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Discussion Starter #1 (Edited)
Checked mine with TuneECU:
Cyl1:510-520
Cyl2:530

Also checked another brand new T120 and both are dead set at exactly 540hPa.

Do I need to worry about mine fluctuating?

Also it seems that the engine oil is low, going to top up tomorrow, it's right at the bottom mark. Engine got 5700miles on it and due for the 1yr service next month.
 

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I've monitored my the throttle body balance using DealerTool since my 500 mile service and found that I had a similar difference crop up around 4000 miles.

DealerTool indicated that this needed to be balanced, but given the recommended service schedule and the amount of work required to balance the throttle bodies I held off until reaching the 10,000 mile service(the first service where throttle body balancing is recommended).

After balancing the throttle bodies, I haven't really noticed a major change in performance but the peace of mind knowing that they are now in sync certainly feels good.

I am by no means a professional mechanic, but such a small difference should have no major impact on performance or engine longevity, topping up the oil and logging miles until the next recommended service interval might be the best way to go!
 

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Discussion Starter #3
Thanks for the feedback! I was hoping that I've found something to cure the throttle snatch... guess not.
 

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Checking throttle balance electronically sure puts a lot of faith in the accuracy of sensors. It was explained to me that the 10,000 mile service should include checking the throttle balance with manometers rather than electronically which essentially validates the accuracy of the sensors, but it seems that many (most?) dealerships don't do that because it's so labor-intensive.

I just had the 10k mile service done on my own Bonneville and I'm quite sure that they just used their scanner, and I'm not sure how (or if) I should address that.

Pete
 

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Checking throttle balance electronically sure puts a lot of faith in the accuracy of sensors. It was explained to me that the 10,000 mile service should include checking the throttle balance with manometers rather than electronically which essentially validates the accuracy of the sensors, but it seems that many (most?) dealerships don't do that because it's so labor-intensive.

I just had the 10k mile service done on my own Bonneville and I'm quite sure that they just used their scanner, and I'm not sure how (or if) I should address that.

Pete
They use the manifold pressure sensors which they read with their scanner. If the values are out of spec, the scanner says so.

I was going to read the sensors with tuneecu but I can’t even locate the adjustment screw, much less take the bike apart to adjust. Anyone done this? How about a tutorial? Thanks.
 

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I was going to read the sensors with tuneecu but I can’t even locate the adjustment screw, much less take the bike apart to adjust. Anyone done this? How about a tutorial? Thanks.

I second this. Anyone out there know where to find it on a bonneville?



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I agree manometers are the best way to check sync. As an back yard mechanic alternative, what I used to do on my old Beemer to check carb balance is install a short piece of bare 12 gauge copper wire between the plug and plug wires. I'd lock the throttle just above an idle and then short out the copper wires, one at a time, to see if the drop in rpm was equal from side to side. (You don't want to just pull the plug wire off on an electronic ignition. They don't always survive that well.) I would adjust the carb cables until the rpm drop was the same for each cylinder. I would suppose this would work to check the throttle body sync on a T120, but I too have no idea how you adjust them if they are out of sync.
 

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I'm thinking with modern technology, todays high quality sensors and diagnostic tools I trust today tools over old technology, the nanometer. Of course, YMMV.

Paul
 
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I wouldn't worry too much about throttle body balance before the stated inspection interval if the bike is idling and running well and gas mileage remains unchanged.
 

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you can usually do a pretty decent job of syncing by using how much light passes through looking from the opposite side, using a flash light or even sun light... works for me on some vehicles.... not sure about this application...
 
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