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 Throttle Body Sync 1200 8 V ! Function grab screw

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MKGuzzi
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PostSubject: Throttle Body Sync 1200 8 V ! Function grab screw   Mon Oct 16, 2017 4:55 am

Hello Guzzisti,

trying to syncronize the throttle bodies, I noticed that the grab screw sitting in a srew nut, left side of the left carb, seems to be not adjusted, there is a gab between the grub screw and the stopper .

Any chance to adjust, how much, how to.....

regards

manfred
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paulbrice
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PostSubject: Re: Throttle Body Sync 1200 8 V ! Function grab screw   Mon Oct 16, 2017 8:10 am


Hi Manfred, BE CAREFUL ...assume you are actually trying to 'balance' the vacuum each side of the inlets using carbtune or manometers or vacuum dials ?? The throttle bodies are already synchronised at the factory & the sacred screws musn't be touched ! I think the screw you mean is the 'coarse' balance screw shown below & it does look like it has a gap but doesn't mean it needs touching unless your vacuum balance is way out of whack.

Suggest you search forum for proper method but here is my version just to show that the coarse screw is only used if vacuums are way out

If you read the forum or elsewhere you should get something like:
1. Make sure cam valves set correctly; Reset TPS to 4.7ish using guzzidiag
2. make sure both air screws (brass vertical ones under throttle bodies) are closed - one should always be closed
3. Warm up engine to 60C plus
4. Fit vacuum guages to inlets
5. Rev to 3500 rpm ish and check balance
6. If imbalance then JUST OPEN THE HIGHEST VACUUM air bleed until they balance
7. If there is a BIG vacuum gap then shut the air bleeds again (& only then) adjust the coarse adjustment screw (see pic below) until it is close to balanced....Go back to 1. and repeat sequence until you get perfect balance
8. Check balance at tick over & if not go back around again.

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Pete Roper
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PostSubject: Re: Throttle Body Sync 1200 8 V ! Function grab screw   Mon Oct 16, 2017 10:39 am

Errrr? Not quite Paul. If you are holding the throttle open so the engine is revving at 3,500 mucking about with the air bleeds will achieve next to nothing as the flow through the TB's is so great at that point.

Connect manometers.

Connect diagnostic tool.

Close both air bleeds.

Warm engine.

Hold engine speed at 3,500-4,000rpm and equalise the depression using the bell crank screw pictured above.

Close throttle fully and kill engine using kill switch.

Re-set TPS.

Re-start engine and at idle whichever side has the highest manifold depression open the air bleed until both sides are equal.

Job done.

NEVER adjust the throttle stop screw or the linkage rod ball joints.
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paulbrice
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PostSubject: Re: Throttle Body Sync 1200 8 V ! Function grab screw   Mon Oct 16, 2017 10:52 am

Thanks Pete; my memory fades as I get further away from the last time I balanced it.....
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MKGuzzi
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PostSubject: Re: Throttle Body Sync 1200 8 V ! Function grab screw   Tue Oct 17, 2017 12:14 am

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Hello,

thank You for this short and clear explanation !!

Unfortunatly it is too late - I touched this screw sitting in the nut and turned a bit, because there was a gap !

Help......

Manfred
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paulbrice
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PostSubject: Re: Throttle Body Sync 1200 8 V ! Function grab screw   Tue Oct 17, 2017 1:17 am

Please tell us you didn't turn the one with the yellow paint on ? - see below. It's one of the scared screws you don't change ever - that's why it's covered in yellow paint.

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2highlander
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PostSubject: Re: Throttle Body Sync 1200 8 V ! Function grab screw   Tue Oct 17, 2017 2:09 am

Ohoh, I think the normally yellow painted sacred screw is exactly the one he means, it doesn't seem to be painted any more... *grzgrmbl

Manfred, are you the same Manfred who had posted the same issue in the red Guzzi forum? So You might first try my posted suggestion there to solve the problem...

Depending on where You live in Germany we might also try this together. Better than investing 900 bucks.
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MKGuzzi
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PostSubject: Re: Throttle Body Sync 1200 8 V ! Function grab screw   Tue Oct 17, 2017 2:42 am

That is exact the screw and the same manfred, dont ask me why i scratched this yellow paint away ...

Read your post and will try this way, thanks from north of hamburg.
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Pete Roper
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PostSubject: Re: Throttle Body Sync 1200 8 V ! Function grab screw   Tue Oct 17, 2017 2:49 am

OK before you panic have you re-set the TPS since you arsed about with it? Also you haven't touched the ball joints on the linkage rod in your fiddling?

Pete
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davem
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PostSubject: Re: Throttle Body Sync 1200 8 V ! Function grab screw   Tue Oct 17, 2017 3:13 am

This should be interesting.
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2highlander
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PostSubject: Re: Throttle Body Sync 1200 8 V ! Function grab screw   Tue Oct 17, 2017 4:15 am

*grzgrmbl, I'm a bavarian native, living near Augsburg. So If necessary I can offer You some online support via phone.
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MKGuzzi
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PostSubject: Re: Throttle Body Sync 1200 8 V ! Function grab screw   Tue Oct 17, 2017 6:31 am

Thank you cool
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2highlander
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PostSubject: Re: Throttle Body Sync 1200 8 V ! Function grab screw   Tue Oct 17, 2017 12:01 pm

Pete, I think You are about to suggest to reposition the screw as before fiddling around, assuming that Manfred knows the appropriate TPS value. To be honest, I'm doubting about he knows. But:

My GRiSO also has a throttle stop at the right side. My suspicion is that mechanics stop here first and therefore causes the gap at the left side stop screw. In theory, Manfred could even remove the left side's screw and the engine will run as before. Don't ask me what I'm thinking about how it was running.

Maybe it could also simply be an issue with the throttle not snapping all the way back because of insufficient cable tolerance but this would have caused the engine reving too high at pseudo idle.
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