Your a tough SOB Ed! I remeber you've been through a lot in this life, but maybe that was all special training for this big fight right now. This one's been extra tough but I'm not worried! See ya back here soon!
Thanks everyone for tuning in here and watching over my work. I really do appreciate it and welcome the experienced oversight! Most of my info is well known to the old pros on this site I'm sure, but hopefully I can contribute a little here and there sometimes to pay ya'll back for watching over the rookie. And hopefully this "ordinary guy" build thread will inspire others that: "if THAT guy can do it.... I could do it!" LOL Here is a video I made of coping the tube:
Ok guys. Looking for help and input here! This will be a big project for me and I'd like to lay out my plan of attack for ya'll to review as I go. It's a such great group here and I will be thankful and greatful for everyone's help.... please don't hold back if you have an idea or advice!! I also hope that this build thread will provide good info for anyone interested in the Yamaha power option. Hopefully people can learn a little from both my successes and from my mistakes. First a little about me so you know what you're up against! Not an EAB builder. Reasonably decent mechanic, but not an experienced fabricator. Aero Mfg. Engineering B.S. degree which helps a little, but mostly put emphasis on the "B.S." since I never actually worked as an engineer. Also keep in mind that I am interested in a functional and safely done repower and install here... but this is NOT going to be a "show plane", so looks, beauty, and a perfectly "clean" install are low on the priority list. So I got my bird crammed into my garage yesterday, pulled the prop of the subaru and am getting ready to dig in. Here's my initial game plan: 1. Take lots of pics of the sooby and measure up location of prop flange to hopefully eliminate too much cowl rework in the end. 2. Pull the motor and take a look at the soob motor mount. I was considering building off it if possible to simplify the fabrication process. Any concerns with that? 3. Get things lined up, plan for airbox and exhaust, then tack together the new mount. I am a novice welder and own only a cheapo wire feed welder. I'd plan to emulate what others have already done and fishmouth the thing together and just tack it, then send it off to a pro to TIG it up and powdercoat. (I'd be glad to hire out the entire mount fabrication but so far I'm the first guy I know of to put a Yamaha in a Kitfox, so it would presumably be hard for someone else to build me a mount without a KF5 firewall jig and a RX-1 motor laying around) Any ideas / thoughts?
The one simple tip I've got for ya (after a couple ground loops of my own early on) is to chant in your head "go around... go around.... go around" as you come down to touchdown. If it doesn't setlle on just right... or if it gets the tiniest bit squirreley on rolllout, put some power in (bringing the tail back to life) and go around. With that in my head (cocked and loaded to go around) I haven't had any further stories to tell... but I have gone around plenty of times!
Thanks for the thanks! I'm just glad if I can help other people out (half as much) as I have been helped along in this project! That R1 box has only been used by one other AFAIK. That is "Yooper Ed" here in the group, but he doesn't frequent the forum often. According to him, it merely required a jetting change (he drilled out his main jets to about 180 size) and he says it runs great. His info is why I chose the R1 box but if you have room you that snowmo airbox will work great as well. But as far as the jetting / tune, no matter which airbox you choose, you will have some fine tuning to do and really should run an AFR guage to get precise jetting for your particular setup since it seems each plane runs just a titch different due to ram air effects and exhaust system differences. Just be sure you dont run avgas on the AFR's O2 sensor! Hey, start up a new post with your motor project! I'm really looking forward to seeing it come together!!
OK, I've got a couple updates here that I'll copy over from the Facebook group.
First I'll post up some conversion tips I have learned from those who have built and flown the Yamaha, then I'll post up my (slow) progress in my build.
