Apex RPM won’t go below 3-4000 after some riding. Clutch? Throttle?

[Hendo85]

I can’t get this idle below 4000rpm after I hit the throttle. The idler nut is tight too..hmmm. What do I do next? Clutch was cleaned, throttle bodies sprayed clean, throttle seems to be moving nicely. What’s my next move? Please help

 

[maim]

try restricting the air flow as it might have a vac leak and the ecu is compensating with more fuel for the added air. iac clean and free as well?

 

[Hendo85]

try restricting the air flow as it might have a vac leak and the ecu is compensating with more fuel for the added air. iac clean and free as well?

How do I do that? Squeeze the lines?

Is that what this is @maim ? I doubt it’s clean since I don’t what it is hahah.

 

[maim]

just put your hand across the end of the airbox horns to restrict the air flow.

 

[74Nitro]

Take it to someone that has experience working on them.

 

[Hendo85]

Take it to someone that has experience working on them.

That’s what I’m afraid of….1000$ later and i won’t get it back until January pfff

i can fix anything if you tell/show me how….I build homes from the ground up. But get me to the point that I cannot go any further on my own

 

[Hendo85]

just put your hand across the end of the airbox horns to restrict the air flow.

So I did this and all 4 horns were different. When sitting on the machine…the far left sucked like a vacuum…next one did half and then the other two didn’t do anything to my hand.

But like @74Nitro said. I may need someone experienced in that department. If anymore has any numbers near Burlington/Hamilton let me know. I just called one guy and he was busy until January.

 

[Hendo85]

So Yamaha says it’s the idle control solenoid. I need a new one but they don’t make them anymore…told me to go find a used one. So this is what you call a IAC, correct?

 

[RobX-1]

I realize you're in Canada but Travis (@hibshman25) at Barn Parts sales good used 4 stroke parts and does ship to Canada.

 

[9Lives]

IAC is (idle air control) on this engine it is adjusted manually. The part you circled in the post above is your idle air control. If you look at the parts manual under intake 2, part #40 is the idle speed adjustment screw. If you turn this and the idle speed does not change something else is wrong. It also has a high idle thermowax device on the other side of the IAC. It may be stuck and allowing to much air into the engine at idle when at operating temp. If that is the case the whole IAC will need to be replaced, they don't sell the thermowax separately. The 4 brass screws on the top of the IAC are for your throttle body sync, just FYI. There is no part number for the complete IAC in the parts manual.

This is from a FZ1 forum, same thermowax unit as this sled. Unfortunately the pics are no longer there.

"The thermowax unit has one job and that's to let more air into the motor when cold and press the idle air linkage assembly to an operating temperature position when hot. It's also the device that the idle screw threads in to provide the right linkage distance for the proper idle speed. Unfortunately, if this part fails, it can cause the bike bike's RPMs to hang/take a long time to return to normal when you shut the throttle, never return to a normal idle even when hot and/or make the idle screw do absolutely nothing.

I've devised a 1 cent solution to thermowax failure.

Disassemble your thermowax unit. Remove the 19x3mm rod from the assembly (put it in your toolbox somewhere), place Abraham Lincoln above the piston, reassemble as shown.

What this does is basically force your thermowax unit to be in the 'warmed up' position 100% of the time. It will disable fast idle entirely, but if you're having drivability issues... it's better to have the bike take a bit longer to warm up than be stuck at a near 3500+ idle. You could use this as a permanent solution if you're cheap/don't want the down time while you're waiting for a replacement.... but you will take slightly longer to warm up on cold starts/not idle as well during that time."

 

[Hendo85]

IAC is (idle air control) on this engine it is adjusted manually. The part you circled in the post above is your idle air control. If you look at the parts manual under intake 2, part #40 is the idle speed adjustment screw. If you turn this and the idle speed does not change something else is wrong. It also has a high idle thermowax device on the other side of the IAC. It may be stuck and allowing to much air into the engine at idle when at operating temp. If that is the case the whole IAC will need to be replaced, they don't sell the thermowax separately. The 4 brass screws on the top of the IAC are for your throttle body sync, just FYI. There is no part number for the complete IAC in the parts manual.

