"Wax" Idle control unit.

The Dark Shadow

The Dark Shadow

Joined
Aug 23, 2022
Messages
355
Age
54
Location
Nova Scotia
This is an idle conversation...

I've started doing some more research into the "wax idle valve", which apparently is no longer wax, but it a bimetal thermo-mechanical device.

The cold-idle is set by the "wax idle valve", and is pre-set at the factory. But several people on online forums with several different honda motorbike models have reported issues with the preset adjustment.

Some people have reported that gas mileage improves with corrected settings.

The warm idle setting shouldn't be resultant on the cold setting, but they may interact with each other.

A few FB group members mentioned that the feed line for the coolant going to the wax idle valve can get clogged (the portion on top of the radiator - top right - that built up corrosion impeding coolant flow for one guy, vs a chip that clogged the intake of the wax unit for another), and when the obstructions were cleared it improved flow, the wax idle valve worked better and the bikes exhibited improved fuel consumption.

So, here's my present situation...

AFTER I changed to 10W30, my bike no longer idles high (3000rpm) after a minute or two of 2000rpm. I thought this was very interesting and peculiar. The high 3000rpm idle when "cool" (not cold) seems to be an issue with the wax idle valve setting and/or coolant flow.

Also, for now, since I didn't want to fully remove my airbox again, I adjusted my warm idle a bit lower. It had been acting strange... Once warm, it would go to the idle where I set it, but then when the bike was "hot" (ie: drive 20min or more), the idle speed would increase. So, for numbers... If I set it at 900rpm (warm idle), the idle would increase to 1100-1300rpm when hot.

Add to this, I was getting 15km/litre, 80 to 90 percent highway driving, mostly near 100-115kph. That's 35.3 US-mpg... Pretty trashy!!

So, after lowering my idle (when HOT, it idles at target 1000rpm+-100rpm), I noticed a vastly improved fuel economy (up to 15-20% improvement depending on speed) - when the bike is hot. Of course, now when the bike is WARM, I have to be careful because the rpm is lower than desired (near 750rpm).

So, as you guys all know, it's a chore to remove the plastics. But I plan to remove them to do some cleaning and maintenance as one guy suggested. It is less of a chore to fully remove the airbox and move the wax idle setting (a few people suggested loosening the stop-nut a quarter turn or so). It's a bummer to have to do that, re-build the airbox, test, then rinse and repeat... But, if I do it once, or even twice, it's still easier than removing the plastics, and I can find out what the effect is.

Have any of you guys had any experience with the wax idle valve...??

There's a few great videos on youtube (honda vfr800) showing how the wax idle valve and warm idle adjustments actually work. Here's some screenshots for the video. And you can search for "honda motorcycle wax idle valve" and find some info on youtube and forums on the internet.

Thanks for any thoughts y'all might have...
 
I was having a similar issue with my 2010.

And since the bike had less than 2,000 miles on it (I bought it wrecked, no warranty ;) ) I figured that the wax assembly was defective. Once I replaced it (from a throttlebody I bought off ebay) , my problem went away.

2010, bought wrecked in 2013
 
Most problems that I have seen related to the SE Thermal valve (wax valve) are caused by problems with something other than the valve itself. One problem is insufficient coolant flow to the valve due to a cooling system problem. Repairing the cooling system defect fixes the SE Thermal valve problem. The other problem is the valve linkages are binding/sticking and not allowing the valve to move freely and/or completely. Cleaning and lubricating the moving parts, and relocating anything that may be interfering with them, corrects that problem.

I find that mine works better with the hot base idle set between 1000 and 1100 RPM. When it is at that stage of the warm up cycle between when the the SE Thermal valve closes, which is just immediately before the first bar illuminates on the coolant temperature gauge, the idle will dip below 1000 RPM but it doesn't go as low as 750. It might get down to around 850 or 900 immediately after the valve closes. I really don't know but I assume that the system is designed to get the engine off of fast idle as quickly as possible to help meet emissions standards. When that happens the engine is still pretty cool and the RPM dips a little as it is now running on the base idle that was set for a fully hot engine, not a cool engine. This is old technology that doesn't have a dynamically computer controlled idle speed that varies the idle RPM based on air and coolant temperature as well as engine load to keep the RPM at a fixed setting, so I don't view this as unusual. This is a very brief stage during the engine warm up cycle that lasts from when the valve first closes to when the second bar on the temperature gauge illuminates at most and then it is pretty much over with.

