is also 5 less horsepower. I have a 3 gal header tank behind the seat along with 2 6 gal wing tanks. Factory states 126 lbs flying weight of the HKS, then add eng mount and prop. I've always added 10% to the factory published weights for actual flying weight. And have been pretty darn close most times. The exhaust will have to be custom fitted and made. And its going to be challenging to say the least.

HKS install 001.JPG

Edited by Allen Sutphin
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Posted

There is an HKS on FB for sale that came off a Kitfox.. Has the exhaust system and oil tank included.  Not sure on the motor mount.  $5000.  JImChuk

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Posted

There is an HKS on FB for sale that came off a Kitfox.. Has the exhaust system and oil tank included.  Not sure on the motor mount.  $5000.  JImChuk

Don't want to waste any more cash on experimenting or at least not that much when all I lack is the exhaust pipes. May have found a temporary solution, 1 1/4" flexible exhaust tubing. Not really a long term solution but would get it running and flyable. At least I would have time to work up a permanent solution.

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Posted

Allen,   wasn't meaning for you to change things to the FB guy, but saw it a day or so ago, and thought I would mention it.  Keep plugging, I want to hear some flight reports soon...:-)  Maybe Skelly will snap it up...  JImChuk

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Posted (edited)

My misunderstanding! I give $5500 for mine with 80 hrs on it. And have to convert it from a pusher to a tractor configuration. That work alone probably adds another $500 to it. No sense in being stupid if you can't prove it now and then!

Edited by Allen Sutphin

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Posted (edited)

Well I finally got the exhaust system made up and tack welded. And the dang thing fits. Now to find someone to do the final welding on the stainless steel pipe. I temporary used a steel rod and torch to hold everything in alignment till I get it final welded. Progress can now move forward. Exhaust about drove me crazy as an outhouse rat!

Edited by Allen Sutphin
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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

That is correct Jim, bikes using these carbs are NOT configured to go wide open but default to idle.

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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

That is correct Jim, bikes using these carbs are NOT configured to go wide open but default to idle.

Mine go to idle per spring tension. Had to go buy four stroke oil today, strange, never done that in several years! Always been two stroke oil.

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Posted

I got a real good deal the other day on oil for the 912.  Couldn't find anymore Valvoline 4 stroke motorcycle 10-40 oil in the local stores.  Went to ebay, got a 6 pack of the oil for way less then the going local rate, and they combined shipping so I only paid $5 for the shipping on the 6 quarts.  And it came right to my door a couple days after I ordered it.  Pep Boys was the company that sold it to me.  JImChuk

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Posted

The HKS manual said pure synthetic oil and most use Mobil 1 in their engines so that's what I got. Oil filter from NAPA so those two things are locally available. Some stuff is pure Yamaha crossover stuff, like coils, regulator,etc. Don't know yet about the CDI boxes, but I suspect they are or can be found somewhere besides HKS. HKS took their price list from Rotax and we know what those prices are.

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I got a real good deal the other day on oil for the 912.  Couldn't find anymore Valvoline 4 stroke motorcycle 10-40 oil in the local stores.  Went to ebay, got a 6 pack of the oil for way less then the going local rate, and they combined shipping so I only paid $5 for the shipping on the 6 quarts.  And it came right to my door a couple days after I ordered it.  Pep Boys was the company that sold it to me.  JImChuk

........and what kind of oil would that be?  Are you using same in Jabiru?

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Rotax 912 needs a motorcycle type oil, Jabiru runs aircraft type oil.   I run Phillips XC 15/50, but have ran Aeroshell 15/50  as well.  JImChuk

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Posted

Got the exhaust installed and mounted in the cowling. Baffles made and installed.  A couple little minor things to do and then add oil and see if it will start. Still have to do a new W&B and see how much weight she gained with the HKS over the rock crusher Hirth..If I have to add weight to the tail I'll use shotgun shot. Its easy to mold into different shapes to mount in the tail area. Hopefully very little weight , if any.

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Posted (edited)

Well the HKS fired up and run! Smooth as silk. Did have some EGT issues to work out. But a smooth running engine. EGT's are running way too high. Since I changed the intakes and brought the engine to a higher climate, re-jetting might be in order. Easy starting. Smooth idle at 1250 RPM which tells me to add more pitch to the prop which goes along with high EGT's.

Final HKS 001.JPG

Final HKS 002.JPG

Edited by Allen Sutphin
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Posted

4 strokes run way higher EGTs then the two stroke, but you probably know that.  What does your manual call out for EGTs with the HKS?   JImChuk

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Posted

I think max is 1400 but I checked the main jet and it is 125 which is for the curved manifold. I now have the straight ones (I made) which calls for 135's so that's part of the issue. Plus most likely prop isn't loading the engine enough so need to add a tad more pitch also. Probably too little pitch is the reason it will idle at 1250 smooth.  I couldn't believe it when I went down to idle and it settled on 1250 and sat there purring. But at least I know I got the wiring correct and oil pressure came up to normal pretty quick. Always a little tweaking to do to get everything set just right. I'll wait till I get the new jets before I do anymore run-ups. But so far, NICE!

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