Yamaha YZ250/WR450 Turbo Tracker/Supermoto

jdyer8989

Member
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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jdyer8989

Member
The moment of no return!



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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jdyer8989

Member
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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NoRiders

Well-Known Member
Basic tooling still gets the job done, nice one. The frame down pipes look spot on...'cos they are!! Will you be drilling, sleeving and bolting the mounting points or welding?
 

jdyer8989

Member
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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der_nanno

Faster!
Where do you want to place it and how much space do you have? I found (when working on cars) that one-off ally radiator cores aren't very expensive anymore these days, if you are able to TIG-weld ally yourself.
 

Popeye SXM

Also used for MX
I'm building a special using a DZR400 as a base. I am going to fit a CR250 rad across the front. It is more square than the SV (a little narrower), fits great above the header and just clears the triple clamps. It feeds top left and exits bottom right so fit easy fit with water pipes. Great project thanks for documenting
 

jdyer8989

Member
@Popeye SXM , thanks for the info. I'm guessing your talking about the single CR250 radiator. I never knew they came in a single unit, It looks like it could be a perfect fit! Would you mind measuring the overall length and width? I can't seem to find the dimensions online.
 

Popeye SXM

Also used for MX
No problem. Next time I visit my garage, maybe tomorrow, I will measure it and get some pics for you. I bought a cheap Chinese knock off from ebay with a 40mm core
 

jdyer8989

Member
The exhaust mock up has started. I purchased a TCbros XS exhaust kit to make the exhaust. It came with various bends, head flange and collars.

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The collar was so close to fitting, but needed to be turned down a few mm to fit theWR exhaust port. Mini lathe to the rescue!

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I bored out the flan bolt holes and got it to work for now, but will eventually make a new flange. The front half of the exhaust was mocked up and tacked. I'm thinking one piece all the way to the turbo will be a pain to fit between the frame and engine so I will make the second half of the exhaust connect with a v-band. Now I need to finalize the turbo position so the second half can be finished.

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