High idle question rpm question. I'm

High idle rpm uestion question.

I'm noticing on the first start of the day, my idle speed will eventually get as high as 4K, then will stay that way until I have about three bars on the water temp, then come back down. This was a start in 65 degrees this morning. Seems way over kill to be running the rpms that high. Also, the other day, the high idle didn't come down for 10 mins. I actually had to stop the engine, put in first gear, and restart so I didn't have to clunk it in gear. About 2 miles down the road, it finally came back to idle at the next stop sign. But it was weird. Does this system use some sort of IAC valve? Perhaps it is sticking or being sluggish.

Re: High idle rpm uestion question.

Maybe you have a faulty wax-sensor. Located in the thrittlebody, controls idling at low temp.
The coolant lines to the sensor may be clogged or air in the system.
Martin.

Re: High idle rpm uestion question.

What should the rpms go to first start of the day in mid 60's-70 degrees?

Just now started my 1300 in the garage. Similar conditions (might be a tad cooler). She idled at a needle's width above 1500, maybe a hair of a space between the needle and the 1500 mark. Bike has been sitting for a few days, though iirc, this is the speed it has always idled at upon startup.

When mine is stone cold with ambient temp below 60F the idle will go up to almost 2000 rpm (per the tach) for a minute or two before it starts gradually working it's way down to normal as the coolant temp reaches its first bar.

Right around 2000 rpm for a minute or so and it will go up to 2500 on occasion for like 15-30 seconds. Weather plays a factor in its decision too. Very clever idea Honda installed on these bikes.

Re: High idle rpm uestion question.

I remember being concerned about mine at one point. It used to do this when starting up, and was very noticeable in the very cold mornings. The bike wouldn't be properly warmed up until I had reached the bottom of the hill, so it involved a lot of use of the clutch. The handbook says to wait until it has warmed up before riding. I never liked leaving the engine running and disturbing neighbours at that hour in the morning. My newer A9 model isn't as bad - but since I no longer make the early morning starts, that could well be the reason - As Al said - it is very much weather dependant.

Re: High idle rpm uestion question.

jfheath said:

I remember being concerned about mine at one point. It used to do this when starting up, and was very noticeable in the very cold mornings. The bike wouldn't be properly warmed up until I had reached the bottom of the hill, so it involved a lot of use of the clutch. The handbook says to wait until it has warmed up before riding. I never liked leaving the engine running and disturbing neighbours at that hour in the morning. My newer A9 model isn't as bad - but since I no longer make the early morning starts, that could well be the reason - As Al said - it is very much weather dependant.

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understood, but it is still my opinion that 65 degrees should not warrant a 4K rpm high idle

Re: High idle rpm uestion question.

between 2000 and 2500 is what I have seen on sub 60 degree days.

Re: High idle rpm uestion question.

etalors said:

between 2000 and 2500 is what I have seen on sub 60 degree days.

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sounds reasonable to me.

4K is higher than it should be. I'd pull off the air box, make sure all of the linkages on the throttle body are free and the joints are clean and check that no critters have moved in and built nests that are obstructing it. This could be a new variant on the mice-ate-my-injector-wiring story.

--Mark

Blrfl said:

4K is higher than it should be. I'd pull off the air box, make sure all of the linkages on the throttle body are free and the joints are clean and check that no critters have moved in and built nests that are obstructing it. This could be a new variant on the mice-ate-my-injector-wiring story.

--Mark

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yup, I agree. I have a new air filter that I had planned to put in at the same time as my new Helibar gen 3.2 riser. I'll look everything over then.

Re: High idle rpm uestion question.

Cloud_master said:

my idle speed will eventually get as high as 4K

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That seems pretty high for anytime of day or night. Mine has never been above 2500rpm but the coldest start it's seen is probably 40ºF.

Well I pulled the air box and inspected the throttle body and starter valves. Nothing obvious. I backed the wax valve adjustment by one full turn. Cleaned the carbon build up on the throttle body butterflies. Started it and the cold idle never went past 1,800. Thought I had it fixed. Went to ride today, 78 degree cold start for the day. Went to 1,800 but then started going up to 3k again. Stayed there for like 10 minutes. So just ordered a new wax valve. Ordered the fuel filter as well and will change it since I'll have to pull the tank. Kinda pissed, just got this bike and already having to wrench on it.

Andrew Shadow said:

Don't use solvent doing this- they are said to have a coating that is supposed to be there and the solvent will destroy it.

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little late. Used throttle body cleaner and a tooth brush to get them clean.

I hate to be the one to point this out, but you just ruined your throttle body assembly, as well as your wax valve assembly. The service manual clearly states that the wax assembly is factory set, and should not be altered. Folks who have tried to alter the settings on various forums have discovered that it causes problem issues in other areas etc. As far as the "carbon build up" on the throttle body butterflies, well, that may have cost you a whole lot of money to replace the entire assembly. The only other way to fix them is to purchase a special paste coating from Honda, re-apply it to both the upper and lower butterfly (after completely detail stripping them down to components) then baking them in an oven for several hours etc. I have never seen this method successfully done, and usually ends up with the owner having to purchase the entire replacement assembly after a failed attempt.
It may be in your best interest to locate someone more knowledgeable with your motorcycle before anything else is damaged by good intentions. No disrespect directed towards you, as we have all made mistakes learning things.
Good luck.

Igofar said:

you just ruined your throttle body assembly, as well as your wax valve assembly.

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Larry, What is the purpose of that coating? Cars have no such coating (at least my GMC truck does not, and it gets cleaned regularly with carb cleaner and a tooth brush). What is the downside of having removed said coating? Might it simply mean that the owner of a bike w/o the coating now has another semi annual item to service?

SMSW said:

Larry, What is the purpose of that coating? Cars have no such coating (at least my GMC truck does not, and it gets cleaned regularly with carb cleaner and a tooth brush). What is the downside of having removed said coating? Might it simply mean that the owner of a bike w/o the coating now has another semi annual item to service?

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Actually, most cars DO have that coating. At least, both my Acura ( 2008) and my Ford truck ( 2017) both do, and a few other cars I've worked on in the past 5 years or so. I found out about it from my FIL, who retired from being a Ford mechanic. He recommends only mild soap and water to clean them, but there is a CLC spray cleaner which will work as well. Only use a soft cloth when cleaning....no toothbrushes or other harsh abrasives.

SMSW said:

What is the downside of having removed said coating? Might it simply mean that the owner of a bike w/o the coating now has another semi annual item to service?

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It might mean that, but it doesn't. The owner of a bike without the coating has a set of throttle bodies which will no longer seal properly when the throttle plates close. The rest of what Larry said is spot on.

Cars have no such coating...

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That's a very broad statement, and it's wrong. Off the top of my head, Ford, Mazda, Nissan and Subaru all sell or have sold sold cars with coatings.

--Mark

I guess I'll find out if any damage was done after I pull the throttle body off. Only "coating" I saw, was carbon.