Hey gang, gotta question. For the past 700 miles I've been running 89 octane in the bike from various stores. Tonight I figured what the heck we'll go back to 87. It seems to have lost some throttle response, noticed it especially in the dirt. 1st and 2nd would easily break the rear loose, now second is kinda blah until the rpm's build. I was the first one to argue with GomerPile about the octane rating of the fuel but dang I went from ripping it up through town to blah. Even idling in neutral and cracking the throttle produces a noticeably slower response. What gives?

FWIW, bike has 3500 miles, I shimmed the valves to be in spec 800 miles ago, and changed the sparkplug at the same time. Has a UNI filter that appears clean but I haven't cleaned and re oiled since last fall, but I generally ride solo, ie little to no dust.

 

Well I think it says to run 89 or higher with the compression our bike has 87 won't cut it..... I run High test in mine 91 I do beleave

 

Could it also be coincidental - the air temps have increased as well which means lower density = less air in the intakes and that could mean you're now not running as good a mixture as you were when it was colder out. Just another possibility, I'm not discounting the octane theory.

 

I checked the plug after the bike cooled and its a chocolate tan, kinda light brown. This was a full throttle run down the road, full throttle back, coast in the driveway and let it cool run. I suppose the air quality could do it but its not that much of a change from 15 miles away at the office to the gas station, its only 68 out right now, low to moderate humidity. I checked all the lines and nothing is kinked, was just weird. Luckily its only one ride worth of fuel anyway. After dinner I may pull the airbox lid and take a peek at the filter.

 

Before you look to far into it drain the 87 and put the other back in and run it. If thats not it then lets dive in. JMO.

 

Hosed it off and checked the filter. Some dust near the bottom of the filter but otherwise pretty clean. Took a spin and it seemed about the same. I suppose if I went and got my gas can I could drain it in there, or use it up either way, its only 60 miles worth anyway.

 

I have always run non-oxygenated gas here as all other gas has Ethyanol. I have a few stations near me that sell it. I'ts used for classic cars and motorcyles and is I believe 92 octane. Bike has always run great on it. (I have 330 miles)Does anyone else run this?

 

You say you just have hte UNI filter and some of the basic mods, but no jet kit? or exhaust? If the only modification is the UNI filter, the bike is probably getting aflat spot from being too lean in the bottm end and midrange, and it richens up a little at higher RPM since the exhaust then becomes the biggest restiction. 87 octane has the effect of somwhat leaning out the bike since it's a little less stable than 89 octane. I personally run 89 octane because I get less popping on deaccleraton.

In summary, you are probably a little lean, and the 87 octane makes it more noticeable. Since you notice it more at low RPM's you probably need to adjust the pilot screw and/or reshim the needle.

 

My sig has my mods listed, 125 main, 40 pilot, air screw ~1 3/4 turns, no snorkel and a KLX 300 stock exhaust with no "butt plug". It ran great until I filled up on the way home. I've been running this setup for nearly 1800 miles.

 

Ran the gas out of it and refilled with 89 and it seems to be back to normal. IE kicking it sideways in 2nd gear again. Gravel covered hills can be fun