big ears
Well-known member
It fun to so the sync but it don't change much.
What signs show when throttle bodies out of sync
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Alakso
Well-known member
TB/Carb sync is important so the cylinders aren't fighting with each other. In an EFI system you want the closest Air volume for each cylinder possible so that each cylinder is syncronized and working in harmony with each other and not fighting each other. Just got my factory manual so I need to check it out to see what's going on with the FJR TB sync. If as I've read on this forum the TB sync involves adjusting the idle/low speed air screw to sync the Air volume for each cylinder then I would think it would also be important to sync the throttle plates first if possible? I wonder if the popsickle stick trick would work on the FJR throttle body butterflies?
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You will find that there is no throttle plate sync called for or described in the FSM. That is what folks do when they are doing the "unauthorized" TBS procedure.
But please let us in on what the popsickle stick trick is. (I think I have a pretty good idea)
Alakso
Well-known member
Back in the day I've used popsickle sticks stuck in the carb throat to sync the carb slides on Mikuni carbs. Just open the slide with the throttle, stick in the sticks and then close the throttle. Very gently open the throttle while observing the pop sticks and adjust until they all sink together at the same time. Crude, but it works when one is on a limited budget.
So it's the "angle of the dangle" that you're adjusting then, right?
Alakso
Well-known member
Of Course, the angle of the dangle is what it's all about!
On another note I miss spoke about syncronizing the AFR for each cylinder when I meant to say the Air volume (EFI system) for each cylinder. Of course with a carb the AFR is set by the venturi size, jets or jets with a slide needle, and the various air bleeds, accelerator pumps, etc.. On an EFI system the AFR is determined by the FI ECU with input from the FI system sensors. I have edited my previous post.
Alakso
Well-known member
Quote (Fred W @Aug 20 2009, 05:06 PM)
"You will find that there is no throttle plate sync called for or described in the FSM. That is what folks do when they are doing the "unauthorized" TBS procedure."
The "unauthorized" TB sync method doesn't make any sense to me?
Syncronizing the throttle valves (butterflies) is a mechanical adjustment and providing all the related mechanical parts are manufactured correctly and are in good working order then a throttle valve sync at idle should also result in syncronized throttle valves at 1/4, 1/2, or full throttle. Why not just seat all the air screws. Open up the throttle valves a hair (so the bike will idle) with any of the various mechanical idle adjustments. Then hook up the sync gauge and sync the throttle plates. Then return the air screws to their original position (you did count the number of turns?) and do the factory recommended TB sync. This way your not beating up your engine by running it at 3-4K RPM with some sort of improvised load. You'll have the throttle valves syncronized and can fine tune the TB sync with the air screws. I would think the factory doesn't have a throttle valve sync in the FSM because they figure that with this being a mechanical adjustment that they got it right at the factory when they assembled the engine. But of course we all know that any mass-produced engine will have some variations of specs that we can adjust to the minimum or sometimes even the correct specs. Now I'll admit I'm no EFI expert as I graduated from M/C school back in '81 so I'd be interested in everyones thoughts on using this method to sync the throttle plates and TB's.
I just received my Morgan CarbTune and will be doing a TB sync ASAP and I'll try out my method to see if it works like I think it should.
"You will find that there is no throttle plate sync called for or described in the FSM. That is what folks do when they are doing the "unauthorized" TBS procedure."
The "unauthorized" TB sync method doesn't make any sense to me?
Syncronizing the throttle valves (butterflies) is a mechanical adjustment and providing all the related mechanical parts are manufactured correctly and are in good working order then a throttle valve sync at idle should also result in syncronized throttle valves at 1/4, 1/2, or full throttle. Why not just seat all the air screws. Open up the throttle valves a hair (so the bike will idle) with any of the various mechanical idle adjustments. Then hook up the sync gauge and sync the throttle plates. Then return the air screws to their original position (you did count the number of turns?) and do the factory recommended TB sync. This way your not beating up your engine by running it at 3-4K RPM with some sort of improvised load. You'll have the throttle valves syncronized and can fine tune the TB sync with the air screws. I would think the factory doesn't have a throttle valve sync in the FSM because they figure that with this being a mechanical adjustment that they got it right at the factory when they assembled the engine. But of course we all know that any mass-produced engine will have some variations of specs that we can adjust to the minimum or sometimes even the correct specs. Now I'll admit I'm no EFI expert as I graduated from M/C school back in '81 so I'd be interested in everyones thoughts on using this method to sync the throttle plates and TB's.
I just received my Morgan CarbTune and will be doing a TB sync ASAP and I'll try out my method to see if it works like I think it should.
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Your method is how I would do it. It's actually superior as any amount of (minor) variation in the butterfly opening will be a greater percentage of the total throttle plate opening, thereby making the adjustment that much more sensitive. I'd just use a throttle lock device to hold the engine rpm near idle as I don't believe the idle adjust screw will have enough range. It doesn't really matter what the rpm is, but, as you say, there is no sense revving the piss out of it.
After setting the plates to parrallel you could operate the throttle through the rpm range to make sure the plates are all moving in unison. I think the reason that folks do it the other way is because they are afraid to close down the air screws all the way. With the air screws in an unknown state of balance you'd want the plates to be more open to diminish the air screw's effect on the total air volume.
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Alakso
Well-known member
I wonder if I could hold the plates open a tad with the throttle cable adjusted tight so as to hold the plates open?
I'll bet there is enough range, yes. That should work. Or you could use a poor man's throttle lock: Put a tie wrap around the twist grip and brake lever. Tighten it enough to get the required friction to hold the throttle where you want it. That way you don't have to go back and readjust the cables again, assuming they are in adjustment before hand.
