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XR250R Do I have a big bore?

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Hi All,

I just purchased a '96 XR250R. Stuff that's been done to it:  hotrod crank, hotcams, upgraded valve springs, titanium keepers, new head studs and gaskets. Plus all the usual uncorking.

Guy I bought it from didn't know if it had a greater than 250cc displacement (i.e. big bore kit).

Based on the upgrades do you think it has a big bore? Is there a way to tell with out taking a caliper to the piston bore?

Thanks! 

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the other way to tell is on the r/h side of the cylinder at the bottom a 250 cylinder will have 249cm cast into it big bore might not have the numbers?

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22 hours ago, vicxr400 said:

the other way to tell is on the r/h side of the cylinder at the bottom a 250 cylinder will have 249cm cast into it big bore might not have the numbers?

Big bore kits use the same jug, just bore or new sleeve.

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yes sir I realise this but   most bbk I have seen have the numbers filed off as the cylinder is no longer that capacity.  just my observations over time.

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9 hours ago, vicxr400 said:

yes sir I realise this but   most bbk I have seen have the numbers filed off as the cylinder is no longer that capacity.  just my observations over time.

They must do things differently in Australia, I've never ever heard of anyone doing that.  Why bother?

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to be honest I don't know  has just been my observations over the years my guess as to why is so it can be identified externally.

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On 9/12/2017 at 4:36 AM, first king said:

Hey man can you show me the voltage regulator of a XR250R? How many wires does it have?

The XR250Rs use an AC voltage regulator with 4 wires, the clue that it is AC is the white/yellow wire rather than red that is on the DC regulator/rectifier. 
The yellow/white wire connect s to the yellow/white wire in the harness, which is spliced to the blue wire in the harness.

The yellow and pink wires connect to the yellow and pink wires from the alternator, and the green wire is ground and connects to the green in the harness.

 

 

59c285f74f1d5_XR250RWiringDiagram96-04.jpg.1123d3f5287a2276dd1cafcb6d1c2aa1.jpg
 

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Thanks for the responses, everyone. Unfortunately, my compression tester can't quite fit down in the spark plug well. Made for diesel trucks. Can't get compression test obviously. If I pick one up that will fit I'll be sure to report back.

Also, I've confirmed the head does have the 249^3 cc casting mark intact. Not filed off per above.

I'm in the middle of a cam chain tensioner replacement right now but plan to keep investigating this.

 

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