This is something I've theorized for a couple years, but never had anyone trusting enough.... until now.
Let me start with why this type of STVA fails. These STVAs have a simple brush contact DC motor that simply wears out. With a list price of nearly $400, not a fun failure to experience.
My theory started with a friend's ZX636. I saw his exhaust actuator a few years ago when we swapped the exhaust. Looked kinda like this generation of STVA. So, I started digging into the much hated 2006 and up exhaust actuator on the GSX-R. Damn... they look very similar.
On the right is the 01 STVA. On the left, a 2006 GSX-R exhaust actuator. There are only two differences here. First, the diameter of the rotor and the position of one of the two mounting points on the housing. So, let's dig inside.
Okay, so we pull the electric motor out of the exhaust actuator and put it in the STVA. NO! It's even simpler than that. You don't have to pull the rotors, you don't have to pull the circuit board. All you have to do is take the rotor side of the STVA and put it on the drive side of the exhaust actuator. Install and you're done. Some of the clips don't line up on the housing, but since the whole thing is screwed together anyway, just break them off. You'll probably break them off taking it apart anyway.
Want some more good news? Nobody wants the exhaust valve on their newer bike. They remove them, and toss them. I'll bet there's a lot of guys on this board that have one laying around taking up space. This trusting person bought one on ebay for $25. Cheap fix, simple and fast to do.
__________________ Never mistake education for intelligence.
"Don't go ninjain nobody that don't need ninjain" - Diemon Dave
I'm glad I trusted you and your hunch on this fix. Like I said before...even if it didn't work I'd only be out $25...but it DID work, and now we have the cheapest and easiest fix for this problem thus far. YOU, sir...are thee bees knees. Thanks again!
Motorcycle: 2004 GSX-R 600(sold), 2003 GSXR600 beater bike
Posts: 1,457
Re: STVA fix for 2000-2003 750 and 2001-2002 1000
good info to know. so y2k bikes stvas fail due to the worn out brushes, huh. not like 04-05 stvas where some electrical connections usually fail. i think it would be even more interesting to find a brushless analog of the motor so it won't fail again. is it stepper or just regular motor, btw?
It's a simple reversible DC motor. There's really nothing special about it besides the extra long spindle with a worm gear on the end. I looked around for a brushless replacement when I first looked at one. That motor configuration was a custom build. Not something that can be purchased off the shelf. I had a little success with replacing the brushes, but it's also the rotor contacts that wear. Very few options. This is by far the best/cheapest route to go to preserve the SDTV functionality which is IMHO important for maximum performance.
Ok. I have a good working non cable one I am trying to sell, from a 600 and was thinking @ you for posting this the day after. My for sale is the other design, and this fix will not work for those...
Small displacement engines are sensitive to sudden vacuum changes. The SDTV system (even the old CV carbs) help maintain a stable vacuum for smooth power.
Quote:
Originally Posted by 600k2
Ok. I have a good working non cable one I am trying to sell, from a 600 and was thinking @ you for posting this the day after. My for sale is the other design, and this fix will not work for those...
There are 4 different STVA types out there. In my experience, these have been the most problematic.
Hello everyone. Just a follow up on the STVA fix that TheGeek did for me here...
I installed the STVA and did the adjustment per the service manual, and alas, NO CODES! A few tips for installing a newly repaird STVA (Since the manual is "as clear as mud," as TheGeek said)
**I did not remove or loosen the TB's at all during my install. Follow the service manual for torque specs and keep in mind that what works for me, may not be as easy for you! This is just my personal experience.**
1. Install the STVA bracket onto the TBs.
2. Loosen the no. 1 and no. 2 cables ALL THE WAY and install them onto the TB's per the service manual.
3. Before attaching the STVA to the bracket, install the cable ends to the STVA per the manual. Make sure that you put the cable ends on the INSIDE section, closest to the STVA casing.
4. Now that the cables are attached to the STVA, place the cables in the rubber stopper (per the manaual), then wiggle the STVA around the bracket while holding the cables in place so that they dont fall. This is MUCH easier than fixing the STVA to the bracket, then trying to get the cable ends into their proper place.
5. Once you fix the STVA to the bracket, plug in the motor and position sensor couplers and follow the procedures for doing a STVA adjustment in the service manaul.
6. Make sure that you follow the adjustment procedures to the LETTER, and then check for proper STV movement.
If you installed the STVA correctly, and did the adjustment correctly, the code should be gone!
I didn't have time to take pictures during my install, but I'll snap a few pictures later to help explain what I described above.
*Read through ALL of the install and adjustment instructions BEFORE starting. Then read them again. Then read each step as you do each step. The last thing you want to do is break something that was just fixed. -_- *
PM me if you have any questions on the install. PS. I did it on an k1 750..
Now...to adress something that I did a lot of research on before making my decision to attempt the FIX vs the ELIMINATOR (and TheGeek can back this up).
IMO, it is much more beneficial to spend the $30 for an unwanted exhaust actuator + however much TheGeek agrees to fix it for you for, than to remove the secondary plates and run an eliminator. During the 2 weeks that I was riding my bike without the STVA (secondary plates held open during this time), power delivery was not smooth at all; especially at the low end. K1 750s are already a bit jumpy at low speed in 1st and second, and the STVAs function is to smooth out the power delivery. After installing the newly fixed STVA I IMMEDIATELY noticed a smoother lower end and a much nice ride all around.
So, you can either fix it on the cheap and easy which will help your bike run efficiently and smoothly; or you can remove the system, run an eliminator harness (good luck finding one these days) and have a choppy lower power band. Pretty simple choice if you ask me. Also, not a lot of places are still doing custom tunes for K1's, so getting the STVA eliminated via custom tune is also pretty hard (and expensive).
IMO, it is much more beneficial to spend the $30 for an unwanted exhaust actuator + however much TheGeek agrees to fix it for you for, than to remove the secondary plates and run an eliminator. During the 2 weeks that I was riding my bike without the STVA (secondary plates held open during this time), power delivery was not smooth at all; especially at the low end. K1 750s are already a bit jumpy at low speed in 1st and second, and the STVAs function is to smooth out the power delivery. After installing the newly fixed STVA I IMMEDIATELY noticed a smoother lower end and a much nice ride all around.
So, you can either fix it on the cheap and easy which will help your bike run efficiently and smoothly; or you can remove the system, run an eliminator harness (good luck finding one these days) and have a choppy lower power band. Pretty simple choice if you ask me. Also, not a lot of places are still doing custom tunes for K1's, so getting the STVA eliminated via custom tune is also pretty hard (and expensive).
To be fair though, you did not have the bike tuned after you mechanically wired the butterflies open, correct? Because your fueling is set up from the factory under the assumption these will be almost completely closed at low RPM. This would affect your throttle response considerably unless you tuned accordingly. I know when I had a zx14, if you removed the secondary butterflies and had it mapped accordingly, it would be just as buttery smooth as factory.
nygged is that true?. i was thinking bout that as well if the geek cant help me, but mid way through the posts i was lost because im not sure if the excva is being confused with the stva of the throttle bodies and the excva of the exhaust.
STVA fix for 2000-2003 750 and 2001-2002 1000
@ you for posting this the day after. My for sale is the other design, and this fix will not work for those... 
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