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xs250 engine swap (with larger engine)?


Merkin
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Gidday, I'm new to the forum (and Yamahas too) and am looking at getting a 1979 xs250 with the intention of customising it a bit. I would like to put a larger engine in it and want to know what size xs engines and from what years (if any) will fit in? I was thinking about 500cc would be good but I think they go up to 750 in the later models? If I can do this will I need to put in different headers or other bits and pieces or is it a straight swap?

Also, I have heard a few nasty things about the xs250 (hard to start, dodgy wiring, poorly made, etc...) and was wondering if any of this is even remotely true?

Thanks!

Brad

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Gidday, I'm new to the forum (and Yamahas too) and am looking at getting a 1979 xs250 with the intention of customising it a bit. I would like to put a larger engine in it and want to know what size xs engines and from what years (if any) will fit in? I was thinking about 500cc would be good but I think they go up to 750 in the later models? If I can do this will I need to put in different headers or other bits and pieces or is it a straight swap?

Also, I have heard a few nasty things about the xs250 (hard to start, dodgy wiring, poorly made, etc...) and was wondering if any of this is even remotely true?

Thanks!

Brad

Hi Brad

an XS360 or 400 will fit right in you will need to change the carbs etc but no major problems. all bigger XS motors 500,650,750,850,1100 would like trying to a Jaguar engine in a mini ! The engines bigger than 650 are shaft driven another headache along with producing a new frame etc etc .... So perhaps look for a 360 or 400 lump to drop in. this will give you a good performance increase and if you keep the 250 decals on it suprise some other bike riders. The electrics were not to bad unless they have been hacked around, Starting issues can be cured with setting the ignition timming & dwell correctly and as for poorly made ... it was the same as anything else around in the late 70's so by todays standards yes but back in '79 the same could have been said of bikes produced 30 years previous.

Regards Jim

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The only viable options to fit the 250 frame are the 360 and 400 engines. The others will physically not fit, plus the added headache of some being shafties as already stated.

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The only viable options to fit the 250 frame are the 360 and 400 engines. The others will physically not fit, plus the added headache of some being shafties as already stated.

Just what I said Jag -> mini i.e no chance and physically not fit. A 360 setup right would be cool from the repair work I did the 360 seemed to be a better tool but as it was so long ago so perhaps you know better

Regards Jim

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Hey thanks everyone, looks like I will grab the bike and keep- an eye out for a 400 engine at a wreckers.

Cheers,

Brad

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  • 4 weeks later...

Hey thanks everyone, looks like I will grab the bike and keep- an eye out for a 400 engine at a wreckers.

Cheers,

Brad

Don't have to get the whole engine, just top end is fine. ;)

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Don't have to get the whole engine, just top end is fine. ;)

but redo the final gearing ie sprockets as you will be undergeared.

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