will not fast idle when cold

So I put the PC5 on and the Pair block off kit . But now it will not fast idle when cold . Anyone ? 2007 VFR800

 

Did you get an answer to this? I have the same bike and fast idle does not work now. I can't trace it to any particular event.

 

Fast idle is driven by the starter valves being opened by the wax unit. Possibly the wax unit is seized in the "hot" position?

 

I'm starting to piece that together after reading some of your replies to another post from a few years ago. Glad it's you who's responding.

First question is how to free that up. I have a 2002 shop manual (mine's an '07); it doesn't mention maintenance, just R&R. Can i just whack it?

But here's a little more to the story; see if this alters your answer. A few months ago (maaaaybe about the time this problem first began to appear), when i was synching the starter valves, i found myself adjusting #4. (No, i had not yet read that it was "White painted" and should not be touched.)

In trying to solve this problem, i've messed with #4's opening, always synching others to it thereafter. BUT, how important is it that it be at some particular setting? And, is it possible that I've "lifted" it so high (using my imagination here) that the wax unit can't reach it in order to raise it to a fast idle? Asked another way, how to get #4 back to where it's supposed to be, if that's crucial?

 

I wonder whether these before and after photos of my 2009 6gen synch might help. No messing with #4 so perhaps you could replicate this situation with another SV Synch and get #4 back to within ball park, idle was at 1200rpm. I had NO cold fast idle issues either before or after the SV synch.

 

Well for the sake of a thought exercise...

The idle speed is controlled by the starter valves. These have to be open to some extent to allow air into the engine, and they have to be sychronised to each other so that the same air flow passes through each. If you open the starter valves more, you get a higher idle speed.

The position of the starter valves is in turn controlled by either the idle stop screw or the wax unit. The wax unit should hold the starter valves open more than the idle screw when the engine is cold, i.e. the idle stop screw should not be bearing onto the starter valve mechanism at all when cold.

Maybe you have closed the starter valves too much by adjustment so that the only way to get a decent idle speed is to extend the idle stop screw much further than "normal". That could make the starter valve position totally dependent on the idle stop screw when the bike is cold, so the fast idle wax unit won't have any effect.

Are you able to eyeball the idle stop screw and see if it is bearing onto the starter valve mechanism when the engine is stone cold? There should be a gap and the cold starter valve position should be dictated by the wax unit.

 

Grum, that did not directly help, i think because mercury levels are going to seek whatever they seek. Yours show 24cm, but i could never get mine above 18, and then it would barely run. They seem to like in the 14-15cm range. BUT, that got me to thinking and seeing other things, so thank you!

Terry, that could very well be exactly what has happened. Now, for some reason i did not get an email alert that you had replied, but going off light bulbs that came on from Grum's input, I came to understand how the wax unit works, and its relation to the starter valve settings and the idle screw. So, i did open the starter valves more, very slightly backed off the idle screw and (i know this has white paint, but i messed with it anyway, since i'm already in the Do Not Disturb zone. And, i noted exactly how much i changed it, so i know where the baseline is, unlike when i first messed with #4!) now it's actually starting to work much more normally. I don't think it's perfectly right, but at least now i have a fast idle, which drops to no effect at 127 degrees F.

To answer a couple of your questions: I did not see your post before i started dinking with things, but it is VERY likely that it was as you said -- the idle screw was doing completely controlling the idle speed, superseding the wax unit. Right now, it is very slightly off the plate when cold, and the wax unit has an adequate fast idle. But I believe that's only because i opened the SVs in an attempt to correct things just as you described.

Currently, the (white-painted) adjuster nut on the wax unit is turned in 1 1/2 turns. I first turned it in 2 1/2 in order to get it to work at all, and that's when i really started to see how the components play together. I've been backing it out in my tests, and adjusting SV and idle screw correspondingly. My hope is, as i get time over the next several days, to eventually get it back to zero and still have everything working as original (fast idle, #4 SV back to what must have been original, warm idle speed, and SV synch).

