Change back to stock pipes

Just a thought. I've been messing with trying to get as much fuel economy out of this thing for a while, and it keeps nagging at the back of my mind. Would swapping out the aftermarket pipes for stock ones help? Everything else is stock (airbox, filter, jets, etc) so that's what I'm thinking. Could not enough back pressure be hurting my mileage. I'm in the mid 30's no matter how hard or soft I get on it. It's got a great sound so I'd hate to give that up. Has anyone had luck with other slip-on pipes. I can probably get a set of sportster ones if those work better. I'm trying not to have to rejet.

 

Possibly. The exhaust you are running now might actually require rejetting for optimum performance. And not to open a can of worms, but "back pressure" is an urban legend, it is the science of SOUNDWAVES that dictate the proper design for a 4-stroke exhaust, moreso for a 2-stroke. One of the bike mags did an extensive write-up on this a few years back, they were trying to figure out why they couldn't improve on the performance of the SR500 (4-stroke single) with an aftermarket pipe. In order to make a typical 4-stroke engine run correctly on a pure straight pipe, the pipe would have to be something like 12 feet long. (The SR has an amazing "collector" box hidden under the motor that effectively mimics the 12-foot long pipe.) All the curves, bends, baffles, etc., are for sound-wave control and containment. T'ain't about back pressure...

 

I would think an aftermarket exhaust would have at least the same performance without rejetting (if everything else was stock). Open pipes may be a completely different issue.

What do your plugs look like ? Are they carboned up at all ie: running too rich ? If it is, you could follow Rick's tweaking guide, run some plug chops and get the optimum settings for your pilot screws.

Sometimes a can of Seafoam works wonders... it's easy, cheap, and certainly can't hurt. A not so easy fix would be to check your compression and see if you have issues there.

It may be a silly question, but have you tried switching brands of fuel ?

 

Not a silly question at all and as I drove home last night, I went to a different gas station than I normally use. Completely different response on the bike (I put in a full tank) even though I was still at 87 octane. I'm going to see what this does. I saw a post a little while ago about 10% ethanol fuel being horrible for these bikes and I wonder if that might have been it. I just usually go to the same station but I might have to change for the XJ.