GN400 engine into a GN250 frame???

**bomba** · 3rd September 2007, 18:21

I was wondering whats involved in fitting a GN400 engine into a GN250 frame. Has anyone heard of this swap being done?

**NighthawkNZ:Me** · 3rd September 2007, 18:26

Originally Posted by bomba

I was wondering whats involved in fitting a GN400 engine into a GN250 frame. Has anyone heard of this swap being done?

I have seen it been done before, and as far as I am aware it should be a straight swap (again as far as I can remember)

**scumdog** · 3rd September 2007, 20:25

Originally Posted by bomba

I was wondering whats involved in fitting a GN400 engine into a GN250 frame. Has anyone heard of this swap being done?

I dunno but I like your line of thought!

**FROSTY:Me** · 3rd September 2007, 20:55

There is one BIG issue. As faras I recall the GN400 was kick start and 6 volt electrics.That'llmake some of ya electrics are gonna be messy--cdi etc
Otherwise its just a matter of altering some brackets

**The Lone Rider** · 3rd September 2007, 21:10

What a great idea.. can this be done with other bikes? Such as the Honda Magnas.. chuck a 750 motor on a 250 ride? Whats some other ones?

**NighthawkNZ:Me** · 3rd September 2007, 21:35

Originally Posted by LLAMA SOLA

What a great idea.. can this be done with other bikes?

depends... some can fit straight in... ie; Xj 650 to XJ750 was the same motor just different bore size. Others may fit with a minor alterations new brackets etc, and some with major alterations.

You wouldn't want to be putting a to high power motor into a frame thats not designed to take the stresses and or the sub frame not being able to handle the higher torque and power etc.

**The Lone Rider** · 3rd September 2007, 21:38

Well I know with some of them each version is the same except the engine size. I think with the Magnas thats the case, although slightly different read-out lay out and such on your bars on the 750

**Bren** · 3rd September 2007, 21:41

I have seen it done myself too....dont think too much alteration is required...there is currently an XS250 on TM with an XS400 engine....

**The Lone Rider** · 3rd September 2007, 21:49

Originally Posted by linuxrunner

I have seen it done myself too....dont think too much alteration is required...there is currently an XS250 on TM with an XS400 engine....

I bet you can guess what I'm thinking for my ride though :P

**xwhatsit** · 3rd September 2007, 21:56

Originally Posted by FROSTY

There is one BIG issue. As faras I recall the GN400 was kick start and 6 volt electrics.That'llmake some of ya electrics are gonna be messy--cdi etc
Otherwise its just a matter of altering some brackets

Would the GN250 alternator drop into the GN400 motor? That would solve it, no?

I thought you'd have to change the CDI anyway, though, although I don't know shit.

**skidMark** · 3rd September 2007, 22:08

other option with gn's is change the bore piston head etc to dr350....bolts straight on.

**FROSTY:Me** · 3rd September 2007, 22:08

Anything is POSSIBLE its just a case of is it worth the effort.
Some conversions are easy because of the bikes being basicly the same bike.
CB250/cb400 XS400/250 rd250/350 rz250/350 xj650/750 xv750/1000
z650/750 gsx750/1100 gb400/500
some not so easy

**xwhatsit** · 3rd September 2007, 22:25

Originally Posted by FROSTY

CB250/cb400

Better qualify that with CB250N/CB400N, or T, or any of the Superdream variants, before GiJoe1313 tries to stuff a CB400/4 lump into his Hornet...

CB250RS/XL500/XR500 is something I briefly investigated.

With this one though, the question is why? You won't gain much horsepower (27hp as opposed to the 22hp of the 250), although you'll get an extra 50% torque. I'd imagine a relatively uncommon bike like the GN400 you wouldn't get an engine particularly cheaply.

Just found out that they made a GN400E, just like they made the GN250E -- so I'm assuming that the E, just as with the 250, means it's got an electric start and (presumably) 12V electrics. Look for a 400 with alloy wheels, that's the E model.

Exhaust system could be a pain in the arse; the 400cc engine has a single exhaust port, whereas the 250 engine does that silly one-port-for-one-valve thing so you've got a 2-into-1 system. Frame looks similar though so you might be lucky.

Quite interesting looking at a photo of the first GN400 model (1980). It's quite pretty; wire-spoke wheels like the early 250s, more normal seat, but best of all, it's got low bars. Quite tasty!

**bimotabob** · 4th September 2007, 07:07

Hi

Yeh for some reason the GN400 was a complete sales failure, they are very rare here in NZ - infact I dont recall actually ever seeing one.

I wish you all the best finding one - you gonna need it.

Cheers