2000 VFR800i throttle and idle nightmare

G'day all. I am going to preface this with the fact that some details may be missed or omitted, as I'm not entirely a slouch with mechanics. I've rebuilt transmissions and transfer cases, swapped fuel and induction system components, swapped axle/steering on my truck, etc. Bikes aren't my forte per sè, but I'm not usually bad at this. 

I'm in a pickle. Well, I got myself into one. 

Last April, I took my VFR apart to do a PAIR delete and starter valve synch. I was in no rush, I work better when I'm not flying along, and had the bike apart a few days. 

Before it went together, I was called out of town for work,  and one thing lead to another, and it never went together properly. I kept everything very carefully, and am missing no parts. 

This past week, I found out that for my 3rd year of trade school, I'm being sent to Moose Jaw, SK, which is 4 hours fromy home, and I will need the bike in order to travel back and forth weekly. 

So, I got down to putting it together. And it all went fairly swimmingly. I replaced all of the vacuum lines under the throttle bodies, and capped off the PAUR related areas of the airbox. 

When I got the bike together, I found it unable to properly idle. I had mucked with the starter valves before, and lost the factory settings, so, as a precaution, I disconnected the cold idle circuit and turned the valves fully closed individually, so as to 'start from scratch' when ready to set them. I kept the bike running until it was ~60°C indicated, and found that it would not idle anywhere near a normal amount. It takes off to 5500rpm. The wax unit is disconnected/slack, the set screw is backed off fully. 

During a bit of playing around, I found that the return side of the throttle cable was not fully returning the throttle bodies to closed. If I disconnect the cables, it'll snap shut. 

But when hooked up, it doesn't. 

Is the return side of the throttle cable somehow adjustable in a way I'm not understanding? The throttle side is, but not the return side. Adding slack to the throttle side does nothing.

What am I missing here? 

Be very mindful of throttle cable routing if the throttle won't snap shut nicely. The service manual has useful diagrams (let me know if you need these). You could also lube the cables if needed. All the return force is in the spring at the throttle body, and cable slack can be adjusted there and finally at the throttle tube. 

Others have had odd high idle events when there were air leaks in the vacuum lines. There is a mess of these, they all need to either connect to somewhere or be capped off. The starter valves are effectively adjustable air leaks, and any other leak will also lead to a higher idle. 

I replaced all the lines, I'll check the routing. We're talking about a millimeter or two of slack required, so it could be routing. 

Although that is odd, as the bracket which holds the cables on screws into place without a hassle. With the bracket removed I can freely move the cable bodies (sleeves and all) back and forth. Its as if the bracket is in the wrong position when screwed into place. 

Try loosening the bar end weight and see what happens. Too tight it may just "grip" the grip...

I'll do that, although why it'd need messing with is beyond me. I never touched it beyond taking off the bracket and cables at the throttle bodies. 

I had a very similar problem with my 5th gen just before I put the bike away for the season this year.  Previously, I had installed heli-bars and not re-routed the throttle cables as per the instructions provided by heli-bars (they appeared to have enough slack even at full lock on turns) when I noticed that the throttle did not snap back as it did before.  After changing the routing of the cables per the instructions, the throttle snapped back better but still not quite as well as before.  Lesson learned.  LOL

The next thing I installed were Throttle-Meister bar ends and once again I had a similar problem with the throttle not snapping back as per normal.  Long story short, it turned out that over time the throttle grip had worked its way down the tube a bit and was rubbing against the bar end.  When I removed the bar end, it worked perfectly, so I removed the throttle grip completely cleaned the throttle tube and re-installed the grip, ensuring the grip did not make contact with the bar end.  Throttle now works perfectly.  

Try the simple things first.  LOL

I'll be back on it this weekend. First step is to start it without the cables hooked up and see if it runs properly. If it dies, the issue is in the cables. 

SlimWhitey, 1/15/2018 at 2:17 PM

When I got the bike together, I found it unable to properly idle. I had mucked with the starter valves before, and lost the factory settings, so, as a precaution, I disconnected the cold idle circuit and turned the valves fully closed individually, so as to 'start from scratch' when ready to set them

Once you achieve full closure of the throttle bodies, this will be your next problem. You will need a valve sync gauge and readjust the starter valves.

There is a sequence for doing this for a 2000 model, but I am not clear on the procedure.

I'm going to guess you'll need to crack the throttles open in order to get her to start and run, then start the procedure, adjusting the idle as you go.

I have a gauge. Although its a little disappointing, as the increments are not marked in inHg, its just an arbitrary scale. 

I may just snag 4 indivual vacuum gauge pods and hook them up. 

Update:

Not the cables. Started it with the cables fully unhooked, and same issue. 

Got it to operating temp so the idle would smooth out if I held the butterflies closed, and hooked up a vacuum gauge to 2 of the cylinder ports used for SV synchronization (for the sake of convenience). 

Needles all over at idle, fluctuating wildly between pressure and vacuum. 

When allowed to free rev to its currently natural idle of 5,000rpm, read about 6inHg. Tells me I have an intake leak below the butterflies. Which makes no sense as my intake boots are well tight. 

And another side thought: 

I did a paid delete on this thing, and the pair system essentially acts as a crankcase vent on a solenoid to my eyeballs, at least with how it's designed. Now... I blocked off the pair plates... What the hell is venting my crankcase? As I thought of this, I noticed a hissing and an oil leak from my front valcecover. Surely my valve cover gasket is now my crankcase vent.  With that thought.... What did I so wrong here?  

