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Discussion Starter · #1 ·
I have a 2006 FJR that will not idle when the engine is cold. Once warm it runs and idles perfectly. When do I start troubleshooting this problem?
 

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Could be several things..... start with the basics... do you have a service manual?
1. Fuel - is it fresh or been sitting... put some Seafoam (or a couple ounces of isopropanol) in it to disperse any water accumulation at the bottom of the tank. Does the symptom occur with fresh fuel?
2. Check the MAP sensor... remove it (two screws), check the vacuum nipple is not blocked by a waxy build-up, including the vacuum hose.
3. You could have a vacuum leak, check hoses and the rubber caps on the sync ports are not cracked.
4. How old are the spark plugs/mileage on them?
4a. How many miles on this bike? Spark plug wires to the spark plug adapter connection may need refreshing... pull/unscrew the adapters, trim 1/4" off the spark plug wire, spread the strands, push/screw the adapters back on.... while they are off, check the resistance of the adapters, in the event you may have to disassemble/clean up the resistor's connection inside....
5. When you do get it going, does it come on to fast idle when cold? There is a wax motor on the throttle bodies, which should be increasing idle at startup. May be possible there's a physical sticking of the linkage not allowing fast idle?

Recommend you put your bike and location in your profile for future reference.
 

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In step 5 of RaYzerman's reply, he mentions a wax motor mounted under the throttle bodies, this is indeed the most likely source of your problem. It operates the fast idle circuit of the fuel injection system.

This wax motor, it's actually called a "plunger control" by Yamaha, is operated by a flow of coolant from the radiator system. Hot coolant melts the wax and allows the plunger to move.

Now, the coolant gets to and from the wax motor via 2 small diameter hoses, which often get blocked by sludge in the coolant. Hot or cold coolant no longer flows to the wax motor, it stops working, and your engine no longer idles properly.

One hose runs from the left side of the radiator to the wax motor, and the other runs from that metal coolant pipe which passes across the top of the engine head assembly. You need to disconnect both hoses and clean them out. Good luck, it will be a hell of a job.
 

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Discussion Starter · #6 ·
I have an service manual, bike has around 180,000 miles on it, located in NC.
I looked for the wax motor but was unable to find a Yamaha part number for it, can someone please provide the part number if possible?
Thanks in advance for the help!
 

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You're jumping..... best find out the cause of the issue first. Might be as simple as cleaning things up at that mileage.....

Not available as a service part, is part of the throttle body assembly....... there have been those who have taken them apart and cleaned them to ensure the plunger is moving properly.
 

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Most interesting thread. A wax motor?? Now I've for sure heard it all. I think if this was my bike I would just use a Go Cruise and manually position the throttle on a cold start up and call it good. This is the method I use for fast cold idle on my '93 R1100RSL because of BMW and their ill conceived single throttle cable system used to operate the two throttle bodies located on opposite sides of the motor. Wonder if a good coolant system flush would do any good, you should be so lucky I suppose but you never know.
 

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'05 FJR, non-ABS
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Here's a picture of an '06 Throttle Body set showing the "wax motor" and coolant inlet/outlets...
Regards,
Mr. BR
Automotive tire Vehicle Rim Motor vehicle Auto part
 

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The problem is not having fast idle..... OTOH, there have been occasional reports of not coming off fast idle, which was related to the coolant passages partially blocked and not letting the wax motor warm up. The tubing is small, the feed is from the left side of the rad, which also has a small tube.....
I'd check the items in post 2 in that order before jumping to step 5 and pulling the TB's. The wax motor could be fine.
 
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I was just thinking, if you disconnected the two coolant feed pipes to the wax motor, at the radiator and head pipe assembly only, and then blew the pipes out with compressed air, it might clear the sludge out, without having to pull the throttle body assembly out.

Of course, as soon as you disconnected the pipes, coolant would start dribbling out of the radiator system. You would need to have something in hand, ready to block the radiator outlet pipes while you did this job.
 

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Agreed, there's lots of wax motor bikes, I'd even guess the majority (that aren't throttle by wire).
 
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Well, it must not be a bad system I mean the OP's bike has 180K miles so pretty reliable. I learn something new every day especially on these forums.

I can certainly see the advantages of throttle by wire besides making cruise control more reliable and cost effective for sure. Not enough to get me interested in a newer FJR or any other new motorcycle for that matter especially at 78 years.
 

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In step 5 of RaYzerman's reply, he mentions a wax motor mounted under the throttle bodies, this is indeed the most likely source of your problem. It operates the fast idle circuit of the fuel injection system.

This wax motor, it's actually called a "plunger control" by Yamaha, is operated by a flow of coolant from the radiator system. Hot coolant melts the wax and allows the plunger to move.

Now, the coolant gets to and from the wax motor via 2 small diameter hoses, which often get blocked by sludge in the coolant. Hot or cold coolant no longer flows to the wax motor, it stops working, and your engine no longer idles properly.

One hose runs from the left side of the radiator to the wax motor, and the other runs from that metal coolant pipe which passes across the top of the engine head assembly. You need to disconnect both hoses and clean them out. Good luck, it will be a hell of a job.
My Yamaha sport bike has this style of setup. It's an auto-choke. There was a time when there was air in the cooling system. (coolant reservoir was empty) There was also a time when I simply had to clean up the little piston that moves in/out of the cyclinder, as well as the spring-loaded apparatus that it pushed against.
 

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Pretty sure Gen 3 have it too. As well as a bunch of other bikes.
 

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Pretty sure Gen 3 have it too. As well as a bunch of other bikes.

For the Gen 3 FJRs starting in 2013, Yamaha replaced the wax motor fast idle system with a stepper motor controlled by the ECU along with the throttle by wire system. All idle speeds, as well as all other engine speeds, must be approved by yo' mama. There are no convenient user adjustments unless you have a way to break into the ECU programming. At idle the ECU reads all the sensor inputs and decides just how much and for how long fast idle is necessary. Some of the sensors are a little sensitive and sometimes problematic, you know, the TPS!!

Ivan has apparently figured out how to break into the ECU and provide a number of "adjustments" to the system.


dan



I worry that the person who thought up Muzak may be thinking up something else. - Lily Tomlin
 

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Ahh thanks Mr. Cooper. I learn something new everyday. (y)

BTW... your middle initial isn't "B" is it? :LOL:
 
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They are more common than you would expect. Cheap and effective thermo-device. If you have a pressure washer it more than likely has one. It operates the by-pass for water pressure.
 
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