Hey guys, I cleaned my 2009 SV650S throttle body because of a sticking issue. My bike has been sitting more than moving lately for personal reasons and I’ve been putting Seafoam in the tank to stabilize the gas. I don’t know if the Seafoam has anything to do with it but something has gummed up the throttle shafts so badly that it takes a lot of force to move them. It’s almost as if the throttle shaft is surrounded in hardened molasses. In fact, when I took the throttle body off some excess gas in the injector manifold spilled into the throat of the TB and this thick brown substance seeped out of the holes where the throttle shafts sit in the body. I don’t know what it is but, like I said, it looks like molasses. Anyway, it was time to clean this thing.
If you look at the manual, the procedure is fairly straightforward. Take lots of digital pictures so you know how it all goes back together.
1. Remove airbox and related electrical connectors and hoses.
2. Disconnect the two hoses from the ISC valve that mounts on the crossbar. There are three hoses from this valve but one has already been disconnected when you removed the air box.
3. Disconnect the three remaining electrical connectors to the Throttle Position and STP sensors and the STVA (big black box on the left rear of the TB that actually moves the Secondary Throttle valves).
4. Disconnect the fuel line from the tank. This is a quick disconnect with a one-way valve in it so very little fuel gets out; just press the grey tabs on the sides and the line comes right off. Watch for any excess fuel remaining in the injector manifold – it will spill.
5. Disconnect the injector electrical connectors. Do yourself a favor and get some curved needle nosed pliers to fully depress the tab on the connector; it makes this a 5 second job.
6. You can now loosen the boots for the TB’s and rock the TB loose. Disconnect your throttle cables at this time and remove the TB to your workbench.
7. Pop off the secondary and primary throttle valve linkages. They simply press off; use a pair of needle nose pliers and get behind the black plastic fitting and gently lever it off the ball. Note that the primary linkage is longer than the secondary one.
8. Now remove the fuel injectors. You can remove the manifold and then remove the injectors but I just pulled them all in one go. The four screws that hold the manifold to the TB casting are torqued to 5N-m so it can be hard to get them off. I used a Vessel Tools hand impact tool with a JIS bit and it came right off. These screws are soft so use the right bit and you won’t have any problems. Once the screws are out gently pull the injectors free by pulling them straight out; do not twist them as you pull. Set the manifold/injectors aside in a clean place.
9. Remove the TP Sensor and STP sensor with a #25 Security Torx bit. Be sure to mark their positions before pulling them. There is usually a broad white paint mark but I drew a fine line with a scale and scriber to make it more precise.
10. There are two vacuum hoses on the bottom of the TB to remove and also two vacuum caps. These latter ports are used when synching the TB’s.
11. That is all that can be removed. Do not touch any other screws or fasteners as they are set at the factory and the manual doesn’t tell you how to reverse any meddling.
12. You can now clean the TB. Note that there is a thin band of gray Molybdenum coating where the butterflies come in contact with the throat of the TB. This stuff is fragile and will come off with regular carb cleaner. To deal with this I used CRC Throttle Body Cleaner from NAPA; this is supposed to be safe for coated TB’s and I found that it sort of is. By that, I mean it won’t dissolve the coating but it can loosen the adhesive that holds the coating on the TB if you’re too aggressive with the spray. The tail of the coating came loose in one of the barrels but reattached when it dried so be warned that you should not directly shoot the coating and shoot in spurts, not continuously when near the coating. The manual also warns not to clean the bore but I think this means not to come in contact with the Molybdenum band; you can clean the rest of it with a Q-tip or toothbrush.
13. I used the TB Cleaner to soften that thick brown sticky substance coating the butterflies and wiped it off with paper towels. I then shot the cleaner into the butterfly shaft holes and worked the linkage and then blew it out with air. (Be very careful not to let go of the linkage or the Molybdenum coating can be damaged when the butterflies forcefully snap shut.) After cleaning the shafts several times I got it working smooth again so I repeated this procedure for the other bore. I then shot some Tri-flow into the shaft holes, worked the linkage until it moved very smoothly, then blew out the excess Tri-flow and wiped everything up.
Reassembly is essentially just reversing the process above, with a few caveats.
1. Mount the STV sensor first. Apply a light coat of (motor) oil to the O-ring of the sensor and some Super-Lube or similar grease to the end of the shaft. Be sure the ST Valve (upper butterfly) is fully closed, then install the STV sensor, align your marks and torque the screw to 3.4N-m.
2. Do the same for the TP sensor. Note that the butterfly may move a little as the shaft and sensor mate; this cannot be helped.
3. Apply a light coat of oil to the rubber bushings on the ends of the injectors and insert each with a straight push; DO NOT twist and push at the same time. Once in place, attach the manifold with the four screws and tighten to 5N-m.
4. Install the primary and secondary linkage rods; they just pop on. No lubrication is necessary here.
5. Hook up the remaining hoses, electrical connectors and your throttle cables. Now is a good time to put a 6” length of 4mm vacuum hose on those nipples that are capped; this greatly eases doing a TB synch, which should be done after you service the TB like this.
6. Reinstall the TB into their boots and reinstall the airbox.
I did a TB Synch using the Healtech OBD tool and found the two barrels to be perfectly synched. I also did a TPS check ala TeeRiver using a DMM and set it to 1.130 volts. The bike started right up and runs smooth and sweet, and the throttle is now snappy as it should be.
This isn’t a difficult procedure. Just avoid damaging the Molybdenum strip if you can. This is a two-hour job from start to finish that you can do with basic hand tools, including the appropriate JIS bits.