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Just a quick update, fitting the Twin Air Pro filter kit totally cured the problem, nice bit of kit. Shame Yamaha can't supply the OE bike with a filter that actually does the job, saying that keeps the people at Twin Air in work.

Well after a bit of searching I have managed to aquire a Twin Air Pro filter kit for £200 that not only replaces the filter but the plastic cage and adapter plate onto the inlet manifold. It is a very well made piece of kit with an alloy frame and a lip that secures the filter onto the housing. Filter...

Ordered a Twin Air filter and cage, so ill check the manifold for sand again after I've fitted it and post the results here

Yes stock filter, bikes only done 8 hours but already had a barrel/piston and valves, appreciate any help or advice, can't afford to break it again.

Cheers I'll check that out

Putoline filter oil and plenty of it. Just had a better look at it and found a couple of things. Firstly the filter has two holes in the middle of it where the spike goes through, interesting! Maybe I did it but I think that might be unlikely, irrespective though the filter had a sock over the top of it...

Bought a new 2019 YZ450F 6 weeks ago, after 8 hours it wouldn't start, checked the inlets valves and they were totally tight so took it into my local dealers for setting. Loads of sand in the inlet manifold and throttle body so I put it down to my bad maintenance and over enthusiastic use of the power wash. Needed...