 

Terry's explanation is spot On, you should not have the Idle Adjuster Rod touching the Synchronising Plate with a Cold Engine.

Your comment......."Grum, that did not directly help, i think because mercury levels are going to seek whatever they seek" is not a good assumption.

My (never adjusted) Number 4 cylinder is showing 240mmHg (24cmHg) both in the Pre and Post SV adjustment photos. The calibrated stainless steel rods in the CarbTune are accurate (You'd hope) and don't just "seek whatever they seek" don't quite understand what you're saying here.

The Service Manual states...
- Map vacuum at Idle = 200 to 250mmHg.

By showing the consistent value of Cylinder 4 in both the Pre and Post adjustment photos, I thought would help you in getting the number 4 reference cylinder back to within spec of the 200 to 250mmHg. As a starting point.

Not being able to get your's above 180mmHg because it will barely run most likley means that ALL SV's and the Idle Adjuster are not correctly adjusted, and this is possibly the cause of your no cold fast idle issue. Assuming no fault with the Wax Unit.

Honda have good reasons for why reference settings/adjustments are white painted with warnings of Not to be adjusted. Adjusting these to mask a fundamental fault or other poor adjustments can be a risky game to play!

Good luck, hopefully you can get it all back to status quo.

 

I finally opened the SVs enough to return the Wax Unit back to its original setting. Then, the challenge was to get them to the sweet spot where it would jump to fast idle as soon as i hit the start button, but also not idle too fast and for too long before settling down to a normal idle speed, controlled only by the idle speed screw. BTW, this might be a fair comparison element -- on #4, the end of the inner shaft is juuuust about flush with the end of the adjustment nut. (It used to be way inside when i had it backed way too far out, by comparison.)

Yes, the idle speed screw is now in a useful range, more "normal", as you said, Terry. So far, by making small changes to the SVs (in about 1/4 turn increments), when i start a cold engine, i still have to hold the throttle open for several seconds before it will idle on its own, then after a few seconds it will go up to about 2k, then drop back down to 1500, then gradually down to 1100 when the coolant is about 132 F.

Yet in all that, the Hg is always -- always -- around 140 once it's warmed up, and never more than about 160. Looking in the manual, Grum, i confirm the spec you referenced - Page 5-3. Therefore, I have two questions: 1) Why does it matter? Once the engine is even a little warm, it idles normally, and it runs normally all through the rpm range. And 2) how would i go about raising the pressure? Does it matter that i live at 6700' above sea level? The one other thing that has changed in the last few months is that my fuel mileage has dropped about 10%. I used to get about 40mpg around town, now it's down to 36. Could that be a clue, or related somehow?

Really appreciate you guys diving in with me, and being a VERY helpful resource to get me back to this point. Looing forward to your thoughts.

Oh, and I'm trying to get a rear shock from Jamie Daugherty, but i just learned he's 6-8 months backlogged and i need something by mid-May, so if you have any other options or recommendations in that area, i'd love to hear.

innokente

 

Hmm good point about your altitude, 6700ft above sea level, assume the Honda vac specs are probably for sea level, I'm at about 800ft above sea level, 6700ft would probably make a big difference!

Not sure how much your fuel economy could change with badly adjusted SV'S as the SV'S are there for idle control, while riding with greater throttle openings the butterflies take over.

 

I did a little research on the possible altitude effect. One website i found gave a chart showing the change of air psi at various altitudes. Sea level being 14.7 psi, 6700' is about 11.3, the drop being about 1 psi/2k'. Another site, https://automotiveamerican.com/2023/05/10/mastering-the-basics-reading-a-vacuum-gauge/ gave an even more helpful chart. Its discussion has specifically to do with car engines and vacuum. Turns out motorcycle engines are just about exactly half the specs of a car (probably due to engine displacement, on average). On that site, average car vacuum is 20" at sea level, dropping 1"/1k' (avg m/c being 1"/2k'). Honda's 240mm is juuust a little below 10". Using those figures, my elevation would drop the vacuum by about 90mm, giving me a range of 110-150mm. Are you at sea level? I'm in Colorado.

