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Discussion Starter #1
realy bad surging, im running 38pilot n2zw needle 2nd from top and a 165main jet,air screw 1.5 turns out, just fitted a fmf gnarly front and rear pipe, should i change to a bigger pilot jet? coz realy bad surging,thanks if you can help
 

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It might be your exhaust back pressure so check your exhaust 'o' ring gaskets (two rubber o rings) on the expansion chamber these affect the running quite a lot. Is the wadding in the muffler in good order, again back pressure. My jetting is 35pilot and like you 2nd clip from top same needle 1 turn out. My main i switch between the 165 and 168 depending on how fast the course is. I've a standard exhaust system. try you 35pilot and check the exhaust i'm sure this will sort your probs.
 

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Discussion Starter #3
hi spud thanks for that, my exhaust is fine,i to run the 165 and 168 main jet pending on tracks ect, im running a 38 pilot at the moment,do you think the 35 will help? wouldnt the 35 pilot be less fuel?and not help with the surging?or does it not work like that
 

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I've raced using a 38 and found when i cracked the throttle the bike could sometimes bog and over a prolonged race the bikes revs sat higher and began to hunt when shutting the throttle. I covered about a lap (20mins) with the 38 pilot to know this and to be honest it was playing up, if your greenlaning you might not notice this. Switching back to the 35pilot makes for a crisper rip out of the corners. I unscrewed the power valve screw on the side of the engine half a turn in from being flush with the engine case, which far outweighs the extra fuel from the 38pilot. Cracking the throttle now out of a corner will either result in a power slide or wheelie, but mostly the bike hooks up and driving out of corners on pipe is a lot better. I ride with the race pv spring and everthing else near max. I like the idea of the new bikes with a 6speed box if the ratios in the box are closer than the 5speed i suspect it be a bit more fierce and better to ride - which year bike do you have?
 

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i run the same jetting as you on a 40:1 mix and have no issues. my money is not on the pilot size....

if the surging started after you chnaged the pipe/sliencer ........ then there is your answer, many pipe combos will require a re-jet.
if the surging has started recently (before pipe change) you have something else going on..... air leak? carb clamps? misseated filter? i have had similar symptons - both times (close together) was a partially bloked pilot, second time i couldnt clear it for love nor money- i think it had varnished up really badly, put a new one - sorted. i read on ktm talk that others have had pilots varnishing up badly - modern fuels they reckon- seems to occur after 2 years ish. while i was at it i chnaged the fuel pipe as there was a blackish sludge in it. no more issues ....... touch wood. hope that helps!
 

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Discussion Starter #6
thanks spud and kt51 very interesting reading, my bikes a 09 and do run a 40.1 mix i have had the problem with surging before changing the pipe,but i will try the things that you have siad,thanks alot
 
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