Anyone put a 4 stroke in a 2 stroke bike?

Treejumper

2 wheeled idiot
Damn Yankees
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#1
Hey i was thinking of putting my 82' XT250's motor in my 86' YZ250's frame. It wouldnt be pernament, just a way to allow me to enjoy the bike until the 2 stoke motor can be rebuilt right. The XT's brakes and suspension died last weekend and i just got the YZ's frame back (see post in general disscusion) and all the suspension work will be done by weekend. I just ran out of money to finish the motor and get a new exhaust for atleast a month. Sucks being poor! :( Atleast this way i would be able to ride while i wait for the motor to be rebuilt. Also i can get use to the increased ride height and a real suspension! :cool:

Anyways the 4 stroke 250 runs strong and it looks like the bolt pattern is the same on both motors. I wont know for sure until i remove it from the bike. Only thing i see is the exhaust will have to have a custom bracket made to mount the back half up with the original hanger bracket. No problem since we have a custom sheetmetal shop.

What do you think, is it doable or should i just sit on the side lines for the next month. That or fix the suspension, brakes and who knows what else on the old beater. Click here to see the old beater and deceide for yourself

Thanks!
 
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#2
engine swaps

I have performed several engine swaps :( XR200 into RM125,XL185 intoTS125X,XR100 into KX80)
In all cases It is a time consuming process.If you have the time it is OK
The most important thing to set up is the front sprocket to swingarm pivot relationship.The sprocket must be at the same height as the swingarm or it will
change the chain tension as the rear wheel goes through its travel.
The sprocket also has to line up with the rear wheel as well,I mention this as many four stroke motors have wider gearboxes.Other things to consider are the kickstarter path when kicked,exhaust and muffler and air cleaner attachment.
 

Treejumper

2 wheeled idiot
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#3
Thanks Gorby!

That's the info i was looking for. I'll test drop the motor in the frame this weekend and see if everything will line up. If it looks like everything will be a bear to aligne then i'll just wait til the 2 stroke motor is done. Thanks!
 
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#4
I'd be willing to bet that it will be MUCH cheaper to fix your 2stroke than to do the engine swap.I am cerrently putting an xr100 into a KX80 frame.It is much more than I bargained fof.See my earlier posts on the subject.
Jeff

Oh,gorby,what did you use for the intake boot,kickstarter,and pipe on your XR/KX swap?E-mail me @ YAM314@HOTMAIL.COM
 

Treejumper

2 wheeled idiot
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#5
Thanks, i am doing the rebuild for the 2 stroke, just dont have the money for atleast another month. I just wanted to know if/how hard it would be to put the 4 stroke motor that i have in it for the time being. It looked like it wouldnt be to bad since the motor is almost identical and the mounting holes are the same. Thanks, looks like it will be alot more work than i hoped for.