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Discussion Starter #1
Kind of disappointed in the numbers I got, but I'm fully happy with the bike, so they are what they are. Just did a few baseline pulls. Guy actually said my FP3 tune is virtually spot on, there'd be no point in tuning it. I've got the V&H Naked O2 intake. NGK Iridium Plugs, Sumax plug wires, Firebrand Grand Prix exhaust, and of course the V&H FP3 tuner. I used the V&H intake and the V&H exhaust w/o baffles tune. Video coming shortly. For now, here's the dyno sheet.
36hp, 31ft/lbs torque. Guy on the dyno was blown away at a Harley revving to 8500rpm. :)
 

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So, that's 72 hp/liter. The 750 develops, as per the Cycle World test, around 77 hp/liter; according to the motorcycle.com test, it's about 72 hp/liter. A Sportster 883 develops about 53hp/liter. Yamaha's Star Bolt makes 49 hp/liter. Honda's NC700X makes 71.6 hp/liter.

I know you expected/wanted more, but really, for a Harley v-twin, these are outstanding numbers. When's the last time a Harley made more power than a comparable-design Honda or Yamaha? Never?

I've got the Nightstick slip-on, V&H Naked intake, and the FP3 for my 750, but haven't had a chance to install 'em yet. Ideally I'd like to find a local shop where I could do a before & after test, on the same dyno, to eliminate as many variables as possible.

I guess the big question is -- how does your 500 perform, real-world, using the butt dyno? Versus when it was stock?

Harley lists the stock XG500 at 29.5 ft/lbs, so 31 isn't a huge jump, but it's over 5%. That's peak though; it'd be nice to see a before & after to see how much it's gained all throughout the rev range.
 

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Not all dynos are created equal.
That's for sure. The only fair way to compare would be to run both bikes on the same day under the same condition on the same dyno. Not the same model of dyno, but the actual same dyno.

What are these dyno runs costing you guys?
 

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https://youtu.be/-zTRAqf-n28
And as far as butt dyno, I was really predicting 45hp. It feels plenty fast to me. Still very happy with the bike. :)
Okay, so here's the thing - the "peak" horsepower may not even be changed at all, but the overall power curve might be somewhat or even greatly enhanced. That's the kind of thing you can only really know if you have a "before" run, and an "after" run.

The K&N Filtercharger is a great example. Look at their chart here:
http://www.knfilters.com/dynocharts/63-1130_dyno.pdf

Now, check that out carefully. If you look at the absolute peak power, the point where both the "stock" and the "filterchargered" bikes are making their absolute most horsepower, that happens at about 7200 to 7800 RPM. And the blue line, the stock bike, actually makes a little more power than the K&N bike does at 7800(!) But if you were to say "a bike with the K&N filtercharger makes less HP than one without", that would be a totally dishonest representation of what really happens. The K&N bike is showing excellent power gains throughout the power band, especially where it counts - 3000 to 6000 RPM, even if the actual "peak" horsepower might be a tiny bit lower than the stock bike.

So it's entirely possible that your bike is doing the same. You might be getting some nice decent substantial increases throughout the power band, but the absolute peak (usually achieved only at the highest RPMs) might not be all that impressive.

So, yeah, I've just talked myself into spending the extra to get a before and an after run for when I install my goodies...
 

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Discussion Starter #8
That's for sure. The only fair way to compare would be to run both bikes on the same day under the same condition on the same dyno. Not the same model of dyno, but the actual same dyno.

What are these dyno runs costing you guys?
$80
 

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Kind of disappointed in the numbers I got, but I'm fully happy with the bike, so they are what they are. Just did a few baseline pulls. Guy actually said my FP3 tune is virtually spot on, there'd be no point in tuning it. I've got the V&H Naked O2 intake. NGK Iridium Plugs, Sumax plug wires, Firebrand Grand Prix exhaust, and of course the V&H FP3 tuner. I used the V&H intake and the V&H exhaust w/o baffles tune. Video coming shortly. For now, here's the dyno sheet.
36hp, 31ft/lbs torque. Guy on the dyno was blown away at a Harley revving to 8500rpm. :)
I was expecting around 40HP at wheel considering the changes you made. One thing I see is that torque starts decreasing quite rapidly after around 5300 RPM. I have not seen the dyno graph of a stock 500 (so this maybe expected) but for 750 torque really starts reducing only after 7000RPM. I would expect this behaviour to be similar for both bikes.

My 750, Same Setup. Different Tune. V&H SO with Baffle and High Velocity Intake Dyno'd at 70 HP and 58 Ft Lbs Torque.
70HP is quite impressive compared to stock which is around 53 to 57HP
 

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Discussion Starter #11
I've read that the 750 has better heads (better flowing ports? Bigger valves? Not sure..), better cams, and I'm almost certain it has a slightly larger throttle body on it. I wonder how the 500 would do with those components swapped onto the 500. It's also odd that the 750 has 10.5:1 compression and the 500 has 11:1 compression, according to the owners manual.. Seems like it'd be the other way around given the dyno results. I agree something is definitely amiss here.
 

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I'm not 100% sure but I think basically the 750 and 500 are the same engine/transmission with the exception of a larger bore and maybe a larger throttle body. Would be interesting to see Harley chime in here with specifics.
 

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I'm not 100% sure but I think basically the 750 and 500 are the same engine/transmission with the exception of a larger bore and maybe a larger throttle body. Would be interesting to see Harley chime in here with specifics.

I check the official specifications from Harley and I was spot on. They are identical bikes in every way except engine bore (3.35 in vs 2.72 in) and throttle body size (38mm vs 35mm). (even their compression ratios are the same).
 
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