Thermostat Replacement

CDA441 · Dec 23, 2018

The pictures don't seem to work for me so I have copied the opening post and inserted the images for future use. Hope you don't mind Action.

My bike was taking a long time to warm up. I checked the rad.s and they were hot at about 150 degrees. I decided to replace the thermostat my self to save some $$$. I though I would post this to supplement what is in the service manual.

First I put a tarp under the bike to help catch any fluids.

The next step is to remove the tank. After you remove the two bolts at the front and rear you can turn it over and let it rest where the seat usually is. This will let you get at the hoses and wires underneath the tank. Place some towels under the tank so you don't scratch it. The banjo fitting takes an 8mm hex key. Note - gas will come out the lines you remove. I wasn't smart and still had a rather full tank.

After you're done with the tank remove the lower fairings and the air box.

Remove the screws around the edge of the air box, lift off the top, and take out the filter. Under the filter are the velocity stacks, take out the two screws on each one. On mine the taller ones were in back.

You'll have to remove the Map Sensor, TPS connection, and other wires and hose's attached to the air box. Don't forget the wire underneath.

With the Air Box removed you can see the throttle bodies.

The next thing to do is loosen the clamps at the base of each throttle body. Some people I talked to used a really long Phillips screwdriver. I found hooking three extensions together and using an 8mm socket on a small ratchet worked better. You have to go in through a cut-out in the left side of the frame, right where the coolant overflow bottle is. The manual says once the straps on the throttle body spacers are loose you can lift it off. Mine was still very much attached! I had to CAREFULLY pry it up using a big screwdriver and a small pry bar.

Drain the coolant and remover the two hoses going to the wax unit, its the cylinder in the center of the throttle body assembly (sorry no close up picture, was getting tired).

Once the throttle bodies are loose you have to remove the throttle cables. I took a close up picture so I could put it back the same way. The idle adjustment cable is also attached to the bottom of the throttle body and needs to be threaded up through the frame.

After the cables were removed I set it on the back side of the motor and started in on the thermostat housing. Remember to plug the intake holes in the block, you don't want to drop anything down there.

On mine all the hose clamps were facing the wrong direction so I had to pull off some extra hoses to get it loose.

This is what you are after.

Split the housing apart and you'll see the Thermostat. Mine was closed but after heating it up enough to open, it stayed open even after cooling to room temp.

I'll post more on the reinstall when the new thermo gets delivered.

Edit: All right, I got the new tstat after 2 tries from Service Honda. Reassembly is the reverse of everything above. Two things I screwed up - First after you reinstall the tstat housing and hoses, make sure you route the idle adjustment cable back where it belongs BEFORE you reinstall the throttle body's. It sucks to pull everything back apart when you notice your idle adjustment is missing. Second, make sure all you electrical connections are snapped together. It sucks even more to see the flashing FI light the first time you start it back up.

I would rate this job as fairly complex. A 7 - if 1 was putting air in the tires and 10 was taking out an engine. Probably a 5 once you've done it the first time.

Action
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Thanks Action for the excellent writeup, I'll need to do it myself too since my thermostat is also defective.

VictorRomeoFrank · Nov 8, 2024

Action said: ↑

I used a small pry bar. I placed a rag on the block and CAREFULLY pried them up. If i remember right, I pried against the outer edge of the throttle body right at each corner. It took a pretty good amount of force. You could also use a small hammer (to pry with - not hit anything with - lol). I also used a blow dyer to heat the spacers up some. I know they seem like they are welded on but they will come off. Good Luck!

Squirrelman - yup, runs great now. No issues with temp, either cold or hot.

Action
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Having done this many times...use wd40 or something similar at intake boot area and they come off much easier. Lube the boots with your favorite grease when reinstalling. Makes life much easier.

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