I've a Jap import TTR250 enduro (Not a official UK import)
any & all advice on mods/tuning would be appreciated.
(hacked off with being blown away by big bore Xr250's!
Have thought about installing a Stroker big bore kit?
Start by removing the airbox snorkel & exh. baffle. You may need to go up one size in both the main & pilot jets. You may also need to change te needle position. Search for a thread on this. I never got the jetting perfect, but I got it close. I put on a Biggun exh and am hapy with the perf. increase. But I still need to order a larger pilot jet.
Jets can be difficult to find. The '95XT600 used the same jets (at least in US) and the 6mm Kehin jets fit as well. These are th short round ones that take a flat screwdriver, not the tall hex head ones.
Put in a hi-perf air filter too.
Yamaha has a hi-comrpession piston and exh in the GYT-R Offroad catalog.
The Stroker kit will definaely give you more power, but it is expensive nad requires case boring.