At some point, when you have your airbox off again, i'm very curious to know what your #4 SV adjuster looks like, specifically, how much does the inner shaft protrude out the back of the adjuster nut. Mine is, as i said, just about exactly flush. (Just a physical way to judge if i've gotten #4 back to factory setting.)

 

I have no photos of the SVs on my bike at present, but eBay has a few sellers offering TBs with pics. This is one of the clearest/cleanest but the others looked about the same.

 

Terry, that one's pretty different from mine, having all SVs in one place, off to the side. Mine are each next to their own intake port. That did prompt me to research ebay, and i found a few pix that show #4 clearly enough to see that the inner shaft either does not protrude at all, or it just barely protrudes. That's about where mine is now. There appears to be just enough difference yo suggest that there is not a single factory correct setting, but that each bike has had its components balanced to achieve the best fast idle and warm idle.

Still struggling to get mine smooth. I have to hold the throttle open manually for a minute before it will fast idle. Then it idles at about 1600 rpm, then gradually drops to 1000 at about 127 F. I would very much like to just hit the start button, and have it run up to its fast idle speed without having to baby it. Wondering if there is yet some other relevant component that i'm overlooking.

 

Sorry, I did not look closely at your user photo to see you're dealing with a 6th gen, not a 5th. However; the principle of operation is still just the same, just with the components moved around.

If you have to add throttle when cold to keep it running, then there is simply not enough air entering the engine, which means the starter valves need to be further open. I guess you could go back to the starter valves and open them all up a little more but that sounds cumbersome. Given you are happy with the idle when hot, then the only component to tweak is the wax unit adjuster nut. The manual warns not to mess with that but it also said not to mess with the reference starter valve screw and you ignored that! I would mark the nut so you know the factory setting, then wind the nut down to open the SVs some more. I have no feel for how much to change it by, so start small!

 

Question is, how to reset the reference starter valve back to (close to) factory..... only way I know is to get the engine up to operating temp, hook up a vaccum gauge, set the idle to spec and adjust it to the range of vacuum the good book says. Should get you close?? Then you adjust all the others to what the good book says (on 5th Gen. there are differences to make note of). Then retweak the reference if you need to and resync again, if you need to.

 

raYzerman, you wrote "adjust it to the range of vacuum the good book says". Exactly how would you do that? Are you able to change the level of vacuum indicated on your manometer any significant amount, say, more than 10 mm? An automotive article i read explained that vacuum is pretty much strictly an indicator of engine health, compression and efficiency; it's not a thing that has 'an adjustment'. If it's low, you have various problems with the engine. So, I think that what mine indicates is a function of air pressure at my altitude.

Terry, your explanation made sense, so i tried opening the wax unit one turn, then 1 1/2, then 2, and there was no difference, other than that it too longer for the wax unit to fully release the SVs. So I don't see my solution down that path. I can live with it the way it is, but geez, it sure would be nice to just have it fast idle with the push of a button even when it's 38F here in Colorado.

I want to introduce one other element that has been present about the same length of time as the fast idle problem. I didn't mention it earlier in order to not muddy the waters. But, it might be relevant. I get an engine knock when cold (and it sounds like it's only from cylinder 4). I did a valve adjustment in December in the hope of finding a mechanical cause. I had 4 tight valves, and adjusted their shims accordingly. No fix there. I also removed both cam chain tensioners and found nothing amiss. I tightened up the springs in them acc'g to a youtube vid, and that worked fine. But again, no fix. I am wondering if it is detonating, due to an incorrect cold mixture.

