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mattswan267

Fuel injected yz250 two-stroke

23 posts in this topic

The first fuel injected two stroke (to my knowledge) dirt bike is here. With dramatic power gains and better throttle response. Take a look at it in my garage. Give me your opinion on this set up.

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its based of an early MRD injection set up for a 750cc twin cylider watercraft. I cut the throttle body in half. I Machined up an adapter plate to fit the stock cylinder, As well as an additional spacer to allow for clearance of the T-valve from the cylinder. Throttle body volocity stack had to be machined of at an angle and aluminum tubing was welded to the throttle body and routed to the stock airbox. A barrel valve is mounted within the throttle body which moniters how much fuel is delivered to the injector. Acess fuel is pumped back into the fuel tank via low/high pressure return lines. As for the fuel pump(keep in mind this is a mechanical injection set up) is mounted directly to the water pump, and driven off the impellor. This set-up dramatically increased horsepower all across the powerban. massive low end power increase. If you have any questions about this set-up feel free to ask me.

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As of right now this set-up is a prototype. They may be for sale in the future. this set-up has yet to be track tested and there are a few bugs i need to work out of it.

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its based of an early MRD injection set up for a 750cc twin cylider watercraft. I cut the throttle body in half. I Machined up an adapter plate to fit the stock cylinder, As well as an additional spacer to allow for clearance of the T-valve from the cylinder. Throttle body volocity stack had to be machined of at an angle and aluminum tubing was welded to the throttle body and routed to the stock airbox. A barrel valve is mounted within the throttle body which moniters how much fuel is delivered to the injector. Acess fuel is pumped back into the fuel tank via low/high pressure return lines. As for the fuel pump(keep in mind this is a mechanical injection set up) is mounted directly to the water pump, and driven off the impellor. This set-up dramatically increased horsepower all across the powerban. massive low end power increase. If you have any questions about this set-up feel free to ask me.

thats cool , but I did the same thing with my 94 KX 250 in 94 , I have it on VHS , I am Dave Harryman the owner of MRD fuel injection now MRD-RACING so its not as cool as you doing it :thumbsup: and just so you know Marty Smith had a CR 125 with MFI in the 70's

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I looked at your pics , and that is a 650cc Kawasaki throttle body those are 46mm bore , the 750cc stuff was 50mm and had the same reed cage as the MX engines so I just had to cut off the extra cyl and bolt it up , nice work:thumbsup:

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thanks! Yeah i think my throttle body is the one off of a 650cc. we had a bigger one for the 750cc i assume. my dad had this set up on a 580cc banshee in the 80's. My dad is the owner of Twister Crankshaft. Are jets still available for this kit?

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thats cool , but I did the same thing with my 94 KX 250 in 94 , I have it on VHS , I am Dave Harryman the owner of MRD fuel injection now MRD-RACING so its not as cool as you doing it :thumbsup: and just so you know Marty Smith had a CR 125 with MFI in the 70's

not sure if this is the same thing but i was looking at a popular cycling magazine from 1974 the other day and some company was marketing a flat slide diaphram type pumper carb like on a weed eater but bigger and they called it fuel injection.

not exactly sure but this might be the same thing on the yz250, but i think that is still considered a carb?

definitely cool though, might think of doing this mechanical fuel injection on a 125 so i can run e85 because it will be 106 octane and cheap!!

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thanks! Yeah i think my throttle body is the one off of a 650cc. we had a bigger one for the 750cc i assume. my dad had this set up on a 580cc banshee in the 80's. My dad is the owner of Twister Crankshaft. Are jets still available for this kit?

it is a 650 jet ski t-body and there were adaptors to put it on a 750 , the Banchee t-body's were a 550 jet ski t-body with an adaptor to fit them to the banchee , I closed MRD injection in 99 and cant service any of the units anymore because all the left over parts have been used up over the years helping guys keep thier stuff running , I would be surprised if your unit is assembled correctly and has all the needed components to work properly , you almost have to be a experienced MFI tech to tune one of these units if it is not setup correctly for the application

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Ill try to make i video lol...

Please!!!

Your starving us of information. It's like having DD's shoved near your face bouncing up and down saying "Look, but don't touch" when you paid 500$ and thought you were going all the way!

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it's a nice little setup, particulary for a home job, however TM has realised in europe an EFI 125 two stroke, using a similar system to current 4 stroke systems, still run's pre mixed fuel.

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