Good morning all.
I had a topic open on vacuum hoses, but my issue appears to be totally different, so opened another topic.
The secondary valves on the throttle body are not moving when the ignition is switched on.
I have the airfilter out and can move the valves manually and this clearly the shaft that operates the STPS.
Has anyone had this and fixed it? I can't see a replacement motor online anywhere.
I am thinking of getting a full used throttle body.
Have a search on here, you should be able to pull the stva apart to see whats wrong, alternatively check the TB once you've removed them from the bike. If you have access to another set of tb's, verify of course that the stva works, you will need a 5V supply, I think 12v will be too much.
Pretty sure it was Snapey repaired his, re glue magnets from vague memory. Worth searching before rushing in IMO
This isn't the best pic as I can't find the ones I took of the STVA in bits, but the big square lump made of thin layers in the centre of the TBs is the STVA. You get to it by taking the TBs apart, there's two long bolts that hold them together end to end with, I think, 10mm heads on the RH side of the bike. Then there's four little nuts from the LH side that hold the plastic cover on the side of the STVA. Once you lift that off you'll see the magnets in there, if they are loose then glue them back (epoxy works) where the marks are from them being glued previously.
14 STVA Rear (600 x 450).jpg
Exactly, as Dr. Hooli says.
Thanks all, brilliant help as always.
Having a weekend off, so will look again next week.
Ian
Well, throttle bodies out and long bolts removed.
Unfortunately I don't have JIS screwdriver head to take the fuel rail off to allow me to separate the bodies. On order for tomorrow.
However, I have found an issue.
There is a spring missing. Can't describe it, but the picture shows it. This missing is stopping the right hand secondaries moving the same as the left two. So definitely needs anew one. Don't suppose anyone would know where I could source such a beast?
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Ahh those springs, they often pop out as you're twisting the TBs put when the long bolts are out.
You can probably get real ones from Webike Japan, but I've often found random springs that look about right and used them. One thing I'd say, is don't use ones that are too soft as the throttle vacuum can overcome the spring and give alsorts of odd issues.
I can't suggest where to find them locally though as I nicked the last ones I needed from some 125cc carbs in the corner of the garage.
If you can get a complete set of TB relatively easily, you could cannibalise one to make a complete full set.
Do not leave out AliExpress. An example:
https://es.aliexpress.com/item/1005008369380644.html?pvid=37e5f6ba-83bd-48ac-9db1-ed6453d6fe99&_t=gps-id%3ApcDetailBottomMoreOtherSeller%2Cscm-url%3A1007.14452.396806.0%2Cpvid%3A37e5f6ba-83bd-48ac-9db1-ed6453d6fe99%2Ctpp_buckets%3A668%232846%238108%231977&pdp_ext_f=%7B%22order%22%3A%22726%22%2C%22spu_best_type%22%3A%22price%22%2C%22eval%22%3A%221%22%2C%22sceneId%22%3A%2230050%22%2C%22fromPage%22%3A%22recommend%22%7D&pdp_npi=6%40dis!EUR!2.43!2.42!!!18.92!18.81!%40210388c917779591547783402ee22d!12000044772289354!rec!ES!135463698!X!1!0!n_tag%3A-29919%3Bd%3A26674c2d%3Bm03_new_user%3A-29895&utparam-url=scene%3ApcDetailBottomMoreOtherSeller%7Cquery_from%3A%7Cx_object_id%3A1005008369380644%7C_p_origin_prod%3A&search_p4p_id=202605042232348122981266911596170176_1
So those springs just sit there, nothing holding top end in just spring tension?What adjustments is the screw for? Never messed with TB on mine, never needed to. Just wondering.
Quote from: grog on Tuesday, 05 May 2026, 04:33 PMSo those springs just sit there, nothing holding top end in just spring tension?What adjustments is the screw for? Never messed with TB on mine, never needed to. Just wondering.
no, there is a screw in the bottom bit, same as the top, but looks like that screw is also missing, that holds it in place. The spring force should hold the screw in. Suspect they may have some loctite on them to ensure. I have adjusted mine, as I found that the voltage reading on the STPS when opening #1-#2 by hand was different when doing the same with #3 and #4, which meant that 1-2 and 3-4 were not opening together. Fine adjustment is possible to ensure that they do, and allows accurate TPS and STPS setting.