CONVERSION AND TUNING TIPS, Yamaha RX-1 engines ---- Airbox considerations: The snowmobile airbox is large and difficult to fit under a cowl, but when it is used, the RX-1 jetting (135 mains) and setup is fairly close to final tune. Typically, smaller custom airboxes are made and, generally speaking they tend to run leaner... requiring larger jetting (up to about 180 sized) to achieve the correct air to fuel ratio. An airbox is generally needed to buffer under cowl turbulence and allow for consistent pressure across the carb rack (RX-1). Individual filters on the carbs have been reported as highly problematic, especially at higher speeds / cowl pressures. Carburetor venting (float bowl) needs to match internal airbox pressure and not the under cowl pressure. This is typically done by running venting inside the airbox. (See note below) Also the crankcase breather is vented into the airbox. It should be noted that when rerouting the float bowl vent lines into the airbox that you should have a way to allow for fuel overflow to exit the bottom of the airbox. I have seen a stuck float in sleds where quite a bit of overflow comes out of those vent lines and you would want a way to evacuate that excess from the airbox and route it to a safe exit point. This airbox exit will also serve as a oil exit if any were to "burp" through the crankcase vent line in the airbox. I ended up going with an airbox off of the Yamaha R1 motorcylce (same engine block as the RX-1) and will make a seperate post on that. ----- Header construction: I chose a custom header from a pvc mock up kit that I will do another post on below. (Pic of my mock up below) Header primary tubes (prior to collector) need to be as long as practical (24"+ ideally) and as equal length as possible. A 4 to1 collector is common in the R1 motorcycle header, snowmobile exhaust (which is later split to dual exhaust) and aircraft fabrication. 4-2-1 designs have also worked very well. The primary tube ID on the RX-1 is 1.28 and 1.38 on the R1 (which uses an EXUP type valve in the collector to "choke" at lower rpms). So there is a 1-3/8 size that is ideally used (It can also be found as a 35mm metric size). It comes out to a 1.37 OD and about 1.32 ID. Keeping proper tube dia, long (and equal) primary length, and smooth inner tube transitions will help throttle response. If you try to deviate from those things too much your run quality will likely suffer. - Modding headers from other vehicles: Using a pre fabricated header off another vehicle can work well for non-cowled applications. For planes with a cowl, I found that the rework on any of these options outweighed a full custom fabrication. Some people have successfully used motorcylce headers such as from the R-1 motorcycle and 07-08 gsxr 1000. The motorcycle headers run about $50 on ebay but are sometimes made of titanium, so modifying them can be problematic. The 1990's Honda Civic headers have identical port spacing and are avail for $60 in steel and stainless steel but the tube diameter is a smidge on the large side which makes the "step up" transition from the snowmo flex flange output a bit problematic and there can be a little bit of throttle lag / hesitation when using tubes that are too large. Suzuki samurai headers have also been used and line up well with the head, but like the civic header they do not bolt right up, so you have to cut them and weld in a flange adapters. If I were working with the civic or samurai header I definitely would buy the one piece header flange (with stubs) for the yamaha 4 cyl from GP Headers to save a ton of time and frustration getting these headers matched up to the head. www.gpheaders.com - As far as mufflers, I am using a 2012-14 gsxr 1000 muff For those of you that have the yamaha three cylinder you can use the yamaha yxz 1000 side by side header pipe . Same engine nice long sweep headers that curve down. (See pic below) --- Tuning with the AFR guage: Some guys here know a ton more about the afr guage than I do, and which one is best to buy. I'll leave it to them to post up their opinions. But generally speaking, my notea show that we should be looking for Air to Fuel Ratios of about 18:1 at idle, 13.5 for cruise, and a little richer for WOT.. about 12.5 to 13.0 Teals note: I have ran a few RX1 aircraft and noticed that a leaner idle (17-19) seems to work really well. I have found that if i set the AFR at 13-14) at idle it will have a little rough spot around 4500-5500 rpm. --- RX-1 Jetting Ok. The RX-1 uses altitude compensating Constant Velocity (CV) carburetors. I'll let an expert explain how they work via the vacuum slides (yamaha calls them "piston valves") in front of the throttle butterfly, but generally speaking the vacuum slides have a spring that can be changed for tuning purposes, the main jets can be changed or drilled out to enlarge, the needle position (in the vaccum slides) can be raised and lowered, and the idle mixture adjustment made via a fuel screw. Alternate vacuum slide springs and main jets are available from Holtzman (Steve Henry's setup uses the blue colored Holtzman slide springs) NOTE THAT IF YOU CONTACT HOLTZMAN, TELL THEM YOU ARE TUNING A "SNOWMOBILE"! They don't understand experimental rules and are a little nervous about supplying parts for aero use. http://www.holtzmaneng.com/carburetion-products - As far as drilling main jets, If you have a full drill index you can open your jets up. A 135 main jet is 1.35 mm in diameter or .051" - Teals