Throttle Body Sync Photos

[Fred W]

Good stuff. Very clear pictures and video.
However, in my mind, synchronizing the throttle bodies at idle via the air screws is only part of the job. It will primarily effect the smoothness of the engine at idle, since as the throttles are opened the air screw's contribution becomes less and less significant.

The second part of synchronizing the throttles is making sure that as the throttles open they do it in unison. This is somewhat controversial as messing with the mechanical linkage can get things completely out of whack. However, this really isn't rocket science, just basic physics, so we should be able to figure out how to do it without messing things up to badly.

Here's a link to an old discussion about throttle body syncing and there is a link in the first post on that page to a Word document that I find to be very helpful.

This is exactly correct and there should be a way to correct the linking at part throttle also. more important than idle to me.

There is. It is here: The RDCUATBS procedure

 

[Gabriel]

Great

Thanks

 

[dirttracker30]

Does the morgan have the mm/hg labeled? I don't think my motion pro has anything labeled

 

[Harnic]

Ok, I am having a good day today! When I synced the throttles the other day, I got too caught up in the actual vacuum generated. As I've since discovered, that's somewhat irrelevant. I read through my service manual thoroughly & the manual said, & I quote: on page 3-9 "If the air screw was removed, turn the screw 3/4 turn in and be sure to synchronize the throttle body."

That didn't sound right, so I called the head technician at the Yamaha dealer I bought my 2012 from new & asked him. He couldn't pull that from memory, but said he would check his charts when he finished the job he was on & phone me back. True to his word, in about an hour he called back & said his info was the same as what I'd found. With this new info in mind, I popped my tank up again & turned one of the air screws all the way out, being careful not to drop it! I turned it slowly counter clockwise so I could feel the last thread drop over, then from that point screwed it back in ¾ of a turn as they said. Any of you familiar with either fuel injected or carbureted systems will realize the same thing I did right away. most of the threads on the air screw were hanging out in space leaving the air screw quite loose. In a matter of a very few miles the vibrations would shake that screw out & it would bounce down the road into oblivion. I went back to my days as a mechanic at a small Yamaha shop 40 years ago & used the same settings we used on carburetors, turn the air screw clockwise til lightly seated, then back off ¾ turn & work from there. I did this with mine, re calibrated my Motion Pro SyncPro manometer, hooked it up to the ports, fired up the engine & after warming it up to 2 bars on the temp gauge, adjusted the screws. They were all quite close together & required very minor adjustments to be in harmony. My bike purrs like a kitten now! It just goes to show you can't believe everything you read. I'm thinking next time I do this I'll put a small drop of Threadlocker Blue on each airscrew, maybe I can make it through a whole season without this bother!

 

[HotRodZilla]

Harnic, what are you doing to your bike that you have to sync the throttle bodies every season? Mine haven't been done for a couple of years and don't seem to have ever changed. What knocks them out?

 

[Twigg]

Does the morgan have the mm/hg labeled? I don't think my motion pro has anything labeled

No the Motion Pro doesn't have absolute pressure markings.

They wouldn't be relevant anyway because of the way you sync the tool before you use it. In most cases that simply means "picking a line" and syncing all four columns to the same line. An easy process but of little use for reading the actual pressure.

Vacuum pressure gauges are cheap if you want to know what it is.

 

[Fred W]

Ok, I am having a good day today! When I synced the throttles the other day, I got too caught up in the actual vacuum generated. As I've since discovered, that's somewhat irrelevant. I read through my service manual thoroughly & the manual said, & I quote: on page 3-9 "If the air screw was removed, turn the screw 3/4 turn in and be sure to synchronize the throttle body." That didn't sound right, so I called the head technician at the Yamaha dealer I bought my 2012 from new & asked him. He couldn't pull that from memory, but said he would check his charts when he finished the job he was on & phone me back. True to his word, in about an hour he called back & said his info was the same as what I'd found. With this new info in mind, I popped my tank up again & turned one of the air screws all the way out, being careful not to drop it! I turned it slowly counter clockwise so I could feel the last thread drop over, then from that point screwed it back in ¾ of a turn as they said. Any of you familiar with either fuel injected or carbureted systems will realize the same thing I did right away. most of the threads on the air screw were hanging out in space leaving the air screw quite loose. In a matter of a very few miles the vibrations would shake that screw out & it would bounce down the road into oblivion. I went back to my days as a mechanic at a small Yamaha shop 40 years ago & used the same settings we used on carburetors, turn the air screw clockwise til lightly seated, then back off ¾ turn & work from there. I did this with mine, re calibrated my Motion Pro SyncPro manometer, hooked it up to the ports, fired up the engine & after warming it up to 2 bars on the temp gauge, adjusted the screws. They were all quite close together & required very minor adjustments to be in harmony. My bike purrs like a kitten now! It just goes to show you can't believe everything you read. I'm thinking next time I do this I'll put a small drop of Threadlocker Blue on each airscrew, maybe I can make it through a whole season without this bother!

Yes, the Yamaha tech had it backwards. If you back out the air screw fully, and then only turn it in one turn from there, you will have way too much bypass air and, after balancing the 4 throttles your idle speed will be too high and unable to be adjusted down.

The correct way to do it is to run the air screws all the way in to lightly seated, then back each one out only 1 turn from there. Knock the high vacuums down (by opening that air screw) and/or raise the lowest ones by turning those air screws a bit.

The absolute vacuum pressure is inconsequential. It will be what ever it will be and these adjustments will not really alter that. All you wan t to do is to make all 4 throttles the same vacuum and have the idle speed at 1000-1100 rpm.

 

[bluesdog]

There are other incorrect/misleading/silly instructions in the FSM. For example, the oil drain plug torque spec of 31lb-ft is insane. The procedure to remove the front forks as outlined in the FSM requires removal of most tupperware, and the battery, when the forks can be just slid out (I've done it. No fairing/battery removal required). Removal of the radiator, according to the FSM, requires throttle body removal (!!??) - which is just weird, considering the throttle body is nowhere near the radiator. (I have removed/replaced the rad on my '11, and can assure you the throttle body remained untouched)

I'm sure there are additional things in there I have not encountered. Maybe we should compile a list?

 

[radiummadman]

hey HRZ, just use the damn tool and quit screwing around !!! You only have 2 weeks to leave for EOM. If you need some help on

your first attempt let me know, I can be there in 3 hours. tu con la boca and yo con los manos