Xr 250 to 280 ?

HI I have a 2001 XR 250R as its in bits I'm looking at doing a 280 conversion Is it as simple as a re-bore and new gaskets Or is there more to it Jetting exhaust etc. I've already got the airbox opened up. When I bought it a silencer from a WR had been made to fit is this gonna be a problem ? :thumbsup:

yes. It is that easy.

If you can accomplish the engine work you mentioned then the re-jetting is a cinch. I spent an hour or two combing through TT posts and made a little spreadsheet with jetting information from other folks "280" kits. I picked one and it was 90% there and made one tweak and was good to go.

hiya doris,

the big bore is well worth doing in my opinion,

my bike was a 277 when i bought it,my mate had a xr250 and when he tried mine he had to go large as well,

ive got a used , low miles 77mm (277cc)piston gathering dust on my garage shelf,if you want to make me a silly offer,no use to me im at 78mm now,

otherwise i can reccomend vic eastwood for your piston and gaskets,you can call them on 01322662426


I have done several 280 conversions, it is the best bang for the buck for getting more oomph out of the 250. My personal preference is to go with the 77mm piston, that leaves room for one more overbore if necessary. Engines vary as to jetting, but as a rule of thumb, start out with a 138 main and a 48 pilot. That would be with the exhaust baffle removed and an aftermarket air filter such as a UNI.

Can you do this to the dual carby 1985 XR250?:thumbsup:

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