Thanks Eric 👍Looks like correct parts needed then. Parts diagram says discontinued, that's if I'm seeing correct bits, lots of little bits in TB diagram.Hard on old eyes to see
Quote from: grog on Tuesday, 05 May 2026, 04:33 PMSo those springs just sit there, nothing holding top end in just spring tension?What adjustments is the screw for? Never messed with TB on mine, never needed to. Just wondering.
As Eric said, you can balance the secondary throttles just like the primaries.
When I've had TBs off I see if they look equal & if not adjust them slightly. I tend to push them nearly shut at the STVA & use a drill bit to slide in past them to check all the gaps are the same without moving anything.
Another update!
All in bits and no loose magnets.
Bugger!!
Next plan is to throw the bike in the skip.... :lol:
Well at least that eliminates one suspect. Im pretty sure the STVA motor only drives the shaft at #3-#4 throttle bodies, and relies on the linkage to #1-#2 for them all to work, so with your missing spring and screw, it may have tried to, but as the secondaries open reverse to the primaries, nothing happens.
But you did mention you saw none of the secondaries move. Also pretty sure the stva motor gets 5v from the loom, so best to check that too.
Quote from: Eric GSX1400K3 on Wednesday, 06 May 2026, 10:39 AMWell at least that eliminates one suspect. Im pretty sure the STVA motor only drives the shaft at #3-#4 throttle bodies, and relies on the linkage to #1-#2 for them all to work, so with your missing spring and screw, it may have tried to, but as the secondaries open reverse to the primaries, nothing happens.
But you did mention you saw none of the secondaries move. Also pretty sure the stva motor gets 5v from the loom, so best to check that too.
No, secondaries never moved. Got a genuine spring coming, so once in place I will temp fit bogy and tank back on the bike to see what does and doesn't move.
In the mean time will give everything a check and clean.
Quote from: Barbastro K6 on Tuesday, 05 May 2026, 03:35 PMDo not leave out AliExpress. An example:
https://es.aliexpress.com/item/1005008369380644.html?pvid=37e5f6ba-83bd-48ac-9db1-ed6453d6fe99&_t=gps-id%3ApcDetailBottomMoreOtherSeller%2Cscm-url%3A1007.14452.396806.0%2Cpvid%3A37e5f6ba-83bd-48ac-9db1-ed6453d6fe99%2Ctpp_buckets%3A668%232846%238108%231977&pdp_ext_f=%7B%22order%22%3A%22726%22%2C%22spu_best_type%22%3A%22price%22%2C%22eval%22%3A%221%22%2C%22sceneId%22%3A%2230050%22%2C%22fromPage%22%3A%22recommend%22%7D&pdp_npi=6%40dis!EUR!2.43!2.42!!!18.92!18.81!%40210388c917779591547783402ee22d!12000044772289354!rec!ES!135463698!X!1!0!n_tag%3A-29919%3Bd%3A26674c2d%3Bm03_new_user%3A-29895&utparam-url=scene%3ApcDetailBottomMoreOtherSeller%7Cquery_from%3A%7Cx_object_id%3A1005008369380644%7C_p_origin_prod%3A&search_p4p_id=202605042232348122981266911596170176_1
Excellent post mate! Would you recommend the spring that is listed when clicking the as the OEM counter part or some different size?
would need a sample to place order or else diameter of the base where it rests and the length.
It is probably a size that is widely shared by other models
and more examples
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I have got two new springs!
Due to my old fingers, I have pinged them both accross the garage!
I surrender!
More ordered, but away at sea for a month tomorrow, so my nc500 trip for when I get back is on hold.
Quote from: Idh on Monday, 11 May 2026, 07:30 AMI have got two new springs!
Due to my old fingers, I have pinged them both accross the garage!
I surrender!
:coffeescreen:
Been there, done that.
D.D.
Quote from: Idh on Monday, 11 May 2026, 07:30 AMI have got two new springs!
Due to my old fingers, I have pinged them both accross the garage!
I surrender!
More ordered, but away at sea for a month tomorrow, so my nc500 trip for when I get back is on hold.
Silly boy!
It's so easy to do though.
Quote from: Idh on Monday, 11 May 2026, 07:30 AMI have got two new springs!
Due to my old fingers, I have pinged them both accross the garage!
I surrender!
More ordered, but away at sea for a month tomorrow, so my nc500 trip for when I get back is on hold.
Happened to me as well mate. The scary thing is that a couple of days later, I found a random spring in the garage which wasn't even the one I had lost...