Hello, I recently acquired a set of Gen 3 Sato slip ons. I am getting an ear splitting resonance with the Satos between 2500 and 2800 RPM. Above or below that RPM range, it isn't too loud but my ears ring within that range. Incidentally, I find myself within this RPM range cruising on the back roads around here. Would a repack fix the issue or is it just a byproduct of the exhaust design? The dyno graph on Rogue Racing shows a little torque peak at 2500 RPM, so I'm thinking it is a resonance issue vs a repacking issue. Thanks for any insight.
Gen 3 Sato Resonance Question
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True, I may just order a repack kit and see. It doesn't look too hard from what I've seen.
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I'm pretty sure I'm looking at the same dyno chart that you are, it's LDH's very skillfull dyno based tuning work you are staring at. Keep in mind that the chart is for Full Throttle and is not representative of partial throttle. The torque curve is essentially somewhat unstable 3700 RPM. Frankly, I don't understand why you'd even cruise at such low revs. I wouldn't be surprised if you got better gas mileage @ 4,000 than in the 2500/2800 band. (Decades ago, I found that my cammed CB750 got better mileage in 4th than 5th at 60/65 mph, and that was with '71 factory pipes not a 4:1 header. The exhaust also sounded better, crisp and steady instead of flat and fluttering some.) I'm not surprised that constant throttle in such a low rev band yields an odd exhaust sound.
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Also, do you have a Power Commander or are you running the stock map?
It is on the stock map currently. I guess I'll just ride at a higher RPM range, sounds better and my ears won't bleed, 😂.
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Please let us all know what you find. I hope it's a pleasant change!
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Did you try a friends helmet. Could be as simple as the enclosure around your ears has a resonance in that spot.
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I’d argue the tuning of you carbs in that low rpm range was off hurting your mileage compared to holding them higher on an old cb750.
for sure turning nearly twice the rpm on a 919 will hurt mileage.
for sure turning nearly twice the rpm on a 919 will hurt mileage.
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If it was the stock broomhandle cam, I'd say a big yes to what you said.
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Intuitively, everyone would agree with what you said. But if the efficiency of the engine goes up as much as I suspect it might by running at 4,000 or so instead of 2500 to 2800, for the same road speed and power output, it might use less gasoline to do so. It'll be interesting to hear what Mckivfan28 comes back with. A good indication will be how much throttle opening he needs at 4000 or so for a given road speed, as compared to 2500-2800. I may end up eating my words, but that's OK. LoLs!
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My money is more efficient at 2800. 4k is a big jump and internal friction of an engine goes up with the square of the speed. And I ride low rpm all the time. I typically get better than average mileage.
When I’m in town I’m still in 6th when going 25mph.
But I’m all for a good test to prove a theory or gut feeling. Hope the op reports back if he gives both ways a fair shot.
When I’m in town I’m still in 6th when going 25mph.
But I’m all for a good test to prove a theory or gut feeling. Hope the op reports back if he gives both ways a fair shot.
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Hey, I just did a super quick search on losses and found this by Kevin Cameron:
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More About Engine Friction
Kevin Cameron responds to questions about friction and pumping losses in motorcycle engines.
www.cycleworld.com
I'm going to swap out for a friend's helmet next time I take it out. My helmet with cheapo foam ear plugs was creating a frequency that drove me nuts. I want to see if his helmet fixes it.
I'll have to track my mileage a little closer and see what it comes down to. I usually go by the amount of trips I take until the light pops on. The new exhaust is definitely gonna affect my numbers as I find myself revving it out more to listen to the Satos.
I probably won't cruise in a higher RPM band now that my ears aren't splitting open. It isn't lugging in the 2500-2800 range and I can always downshift when I need the extra power/revs.
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