HELP: Can i make a complete motor from these two?

Ketchup pusher

For more of my xs 400 Instagram: Ketchup Pusher
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Hi there
I'm new here, only just got my xs 400 last month. My plan is to make it into a cafe racer, but before i come to that i saw when i first got it that i needed to change the gaskets, no biggie, it was missing it's kickstarted axle too so i thought i might as well add that while i was at it. Then this morning when i took the right cover of i saw the bracket thing, where the axle is attached too inside the motor, was broken :(

Now i'm wondering if i can switch the bottom part of the motor with an other xs 400 motor i got with the bike?

The bike is a XS 400 Special from 81', the motor has been swapped for a XS 400 1979 3N7 motor, the original XS 400 4G5 81' motor came along.

Now the question is can i take the cylinders and that stuff from the 3N7 motor, which is slightly bigger (391 ccm in 3N7 and 386 ccm in the 4G5) on top of the 4G5 motor which bracket is still intact??? :confused: :confused: :bike: :)

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and my plans for the bike: :D
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Have anyone in here tried to assemble one motor from two different xs 400 motors
Please this is my first bike, i have only had it for a month, i have no idea on what to do :/
 
if the original engine was replaced I would guess, there was a reason ;-)

As Drewpy said, the crankcase is a pair but of course you can put the cylinders from one engine to the other. The cylinder head is machined as pair (head and cover) as well.

The cylinders are of the same size, Yamaha just calculated wrong in the beginning:D
 
Wait a second, so the engines have the same ccm or what?
I just read that the 3N7 motor has 38 hp while the 4G5 has 27 hp, which to me is quite some difference. Where does the extra horsepowers in the 3N7 motor come from? :confused: :)
 
It's not extra, it's stock.
The 27hp models were restricted for use in Germany. The displacement was the same, intake tract and carb modifications lowered the overall hosepower.
 
my plan for the coming season is to just use the engine with no kickstarted axle bracket, which i know for certain works, and then during next season i'm going to check up on the original motor, and then hopefully have it running for the seasons to come later.
this winter i'm mainly going to focus on the looks of my bike, so if you haven't seen it, check out my album with photoshop plans on the future.

the key features will be the wooden seat, with some leather seat plate on it. and of course a killer paint job, which isn't in any pictures jet, as it's a surprise :D:yikes::bike:
 
Update*
Thanks for all the help.
from the 4g5, i took the motorblock, the outer cylinder wither the older inner tube (3n7 liner), changed the pistons and valves from the 3n7 to the 4g5 cylinder/cylinderhead, and camschaft from the 3n7 to the 4g5. (noticed some big differences from 3n7 to the 4g5)
As you might have guessed this took quite some work, and hopefully when i start it up it will all work :cautious:
Cheers :cheers:
 
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