Cylinder sleeve swap for gsx250

[Guest]

Hi folks,
I've had a wee 250 sitting forlornly in my garage for the last few years that I picked up cheap. I've decided to show it some love and I'm hoping to wring it's neck a wee bit.

Anyways, I recently picked up a spare cylinder block and I'm thinking of attempting to take it out to mebbe 400 or so?? I just picked up a set of 4 gs750 pistons for 9 bucks and there's a 400 crank for not TOO much money on the evilbay as well.

What I need to know is what a decent candidate for a cylinder sleeve swap would be?? I read somewhere yesterday that there was one that had been used but try as I might I can't seem to get my computer pointed in the direction of that particular page (old age and memory eh??)

Soooo, if anyone would know of a decent candidate, or even if it's possible to take the 250 sleeve out to 400 size that would be brilliant.

Oh and also if anyone has an idea of whether I'd need to swap the 250 gearbox out for a 400 one to match the new crank I'd love to hear about that too..

Cheers folks
Raff

[Nessism]

There is no reasonable way to turn that 250 engine into a 400.

Your easiest path forward is to sell the bike and buy a 400. Another option is to purchase a 400 engine/carbs/exhaust and do a swap. Way more trouble than it's worth though.

[hugo151]

There is no reasonable way to turn that 250 engine into a 400.

Your easiest path forward is to sell the bike and buy a 400. Another option is to purchase a 400 engine/carbs/exhaust and do a swap. Way more trouble than it's worth though.

you should be able to take it to 300cc as they sold them as such in usa. The engine goes well if its allowed to rev. Ie not much restriction in the exhaust !

[Raffspeed]

I've got them pistons on the way which should give it some more power, plus I'm gonna fit 400/750 spec valves and mebbe a new cam as well... It would be good to at least have a craic at the 400 crank as well though...

[GregT]

I've got them pistons on the way which should give it some more power, plus I'm gonna fit 400/750 spec valves and mebbe a new cam as well... It would be good to at least have a craic at the 400 crank as well though...

Won't fit. The 400(4v/cyl) 450, 500 and GR650 all share the same size crank bearings - and pretty much the same crank. The 250/300 is a small scale version of that. Smaller bearings, smaller crankcase, gearbox looks like it came from a small 2 stroke...

[Raffspeed]

You wouldn't read about it eh??? Here I was thinking about doing this 250 to 400 conversion and lo and behold I was on facebook a few hours ago and a bloke is selling a 450 with a spare frame... I mentioned my wee project and that I might consider his 450.. He then tells me he's actually got a spare 400 donk hidden away. Anyways, deal just done for the 400 engine and 450 frame (I'm hoping their reasonably compatible..) Sooooo, part of the problem solved and all for 200usd and the petrol to go and pick em up...