Kev,

Firstly, I am very conscious of the fact that this subject has been covered many times after reading through posts on the forum. I suppose that my ability to comprehend the vast information available here has been demonstrated by not initially recognising the problem as �Surging�.

I am amazed at the technical knowledge available on this forum and you really are the man when it comes to the XT660; I think you know more about it than the clever folk at Yamaha who designed and built the bike.

The chain and sprockets look fine to me; I maybe should have mentioned that it has only done 2000 miles? It looks like it has been wrapped up in cotton wool for 5 years.

Done what you asked and the ECU part number is 5VK-8591A-00. So from what I have read the first owner did not complain to Yamaha and get the -01 ECU upgrade under warranty which was probably due to the fact that he never rode the damn thing!

So, I am slightly worried now � as I have the -00 ECU what is my best option?

I think I can afford the Stage 1 & 2 DNA filters at about �100 but the PCIII on top of that is not affordable to me (as simo1432 recommends).

I have noticed that the problem is non existent when first riding the bike from cold, but then once the engine warms up it becomes a real pain at slow speed which spoils my enjoyment of what I think is a great bike.

So, what do you recommend? The Kev fuel mod looks fairly straight forward and cheap but as I have the -00 ECU am I on a looser without the -01 ECU?

Thanks again for any advice,
Lee.