So, my question is: What exactly do the SVs regulate? Only air? Both air and fuel? I think of detonation as a timing problem, not a mixture problem. Buuuut, i'm open to anything now. (And FWIW, my poor besmirched reputation, I did not "ignore" the white paint; i just didn't see that warning. Didn't read the fine print carefully enough before beginning!) Interesting that this steady knocking occurs when the engine is cold, but at about 132F, it's less steady, until about 144F it stops altogether, and doesn't recur until the engine is once again cold.

BTW, here's a pic of SVs 2 and 4. You can see how far out the shaft of 4 protrudes. I don't want anyone to have to pull their airbox to check, but i wd sure like to see a stock #4 setting, in comparison, at some point.

 

Fast idle on FI bikes is controlled by how much air the engine can draw in. On the VFR800 the throttle butterflies seal completely, so the only air entering is via the starter valves. These just control the size of a bypass passage around the butterfly. To idle faster, the SVs are opened more, to admit more air. Later bikes with ride by wire throttles have the idle controlled directly by the ECM opening the throttle butterflies.

The other aspect of cold running is mixture and in this case the FI system is looking at the engine coolant temperature and adjusting the injection pulse length to fire in more fuel in when cold (just like a carburettor with a enrichening circuit). I suppose it is possible that the ECT may not be working all that well and there are specific diagnostic measures of ground and resistance that you can do. I believe the ECT unit has two measuring circuits, one connects to the dash readout, the other to the ECM. However I would expect a faulty ECT to trigger the FI fault light.

I do also wonder whether the altitude is a factor in your bike behaviour.

 

There is a difference between total engine vacuum, and what is allowed to pass via the starter valves. I was hoping your service manual might give a general vacuum reading for the reference starter valve, and you could reset that. It won't likely be as high a vacuum reading as the engine vacuum.
When I read my manual for starter valve removal, it says to turn each in and count the turns, but no vacuum reading given for 5th Gen.... which has two of the starter valves set to a higher vacuum than the reference..... just saying the reference will be not as high as engine vacuum, and I don't know any other way to reset the reference if you didn't count turns.

 

raYzerman, yeah, my manual says the same thing -- "count the turns". It wd be SO helpful right now if they gave a recommended range (you know, like the 200-240mm vacuum range). BUT, i'm getting closer to success. Terry, processing your input. Every time you write, i get another piece to the puzzle of "how the VFR induction system works". I will absolutely do the ECT checks later this week (riding weather is back for 3 days).

Question 1: Do the SVs provide air intake throughout the entire throttle range? Such that, even though at idle they provide 100% of the airflow, at full throttle, are they still providing, say 5%? I ask because if they are too open, are they leaning out the mixture?
Question 2: There appears to be an ideal SV opening, like there apparently is for the Wax Unit (hence the now infamous white paint). How is that arrived it? IOW, is the goal to close the SVs as much as possible while still achieving 1) instant cold start, 2) reasonable fast idle speed, and 3) reasonable temp at which the fast idle ceases to affect idle? This approach/goal seems like it would be the most fuel-efficient way to setup induction.

Btw, anyone, at what temp does your cold start/fast idle cease its effect? Looking for yet one more reference point from stock (unadulterated) systems.

 

I'm getting close to my knowledge limit here, but yes the SVs are always open (in their hot idle position) so there is airflow through them at all speeds. So yes they would have some effect on the fuel/air mixture at all throttle openings, however I would expect the effect would diminish as the throttle was opened as the throttle bore is so much bigger than the SV.

I only have a wax unit on my ST1300 (quite similar in layout to your VFR but turned around 90 degrees) but that has no actual temperature gauge, just bars that represent the different zones. My guess is that around 40C the SVs are pretty much back to the warm idle setting.

It is good to examine the logic for the SVs, but ultimately they should be kept open by the idle stop screw at whatever position gives you the correct hot idle rpm. That would mean your possibly misadjusted SVs will be in exactly the same hot position as someone who had read the manual. The only mismatch that I can see from your screw miadventures would be the relative position of the SV linkage and the wax unit when hot, and that should be adjustable with the wax unit screw.