Strange Dyno Result - 2010 Honda Hornet 600

[Zen Dog]

Dear depraved inhabitants of BCF. I put my bike on the dyno, and the results are.... odd.

Some context -

Bike is a 2010 Honda CB600F Hornet ABS - https://www.motorcyclenews.com/bike-reviews/honda/cb600f-hornet/2007/ I bought it a couple of months ago. It's in generally very nice condition. It's done 16k miles and just had the valve clearances done. It has a Healtech gear indicator, and a quickshifter (which is ignition only). I don't like the quickshifter so it's been disabled/bypassed and wasn't powered when the dyno run was done. The previous owner fitted a set of aftermarket headers and silencer, replacing the original system. But he didn't get it remapped. This last point is the reason I put it on the dyno, as I was worried it might be running too lean with the reduced backpressure of the new pipe.

So, the dyno graphs. There are 3 runs on the printout.
1 Slow Throttle Roll On
1 Wide Open Throttle (WOT) without load
1 Wide Open Throttle (WOT) with load.

The dyno tester is a specialist in classic bikes, modern FI bikes aren't really his forte. But he didn't seem worried about most of it, particularly the air/fuel ratio which he said was "acceptable". Also the big spike in the WOT load run is because he was getting a dirty signal from the ignition (this is also the reason there is no measured torque), so that can be ignored.

What he did seem very confused about is the power just flatlining at 70hp. This bike is listed as being 100hp (at the crank). That should be around 85hp at the wheel/dyno. He said it looks as though the bike is going to make exactly that, and then it just stops making any more. He asked me if it was electronically limited, or an import, or if I'd heard of any speed limiters applied to this model. As far as I know, none of those things are true, and the bike is completely standard apart from the mods I've mentioned.

I did find this thread on reddit, and the symptoms aren't the same, but I wonder if I could be seeing early signs of this issue - https://www.reddit.com/r/MotorcycleMechanics/comments/1nk8ddx/honda_hornet_600_2012_bike_wont_rev_past_7k_under/

So, what could be the cause? And how can I fix it?
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Current - '94 VFR750FR (Dead), '00 VFR800FI, '10 600 Hornet - Previous - '11 CBF125, '10 Street Triple R, '92 MZ ETZ301, '05 TTR250, NSR125R, KMX125, "Honda" Win
My bike trip around S.E. Asia 2010/2011

[stinkwheel]

The bikes own gear sensor and clutch switch both working as they should? Effectively does the bike know it's in top gear with the clutch out?

They'll sometimes pancake the power curves if the bike thinks it's in got the clutch pulled or is in neutral/a lower gear to stop you rev-bombing it to death or flipping it.

Both systems may have been messed with if you have an aftermarket gear indicator and a quick shifter.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Zen Dog]

[A100man]

[stinkwheel]

[Zen Dog]

[stinkwheel]

Also check it's an official UK model. I bought a VFR750 a few years ago and it wasn't until I found an optical switch taped up in the back of the clocks I did some more digging and found it was a Japanese import with UK clocks fitted.

Restricted in various ways to about 30% less power than the UK model. I'd thought it was a bit lacklusture compared to my previous one and had put it down to it being an older model. Not all of the differences were reversible either.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[sickpup]

I can't find any information on it but I'm wondering if it's restricted?

There was a European country, I think it was Germany who used to have stepped licensing. First step at 40ish BHP and the second step at 70ish BHP.
There was also a Japanese restriction of 70ish BHP, I worked on a GSXR750M that was restricted via ignition, carbs and cams.

If it was mine, before I did anything I would check whether or not its an import and whether or not it's a UK spec bike. The print out does suggest its restricted to me.

[stinkwheel]

[A100man]

[sickpup]

So the Japanese restriction would be 77bhp and a 10% or so loss through the gearbox would take us down to 70bhp or thereabouts so it fits. Now just because it fits doesn't make the idea right.

If it was a carbed bike I would think the slides weren't moving or had a restriction in the carb tops to restrict movement as a lot of European bikes had when there was a gentlemans 100bhp agreement.

Is there a throttle movement restriction on the bike? could either be on the throttle tube inside the housing or could be on the throttle bodies.
Could even be a movement restriction on the throttle body butterflys.

What exhaust was fitted? potentially the exhaust could reduce the engine breathing or the Lambda sensor not refitted.

The fuel pump could be on the way out and not flowing enough fuel.

The air filter could be blocked or the airbox trumpets removed to 'flow more air'.
Inlet snorkels still in place, again people remove them thinking they restrict air flow.

Why does the ignition have a dirty signal, what's causing this?
Have the plugs ever been changed? HT's trimmed? plug caps/coils checked?
Pretty sure you have replaceable HT leads so these are worth changing. If the the spring retainer in the plug cap, the bit that clips onto the plug top is broken it would give a dirty ignition signal and loads of interference so these may also need changing. Check the resistance of the plug caps as well, likely around 5K ohms.

