1300AE Fast idle, shift error code SH__48, intake clean and recondition, bench testing wax motor (gen 1, gen 2 relevant)

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Mar 25, 2023
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First, anyone working on fast idle and AE shift error issues, there are many related posts across this forum and others. I learned from all, in particular this one from RadioHowie, which has terrific pics and info.

Here are some things I did to restore correct function for my recently-acquired 2007 1300AE, after experiencing issues with fast idle taking forever to drop to a useful range, and repeated SH 48 error codes that prevented shifting at all until the bike had been running for at least 8 minutes. TLDR: was able to solve this with a thorough cleaning / reconditioning and balance.

1. If you experience similar issues (or even as part of a recurrring maintenance cycle), as RadioHowie recommended, I recommend digging in and pulling the throttle bodies: Clean/recondition, bench test the fast idle circuit (more on that below), get your injectors cleaned/rebuilt by a capable shop (I like Dr. Injector in Portland) and get new seals/o-rings for them, check all the vacuum lines and such for cracks, etc. Well worth the $70-$130 to have injectors properly cleaned and bench tested!!

2. Issues with idle speed, fast and slow, seem common on these, at least in part due to buildup of crud typically caused by crankcase vapor condensing and hardening over time, and possibly due to blowback from backfires into throttle bodies. Whatever the causes, these TBs are relatively simple, and the slow and fast idle circuits are easily cleaned when off the bike.

3. Make sure the coolant circuit to/from the fast idle wax motor is flowing and clear, both at the radiator and at the wax motor. I used a 150mL syringe to pull fluid through both parts of the circuit to confirm flow.

4. Pull all the fast idle valve plungers out completely to clean them. Here is RadioHowie's pic of his, mine all looked as bad, and two were firmly gunked in place, not moving at all at room temp. This seriously impacts fast idle circuit performance. Pretty sure in my case these two never closed, so I was riding with those two circuits always contributing to the vacuum and fuel flow to those cylinders. Other symptoms included backfire on deceleration and less-then-smooth acceleration when cold, etc. My gas mileage was horrible too.

5. There is a challenge, as RH noted, in getting these out due to clearance between TBs. #1 (numbered by associated cylinder) comes out readily since it faces the open end. On mine, I was also able to pull #3 and #4 with a bit of fiddling. To get #2 out, I removed the screws holding TB #1 in place and wiggled it just slightly, enabling me to pull valve #2 out. I was careful to not let the linkage between the TBs separate...springs gonna fly far!! You only need an extra fraction of an inch to clear.

View attachment IMG_5400.MOV

6. After thoroughly brushing, blasting, scrubbing, soaking, swishing, and wiping every circuit and surface (pull the slow idle/balance adjust screws from each TB as well, don't let your carb cleaner interact with rubber or Viton seals, can ruin them pretty quick) I pieced it all back together and checked for smooth, easy operation of the fast idle valves and the entire linked throttle assembly. The internal springs on each fast idle valve should be plenty strong enough to pull them closed smoothly and easily.

View attachment IMG_5402.MOV

then reassembled the fast idle control rail and confirmed ease-of-movement of the entire thing. Getting all the little plastic bits in place and the screws secured is important so it all moves smoothly:

View attachment IMG_5405.MOV

7. I bench tested the wax motor on its own, completely off the TB assembly, by slowly heating the piped end with a heat gun. Took about 5 minutes the first time, just needed to be patient. Could have also used hot water, your choice. Just go easy on it, don't over heat it. I put DI (distilled) water in the end of it to make sure temp didn't climb above boiling. My shop temp probe is dead so I couldn't track actual temp during the test, but I tried it a couple of times (slowly) and felt it with my hand to confirm it wasn't excessively hot, and was satisfied it worked. Total range of motion from cold to hot of the plunger that sticks out of the end of the wax motor was about 3/8" which is more than it needs to operate the fast idle circuit.

8. THEN, I put it all together on the bench and did the same test with all parts. This vid is the last 20 seconds or so, and I realize it's about as exciting as watching grass grow, but it worked. It took about 2 minutes to heat it up from room temp. Watch for the small separation between the rail and the end of each valve assembly. As soon as there is clearance, the valves are completely closed, and the fast idle circuit is no longer active for the intake system. All valves should close simultaneously. There is no adjustment to change that unless you bend the tabs on the rail (no reason to do so unless it's been damaged)

View attachment bench_test_fast_idle_wax_motor.mp4

No gap, control rail still holding valves slightly open:

Gap appears, wax motor has pushed control rail enough to allow all fast idle valves to close:

Fuzzy closeup showing gap between the tab on the control rail and the end of the fast idle control valve. This valve is now seated and closed:

8. All that done, injectors rebuilt and shop tested by someone else who knew how, put it all back together carefully on the bike, made sure to fill coolant as close to the top as possible (there's a manifold above the valve cover) I did not change the setting of the fast idle adjust screw during this process, because any position would have been a pure guess. There was about one full thread clear at the tip of the screw. Turns out that was fine upon startup.

Fast idle adjust screw. Note I added the bit of tubing with zip tie to hold it in place. This is to make an easy target to slip the screwdriver in should I need to adjust the screw,

9. Upon initial (and very quick) startup, fast idle speed was about 1550 rpm. I chose not to mess with it, but I do have a long skinny screwdriver that can reach the screw if I change my mind one day. I made the srewdriver using a long 1/8" drill bit and a little piece of tubing glued to the end. You have to pull the right side faring plastic to do it, but it's doable. Insert screwdriver just behind and above slow idle thumbscrew knob, which is right side just below gas tank and upper frame assembly.

10. Fast idle dropped off in less than a minute for me. I did a throttle body balance at this point, since everything was newly cleaned and I previously had bench-set (i.e. guessed) the slow idle adjust screws. It took a few iterations of balancing and re-adjusting (lowering) the slow idle before I got it right. Left slow idle at 1050rpm, idles beautifully now.

After a few days of riding, I have not experienced any more shift error codes. I did experience one during the balancing process, however, when the balance had improved and caused the idle to rise to ~1200rpm. I am not equipped to mess with programming of the system that checks temp, idle speed, and allows auto-clutch and shifting ops to work together, nor do I know if such things are even possible to modify, but getting the intake assembly working smoothly and balancing it to spec seems to have done the job. Interested in any questions or comments!

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Nicely done and nicely documented. I recall RH's issues with his idle circuit/wax motors and made a note to myself to remember for future reference. For all the system appears to have multiple points for potential failure, it is remarkably resilient - I have not heard of many problems that were attributed to the fast idle circuit. I haven't had any problems (yet) related to the idle circuit in 295,000 km on my '07 before I sold it or on the 2011 I bought (now 160,000 km).

Because of the sensitivity to idle speed, this becomes a greater issue for AE models. I suppose I wouldn't even notice if my "A" model took a little longer than usual to drop to normal idle although I would certainly notice if it was stuck on fast idle any more than a few extra minutes.

Still, I'll bookmark this thread for possible future consideration or to recommend to someone who appears to be having related issues.

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Excellent I’ll keep that in mind for if my 2007 AE decides to give problems. Up to now it’s been good without any auto-clutch issues, love the bike and helps when you have arthritis in your hands.