Having played around a bit with the 250 I was starting to feel a tad disappointed with the performance. OK, I've been used to the big bang of the 600 when you turn it loose but the drop seemed more than I had anticipated. The performance was gooey and the bike seemed to lack character. I found that I was having to rev it much higher than I'm used to to get some sort of acceptable performance out of it and it was somewhat similar to a plugged 125 when I got out on the road.

I started to search around and found an article on removing the bung from the header pipe but it advised cutting off around 1cm to remove the restricter. After a few days of mulling over what I could make with 1cm of stainless tube (most of you know I don't like waisting things ) I decided to have a look this morning. I was shocked by what I found ... the end of the pipe was folded back to leave a flat inner plate (about 1cm into the main pipe) which the offending inner pipe was welded to. The bore of the main pipe measured 32mm and the inner bore was 17mm . On the basis of the bore alone I calculated a gas flow restriction of over 70% not taking into account the depth of the inner pipe .



The good news was that removing the cork was as easy as corking a bottle. In point of fact it was only necessary to cut off around 2mm off the pipe and after about 5 mins with a heavily worn hack saw the cork simply fell out. I suspect 30 seconds of grinding the end of the pipe would achieve the same result but you don't want stainless in your lungs so a mask would be wise.

I have seen a considerable improvement in performance and the bike feels like a good 250 now. A pleasing punch rather than a slither.

I am not advising you do this just describing the procedure. I have no idea if there are any ill effects.

Good man! like to see you are already out thrashing the beast!!

Might be an idea to do a plug chop to check your jetting now as i expect you will be running a bit lean with better gas flow.

+1. You dont want melted valves or a sieze

Thanks both. All the info I've come across so far says that rejetting is not needed after taking the cork out and the amount of crap in the ports would possibly support that view. This is taking into consideration that I'm still on a standard tail pipe and I'm sure it will still be getting pleanty of back pressure from that little laberynth

However, I do have a flat spot at bottom end which suggests too weak. Runs fine mid and top range and adjusting the pilot screw makes nil difference so I'm sure I have an issue with the pilot. None-the-less this issue was there pre removing the cork. The bike has spent a lot of time standing around so I think there is a possiblity its crusty or filmed. Going to give the carb a major once over and see what I find