Boyesen Boyesen

Yz250f 2 stroke conversion 10

442 of 4089
(17 people)
McBain318
3/3/2022 9:10am
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General Info
Additional Info

General Info

Model Year
2017
Model Year:
2017
Brand
Yamaha
Brand:
Yamaha
Model
YZF
Model:
YZF
Engine Size
250
Engine Size:
250
Engine Type
2-Stroke
Engine Type:
2-Stroke
Parts
Brand
Model
Additional info

Parts

Graphics
Other
Graphics: Other
Plastic
Cycra
Plastic: Cycra
Handlebar
Pro Taper
Handlebar: Pro Taper
Grips
ODI
Grips: ODI
Clutch Lever
Other
Clutch Lever: Other
Seat
Guts
Seat: Guts
Footpegs
Other
Footpegs: Other
Shifter
Other
Shifter: Other
Exhaust
Pro Circuit
Exhaust: Pro Circuit
Clutch
Rekluse
Clutch: Rekluse
Piston
Vertex
Piston: Vertex
Air Filter
Twin Air
Air Filter: Twin Air
Air Intake
Boysesen
Air Intake: Boysesen
Fork
Kayaba
Fork: Kayaba
Rear Shock
Kayaba
Rear Shock: Kayaba
Suspension Mods
Factory Connection
Suspension Mods: Factory Connection
Tires
Other
Tires: Other
Rims
Excel
Rims: Excel
Sprockets
Other
Sprockets: Other
Brakes
Other
Brakes: Other
Brake Pads
Other
Brake Pads: Other
Brake Rotors
Other
Brake Rotors: Other
Oils Lubes
Maxima
Oils Lubes: Maxima
Additional Info
I started with a 2017 yz250f rolling chassis. Vapor blasted everything. Added all new bearings and seals. Stuffed a 2018 yz250 motor in it. Fabricated multiple engine mounts. And fabricated the intake to work with the 4 stroke air box.
Additional Info:
I started with a 2017 yz250f rolling chassis. Vapor blasted everything. Added all new bearings and seals. Stuffed a 2018 yz250 motor in it. Fabricated multiple engine mounts. And fabricated the intake to work with the 4 stroke air box.
McBain318
3/3/2022 9:10am
442 of 4089
10 comments

View replies to: Yz250f 2 stroke conversion

c50 IMG 1533 1514844760
cdoggy81
1 year ago
Awesome stuff buddy! You sure don’t see that conversion every day! Do you have a build thread on it? If so post the link please.
I noticed that intake track has some sharp 90* turns in it. I know space is limited but is there any way to smooth those out some as your probably loosing some good top end on it.
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McBain318
1 year ago
No this is the only place I’ve posted anything on it. Space is the limiting factor with my intake. I’ve only rode it once, and I didn’t have the jetting 100% because it’s still winter and didn’t see the point in wasting my time dialing it In for a random 50* day. But it certainly wasn’t lacking top end. It had a slight dead spot on the bottom that I feel can be fixed when I spend some time jetting.
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c50 IMG 1533 1514844760
cdoggy81
1 year ago
Roger that. Glad to hear she was running good then!
If you do a build thread be sure to let us know 😎
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McBain318
1 year ago
It runs surprisingly well. I’ve only been able to ride it once so far. Being it’s not riding season yet I got the jetting close enough…. When the weather comes around I’ll Take my time with it and get it really dialed in.
c50 7625CBF8 C55A 473A B56D A77C67771C9C 1545277049
thatswhathappens
1 year ago
The routing for the intake is crazy, this is such a unique build. Unique to me at least, I haven't seen anyone do this yet.
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McBain318
1 year ago
Thanks. The intake is what took me the most time. And 50% of the reason why I did it was to have something that no one else has.
c50 E2E24824 9DC5 4F83 9B48 6C1EBB1A93A2 1643055056
MotoRoss678
1 year ago
First! Awesome work!!! Second, do you have a bike build thread or pics and videos of the process?
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