Unless you had an extremely heavy weight oil in there, it is curious that changing to 10W30 oil caused a change in the warm up idle behaviour. If there was nothing else done except changing the oil I have no idea why that would be.
 
I’ve had that system completely disassembled and reassembled a couple times. Setting the cold-to-warming idle speed is a bit of a PITA, because it has to be done with the engine cold and you have only a minute or so to make the adjustment before the engine warms enough causing the starter valves to close, transferring idle speed control to the throttle stop screw. You then have to let the engine cool off in order to do another cold start and see what you accomplished. It might take more than one cycle.

I will caution to make sure the thermostat is functioning properly and reaches 3 bars on the temp gauge under all riding conditions. It should allow the first bar to appear in about one minute. Any flaky behavior from the t-stat will have you chasing your tail on this.
 
Andrew Shadow said:
Most problems that I have seen related to the SE Thermal valve (wax valve) are caused by problems with something other than the valve itself. One problem is insufficient coolant flow to the valve due to a cooling system problem. Repairing the cooling system defect fixes the SE Thermal valve problem. The other problem is the valve linkages are binding/sticking and not allowing the valve to move freely and/or completely. Cleaning and lubricating the moving parts, and relocating anything that may be interfering with them, corrects that problem.

I find that mine works better with the hot base idle set between 1000 and 1100 RPM. When it is at that stage of the warm up cycle between when the the SE Thermal valve closes, which is just immediately before the first bar illuminates on the coolant temperature gauge, the idle will dip below 1000 RPM but it doesn't go as low as 750. It might get down to around 850 or 900 immediately after the valve closes. I really don't know but I assume that the system is designed to get the engine off of fast idle as quickly as possible to help meet emissions standards. When that happens the engine is still pretty cool and the RPM dips a little as it is now running on the base idle that was set for a fully hot engine, not a cool engine. This is old technology that doesn't have a dynamically computer controlled idle speed that varies the idle RPM based on air and coolant temperature as well as engine load to keep the RPM at a fixed setting, so I don't view this as unusual. This is a very brief stage during the engine warm up cycle that lasts from when the valve first closes to when the second bar on the temperature gauge illuminates at most and then it is pretty much over with.

Unless you had an extremely heavy weight oil in there, it is curious that changing to 10W30 oil caused a change in the warm up idle behaviour. If there was nothing else done except changing the oil I have no idea why that would be.
Click to expand...
Thanks Andrew. You've shared some good info. And I too don't know why the oil change would affect things as it did, but indeed that's what happened... Intriguing, eh...
 
wjbertrand said:
I’ve had that system completely disassembled and reassembled a couple times. Setting the cold-to-warming idle speed is a bit of a PITA, because it has to be done with the engine cold and you have only a minute or so to make the adjustment before the engine warms enough causing the starter valves to close, transferring idle speed control to the throttle stop screw. You then have to let the engine cool off in order to do another cold start and see what you accomplished. It might take more than one cycle.

I will caution to make sure the thermostat is functioning properly and reaches 3 bars on the temp gauge under all riding conditions. It should allow the first bar to appear in about one minute. Any flaky behavior from the t-stat will have you chasing your tail on this.
Click to expand...
Yes, it's funny... So many people say that Honda's are virtually maintenance free, but this bike has several idiosyncrasies that make maintenance a PITA.

My thermostat is verified working properly but that's a good point. Thanks.
 
The Dark Shadow said:
Yes, it's funny... So many people say that Honda's are virtually maintenance free, but this bike has several idiosyncrasies that make maintenance a PITA.
Click to expand...

I have no idea what you are talking about?

20250501_backTogether5.jpg

:rofl1:
 
The Dark Shadow said:
Thanks Andrew. You've shared some good info. And I too don't know why the oil change would affect things as it did, but indeed that's what happened... Intriguing, eh...
Click to expand...

Some here in Houston observe the RPMs climbing higher and longer at start up during our few cold Winter days, and don't bother adjusting as we don't have very many of these.

Is it possible your oil change coincided with warmer Nova Scotia days as well?
 
MidLife said:
Some here in Houston observe the RPMs climbing higher and longer at start up during our few cold Winter days, and don't bother adjusting as we don't have very many of these.

Is it possible your oil change coincided with warmer Nova Scotia days as well?
Click to expand...
Good question but the answer is negative. The outdoor temp has no effect on that aspect.
 
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I should have also asked... Have any of you removed the coolant lines from the wax idle valve in situ (while installed on the bike) in order to clean them...?

If yes, what about coolant drips and spillage...??

I know the space is small and access is not fun, especially with the tank still on.

Thanks.
 
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