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performance degradation

Discussion in 'The Garage' started by NewHavenMike, Oct 2, 2017.

  1. NewHavenMike

    NewHavenMike 1976 XS360C Top Contributor

    Hey guys just looking for some feedback on those who have riden their bikes a lot longer than I have and have more aircooled experience than myself.

    This has been an occurring condition when I go on rides.

    I went out today for maybe 35 miles. Temps were around 65-70F. Mostly cruising backroads (<50mph) avoiding stop-and-go. Bike is nice and warmed up, idles perfectly stable around 1500. Doesnt dip down or rise in rpms everything is great. I hopped on the highway and took it up to around 80mph for a couple miles. Im always easy on the engine after running it hard like that, I bring down speeds gradually and give the engine a chance to cool off and still push oil.

    Now Im cruising again and after a couple miles of that im in light traffic slow speeds and stop lights.

    Engine wants to idle low and basically stall but if i tap the gas itll be OK. Then when Im shifting, rpms seem to drop faster than normal and I need to give it more gas when I shift. Bike doesnt have the power it had before.

    Then when I got back on another highway, I could only get it up to around 70mph full throttle in 6th. Wouldnt go anymore, its like it was just stuck there.

    It seemed to help when I let off the gas a bit and it started picking up slightly.

    Is this sort of degradation normal for an aircooled bike? The dropping idle makes me think im too rich still but when Im on the gas it seems like its too lean.

    This plug has some miles on it. Maybe 200. I went with a BP7 plug because Ive been riding on the highway to work and thats 40 miles each way. Heres a plug,

    IMG_0091 (1).JPG
  2. 16VGTIDave

    16VGTIDave XS400 Guru Top Contributor

    Cruising back roads will NOT get the engine fully warmed up at those ambient temps. But a highway run will, especially at that speed! Oil temp is what you really need to consider.

    I'm going to suggest that your main jets are too large. You didn't mention surging, which is often an indication of a lean mixture. This would explain why closing the throttle slightly results in an increase in power. The float levels may be slightly high as well.

    The "fuel ring" at the base of the ceramic insulator is dark grey. That indicates rich.

    By the way, good job cutting apart the plug!
  3. NewHavenMike

    NewHavenMike 1976 XS360C Top Contributor

    I thought I was still too rich on the mains..

    The symptoms take a while before they show up, but I still get very very small hesitations like I did when I was running 140 mains. The 140 hesitation was really bad though.

    Ive gone through every size from 142.5 to 130. I just ordered 3 more sets going down from the 130 I have installed now. Honestly, Im starting to get nervous from how much smaller than stock Im going.. I know each size is like a half a thou difference right? so maybe its not that big of a deal.

    About the plug chop, its a HUGE hassle lol. I have no work bench in my "shed" and no vise hard-mounted. Theres a crappy cheap clamping vise that I used and I also have nothing to mount it on. I had to make a cut, then loosen the plug and rotate it. So you get the idea there lol.

    I was on my way to work last night (night shift) and had to turn back when I was a few miles from my house. Im surprised I didnt think to check multiple times before, But for whatever reason, I was riding and decided to look back and make sure my tail light was working. To my surprise, it wasnt! The bulb blew out leaving me with only a brake light. Very dangerous situation especially on the highway so I had to take the car instead. Theres not many good nights left around here before its just too cold.

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