A simpler and relatively cheap fix is to replace the mudguard with an after-market one from a YZ or WRF which have water-cooled engines and longer sections on the rear of the mudguard.
Not sure what the original TTR one was made for but it looks to have been fairly crudely sawn off at the bottom to shorten it!
On my new to me 2003 ttr 250 I noticed that the rear of the front fender seems so short. I hate to have all the nasty dirt and water flinging on my cylinder head! Is this an issue? Is there an adapter or a different fender to use or will this mess up the cooling aspect and block air flow?
I couldn't see anything when I clicked Brian's link but if you plan to use the YZ/WR front fender, bear in mind that there is an air flow holes in the cylinder head that must not be blocked by the longer fender or the engine may overheat.
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2000 TT-R250M-
Spoiler
Ported & polished, 73mm bore, Wizeco piston, US header pipe, FMF Q4, #150 main jet, #52.5 pilot jet, throttle stop screw adjusted, larger snorkel, GYT-R air filter, NGK Iridium spark plug, 14/51 gearing, NOS +
I think the issue is that, if riding in muddy conditions, the cylinder barrel and head get plastered in mud so any air holes or fin cooling is negated - so better to keep them mud free and have slightly reduced airflow?