What is the diff between engines in 1980 250 and 400?

[sclarke7171]

Silly questions.
I'll start on what I'm doing.
I've got a GSX400 1982 complianced bike.
Has had the valve cover taken off and cams pulled out. Chain broke I would guess. This was done by previous owner.
The bearing caps are missing. So the head is useless.
Will a GSX250 head fit? Why I ask, is the 400 is rare in Australia. No one has a used engine.
So I can get a 250 and use bits. Only if that's an option.

What other engines can I fit to the 400 frame. I would like a bigger engine. A 750 or 1000.
Happy to convert to a 4 cylinder. What ever works. Lol.
Other option is to wreck it and get a complete 750 and build it up.

Steve
Australia.

[SqDancerLynn1]

You are not going to get a 750 to fit into a 400 frame. Keep looking 400,425,450 motor

[pete]

Yep, 400,425, and 450's will be your best bet.

A 500 will fit as well, but you will need to do fancy exhaust bending as the exhaust ports on the 500 head point directly at the frame rails.

[hugo151]

Yep, 400,425, and 450's will be your best bet.

A 500 will fit as well, but you will need to do fancy exhaust bending as the exhaust ports on the 500 head point directly at the frame rails.

pete, does that mean a 500 would fit in a 250 frame ? everything else is the same except a single tube frame.

[sclarke7171]

Ill measure the current 400 I have and attempt to measure the 250 in the frame. I just bought a 450 complete bike. So I should have enough to play with.
If you can get a 450 in a 250 frame I may go that option as the 250 is half cafe'ed.
But it's summer here. So lots of time to play and ride


Steve

[pete]

Good question on the 500 in a 250 frame, but yeah the bottom ends seem to be quite similar, so if they're the same physical size and the mounts are the same or at least close, then it shouldn't be too much of a problem... except for the department of transport Nazi's of course who will probably require an engineering certificate for such a major upgrade...

[sclarke7171]

Blah. Engineers. That's crazy talk. Lol

[pete]

Hahahahaha mate you can't do nothin' up here without an engineer's certificate...

[Mekanix]

Really its still a 250 officer.
I don't use that other cylinder... often


lets see,

1 the 400 has a longer stroke than a 250 so the head volume is wrong and the compression would be way too high.

2 the 500 would drop into a 250 frame with some work but at least the exhaust wouldn't be such a problem :P

You might be able to recover that 400 head if you get a set of caps and have them line bored to the proper size for the cam's

You can get a timing chain for a 1981 xs 400 that has a master link so you wouldn't have to split the case.

lots of options but I would go for the the 450 or 500 in the 250 frame just for kicks

[hugo151]

the bottom engine mount area on a 250 is a bit restricted && the sump area of the engine goes between the frame tubes, & is quite tight. don't know if this area would be a problem when fitting a bigger engine., or are they the same crank cases ?

[pete]

I know the 450 goes between the frame rails too, and I suspect the 500 will be the same or at least the early ones.

The bottom end cases look very similar but I haven't seen a 250 up close in person to compare with my 450.

[sclarke7171]

I solved the problem. Bought a GS450. Drove 1100km to get it. Was a mercy dash. Drove there. Put bike and spares in trailer and drove home. Crazy I know. Took the 450 out. It wallows and walks a little. Going to try a diff set of wheels. I now have lots of spares. Stiffening the suspension is next.

[pete]

Well... you know I should just believe you but... didn't happen if there're no pic's right

Hahaha good stuff, I put Ikons front and back on my 450 and there's a world of difference! They ain't the cheapest option though...

[sclarke7171]

Can't post pix to here from my Ibone

[pete]

Aaah ok... I stick all my pic's up on Photobucket and link to there...