Yamaha YZ250/WR450 Turbo Tracker/Supermoto

Discussion in 'Some Assembly Required' started by jdyer8989, Apr 18, 2020.

  1. jdyer8989

    jdyer8989 n00b

    Joined:
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    Oddometer:
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    Hey Everyone,

    I thought I would start to share my project now that I've passed the moment of no return. First a little background. About 6 years back I was getting tired of my current career as an auto mechanic and decided to go back to school for mechanical engineering. I have since completed my degree and working in the aerospace industry. I have always been a motorcycle enthusiast, but I have not had a bike since I made the decision to return to school. In my past I have built many bikes and have missed it greatly, so its finally time to start building again.

    The bike:
    I had to sell all my bikes when returning to school other then my 2002 YZ250 motocross bike. Why didn’t I sell it? Because I would get nothing for it, and I had too much time invested into it. It was a 2002, but I gone through it several times including a full engine rebuilds, KYB SSS suspension swap, reduced offset triple clamps from a 2014 YZ450, and the best part I had a street legal title for it.


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    The Plan:

    While at my university I was a part of the Formula SAE competition and had built a small race car for my capstone design project. I guess they were doing some shop cleaning and I was lucky enough to be able to purchase one of their used engines, a 2015 Yamaha WR450f engine. I was at the school when they were using this engine, so I know that it was purchased new and has very low hours. So, after acquiring this engine I got the bad idea to combine my street legal YZ250 frame with the WR450 engine.

    To be honest throughout my education and my current career I have become so use to creating designs and then running some form of analysis to validate the design before even creating a prototype. Obviously, there is nothing wrong with this mentality, but I feel like I need to get back to my roots and just say what the hell and chop a perfectly good frame in half before knowing it will work. Well, I couldn’t completely chop it up before checking a few things.

    First step was to try to make a somewhat accurate CAD model of the frame so I could see what the engine would look like in the frame. I would have skipped this step, but the engine also came with a 3D scan file so how could I.


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    I was able to bring the frame into my work and use the FARO arm, a portable CMM, to measure all the critical points of the frame. I wish I had a 3D scanner, but only could record the center points of features such as motor mount bolts, suspension linkage bolts, sub frame attachment bolts, etc. The recorded measurements were imported into my CAD model, which resulted in this.

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    From there I started to model the frame. I had to make several dimensional assumptions based on traced photos of the frame, but for the what I was using it for it would be fine.


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    The rear engine mount, the one through the swingarm, was the same for both the YZ250 engine and WR450 engine. This made the swap somewhat easier because I did not need to worry about the chain alignment. However, you can see this engine was not going to fit into the frame.


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    To fix this I modeled new frame tubes to clear the engine and give some extra room for adjusting the engine angle.


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    The moment of no return!

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    Next was to install the engine in to check how well the frame CAD model matched the actual frame. As mentioned the rear engine mount was the same as the YZ250 engine which allowed the engine to be installed into the frame, with the help of a strap. The sprockets lined up perfectly! It will be a tight fit for the intake and exhaust through the frame by the shock. I will need to separate the fuel injector and throttle body, the injector near the intake port and the throttle body before the plenum.


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    The engine needed to be rotated rearward to bring the engine sprocket above the swing arm which required removing the top engine mount lug. While cutting the lug out I cleaned up the cuto off frame tubes.


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    The engine has more room to rotate back. I will need to order the sprocket combo I plan on running to find the right engine position. It will most likely be farther away from the frame than this. Currently there is a 13T front sprocket and I plan on running a 15T. Its not the greatest engine position, I will 100% need to pull the engine if I need to check/adjust the valves.


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    #1
    nuggets, AK650, sidetrack one and 3 others like this.
  2. jdyer8989

    jdyer8989 n00b

    Joined:
    May 5, 2014
    Oddometer:
    8
    A friend of mine had a set of KTM 690 supermoto wheels laying around and I thought I would try to make them work to keep the budget down. I am still going back and forth on what wheels to run. I am leaning toward running a 17" supermoto setup rather than 19" tracker wheels. My goal is about 80HP at the wheel with the turbo so the wider supermoto 17" should help. It looks like I can make the KTM wheels fit with new wheel spacer, but the only problem I am running into is with the rear rotor. The YZ has a 245mm rear rotor and the KTM 690 has a 220mm rotor with a smaller bolt pattern diameter so no swapping the rotors. The two options I found are to make my own rotor or possibly use a KTM 950 rotor, which is 240mm. Does anyone know if the 240mm 950 rotor has the same bolt pattern diameter as the 690 rotor?


