DIY Manometer / Throttle Body Synching

[Namastebuzz]

Made a manometer with water and 24 ft of tubing on a 6' board.

Worked fine to set idle speed. Have previously set the valve clearances so they're spot on.

When I try to use it for higher up the range it just goes crazy. You're not supposed to adjust the left hand throttle cable but I'd played about with it earlier on the trip so it's no longer set as it was.

As I adjust the right hand cable it makes a small difference but when I increase the revs the water get sucked towards the left hand TB, and sometimes into it.

Where do I start?

 

[Noel]

Throttle bodies should be balanced at a fast tick over of about 2kRPM, even with mercury gauges it would pull the mercury out and dial gauges it would probably go off the scale.

 

[roddy]

I've had a similar problem with my 1100GS, when I messed about with the throttle cables.

what's happened is your synching the TB using the idle by-pass screws these only have any effect when the throttle is in it's rest position as soon as you start to use the throttle the by-pass is no longer effective and its the balance of the cable moving both TB cams together that dictates the synch from here on in, the following procedure may help you it's the one I used to get everything back to normal

I assume you haven't touch the throttle stop screws ? if you haven't try the following, if you have you'll need to set up the throttle stop screws first as a guide the throttle butterflys at rest need to be the same distance from the bottom of the TB.

1. check when the throttle is in it's rest position that both throttle cam plates (the bit the wire wraps round I think thats what it's called)
are resting on the stop screws even when the bars are moved through there full range of movement. if there not then you need to adjust you throttle cables adjusters so there is enough slack to do this it varys depending on what bike you have but 1mm of slack at the TB end is a good rule of thumb

2. with engine off put one of your fingers on the throttle cam plate

3. now watching the plate you don't have your finger on twist the throttle slowly, after you do this a few times you get the feel for it, what your looking for is the cam plates to start to move together at the same time if they don't you'll get the effect you have of then being out of balance as you use the throttle, if they are out adjust the RH cable adjuster only till they feel like there moving together.

you now have a reasonable base position to do the synch from.

adjust the by-pass screws to give you balance at idle them slowly increase the throttle till about 2k RPM is showing and adjust the RH cable adjuster till the manometer shows there balanced.

and voila your done the only other thing that may help is to put a bit resistance in the tubing of the manometer I used a small bit of sponge in equal sizes to help dampen the pulses so it was easier to read the manometer.

HTH the above helps.
cheers

 

[roddy]

I forgot to mention, check that your throttle cables are sitting in there adjusters on the TB properly and one hasn't got caught on the edge of the adjuster, this could also cause something similar to what you described.

cheers

 

[Namastebuzz]

many thanks roddy - will get on it

 

[Namastebuzz]

Did just as you said Roddy - worked perfectly, balancing nicely at 2000rpm.

Then went on a test ride and it ran like sh*t!

Next day realised the RH throttle cable was unseated - which you'd warned about AND I already knew about but still missed it.

Sorted that and now it runs perfectly. Even better than when I set out on this trip.