This is from a FZ1 forum, same thermowax unit as this sled. Unfortunately the pics are no longer there.

"The thermowax unit has one job and that's to let more air into the motor when cold and press the idle air linkage assembly to an operating temperature position when hot. It's also the device that the idle screw threads in to provide the right linkage distance for the proper idle speed. Unfortunately, if this part fails, it can cause the bike bike's RPMs to hang/take a long time to return to normal when you shut the throttle, never return to a normal idle even when hot and/or make the idle screw do absolutely nothing.

I've devised a 1 cent solution to thermowax failure.

Disassemble your thermowax unit. Remove the 19x3mm rod from the assembly (put it in your toolbox somewhere), place Abraham Lincoln above the piston, reassemble as shown.

What this does is basically force your thermowax unit to be in the 'warmed up' position 100% of the time. It will disable fast idle entirely, but if you're having drivability issues... it's better to have the bike take a bit longer to warm up than be stuck at a near 3500+ idle. You could use this as a permanent solution if you're cheap/don't want the down time while you're waiting for a replacement.... but you will take slightly longer to warm up on cold starts/not idle as well during that time."

Great info, thanks! This is the thermowax? The mechanic at Yamaha did say the spring is probably broke inside here. But yes the idle adjustment screw does nothing at all when turned.

 

[9Lives]

Yes that is the thermowax, the 2 lines that hook up to it are coolant lines. When the engine is cold it allows more air to bypass the throttle plates through the IAC. As the coolant warms up the wax, it slowly closes off this extra air, then your idle adjustment screw takes over. Your throttle plates should be completely closed when at idle, If they are open slightly then your issue is either the linkage holding them open (ie) cable is tight, or the shaft that your throttle plates are attached to are starting to get stiff (usually caused by corrosion) and not allowing the plates to close. If the plates are completely closed, then the engine is getting too much air from another source such as the thermowax or cracked TB boots, gaskets or loose clamps. I am referring to the rubber ones that connect the TBs to the engine. The thermowax has been an issue with motorcycles that have the same setup. With the symptoms you are describing it sounds like the thermowax is causing it, but I would check the boots to rule that out.

 

[Hendo85]

Yes that is the thermowax, the 2 lines that hook up to it are coolant lines. When the engine is cold it allows more air to bypass the throttle plates through the IAC. As the coolant warms up the wax, it slowly closes off this extra air, then your idle adjustment screw takes over. Your throttle plates should be completely closed when at idle, If they are open slightly then your issue is either the linkage holding them open (ie) cable is tight, or the shaft that your throttle plates are attached to are starting to get stiff (usually caused by corrosion) and not allowing the plates to close. If the plates are completely closed, then the engine is getting too much air from another source such as the thermowax or cracked TB boots, gaskets or loose clamps. I am referring to the rubber ones that connect the TBs to the engine. The thermowax has been an issue with motorcycles that have the same setup. With the symptoms you are describing it sounds like the thermowax is causing it, but I would check the boots to rule that out.

I can’t get the IAC off…I guess I need to take the whole throttle body off eh? Hoses and everything is so tight…probably should check those boots at the back as you can’t even see them

 

[9Lives]

It would be a good idea to remove the TBs and check the boots, but you don’t need to take them off just to replace IAC. The boots tend to dry out over time and crack. The hoses are going to be tight as they bond them selves to the fittings over time. I normally use a pair of pliers on the hose where it goes on the fitting and try to twist the hose to break the bond.

 

[Hendo85]

I got the IAC off. Not sure if there’s any issue lol. But there’s no spring in the thermowax and I thought for sure the Yamaha mechanic said there would be…

Maybe it’s the boots!! They’ve never been touched