Second update: I'm an idiot. Haha. Going to see if this works, if it does, you can all have a great big laugh at me. ?

So, update. 

Crazy high idle and crankcase breather issue fixed. Now I'm setting a TPS, MAP, and MAP vacuum tube code. 

Stumbles on throttle, and when it doea rev it doesn't come back down. Not really sure why I'm randomly setting codes that didn't exist before, but I'm quitting for tonight because its midnight or near to it and I'm going to set this bike on fire and buy a 600 like everyone else right away. 

Hahahahaha, been there, done that line of thought...

Patience grasshopper.....

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If you have turned on the ignition before reconnecting all the sensors, that will register as multiple faults in the FI system. It would pay to clear the fault register and restart the bike, then you will only see the current faults.

How do I clear the faults? Tried the age old 'disconnect the battery and tough the cables together to drain the system power", but it didn't work. 

Last time I did a valve sync I used a 4 gauge instrument with each vac hose having a small plastic screw valve to eliminate that "bounce".

For a 98-99 it's a fairly straight-forward procedure. Someone with a 00-01 could tell you more about doing this with the "wax unit".

To clear the codes:

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My synch tool has the adapters, my single gauge pod does not. Good point.

I'll clear the codes and start over. Thank you! 

Dammit if I can rebuild an nv4500 and decide to swap the entire front end in my truck on a whim I can get a motorcycle to run. 

Tested the harness and TPS. 

Got 330ohm resistance on the TPS when closed, when the throttle is opened it climbs steadily to 1350ohm. 

Got 5v power at the power wire, have no resistance at the ground wire, have 160Kohm at the signal wire. 

To me, resistance climbing as the throttle opens in the TPS is a bit odd, but its steady and not random. Honda spins engines backwards, if they wanna run a TPS backwards so be it. 

The factory manual is useless as it wants me to use a Honda test harness that I obviously don't have. It lists output voltages from the TPS, but not resistance, which is kinda off to me since testing a potentiometer like a TPS is as simple as testing resistance...

My VTR1000F also use a TPS, and the service manual has some detail on its operation (in Ignition section):

Check that the resistance between the red/yellow and green/black wire terminals varies with the throttle position while operating the throttle grip.
Fully open - Fully closed position: Resistance decreases
Fully closed-Fully open position: Resistance increases
If the correct measurements cannot be obtained, disconnect the throttle sensor 3P connector and perform the same inspections at the sensor terminals.
- If the measurement at the leM is abnormal and the one at the throttle sensor is normal, check for open or short circuit, or loose or poor connections
in the wire harness.
-If both measurements are abnormal, replace the throttle sensor.
Connect the ICM connector.
Turn the engine stop switch to RUN and the ignition switch ON.
Measure the input voltage between the yellow/black (+) and green/black (-) wire terminals of the
wire harness side throttle sensor connector.
STANDARD: 4.7 - 5.3 V
If the input voltage is abnormal, or if there is no input voltage, check for open or short circuit in the wire harness, or loose or poor ICM connector contact.

It is accepted VTR1000F owner's lore that the TPS should be set to 500 Ohms at idle, for best low speed operation. On the VTR you can adjust the relative position of the TPS body to the butterfly shaft to set the resistance. 

I've got the factory manual section and figured things out a bit better, going to test tonight. What the manual does not note is proper resistance at idle, but with some math I can figure it out from the factory values of voltage and amperage. Then if I need to reset the TPS I can. 

Just out of interest, where in the manual did you find that?

Page 198 I believe has the formula for signal voltages and values for input voltages. 

With the formula for signal voltages and the value for input amperage (which I could measure), a guy could derive the desired resistance with the throttle closed. 

No matter however. I used a pin to tie into the connector for the TPS while it was hooked up, and ran my tests on output voltages. They're way low. 

Remembering my old dodge TPS, I marked clearly the factory location and attempted to adjust the positioning of the TPS to see if it could be 'advanced', so to speak, but to no avail. She's hooped. Odd that it calved out during my work, but not unheard of I suppose. 

I'm going to buy a used one and set it in the factory position, see how it goes. Honda dies not sell the TPS, and those bastards want 2500 CAD for the complete throttle body setup. Like hell. I could buy another VFR for that. 

Got a set of used TB's, slammed em on, she's perfect. Airbox and pair mods worked well. 

Good news,

was watching this as it developed, so TPS possibly was the issue?

TPS was certainly the issue, as I bought bare throttle bodies. I tested the TPS I had according to the factory service manual, and the voltage was low. 

I also made sure to purchase one from a 98, in order to ditch the wax unit. Took the choke cable and lever from a CBR F4, works like a treat. 

Gotta set the 98 Starter valves for my bike, and then mark where the choke actually starts doing any good. If its going to be a pain in the ass I'll order a factory cable and lever. 

yeah starter valve sync is on my list at moment,

but doing a suspension sort out, New Ohlins rear shock is in and my F4i fork internals have arrived just waiting for the new 9.0N K Tech linear springs to show and do a full set up and lastly fit my new carbon hugger to protect the Ohlins and I will be ready to go for a few miles/years.

14 hours ago, manoil

yeah starter valve sync is on my list at moment,

but doing a suspension sort out, New Ohlins rear shock is in and my F4i fork internals have arrived just waiting for the new 9.0N K Tech linear springs to show and do a full set up and lastly fit my new carbon hugger to protect the Ohlins and I will be ready to go for a few miles/years.

You're bike sounds much more well cared for than mine. The last few years have been very lean and I've had to neglect her so.