2000 has idle issue

So ... I recently overhauled the cooling system on my 2000 VFR.

- Replaced all coolant system o-rings – two in engine valley, two on left side

- Replaced thermostat and housing o-ring

- Replaced all old hoses with new AS3 silicone hoses

- Replaced coolant reservoir (old one had cracks but not leaking)

- Replaced water pump gasket and o-ring

- Flushed the system with distilled water before filling with new Honda blue coolant

- Replaced all old hoses on throttle body with new silicone hoses (4mm & 8mm)

- Replaced both valve cover gaskets – rear was leaking slightly


I labeled everything as I took it apart, and I also took pictures of every step. I put it back together in reverse order – according to my pictures, my labels, the service manual, and the parts microfiche on BikeBandit.com. Everything matched. I was confident in the way the VFR went back together.


I currently have the bike put back together and it is NOT leaking anything.


It starts and idles – and all fluids are contained.


I did NOT replace the high idle wax unit while it was apart. I thought, “it was not an issue before, so it should be fine and working correctly.”


Now, I have a high and wandering idle. I start the bike and let it get to normal operating temperature.


Then the idle keeps going up and up. If the bike is on the kickstand and in neutral, the idle will be around 2000-2500 RPM. I rode the VFR down the block from my house, and the idle went north of 3000 RPM, even with the clutch pulled in.


I have done the factory-recommended process … uncap the radiator and coolant reserve tank, idle the bike until normal temp, blip the throttle a few times, turn the bike off, then fill coolant to necessary levels (if low). I also squeezed the coolant lines while doing this, to “burp” excess air out of the system.


None of that worked. I still have a high and wandering idle, the same as it was.


What is my issue here?

 

You'll have to excuse my ignorance of the wax motor on a VFR, but most bikes with one have two small cooling lines to warm it up. If those are clear and flowing, perhaps go for a longer ride to full operating temperature and a full cooling cycle should replace any residual air in the system. You could take the rad cap off when cold to see if rad is indeed full.

However, idling up beyond normal fast idle of the wax motor...... you had the throttle bodies off, and high/inconsistent idle would indicate a potential vacuum leak, more likely at the TB boots I'd suspect at this point since you replaced all the vacuum lines....

 

I don't think the issue has anything to do with the cooling system. It sounds more like a vacuum leak when the FI and airbox were reinstalled. Go back through all the hoses and carb boots and make sure you have everything installed correctly and all the hoses back in their rightful places. While doing that, check to make sure you have no small splits in any of the hoses and no cracks in the boots and that the boots are not overtightened. Sometimes a little starting fluid can help pin down the location of an air leak.

 

Just for insurance, I've already ordered a new wax unit with o-rings. I plan to take the bike apart again, as soon as life allows me the garage time.
I want to do everything at one time, and take extra time when I do it.
I just replaced most of the old hoses under the tank with new silicone stuff.
I removed one at a time, cut to length, then installed the new hose in place of the old.
Of course, I will take even more of a keen eye to the hoses when it all gets pulled apart again.
I will definitely try the starting fluid trick, too. I was hoping it wouldn't resort to that.
I will keep ya updated, folks. Thanks for the tips.
Until next time ... keep the sticky side down.

 

I recently replaced the thermostat on my 99. Upon restarting with the manual starter valves open it was great and steady, once warm at normal idle and with the SVs closed I gave the throttle a blip and then the idle hung up around 3k. Not good. When I started fault finding I discovered that I had trapped one of the vacuum hoses (going to the vacuum solenoid for the flapper I think) in the area alongside the front throttle shaft, right side. There is a stopper there for the throttle plates and the hose popped in when I blipped the throttle and then held it open. Maybe check you've not done something similar. Otherwise Norcalboy is right, you have an air leak somewhere. I did find the intake rubbers did not seal too well initially on refitting and made the idle a bit faster and unsteady, but these settled down after a ride/heat cycle.