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What does this screw do ??

magoo

magoo

Tuned and Synch'ed
Joined
Dec 28, 2008
Messages
62
Hi all, I own an '08 Breva 1200 with 9000 kms that pops and farts like crazy on decel when coming back through about 3000 rpm. When I get cashed up I'll get the ECU reflash PCV thingies but in the meantime while I was poking around and cleaning the other day I came across this screw (with the factory yellow paint daub) that sits behind the left side pot. Looks like an old fashioned idle adjustment to me and as mine has always idled a bit low thought I'd see what difference it made.

One full turn clockwise (engine warm and running) increased the idle from 900 to 1400 rpm. I took it for a quick spin and lo and behold almost no popping at all on decel. The idle settled down to around 1500 when it was fully hot and it was sluggish to return to idle from 2000 to 1500.

I'm no mechanic and I don't have the tools or knowledge to mess with the TPS and thrrottle bodies and I didn't want to cause any problems so I promptly returned the screw to the original setting and low idle and popping are back again.

If it's just a simple idle adjustment I'd like to set it somewhere around 1200 which seems to be the right level for most bikes.

Thanks in advance for your replies,
 

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If you don't have the tools, you shouldn't have touched it. That screw is the adjustment for the high speed idle. If you do you need to reset the TPS. You need a sync and reset. Either buy the tools (VDSTS and sync tool) and read the Breva Service manual for the procedure (In the download section of this site) or take it to someone with the tools and knowledge to set it up properly. Do not attempt to set the idle by changing the position of the idle stop screw. If you do, you will need to replace the TB. Idle is controlled by the stepper motor. Get it properly set up, then see how it does.
 
Looking at the pic it looks like the high speed ballance screw. I think simply a slip of the keyboard finger by John. While it may of 'Cured' the popping it will mean that your TPS and the TB ballance will be out, (Unless you were very lucky!)

Proper instructions for TB ballance etc are readily available here or in the manual and while messing about with stuff may 'Cure' popping on the over-run by artificially enrichening the idle mix it will come at a cost elsewhere in the map and in this situation will upset the high speed throttle ballance which may make for a higher level of vibration and worse fuel ecconomy.

Pete
 
The screw you are asking about should not be messed with. They are set at the factory and they do a good job of it. You are stuck with the popping until you can swing the $1200. Todd has the best set-up and once he flash, PC5, auto tune, etc you will think you got a new bike, Get the pipes done to it if you can.


I went through a similar issue with my Norge. Many people with these bikes have too. There may be one thing... but I can not say it will work and that is the O2 optimizer. Since you are not happy with the popping at decell the O2 optimizer will enrichen the idle circuit and that is usually why you get the popping... to lean. It is $135 or so vs $1200 and I was considering it, but had the money for the bigger step up and I wanted to get more than richer mix at lower throttle.

That is my opinion for what it is worth...
 
Thanks guys, I did mention that I was careful to put the position of the screw back to exactly where it was at the outset and I only rode it for a couple of minutes. Hope I haven't done any damage.

Argiwhomp I am awaiting one of Todd's O2 optimisers as we speak. I'm having the 10,000 km service done in a few weeks too, any opinions on whether I should fit the optimiser before or after the service ?

Cheers,
 
No, you won't of done any damage. If you are reffering to the screw with a spring behind it on the actual linkage? That you can muck about with, if you have the tools to re-set the TPS and ballance the TB's. It is the screw that the plate on the bottom of the TB that it hits against when the throttle is 'Completely Closed' that is the real 'No Touchee' screw.

Pete
 
O2 optimizer before or after... hmmmm I guess, because of my paranoia if you have any warranty time left do it after since there are those that have "issues" with either other mechanics, esp. if they get as much attention as Todd does and well, lets face it he doesn't always play well with wanna be mechanics who DO NOT LISTEN and WASTE HIS TIME. I can understand there was a time... well, lets not go there.

So, back to my point.. if I ever had one, if the mechanic or service dept you are dealing with are okay with what Todd does then by all means do it when it is convenient. Otherwise after. Save your money because you will be happier with the whole hog later.
 
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