Clutch Operation

[BiKenG]

One thing I have noticed on my bike, that I did not notice on previous VFR1200s I've ridden is that as you let the clutch out while in gear, the revs rise a few hundred rpm. Probably some misguided attempt to 'assist' the rider in some way, but even more annoying when I currently have an idle speed problem with it racing at 3K rpm. However, the fact that I've not noticed it on other bikes may indicate a problem there. Or maybe I've simply forgotten about those other bikes or maybe when tick over is normal, you don't notice it.

Can anyone please confirm that this is normal and the revs do rise slightly as you let out the clutch when in gear?

[DaveVXR8]

I've never notice do that on mine.

[andy]

not on mine either.

[jekrumpe]

Not on mine.

[lshark]

i think that that bike is haunted !!!

[BiKenG]

This rise in engine speed is definitely initiated by the clutch switch, but I have now found that it is not due to the throttle butterflies opening further. With the bike on the stand, engine running, in gear and watching the butterflies, they do NOT move as I let the clutch in and out, but the engine speed changes by several hundred rpm.

So if it's not being done by the throttles, it must be ignition timing. As you let the clutch out in gear it advances the timing, probably to the normal correct running value. I can only assume retarding the ignition in this way while not being driven in some way improves emissions or some other aspect of the running of the engine. I guess this doesn't altogether surprise me.

But why does no-one else notice it? Well, I currently have a problem of the engine idling at 3K rpm, whereas normally this would be about 1100 rpm and it occurs to me that a change in ignition timing at that low rpm would not make such a big difference in engine speed, indeed, possibly not even noticeable. But an engine that is already spinning at 3K rpm, it is likely to have a much greater impact and hence a noticeable rise in engine speed.

In fact, maybe it switches the whole timing curve, so at low rpm there is no change, but it simply advances at a faster rate as the revs rise. So under normal circumstances at the correct idle speed, there is NO change. But because my engine is already spinning at 3K rpm the timing curve switch causes a sudden advance, hence the noticeable rise in rpm.

Either way, I'm thinking it's unlikely this is a fault with my bike, just that the actual problem (too fast idle) is exacerbating and obfuscating the clutch/timing issue.

Unless anyone has anything more definitive on this, I will assume there is no actual problem here.

[BiKenG]

I have heard from several other people who have experienced this same rise in rpm as you let in the clutch (i.e. let the lever out) on other Hondas. But now my tickover is back to normal, I simply haven't noticed it, so I'm sure it is as I surmised earlier, it only becomes apparent when the engine is running too fast.

[f3racer]

Every honda I've ever owned does it. From what I've read its to aid in take off from full stop.

[BiKenG]

I've owned Hondas since 1969, currently have about half a dozen of them and I used to work for Honda UK and this is the first time I've come across it. You must have owned those that do it, but no other VFR1200 owner seems to have noticed it - except you it would now appear.

Still, my original question has been answered thanks.

[swimmer]

My 07 CBR600RR had the idle rpm rise with the releasing of the clutch lever.

[BiKenG]

There has been a fair bit of controversy over this in another thread, but it really should be brought into this one which is specifically about this issue.

The following concerns both the 2012 VFR1200F and also a 2012 CBR1000RR FireBlade as I have conducted tests on both.

First of all, it can be seen on each wiring diagram, that the clutch, neutral and side stand switches (which together are used to stop the bike being started inappropriately) are also collectively connected to the ECU (ECM as Honda likes to call it) which is therefore aware of the current interlock status.

When the bike idles at normal speed, there is no effect, but with the bike stationary and the engine running at 3,000 rpm (or close), when the interlock status changes (in this case let out the clutch lever), the engine speed increases by several hundred rpm and back down again when the clutch lever is pulled back in again. It is the clutch switch changing state that activates this. My assertion is that it is the ECU which controls this effect

However, it is NOT achieved by control of the throttle. I have watched the actual butterflies on the VFR as this occurs and they do NOT move and the FireBlade is NOT TBW, so it is quite impossible for the ECU to control its throttle position.

The above facts can be easily verified. What I do not know with any certainty is how the ECU achieves this effect. I suspect it is done with ignition timing, but I cannot verify this.