Was the bike connected to a reader while it was run on the dyno? this would let you know if anything odd was going on.

[Zen Dog]

Thank you for the suggestions. I've been doing some investigating.

Restriction was my first port of call as it fits the symptoms so well. The ECU is marked 38770MFGD02 Keihin, made in the UK, which seems to be standard (according to fowlers parts fiche). Checking for airbox/intake restrictions is harder than I expected. The airbox access for changing the airfilter is separated from the intake trumpets by a mesh divider, and (due to the spine frame) getting past that requires removing the entire EFI system off the bike. So I got a torch and spent a long time shining it through the mesh instead. They look exactly like the ones in the italian service manual I found to me, but because I can't actually get my fingers/eyeballs to them properly, I can't be 100%.

The bike gives every impression of being a standard UK model. Labels are all in english, I've got the service book and owners manual and they're in english too. HPI check says it was first registered 2011. Code under the seat says it's a CB600FA9. That may mean it's a 2009 model, but I can't find anywhere that can properly confirm that. So it's possible it was somewhere else for 2 years and imported. It's also possible it sat in a Honda dealer for 2 years. This is exactly the period that everyone who wanted a naked 600 bought a Street Triple. Overall I'm not sure how I can 100% confirm it's a UK model, but I'm going to say it probably is. If it's not a UK model, that fact has been deliberately obscured.

I've removed the quickshifter. The previous owner had fitted it, and lets say the attempt was amateurish at best, and I say that as an amateur. One of the new quickshifter coil connections was taped to the old one in order to make the connection. It's now been completely removed, though I did have to leave one wire tap in place and just cut the connection to the quickshifter. I wonder if this was the cause of the "dirty ignition signal" issues the dyno guy reported.

I've also been riding it a bit. Partially this is just to run the tank down so I can get in there and have a look at the fuel pump. But it was also to see if I could feel the power flatlining. Straight after I picked the bike up from the dyno, I took it out and redlined it a couple of times, and it felt like it wasn't giving more above 10k. But I took it out today and now I'm not so sure. The bike is so high geared it will do about 70mph in first, so opportunities to rev it out properly aren't actually that easy to come by, and IL4s increase power in such a linear fashion that the expected change in feel between it continuing to increase power, and "only" giving 70hp, can feel pretty subtle. There were times today that I felt it kept building power to the redline, and other times that it lacked that final zing at the top. But I can't be sure that either feeling wasn't just in my head. Partially this difficulty and subtlety makes me wonder if it's even worth worrying about. But now I know there's an issue I need to get to the bottom of it.

Sickpup, hopefully some answers to your other questions. I've been thinking about throttle movement/body restrictions. I don't think movement restriction is likely, because I'd expect the resulting power curve shape to be normal, but it would happen to top out at ~70hp. Not this strange flatline. Body restrictions are definitely possible, but again like checking the intake trumpets, I'd have to take the whole EFI system off to check and honestly it's like spagetti with all the pipework and wiring. I'm going to try to exclude some other possibilities first.

The exhaust is a set of Black Widow headers, and some cheap baffled silencer (I can never remember the name for some reason). They are definitely not fancy, but they don't look obviously awful, if you know what I mean. The lambda sensor has been refitted. I've got the original exhaust, and I'm tempted to refit it, partially to exclude it as a cause, and also because I'm not really into anti-social exhausts, and this one is borderline. But I need to check over the old exhaust and check all the parts are there, as the previous owner may have not given me everything, may have buggered the thread for the lambda sensor getting it off etc. etc.

Fuel pump is definitely a possibility, I've seen it mentioned multiple times by owners, and it was a known issue with the generation of CBR600RR that the Hornet's engine was based on. Officially the fuel pump and filter are all one (incredibly expensive, and now unavailable) unit, so no one ever changes them. I'm just about to order a chinese replacement, then I'll take it apart and compare them. I'll probably try to keep the original pump unless theres something obviously wrong with it, and just change the filter, but we'll see.

I'm not sure on the cause of the dirty signal. But I got the impression that the dyno guy was having a problem getting a good reading, not that he thought there was something wrong with the bike's ignition. But I didn't question him further about this. The plugs have been changed, the previous owner gave me the old ones, they look ok to my unpracticed eyes.

I don't think the bike was connected to a diagnostics reader when it was on the dyno. That does remind me though, I found the procedure for reading any stored codes, so I need to do that and see if there is anything in there.
____________________
Current - '94 VFR750FR (Dead), '00 VFR800FI, '10 600 Hornet - Previous - '11 CBF125, '10 Street Triple R, '92 MZ ETZ301, '05 TTR250, NSR125R, KMX125, "Honda" Win
My bike trip around S.E. Asia 2010/2011