What signs show when throttle bodies out of sync

KhromalusionaL · Aug 7, 2009

Guys,

I have done the first service on my 08 but did not do the throttle body sync. Is there things to look for if they are way out of spec. Stumble, rough idle, etc. Is it super important to have it done at the 600 mark or can i wait till the 5000 mark? I have also seen i might have to do a idle adjustment. Anyone have a write up on that?

On another note i have noticed in 1st gear rolling on throttle up into 4 grand it seams to stumble and hicup but very slightly. It goes away as soon as i get closer to 5 grand. other gears are fine.

Bike has 1500 mile as of today.

Thanks guys.

fjrrider · Aug 7, 2009

The simple answer is "You want your FI's inputing the same amount of fuel to each cylinder" if there not in sync, some cylinders are working harder than the others.

Fred W · Aug 7, 2009

That is a little bit too simple, and a bit wrong.

The FI system will (theoretically) be sending equal amounts of fuel to each cylinder regardless of the state of throttle body balance. What we are adjusting is the amount of air being supplied to each cylinder to mix with that fuel. And the adjustment, assuming you are doing the "authorized" version of the TBS, is merely adjusting the amount of air that is allowed to bypass the fully closed throttle butterflys. The majority of the effect of the bypass air will be when the throttle is fully closed. It will stiull have a minor effect on balance off idle, but it decreases rapidly as the throttle is opened.

So, the way to know you need to do a TBS is the idle (or at cruise, just off idle) is a bit rough.

IMO, the TBS procedure is a big revenue generator for the repair shops and has very little effect on how the engine actually runs. Lots of folks will tell you that theirs got a lot smoother after paying $100 (or more) for a TBS, but I am chocking that up mostly to placebo effect.

Non-authorized syncs (where you actually adjust the angles of the throttle plates (butterflys) is a whole different thing, but repair shops don't generally do those. In fact the FSM specifically prohibits them from tweaking those plates. Factory set, don't you know...

The stumbling that you observe is probably due to the stock state of tune (being lean). It's one reason that a lot of folks will put a PCIII USB on their bikes to allow them to add fuel in the lower rpm / low throttle opening ranges. A TBS will not improve that feeling, but adding a Barbarian jumper and adjustment of the CO settings may get you what you seek. Search on those highlighted terms and you will find many hours of fun reading

KhromalusionaL · Aug 7, 2009

Thanks! Good to know. will start reading a little bit more. Raining a bit today so no riding = research and info gathering.

Bustanut joker · Aug 7, 2009

Being it's Friday an all, I think we should dogpile yer *** for being so logical Fred.. B)

Good answer though

:jester:

HaulinAshe · Aug 7, 2009

Fred W said:
(...)IMO, the TBS procedure is a big revenue generator for the repair shops and has very little effect on how the engine actually runs. Lots of folks will tell you that theirs got a lot smoother after paying $100 (or more) for a TBS, but I am chocking that up mostly to placebo effect. (...)

Could not agree with FredW more!

Like many other newbie FJR owners, I got all caught up in the TBS sync and struggling to exactly match cylinders with it. It effects idle the most, and is nearly intangible by 10% throttle. Do it once per year when you change spark plugs.

fjrob1300 · Aug 7, 2009

Sparkplugs only last a year!?

08FJR4ME · Aug 7, 2009

fjrob1300 said:
Sparkplugs only last a year!?

Yes for those of us that ride. Now Howie on the other hand?

It is Friday. Sorry How!

Fred W · Aug 7, 2009

fjrob1300 said:
Sparkplugs only last a year!?

No. TBS'es last 16k miles.

timk · Aug 7, 2009

Hell, wasn't someone syncing thheFI at, like 4000rpm?

fjrob1300 · Aug 8, 2009

08FJR4ME said:
fjrob1300 said:

Sparkplugs only last a year!?

Click to expand...

Yes for those of us that ride. Now Howie on the other hand?

It is Friday. Sorry How!

Ha ha ha for those of us that ride!!! ha ha ha

Fred W · Aug 8, 2009

timk said:
Hell, wasn't someone syncing thheFI at, like 4000rpm?

yes. That is the "unauthorized" TBS.

That is worth doing once. It should not change much over time.

MCML · Aug 8, 2009

FWIW, I now have 50,000 miles on my '04 and have performed a half-dozen TBSs. They have never been far out of balance, I have never been able to get them perfectly in balance, and I cannot say that any of it has made any difference at all.

OBFJR · Aug 10, 2009

MCML said:
FWIW, I now have 50,000 miles on my '04 and have performed a half-dozen TBSs. They have never been far out of balance, I have never been able to get them perfectly in balance, and I cannot say that any of it has made any difference at all.

Not being a smart ***, why keep doing it? I'm all about owner maintenance and I've yet to hear anyone give a compelling reason to do this one. Thanks for replies.

MCML · Aug 12, 2009

Why keep doing it? Reasonable question. I bought the sync gauge early on and it gets lonely hanging from the ski rack.

Besdies, it's so easy to perform the throttle body sync that, if I am under the tank changing plugs or routing some wire or another, I sometimes do one.

quicksilver · Aug 12, 2009

If mine are out of sync. F Jr. will start bucking like a horse during low speed no throttle deceleration.

Kind of like what it does if you forget to pull the clutch in when coming to a stop.

Except it happens much earlier during coast down.

I didn't know what it was until it went away after a sync.

Zorlac · Aug 12, 2009

MCML said:
FWIW, I now have 50,000 miles on my '04 and have performed a half-dozen TBSs. They have never been far out of balance, I have never been able to get them perfectly in balance, and I cannot say that any of it has made any difference at all.

Good answer.I did mine once, I figure that's good enough till the CCT fails. :dribble:

Constant Mesh · Aug 12, 2009

The engine will accelerate more smoothly from a low rpm condition if it's synchronized well.

If you're in a higher gear just leisurely riding at a slow pace and you'd like to slowly accelerate to a higher speed without downshifting you can easily detect when the sync is off as you slowly open the throttle. Under low load conditions one can easily do this without lugging the engine.

And, of course, the requirement for syncing is primarily for reducing emissions. That's why syncing is mentioned in the Emissions Control section of the maintenance chart.

johnny80s · Aug 12, 2009

Fred W said:
fjrob1300 said:

Sparkplugs only last a year!?

Click to expand...

No. TBS'es last 16k miles.

So for me that's 29k miles. TBS and plugs at the same time. I also found you can get 33k out of an air filter. I blew it out once at 28k.

What signs show when throttle bodies out of sync

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