Since others on this forum and elsewhere also claim to have observed this effect, I think we can conclude it is a design feature. For what purpose, I have no real idea, but with the above hard evidence, there can be no doubt of its existence.

I'm sorry if this contradicts what others may believe, but facts is facts.

[BiKenG]

Some further points to make. Mine are both UK bikes and it is quite possible that this 'feature' is not implemented in all markets. So some models in other countries may not exhibit the same behaviour.

It might also be difficult to observe if the clutch take up point is close to the switch operation as the engine is then trying to drive forward at the exact time the revs would rise and that can nullify the effect. It was not a problem on my VFR, but on the FireBlade I needed to connect an independent clutch switch and simply held in the lever while operating just the switch (at 3K rpm) and the engine speed would rise and fall by about 300 rpm as I pushed and released the switch. Every time, no question.

I would like to re-iterate that in my previous post I tried to keep my speculation separate from what are clearly observable and repeatable facts. I think it's an interesting topic to discuss further as long as it can be discussed rationally and without repeated assertions that I am in some way lying.

[hvfrdave]

My VFR1200F is a 2011 UK model, and I have owned it from new, and mine certainly does not do it.

[BiKenG]

My VFR1200F is a 2011 UK model, and I have owned it from new, and mine certainly does not do it.

OK, that's interesting. Both my bikes are 2012 so it is possible it was only introduced then. Others who've observed it might like to chime in here with info about the age of the bikes on which they've seen it.

I'll check out some other bikes at my local dealer. See if we can get to the bottom of this.

[Dutchy]

and without repeated assertions that I am in some way lying.

hhhm I re-read the topic and at no point do I read assertions of lying. But then again, my command of the English language may be lacking :-)

Now, if you got PM's calling you a holy friar...........

[BiKenG]

Not in so many words, no, but this thread doesn't contain all relevant posts and the inference has been made quite clear.

However it IS getting tiresome so let's concentrate on the technical matter under discussion shall we.

[lshark]

i tried it on my U.S. 2010 model and ....yeah, it did seem to increase rpm....i held the throttle as steady as i could at 3000 rpm and pulled the clutch and it rose about 300-400 rpm.....i have no idea why they would engineer this in,but i'm sure Honda has an explanation which they prob won't tell us....i'm going to try it again and experiment a bit once the neighbors leave for work....it was a bit difficult to hold a steady rpm and i'm not completely sure that my movement to pull the clutch didn't cause my throttle hand to move.....but it did it seem to happen automatically

[BiKenG]

To make it easier, adjust the clutch cable as tight as possible. If the cable is slack, the engine will begin to drive the bike before the clutch switch operates. So temporarily adjust it too tight, you can re-adjust it correctly afterwords.

Pull in the clutch lever, put it into gear (I think I saw it in all gears I tried, but it HAS to be in gear and first will do). Hold the rpm as steady as you can at about 3K and slowly let out the clutch lever. As the switch operates, the engine speed rises by several hundred rpm. Pull the lever back in and it drops. You can do this repeatedly and the rpm changes every time.

I agree, holding steady rpm is tricky. I probably noticed it originally because the engine was idling at 3K and I didn't have to try and hold it. In fact I was trying to make it go slower. I would think that the higher the rpm, the more pronounced the effect.

[BiKenG]

OK, some further, perhaps final enlightenment on this subject.

As I may have mentioned elsewhere, I used to work for Honda UK and so asked one of my remaining contacts about this. Here's the reply:-

"this is something that is built into quite a few models these days to enable a smooth pull away, this is activated as you release the clutch lever through the switch which advances the timing through the ECU"

So there we have it, right from the horses mouth as it were. It does occur and by the exact method I surmised and everyone can be happy that they now know more about their bike than they did before.

[lshark]

well the VFR has a hydraulic clutch so no cable adjustment.....mine did it in neutral ...but the explanation makes sense, although i usually have the clutch engaged and the bike underway before that

[BiKenG]

well the VFR has a hydraulic clutch so no cable adjustment.....mine did it in neutral ...but the explanation makes sense, although i usually have the clutch engaged and the bike underway before that

Yes of course, the VFR is indeed hydraulic. I was thinking of when I tested my FireBlade which seemed to want to move forward before the clutch switch operated. But no way to change that with the VFR. Good call.