Un-Authorized Throttle Body Sync / Cleaning

[TownsendsFJR1300]

The below links were taken from an FJR forum which I frequent.

The main difference between the FJR and the FZ6 TB's is that there is ONLY ONE throttle plate butterfly adjustment (between the 2 TB's for cylnders 1&2, adjustment screw, TB's 3&4), vs THREE on the FJR (4 separate TB's).

For some bikes that have more vibs than normal, especially in the higher rev range (where the a TBS has been done, Spark plug caps checked, etc), this is something to be checked should someone have previously dinked with the center adjustment , butterfly adjuster screw inadvertantly or on purpose.

NOTE, from personal experiance, (prior to purchasing a Morgan Carbtune) I had a Yamaha dealership do a sync on my old FJR. They ADJUSTED the TB 1/2 cylinder butterfly screw which is NOT SUPPOSED TO BE ADJUSTED. I had to set it back and do the sync correctly. (it was easier to access that butterfly screw than the air screw. Why they did this, ignorance, laziness, ?)

Some interesting reading and something to check for a bike vibrating more than usual, especially in the higher RPM range;

http://home.comcast.net/~FJR-NERDS/FJR_Tech_Stuff/The_RDCUA_TBS.htm

Error - FJRForum


And for filthy throttle plates and why;

Error - FJRForum

Just as a side re the links. "Fred W" is HIGHLY REGARDED on the forum and probably the most knowledgable person there with hands on experiance...

 

[FinalImpact]

The below links were taken from an FJR forum which I frequent.

Hey, two of the links are busted.... Best effort returned nil after several tries... FJRforum.com "cleaning-throttle-bodies-worth-the-time" & "the-really-definitely-completely-un-authorized-tbs"

Search engines find the forum thread but no good comes of it. Like it wants us logged in perhaps???

I used a own a cage with 4 one barrel carbs. Same issue - get the throttle plates/blades at the same angle for best results. i.e. 65 Chev Corvair 140HP...

Back on topic: from the comcast page, it doesn't mention complete tune up starting with a:
- valve adjust
- vacuum leak inspection (boot from head to TB), all hoses
- TB shafts on high mileage vehicles be inspected
- Plugs, fuel treatments are DONE before doing this TB sync

The engine is pump essentially. Spin the pump at a different speed and it generates more/less vacuum. So, mechanically its VERY IMPORTANT to get everything balanced before relying on vacuum to sort out flow (pressure drop in this case), as there are so many variables that can effect the crankshaft velocity during the firing stroke.

Other options include flow bench testing which isn't all that difficult (well until you try to suspend 4 TBs in the air). You just need a constant source of air flow and some form of flow meter. Then mechanically align the TB blade angles and see how much air they flow at for example 3 different blade angles.

Thankfully the Mikuni's on the FZ are in pairs and not Singles! :thumbup: See if you can extract some key notes from the threads or working links. It seems kinda crazy it wants us logged in for that.... Tks

 

[TownsendsFJR1300]

Hey, two of the links are busted....

Yep, I signed out and tried and they don't work . Signed in, their accessable..


The first link, pretty much tells all.

As noted in my initial post, it basically addresses the butterfly adjustment screws for the FJR, however, the FZ6 has ONE butterfly adjustment screw between both TB's. If this adjustment is dinked with (not set correctly), it will increase vib's, poor performance.

Should all the regular "fixes/checks" not work, the TB plates/adjustment should be checked... It is another thing that can indeed induce unnecessary vibs..

As I noted above, one of those butterfly screws (on my FJR) were adjusted approx 1/4 turn, by a Yamaha mechanic when I paid for a throttle sync. So mis-adjustment or just someone (knowledgable or not) can easily screw up something that should NOT be adjusted from tha factory.

The "Un-Authorized sync", especially for the FJR (as there's more room for adjustment with 4 separate TB's) does help if there is an issue. Being the FZ6 only has one adjuster, results wouldn't be as effective but none the less, adjusted as close as possible, for the closest sync for good overall performance..

Re the dirty throttle plate link; it basically showed that wil the crankcase breather, often putting oil fumes into the air filter compartment, (with the normal vacuum of the engine running). That oil, gets sucked to the throttle plates. Crap/oil and build up then sticks to the plates.

 

[FinalImpact]

Here you can see the screw between the two separate throttle bodies!

Messing with this screw is can unbalance the TB's volume or air it supples the engine. In rare cases, it may be unbalanced.

With the throttle bodies removed, you can pour solvent into the venturi and verify all 4 venturis leak the fluid past the throttle blades at the SAME RATE! i.e. Use equal fluid volumes and a stop watch. This test works great as the bleed holes for sync and vacuum are below the blades so they have no impact. If they do not leak at the same rate, it **may help** to adjust the balance screw.


Just to connect a few dots for some folks, in this picture is the idle air control valve. It has the 4 sync screws which control the volume of air the engine gets at idle. Idle air passes from the LARGE openings (Inlet) through the body and past the sync screws into those 4 chambers. The 4 chambers are connected to the TB via the rubber hoses.
This accounts for idle to roughly 2000 RPM. As the the throttle plates open, the signal through the IACV decreases taking the path of least resistance.

Description of items:
Notice the 4 hoses from the IACV going to the TB's and the two separate bodies.