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    The turbo Arrived! Its a cheap Ebay GT15. It is a little large for a 450, but I have a friend that runs on on a KTM 525 with good results. I gave it my best to make a quick CAD model. Its not the great, but it is only being used to mock up other components in the model.


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    I could not justify purchasing a tubing bender for this project. I am working out a small apartment and it wouldn't be the best idea to drill holes in the garage floor the mount the bender. Since I had the fame tubes made in the CAD model I was able to send them out to have them bent on a CNC bender. It was a little pricey for only two tubes, but I could not find another way. I tried asking some local auto racing chassis shops, but had no luck. On the plus side I sent out the CAD files and one week later the tubes arrived.


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    Miter templates were made from the CAD model. The general process in Solidworks is to take the mitered tube end cut a slit down its length and then convert it to a sheet metal part. It can then be unrolled and the template can be printed and rolled around the tube.


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    No tubing notchers here. Only basic hand tools, hacksaw and a couple files.


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    After hours of filing and checking the fitment the tubes were good enough and I tacked them in with my Mig. Once everything is in its final position I will need to bring the frame into my work to use the Tig.


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    #2
    nuggets, Franque, AK650 and 3 others like this.
  3. jdyer8989

    jdyer8989 n00b

    Joined:
    May 5, 2014
    Oddometer:
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    Spent some time this weekend working on the lower motor mounts. The hacksaw and files came out again. I cant wait until I can use an angle grinder without the possibility of being evicted.

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    I am really kicking myself for this. I had a fully restored tank from an old Yamaha CT175 I built and it would be perfect for this bike. Sadly, a while ago I had no clue I would have a project like this and decided to cut the tank in half to make it into a decorative wall ordainment. I found another beat up tank which I will use but it will need a full restoration. At least I can use this one for mock up.


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    The next hurdle is going to be finding a radiator since the stock YZ radiators will interfere with the tank, exhaust, and forks. I have tried to mock up the stock radiators and see if they can be lowered or moved forward but I don't think it will work out. So far I have looked into radiators from a KLR650 and a SV650. The KLR only uses a large left side mount radiator which might work since it could be lowered due to no exhaust on the left side. The SV radiator is a front mount and may be the easier option, but I'm not sure if I will like the look of a front mounted rad. Let me know if you have any ideas for a radiator.


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    I have also been working on some ideas for the intake. One idea was to use a 6" aluminum tube for the plenum and then some aluminum plate to bring it around the shock. I was thinking about 3D printing a intake and then warping the print with carbon fiber. I had designed an intake for a formula SAE race car this way and the results were good, but in this application I am worried about the intake temps increasing enough to melt the intake. PETG filament is my go to, which has a glass transition temp of around 80°C (176°F). This is a little to low for me to be comfortable.

    I am aiming for a plenum volume about 5 times larger then the cylinder volume to help with the intake pulses. I have heard single cylinders are a bit finicky with turbos and the larger plenum volume should help to smooth thing out. The throttle body is from a newer yz450 and will sit between the turbo and plenum. Since the throttle body is before the plenum the injector hole will need to be plugged and the injector will be installed closer to the intake port.

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    Couldn't help myself, had to mock up the turbo!!


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    #3
    JagLite, Bowler, nuggets and 4 others like this.
  4. Fast Idle

    Fast Idle Since the Sixties Supporter

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    Holy hot section, you working at a turbine repair facility?
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    In :lurk
    #4
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  5. jdyer8989

    jdyer8989 n00b

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    Haha, yes sir!
    #5
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  6. Tim_Tom

    Tim_Tom Long timer

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    Awesome project! I was going to suggest putting the radiator under the tail section, but there’s a turbo there!
    #6
    AK650 likes this.
  7. villageidiot

    villageidiot Long timer Supporter

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    Very cool so far.

    with regard to radiator, a lot of flat track bikes run a side mounted radiator like where a number plate would be. Could put one there, or in normal placement and mod the tank around the radiators.
    #7
    AK650 likes this.
  8. jake28

    jake28 Riding to the horizon.

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    Bay Area, CA
    Great skills, mix of processes, and goal. This is fun to watch.
    #8
    AK650 likes this.
  9. offroadtoys

    offroadtoys Been here awhile Supporter

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    Oak Harbor, OH
    DAMN! Just damn! I love it.
    #9
    AK650 likes this.
  10. jamracing

    jamracing Adventurer

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    Holy engineering feat Batman! This is super cool, following!
    #10
  11. cedric

    cedric Been here awhile

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    Calgary
    I was kinda bummed to see that solid yz get cut up, but this looks cool!
    #11
  12. Dino de Laurentiis

    Dino de Laurentiis Working on it

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    Very cool, keep it coming! You’re right about plenum size and thumper, the larger the better so make it as large as can possibly fit.

