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Not sure if PO rejetted bike properly/at all...

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Bike is a stock SM with a poorly measured and cut 3x3 and a FMF Powercore 4 full exhaust with Powerbomb header.

 

Backfiring on decel,  a lot, I've ripped 2 of the 3 rivets out of the baffle somehow.

There's a low spot at the bottom of the mid range, right at cruising RPM that feels like it's about to bog down, and then doesn't, but there's an obvious lack of throttle response right in the sweet spot. Could be the spark plug or something though.

 

PO said the the original owner did the pipe before he got it and just assumed it was jetted.

 

The frame is currently ripped open and I'm going to be rebuilding the entire bike on a new frame, so figure I would do whatever needs to be done while I have it torn down, but I don't want to pay for a jet kit if I don't need to.

 

What do you guys think? Improperly jetted? Get off my lazy ass and check the plug?

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Gut your carb and show pic of needle, then describe pj & mj sizes.

Edited by billdirt1
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open up the carb and check the top of the main jet and pilot jet but a obvious indication of a jetted bike will be the needle. red or blue needle is from a jd jetting kit not sure on the dyno jet kit though others would have to tune in for that. for the plug. i wouldnt say entirely it is the plug, doesn't sound like it is misfiring at idle? or is it real smooth if it sounds like its running like crap? then it may be a fouled plug.i would go ahead and check it anyways  why not.. but cruizing while bogging is a jetting issue, i had that problem but i got it tuned right with a 22.5 pilot with kientech ex. fuel screw 155 main jet blue needle 4th clip postion (jd jetting kit). ive always had that poping problem on decel i just ignore it im told by several people its normal who knows lol

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