XS360 and XS400 motor swap

[Audizway]

Hi, I am new to the site, and really happy it exists! I am 41 and live in Connecticut, have had bikes all my life. I bought a 78 XS400 (wire wheels, drum brakes) for a cafe project 2 years ago, and progress has been slow. This week I bought a really clean 77 XS360 (drums and spokes as well) with only 4000 miles. $400 with a title (1 owner) so I am pretty chuffed!

My question is about swapping the 400 motor into the 360 chassis, they look the exact same. With a top end rebuild and some cleaning, I figure I could get a nice little hp bump.

Thanks!

 

[drewpy]

welcome Audizway.

Looking at the german xs400 site, there is a racer on there who says the 360 crank is lighter then the 400, I would keep the bottom end and just swap the pistons.jugs and head over. not too sure on the crankcase mouth for the piston clearance though, but i recon there's very little difference.

 

[volcomskater77]

that would be really cool to see a nice little write up if it works. and welcome to the forum!
nice score on the wire wheels and drums. i got shafted with the mags and discs. if you start a build thread, i will deffinatly be following it. its nice to see something different. keep updating!
lol

 

[XS400Cup]

Welcome Audizway

My question is about swapping the 400 motor into the 360 chassis, they look the exact same.

No problem.
The differences are inside only:
The 400 cylinder does not fit the 360 crankcase. The bore of the crankcase is too small.
Thats the problem.

 

[XS400Cup]

the 360 crank is lighter then the 400

Approximately 950 grams

 

[Audizway]

Thanks for the info, I would straight-up swap the engines, so I could still ride while I rebuild the 400.

My 360 came without a battery (and a ground wire, strangely enough), so I thought I would stick the battery from the 400 in there. Turns out the 400's battery is about an inch taller, and the battery cavity goes farther down. I wonder if they did this for the electric start on the deluxe 400?

I am curious to see how well those drums work...

 

[hardtailed77]

Thanks for the info, I would straight-up swap the engines, so I could still ride while I rebuild the 400.

My 360 came without a battery (and a ground wire, strangely enough), so I thought I would stick the battery from the 400 in there. Turns out the 400's battery is about an inch taller, and the battery cavity goes farther down. I wonder if they did this for the electric start on the deluxe 400?

I am curious to see how well those drums work...

Properly adjusted drums work just as good, if not better than discs. A lot of Honda CB racers, among many other makes/models, prefer to run the drums over discs. Now retro-fitting a sport bike disc set-up opens up a whole different area of performance compared to stock.

 

[hardtailed77]

Oh, and welcome! lol

 

[ivor]

Welcome Audizway


No problem.
The differences are inside only:
The 400 cylinder does not fit the 360 crankcase. The bore of the crankcase is too small.
Thats the problem.

Oh, this is interesting, my parts book shows the part number for the 250 and 400 was the same, are they identical, or did the factory put out differently bored cases with the same part number ??

 

[drewpy]

I just thought, I used an xs360 NOS crankcase last year for my 400, and never had any probs.
I wonder if it was just a 400 which would also suit the 360!

 

[drewpy]

Oh, this is interesting, my parts book shows the part number for the 250 and 400 was the same, are they identical, or did the factory put out differently bored cases with the same part number ??

yep your right, just checked mine!

 

[XS400Cup]

It´s possible that not all XS360 crankcases have the small hole. Yamaha has modified the crankcase.

 

[drewpy]

thought I'd seen that somewhere, thanks for the info xs400cup

 

[kevin]

Hi I live in eastern Canada 1 hour NE of Calais Maine and I own a XS360 Yamaha. It needs a piston and rings which I am not able to locate at our local dealer. I am told that I can swap a XS400 . I am interested in parts to fix my 360 0r a complete XS400 motor or XS400 with complete parts to rebuild, I can have everything shipped to an adress in Calais Maine Thank You My number is 1-506-485-1808 or e-mail patrick_boyle13@hotmail.com
PS, i have a complete gasget set for a 360 top and bottom.

 

[drewpy]

kevin. take off your number and email address; spammers will harvest it and use it against you! get peeps to PM you instead

 

[dO-bOy]

welcome! i personally like the looks of drum brakes better for wirewheels. so classy! And i agree that drums lock up just as good and usually better than disks if theyre properly tuned. Think about all the surface area shoes have. Coming from drifting cars, i found that drum brake ebrakes were always far superior. The main disadvantage of drums though is they do not dissipate heat nearly as quick.

 

[foul]

Approximately 950 grams

Isnt it lighter because 360 has lighter pistons so it has less counterweight in the crank?
Then if you swap the cranks you will get more vibration, no?

 

[drewpy]

I think the crank in the 400 is heavier because it dampens vibrations. yamaha wanted better riding comfort so they also put in engine dampers in later models.

I think the piston size has some merit but not nearly 1 kilo's worth!

 

[Phoenix]

Hey gang, time to wake this thread up! I just got myself an xs400 dohc and it's in bad shape, so I'm resurrecting her and saving her from the scrap yard. Question: How bad will the vibrations be if I swap for a 360 crank? I REALLY like that weight savings, especially at the crank, but am wondering if it will hamper my ability to enjoy longer 500km trips?
Thanks, love this site and all your brains

 

[xschris]

DOHC bikes and SOHC bikes can't swap motor parts. They are totally different.