A forum for owners of Yamaha TTR250 trail and enduro bikes!

Vic - they're already available right here, on this site:-

CLICKY LINKY    

With a detailed description and advice here:-

Another CLICKY LINKY

Martyn

Air filter obtainable from the same place, Vic.

AIR FILTER CLICKY

Another article in the FAQ describes one rider's view on filters:-

"Dave Maddock found that the oil filter is the same as the YZ\WR 400\426 (not the 450) and the pre-03 YZ250F, which makes pattern ones widely available. He got his from Racespec in the UK (part number 78-142 - £5.20) who also supplied a CRD air filter (part number 23-1015 - £7.50)."

Martyn

Here's some interesting information from a bloke I know:

I worked for race teams for years. One Toyota Atlantic team I worked on the driver thought the car was loosing power from the start of a race to the end. We did leak down checks when we got new engines in. 3% is the leak down of a new engine. At the end of a race we checked again and we got 29% leak down. So we sent the head to get the valves done and checked the leak down when the head returned. 4% leak down. At the end of the next race it was 31% leak down. No good.

We put three dabs of grease down stream of the K&N air filter. At the end of the next race the engine had 32% leak down and the dabs of grease were full of grit. We changed the filter to an oiled foam filter and fitted a new engine. At the end of the next race? 18% leak down. Better but still not good. We made a new air box and used a Mustang GT stock paper air filter. Fitted a new engine. At the end of the next race? 1% leak down, yes I said "1%". The rings bed in and the engine seals up. We went from changing a engine at 300 miles with 29 to 34% leak down to changing the engine at 800 miles with 7% leak down.

So the bottom line is. You might gain a little more power (1 to 2hp) with a K&N filter but it will not last long, and before you know it you will have a LOT less.
I work on Porsche 944s only now, and when I tear down a 944 engine that has had a K&N filter the cylinders have a LOT of scoring from dirt that got through the filter. If you don't beleve me do the grease test your self. Take out the filter and put a dab of grease in the air box. Then put your K&N filter in and drive the car for a few weeks and pull the filter out and check the dab of grease.