Big Bore??

[OFP]

I got a 94 xr250 that’s having problems starting. I’m going through it… I did the valve adjustment and next I’m going to clean the carb.

The guy I got it from said he thinks the guy he bought it from said it was bored out. Is there any way to tell if this is the case?

[XR250rdr]

You would have to tear it down to be sure.

However, assuming the cylinder and piston are in good shape, your issue more than likely lies with a dirty carburetor and/or a fouled spark plug. A bored out XR250 usually will start as easily as a stock one.

[ThumperTDC]

I built a 95 280 for a buddy, which ran awesome when the carb was clean, but he would always let it sit for months with gas in the carb and would never start and if it di ran like poo. The carb is more than likely the issue.

[OFP]

I took the carb apart last night. It's dirty, but the jets and everything looked fine, I didn't see any obvious clogs or anything. It's missing some pieces, but I'm using a manual for a 1996 rather than 94 so I'm not sure if it's supposed to be this way. It has the main jet, the needle jet holder, but no needle jet. It was missing the o-ring and washer for the set screw. It's also missing the choke lever. The needles are also lower numbers than the manual for the 96 says.

I was wondering if the bike has been bored out, if the stock carb can keep up with it or if I should add anything like a jet kit.

[XR250rdr]

I would buy a carb rebuild kit and any other required parts first. Once the carb is clean and complete then start a real diagnosis.