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jf83d420
Hermon, NY
USA
64 Posts |
Topic started on 06/22/2012 at 03:56:13 AM
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I'm just curious as to whether or not the octane rating of gas effects the jetting in anyway? I used to run 87 octane but I'm now running 93 octane and it doesn't seem the same? Was running 58/160 I ended up jumping up to 60/165 and everything seems kosher but no power to lift the front end up. OF course my xr650l really never has had the power (got screwed when i bought it and when someone claimed it didn't need to be bored when i paid them to rebuild it,but that's a diff story)I can say its got smooth roll on of throttle which it has never had and seems like its getting the best response out of any combo i ever had. I'm just curious as to whether the bike is getting burned out or if the octane is effecting the jetting and if i should switch anything? Also no matter what speed your doing whether it is 15mph or 65mph the pilot is still in control if you haven't passed the 1/4 throttle mark correct? I did pull my plug after taking a ride and letting it idle for a few mins afterwards and the plug was a nice tanish color,AS i was thinking the pilot was a lil rich but plug says no. Bike is going the fastest it ever has so i know the main is spot on, IM thinking the bike is just whooped and i need to find a compression tester? But any input on the octane rating and the 1/4 throttle at any speed would be appreciated and any other advice. Thanks in advance  <== what i feel like for buying this bike,ill never buy used again  |
04 XR650L - Uni filter, de smogged, snorkel removed, Dave's carb mods, 58 pilot 165 main, XR650R front sprocket, 14/48 gearing, DG slip-on w/1" quiet core, Stage 1 Hotcam, Acerbis Supermoto fr fender, smaller signal & tail lights, Corbin seat, Warp 9 rr rim, 4.7g Clarke tank, Xenon headlight, Xrs only temp dipstick, D-flex handguards, Tusk 1" bar risers, Rubecon manrack. |
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dave_cl
Central NY
USA
1404 Posts |
Posted on 06/22/2012 at 11:42:06 AM
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Jetting, no. Lower power from higher octane gas, a little bit. That with all things being equal.
All things not being equal, the higher octane grade may have contained more ethanol, and the more ethanol the leaner it becomes.
60/165 seems a bit rich unless they are putting in a real genuine 10% ethanol.
If you are going 65mph, I think it is beyond the pilot jet, because the throttle only affects the butterfly, but the vacuum slide decides if you are on the main jet or not. |
01 XR650L - Keihin 158 main jet, 55 'long' pilot jet, screw out 2.5 turns, stock needle shimmed 0.035, slide holes drilled to 5/32, dynojet shorter CV spring installed, foam filter, snorkel removed, stock exhaust, air pump removed, thermometer dipstick, XCMH fr/r tires, 14-48 spkts. |
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jf83d420
Hermon, NY
USA
64 Posts |
Posted on 06/23/2012 at 06:14:00 AM
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| Thanks Dave for the input im gonna put the 58 back in and see what happens. I'm thinking the main is whats making the difference? because its when I'm cruising at about 65 is when the throttle is rolling on nice and smoothly like never before and getting 95 out of it.So, if higher octane is less power?, I should go back to 87 octane? So, whats the point of higher octane? I always thought it was that it burned cleaner and gave more power? Hence why racers use jet fuel or so..... |
04 XR650L - Uni filter, de smogged, snorkel removed, Dave's carb mods, 58 pilot 165 main, XR650R front sprocket, 14/48 gearing, DG slip-on w/1" quiet core, Stage 1 Hotcam, Acerbis Supermoto fr fender, smaller signal & tail lights, Corbin seat, Warp 9 rr rim, 4.7g Clarke tank, Xenon headlight, Xrs only temp dipstick, D-flex handguards, Tusk 1" bar risers, Rubecon manrack. |
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dave_cl
Central NY
USA
1404 Posts |
Posted on 06/25/2012 at 09:28:30 AM
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If an engine is built with lots of compression, it needs the higher octane fuel to stop detonation. That higher compression lets the engine make a lot more power and more than makes up for the small amount of difference in energy density between low and high octane fuel.
It's much more likely the higher octane fuel you tried had more ethanol than anything to do with the octane itself.
At 65 you are on the main jet and the slide needle. |
01 XR650L - Keihin 158 main jet, 55 'long' pilot jet, screw out 2.5 turns, stock needle shimmed 0.035, slide holes drilled to 5/32, dynojet shorter CV spring installed, foam filter, snorkel removed, stock exhaust, air pump removed, thermometer dipstick, XCMH fr/r tires, 14-48 spkts. |
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xs11ernie
Corona, CA
USA
20 Posts |
Posted on 09/20/2012 at 10:12:47 AM
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Octane increase is for pinging ... if it does not ping, use 87 octane or what the Owners Manual says
Higher Octane does not increase power, it stops detonation
Go to Utah or Colorado and over 5000 ft, gas stations may also have 85 octane due to lower engine compression at altitude |
86 XR600R, 93 XR650L, 89 CR500, still riding after 40 yrs @ 76 |
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Octane rating effect on jetting