note: These carbs have 3 jets. A idle jet thatvis normally a 17.5 (.175 mm) a main jet (stock is around 135) and a starter jet (choke or enficher circuit). The idle jet is used up to about 1/4 throttle then the the needle positioning inside the the needle jet sets mixture. As the slide rises and the needle rises out of the needle jet (needle is tapered so the more it is pulled out the more fuel can pass) the more the main jet controls mixture. The main jet controls mixture mainly at 1/2 throttle and above. More so at 3/4 to wot. The needles have 5 positions just like most other carbs. Needle position is used for midrange tuning. There is also a screw on the bottom of the carb that sets air fuel ratio at idle and just above idle. One other thing ive noticed on a number of RX1 carbs ifs that idle jet is opened up. Im not sure if by normal cleaning or drilled. The hole in the idle or pilot jet is tiny at 17.5 (1.75 mm or .007" in diameter). One way to tell is to measure the cleaning wire with a caliper and see how it fits in the jet. Ive found that running these engines with opened up pilot jets causes a slightly rougher transition to the midrange and doesnr idle as smooth. Also this jet doesnt have anything to do with what airbox your using because at what throttle position that these jets are being used at the slides are causing the correct back pressure. Unlike when the slides are opened up at higher throttle settings and there is a lot of air flow through the airbox. FUEL TYPES: The Yamaha manuals call for a min octane of 86, and use of fuel with ethanol up to 10%. That ethanol content may not, however, be suitable in many aircraft fuel systems. As far as 100LL, the three main concerns are in lead contamination on the valves, O2 sensor (if equipped), and oil. The screenshots below are advice from members here about the lead problem, but it should be noted that no problems have been reported in occasional use of 100LL (when that is all that is available) from flyers of the Yamaha. Consensus here probably being: If you run avgas (100LL), do so sparingly and remove your O2 sensor when you do. If you run it more often, use the appropriate oil, plan oil changes more often, and use additives in the fuel that help reduce lead deposits. Running it exclusively is not advised, but no one has yet found the exact results in doing so.
COOLING SYSTEM ROUTING: Reference the pics below of the cooling system components where each port is labeled. (NOTE: Pics are of an RX-1. As I understand, the APEX should be the same except it would not have C1,C2, or H2 connections.) The matching connections are listed here: H2 goes to C1 H1 to 10 X2 to 14 X1 to J I to the engine block below the headers H is cold feed from radiator 13 "T's" into that cold radiator line connecing to H (13 is a cold engine bypass route (bypassing radiator) when t-stat is closed, see hand drawn diagram below) 11 is Hot outlet off expansion tank (white tank in my pic) which goes to hot side radiator. C2 to K B1 to L 12 is unused, and can either be capped off or drilled out and tapped to 1/8 NPT for a coolant temp sender (note that aluminum is thin for tapping, so take caution if you choose to thread it)
CRANKCASE BREATHER: The crank breather is labeled in the bottom pic here and it this is connected with a hose to an oil "trap" (top pic) and then typically routed into the airbox, but some people have reported just running it to a negative pressure location (non ram air location) with a filter at the end of the breather hose.
I had the same thoughts guys, and have had 16 subaru cars in the family with millions of low maintenance miles on them. But here's what I came to: Subaru car runs avg 2800 rpm and what maybe 60ish hp avg cruising along at highway speeds. The Subaru in airplane works much harder for sure, and is typically modded up for more hp, which I find troubling. The yamaha on the other hand runs 10,300 rpm in a snowmobile and the R1 motorcycle that the engine was born from raps out 15,000! Stock HP is 140, but sled guys run turbos in the 200+ HP range with very reliable results. It therefore, conversely to the subaru, is running detuned in the airplane (which I find comforting) at about 9200 rpm and is internally geared at 1.19 to an output shaft rpm of 7700 and 125-130 hp. The snowmobile guys have reported it very reliable with many machines over 30,000 miles (approx 1000 hrs at an avg speed about 30-35 mph) and mote than one example with over 100,000 miles. That can be contrasted to the generally accepted rebuild time for a 2 stroke snowmobile in the 6,000-9,000 mile timeframe. Is the RX-1 perfect in the snowmobile? NO. Do they break down or fail in the snowmobile? Rarely, but yes. But so would some Subarus that were modded up for more hp by shaving heads and changing cams (as I understand my 118hp NSI e-81 was). Especially if that modded subaru car was pushed for near max hp for 10 min straight like it often is during takeoff and climb in an airplane. Yes, sooby lovers, they do do well in airplanes, but they are not perfect either! So along those lines of thought I found more comfort in the Yamaha over a Subaru (detune vs. "uptune"). The big question then was how about yamaha over rotax (912/914). To that I entirely concede that a 80 or 100 hp rotax has an outstanding reliability factor, with decades of data to back it up. Problem for me is that I want to run a continuous 100 hp, with 130 available to get off the water and over the hill