The previous owner of my 2009 XTR removed the snorkel and fitted a stage 1 filter. I bought it in great condition at 2500 miles. Now, at 4500 miles, I'm wondering how it's running, as I'm not sure about these mods without changing the fuelling.

So this morning I took the bike into my local dyno centre for an air/fuel run. My expectation was that it would be a little lean, but nothing to worry about, as that seems to be the consensus on the forum: stage 1 filter and snorkel removal is OK without more fuel.

After an hour, the tech comes back clutching pieces of paper and starts explaining things. His view, in a nutshell, is that at low throttle it's so lean it's almost off the chart. His opinion is that if the bike is used regularly at low throttle or cruising, that it's lean enough to eventually cause problems. On the plus side, power does seem up a couple of bhp on the default XT660 chart. I mentioned a 2000-mile trip coming up and the tech's view was not to use the bike for the trip without sorting the lean mixture.

So I have 4 options.

1) Leave it and hope it doesn't go pop.

2) Buy a standard OEM filter, take the performance hit, and hope for the best. Maybe pay another �35 for a dyno run to see if it's at least better. Keep an eye out for an old snorkel.

3) Buy Kev's fuel and O2 mods. With all respect to Kev, I had hoped to leave the bike as stock as possible without resorting to the DIY wiring that one finds on used vehicles. The stock running of the bike doesn't bother me too much.

4) Cough up the �500+ for a Power Commander. Their usual price is �300 including fitting, plus �150 for the custom map. However, they said the inclusion of the O2 module in the XT kit would probably add cost at all stages, so expect �500-�600. Yikes!

Needless to say, I'm pretty gutted. I certainly didn't want the bike with less performance, and I did expect it to be on the safe side of lean. I'll wait for the quote on the Power Commander option and then see what to do.



Here's the dyno chart.

That is rediculously lean between 3000 and 4500rpm!
You'll need to either go back to stock for now (which is still rather lean in that area), or get a Kev mod/O2 controller sharpish. You really don't need to spend big bucks on a PC to sort this out; the only significant benefit of a PC is you can "fine tune" everything in small increments with a custom map. The PC is the perfect solution, but you'll have to ask yourself is it �400-500 better?

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Doesn't the Kev mod simply enrichen the mixture by X at all times (in open loop)? Wouldn't that mean that the setting that sorts the lean range would then cause the 5500 to 7000 range to run incredible rich at around 10:1?

Yes, in a way, but it is adjustable. The O2 controller is more what I was thinking. Looking at your problem, it is controlling the closed loop that would see the best results.

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I considered removing the snorkel removed but I seen an ad for DNA filter mods and I noticed that that they recommend a restrictor being fitted to reduce the size of the aperture into the mouth of the air filter when not using a power commander,
I have fitted a Kev's Mod, Pipercross airfilter and a GPR exhaust, so instead of removing the snorkel I shortened it considerably but the aperture into the airfilter has remained the same I have set the Kev mod to 9 oclock and WOW what a difference (brilliant).

Hope this helps

I don't know if the DNA filter is what's made the bike so lean, but I have a K&N version I could try. Unfortunately, each dyno run takes about 3 hours of my time and �35, so I could spend a lot of money swapping filters and blocking the air intake before I get any safe results.

Pleiades could be right that the O2 controller alone would sort my problem, but I'm looking for Kev to spot this thread before I take any action. If I spend �70 on the O2 controller, plus another �35 on a dyno run, and it's not solved the problem, I've spent �100 of the money that could have gone on a PC and custom map.

If I could find a used snorkel online I'd go back to stock for now, but it seems people must hang on to them. I wish the previous own had kept the one from my bike!!