    Curious to why you chose to mount the turbo at the rear, and why you want the throttle body before the plenum? Not that I’m doubting you’re on top of things, but what about turbo lag? Also, oil pressure to the turbo with such long oil lines?
    #12
  13. Salsa

    Salsa Long timer

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    When I was building a Crosley race car, I built and dyno'd a large plenum and small plenum with bell individual tubes to the cylinders. I was trying to see what the backside of the plenum was. A carb was feeding the plenum.
    The small plenum won big time.

    Don
    #13
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  14. Franque

    Franque Been here awhile

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    @Salsa Plenum size requirements are different for forced induction applications. For N/A applications, the harmonics of the plenum are the chief concern, whereas for a turbocharger, a bigger plenum smooths out the pulses from the turbocharger.

    One question I have: granted, I'm not an engineer, but I have a bit of knowledge about turbos.

    Why is the turbocharger mounted so far from the exhaust valves? Generally (I'm no engineer, perhaps this is a gross oversimplification), the closer to the exhaust valve that the turbo is, the more thermal energy can be captured, making the turbocharger produce boost more efficiently, and helping reduce lag. Did you relocate the turbo for packaging concerns, or do you have another motive in mind?
    #14
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  15. villageidiot

    villageidiot Long timer Supporter

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    Rear mount turbo is a thing.

    I look at it this way, an engine is just an air pump. How many revolutions of pumped air will it take to fill the duct work? 3, 5? If you can feel that, I dunno.

    The longer duct runs also act as a cooler for the turbo’d charge.
    #15
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  16. Salsa

    Salsa Long timer

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    Harmonics of a turbocharger ought to be very high !!!

    Don
    #16
  17. sanjoh

    sanjoh Purveyor of Light

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    Interesting build. Why such a large turbo? Have you seen this engine/turbo combo used before?
    #17
  18. Arktasian

    Arktasian Lets call it Naturalized

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    I'm "naturally" subscribed to any project involving forced induction, this being a remote mount turbo holds interest and thanks for posting your work.
    One thing that you haven't mentioned, but perhaps being a donor engine from Formula SAE competition - you already have a tunable ecu? If not the turbo and other notable benefits won't really be capitalized on. I'm happy to promote the benefits if given the chance. And should your system be an MS, then congrats and you'll find lots of help over on those forums, should the need arise.
    Looking forward to following.
    #18
  19. jdyer8989

    jdyer8989 n00b

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    @Franque, my decision to rear mount it was for packaging. I thought about mounting it closer to the engine, but I really don't like how the turbo would hang out. One drop of the bike and the turbo/exhaust would be scrap. I plan on riding the crap out of this bike so I'm already planing on dropping it at some point:rofl. The throttle body will need to be mounted before the plenum due to no space near the intake port, the injector will still be near the intake port. On the Formula SAE car I built the throttle body was the first component in the intake tract and throttle response was not an issue, even with a 20mm intake restrictor. The trick is to have a larger plenum to provide enough air storage for quick throttle movements (If its to large throttle response can suffer). That way the air does not need to be pulled all the way from the throttle plate to the cylinder. On the car I built we ran a 4L plenum. I do not have much experience with the turbo on this engine, but i'm thinking it can be treated like an intake restriction and the larger plenum will help compensate for the throttle body location as well as smoothing the intake pulses.
    IMG_8818 (2).jpg

    I am going to try to mount the turbo as close as possible to the engine, but by moving it forward it will need to mount lower in the subframe. I am a little worried that the wheel could come in contact with the turbo if mounted to low.
    turbo forward.JPG

    The GT15 turbo is on the large size for a 450, but I have seen the turbo in use on a KTM 525 with good results. I feel the power band with the larger turbo will actually be safer for the engine with the boost coming on in the higher RPM range. A friend of mine made 92hp on his ktm with the GT15.

    pats ktm.JPG pats ktm 2.JPG

    I will be running a microsquirt ECU to control both fuel and ignition timing. I will probably need to make a hall effect crank sensor because I have been told microsquirts don't like VR sensors to much.
    #19
  20. CRW

    CRW I dont want a pickle

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    This looks fun. Just don't loop it out!
    #20