on the other side of the lake. Rotax wouldn't do that unless I did a zipper type kit. But a zipper kit strips the top half off that ultra reliable rotax and replaces it with aftermarket parts... and again we are trying to get MORE out of an engine than it was designed for, instead of detuning from it's design. That (zipper) was going in the wrong direction for my taste, and also way out of budget. So then along comes Steve Henry. The first big name to run the RX-1 in a fixed wing plane, tune it correctly, push it hard, and prove it out. Teal's kit had been out for a few years (run mostly in gyros) and the motor and c gearbox proved to hold up well, then Steve proved it for us airplane guys and worked out some important details along the way. With steve now at about 500 hours between his yamahas, and 20 or 30 other skytrax conversions along with approcimately 100 other Yamahas out flying, so far we have no reports of engine failures and only two reported significant malfunctions, both in the rotax c gearbox due to improper assembly on one and the pinion shaft bolt coming loose on the other. In both cases, the gearboxes held up for some time before the problem was noticed and the pilot did not suffer power loss. So the track record in the air has been very very good so far. Anyhoo, with that background on Teal's Skytrax kit, along with my experience with my RX-1 snowmobile, I decided to move ahead with this project. And as with any single example of a particular plane and engine, only time (and some luck) will tell if I made a good choice
My throttle cable "cylinder " hole will get drilled through other half after welding (pic below). Also the spring in pic above is obviously there to balance out the throttle return spring on the carbs / throttle bodies. I got one at ACE hardware that was strong enough to naturally pull to about 3/4 throttle, which under some failure scenarios would leave me with some thrust in the air.
THROTTLE REVERSER: Since the yamaha snowmobiles use a "pull" throttle, there is a need to reverse that to a "push" for aircraft use just like the 2 stroke Rotaxes. Yet another big thanks to Steve Henry for sharing his ingenuity. This time on his panel mount throttle reverser. Steve also sells these at a very reasonable price. When I counted my time, welding, and materials, I was none ahead in doing this myself, but was itching to work in the shop today and knocked this out. Pic with tape measurer is the one steve shared, other is my copy ready to send to the welder who will cut my throttle control hole and tig up 3 places. And YEAH, my "rivet in pivot" is temporary!
I count our freedoms in the EAB world high among those that we still have left! You imagine it... create it... fly it. And if you think about it, there's not really a lot of oversight or regulation hancuffing or confining us. I think that is so damn awesome!! Funny though how some people are appalled by the thought of things not being regulated or limited and are just beside themselves in angry attempts to take freedoms away from others. Really pisses me off. OK... hijack and rant over.
The Yamaha oil cooler is integrated on the side of the engine next to the oil filter. It routes engine coolant through it to do the primary cooling then oil also goes to the large remote tank where it is cooled further. So no addnl oil cooler like the 912. As for my external components, I'm putting the oil tank fwd of the header where ram air comes in the cowl, my belly radiator will likely get moved under the engine with an aux fan, voltage regulator + starter relay on the engine mount, and on the firewall I plan to mount the fuel pump and coolant tank. Behind the panel I have the ECU.
Being in the "vented tank" camp, I really do not want to bring us back to an old debate, but FWIW my old KF2 (with a big "header tank" LOL) would get an airlock in the feed line from the wing tank to the main "header" tank. I would draw the main tank down to about half then turn the wing feed on (in the air). Air would then rise up (mostly due to more pressure in the main due to a main tank cap tube that produced pressure better) and that higher pressure would push air (in the half empty tank) up into the feed line to the wing and "lock" out the flow. I'd have to land and blow air into the wing cap tube to restart flow. So, possibly like the OP here, I was in a situation with unusable fuel in a wing (due to more pressure in one tank than the other). Here's a possible scenario that would be like what I experienced: If his right tank pressurized better, then it may have fed better and went empty sooner. Then, when empty, the pressure tube on the right continued to push across to his feeder / header (assuming no vent from header to left tank). The pressure from the right may have had nowhere to go except up the fuel line to the left, stopping flow similarly to what I experienced. If you think about it, it would be possible, (on the ground without header tank venting) to pressurize one empty tank enough to even reverse flow or blow air bubbles across to the other tank (if it were empty enough without a lot of head pressure), and that is why I am in the camp of header tank venting. But, admittedly, this scenario I purpose only arises in the air with a significant pressure differential (uncommon) and low head pressure (low quantity in other tank). Kind of a rare scenario, and that is probably why systems without vents work just fine for people most all of the time.