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Discussion Starter · #1 ·
I have recently acquired a 1982 suzuki gs250 that I'm turning into a cafe racer. The current powerplant is shall we say...lacking...in the get up and go department. i was wondering what engine would be the cheapest to put into my frame. I'm willing to get an engine and rebuild it but i don't have the ability to do any fab work as of now. i was thinking gs 400 or gs 450 engine? I heared they bolt in? I could be wrong. wiring isn't an issue for me.
 

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Senior Member
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Yep - IF the 450 engine fits in the 250 frame then the 500 will.

I've never seen anyone do it though, which makes me wonder if it truly is a bolt-in swap.
 

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Gs500 exhaust will hit the front frame rails. I can take some pics of both frames when I'm in the garage next
The 250 frame has a single down tube so the exhausts wouldn't be a problem for both the 450 and 500 motors.

The 450 frame has the twin cradle and the 500 exhaust ports aim straight at it.

So hence my curiosity about if the 450/500 fits in the 250 frame. It would be an easy way of getting a 500 into a tubular frame if it fits. I'm skeptical though - I think the 250 bottom end is smaller / different than the 450. I'd certainly like to think that it's at least lighter, because the 450 motor is ridiculously heavy for a small twin.
 

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sickboy
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As said the 250 is a single down tube and the 400/450/500 is a twin downtube. On the 400/450/500 bikes the front motor mount is bolted directly to the frame where as the 250 motor uses a bracket to attach it to the single downtube. I am not sure if the bracket will bolt to the bigger motors and just let you bolt it in or not so it may not be a direct bolt it but either way it shouldnt be hard to make new motor mounts if needed.
 

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UnicycleMode
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I'll swing out to the shop today and get GS500 engine measurements. Got one out of the bike just sitting there, as well as the main engine cradle portion of the frame it came from too (chopped off the subframe for easy storage) so I can grab those measurements as well.


The 500 I'll be taking numbers from is a '91 model if that matters at all. Had it, and a '82(?) GS450 in the same place at once years ago, not realizing I should have measured it all and written it down.
 
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