Un-molesting of the sacred screw - Breva 1100

[tris]

I bought my bike with a molested sacred screw before I knew such a thing existed, and I'm determined to get it back to where it should be so have started on a mission to fix it!

I think that I have read every written solution to this issue (thanks Pete R and all the others) so think I have as much knowledge of my options as there is to have!

So far I have removed and cleaned the throttle bodies and idle control valve within an inch of their lives plus the air box & lines

I then set the TBs on the bench using the butterfly/throat gap and measuring in from the intake side - measuring in is PANTS - poor repeatability

That ran as rich as hell, and I have now set idle stop to roughly 0.75mm (0.73mm as best I can measure at the moment) proud of the surface and the bike runs "reasonably" well but still surgey at low throttle openings

Now I have it running my plan is to double check the valve clearances despite their being set only a couple thousand miles ago before proceeding and replace the plugs and balance the TBs

On the assumption that I now have as a good base line as I'm likely to get, I have a question

If it still surges do I need to turn the sacred screw in or out a gnats cock (inc TPS reset) to dial the issue out? - I appreciate that this might take multiple rides

Cheers

Tris

PS
Once I have it set as best I can I intend to upload a standard map but with the Lambda sensor switched off

 

[molly]

I would thought it is worth setting the throttle body balance, TPS  and adapting paprameters to see if the surging is improved. Unless the tappets are way off then checking them won't make a great deal of difference.
Is there no one in your area (Louth?) that knows how to set up the throttle bodies?  At one time being near Cadwell race circuit there was a number of tuning shops in  the area.

[tris]

To be honest Molly, if the surging has gone after the valve check, TB balance and TPS reset I'll probably call it good - I'm just not over optimistic!!

I'm in Gainsborough but don't know of anyone around here - anyway part of the fun is not being beaten 

[guzzisteve]

For the reset, find the absolute closed(point where it stops moving closed) hit reset TPS button. Turn back on and move screw till software says 9.2*, hit reset TPS button. It should be on the money or within a couple tenths of degree.
Where your bodies level out synced has to do w/TPS setting, if you have to crank IN the screw too much to be in sync it will move the TPS to the positive side.
This could be where you get the surging. You will also get a higher idle w/pull clutch in gear.

[MMRanch]

Guys , it my sacred screw must need a 1/4 turn out --- mine lunges at really slow speed too.     Where is this  sacred screw  , I'm guessing we're talking about Syn. the throttle bodies .   

[Wayne Orwig]

I then set the TBs on the bench using the butterfly/throat gap and measuring in from the intake side - measuring in is PANTS - poor repeatability

That ran as rich as hell, and I have now set idle stop to roughly 0.75mm (0.73mm as best I can measure at the moment) proud of the surface and the bike runs "reasonably" well but still surgey at low throttle openings

Why would setting the sacred screw make it run too rich?
You are doing a total throttle balance AND TPS reset at the same time, right?
The idle speed is correct, right?

[Chuck in Indiana]

Guys , it my sacred screw must need a 1/4 turn out --- mine lunges at really slow speed too.     Where is this  sacred screw  , I'm guessing we're talking about Syn. the throttle bodies .   

There is no sacred screw on the small blocks.. and if there were, there is a reason it's called the sacred screw. It's set at the factory on a flow bench, and not to be fooled with.

[tris]

Why would setting the sacred screw make it run too rich?
You are doing a total throttle balance AND TPS reset at the same time, right?
The idle speed is correct, right?

Either I did it wrong initially OR I had the TB butterflies too tight so that at idle there was just not enough air going around the butterflies and the balance couldn't be made up by the ICV

Idle appears to be on the low side of the target window hence my move to set every to base and go again

[pete roper]

There is no sacred screw on the small blocks.. and if there were, there is a reason it's called the sacred screw. It's set at the factory on a flow bench, and not to be fooled with.

Oh yes there is! Luckily though it is hidden deep in the bowels of the bike which means Harry Hometune has to be really determined to screw his bike up to find it!

Tris? To save yourself a ton of heartache why not just buy a set of unmollested TB's off fleabay and be done with it? I've had limited success with all of the suggested 'Cures' for molestation. You might get lucky, you might not. It really depends on what has been molested and what else it's been combined with.

Pete

[Chuck in Indiana]

Oh yes there is! Luckily though it is hidden deep in the bowels of the bike which means Harry Hometune has to be really determined to screw his bike up to find it!

Well, I'll be durned. That's the first time I've heard of that. Live and learn. 

[tris]

Oh yes there is! Luckily though it is hidden deep in the bowels of the bike which means Harry Hometune has to be really determined to screw his bike up to find it!

Tris? To save yourself a ton of heartache why not just buy a set of unmollested TB's off fleabay and be done with it? I've had limited success with all of the suggested 'Cures' for molestation. You might get lucky, you might not. It really depends on what has been molested and what else it's been combined with.

Pete

My eyes are peeled Pete!!

Funnily enough when I got it MOT'd the other day there was a B11 in the shop in bits -  apparently its got a cam follower gone on one side??

Anyway, I have the weirdest feeling that I saw it there in the same condition last year!

So, my current plan is to try and scoop it for a grand then if the TBs are good that solves one problem and if the LCD in the clocks work then that solves another and with any luck I can make my money back on the carcass

Sound like a plan