TPS/STV/FI...adjusting issues, possible HOWTO in the future

[Dave-the-rave]

My curvy is a vtwin and isn't jerky. Not unless I forget it has a high compression engine.

Today I took the bike apart again, and removed the rest of the screws that were there. Now both screw holes are drilled through and STV plates are gone. While I was at it, I cleaned the throttle body a bit.
I have to say, I don't notice much of a difference with the STV plates removed. It's still jerky and engine is braking hard. I also notice that the bike is unable to hold stable RPM, meaning when I hold the throttle, it fluctuates noticeably. In example, I try to hold stable 3000RPM, but it's not possible to keep it at it, it's fluctuating +-150rpm, therefore it's behaving jerky while trying to keep stable speed. I suspect faulty/worn TPS.
Also when I had the TB's removed completely, I looked down the intakes and it's pretty dirty down there, the black greasy crap everywhere. I would not expect that from a bike with 32000km.

Does it really make that much of a difference? Just tried mine and was reallllllly carefull but only managed to get 3 off and the last one just rounded straight off first go with no effort!!! I was gutted, wanted to see if it'll make a difference lol


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On mine, not really I'd say. And I had to drill two screws through, as they stripped so easily.

Yeah so all that effort for not much of a difference? I did the other 3 back up and left it for now. If it made a hugeee improvement i mite of made the effort to get that last one out hmmmm


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Well, I'm not saying there is NO difference, just that I didn't notice much. But personally, I prefer smoothness over power and that was not delivered in my case.

Only thing I may have noticed is, there is some noticeable power kick at higher RPMs that was not there as far as I remember.

YMMV, other people said they noticed a lot of improvement. On the other hand, I can't say I'd noticed any shortcomings either, so it won't hurt if you remove it, it can only get better.

[Bibio]

you have rounded the screws as you didn't know that they are thread-locked in and that the screws are JIS type. you need a soldering iron to heat the screws to soften the thread-lock and a proper JIS screwdriver to remove the screws.

my advice is to get yourself a second hand set of throttle bodies.

its not just the TB's that can cause lumpy running it can also be caused by a faulty rec/reg, low oil, bad spark plugs and lots of other things.

i'll butt out now and let you get on with it but my last words are, the suzuki techs put the STV in for a reason.

I knew about the thread lock, not about JIS though. Does not matter now, holes are drilled and screws are gone, I don't see a reason to buy another TB yet.

And twitchy behavior because of faulty regulator? Never heard of it.


P.S. The reasons are fairly well-known, among others, it's less noise produced and emission thing at some RPM ranges. Not every reason is worth, or good at all. Think about the retarded timing on Suzuki's, for example. Or max speed limiters, etc. You can't argue like that.

[Seeker]

What's the purpose of the secondary throttle valve?

When the primary throttle valve is opened it initially causes the vacuum through the throttle body to collapse depending on engine speed and the amount the valve is opened. Using a secondary throttle valve to modulate the airflow smooths out the vacuum transitions and gives a smoother ride. The bigger the pistons the more pronounced the effect will be, so a 1000 cc V twin benefits more with a secondary throttle valve system than a 650 cc V twin, but a high revving 4 cylinder bike will also see advantages to having such a system.

[Bibio]

Originally Posted by Riotstarterr

I don't see a reason to buy another TB yet.

And twitchy behavior because of faulty regulator? Never heard of it.

P.S. The reasons are fairly well-known, among others, it's less noise produced and emission thing at some RPM ranges. Not every reason is worth, or good at all. Think about the retarded timing on Suzuki's, for example. Or max speed limiters, etc. You can't argue like that.

i'm going to be blunt but hey its a forum, who cares and this will be the last time i answer anything in this thread.

coz you have feked the ones you have by not understanding how to solve the problem you have.

well its part of the ignition/charging system so if its faulty then will cause running issues, i'm not saying it is the rec/reg but have you checked it?

yes i can read lots of things on the internet to but let me assure you that all motorcycle manufacturers are doing the exact same thing, if they never you would not have new motorcycles. this does not mean that they are wrong or indeed need to be removed.

... you say that the revs are fluctuating.. why would that be?

i'm not trying to be negative, far from it. i am actually trying to help.

Originally Posted by Seeker

What's the purpose of the secondary throttle valve?

When the primary throttle valve is opened it initially causes the vacuum through the throttle body to collapse depending on engine speed and the amount the valve is opened. Using a secondary throttle valve to modulate the airflow smooths out the vacuum transitions and gives a smoother ride. The bigger the pistons the more pronounced the effect will be, so a 1000 cc V twin benefits more with a secondary throttle valve system than a 650 cc V twin, but a high revving 4 cylinder bike will also see advantages to having such a system.

i was hoping that the OP might just go and find that out for themselves but the rabbit is out the hat now.