Throttle Reponse Question

[Speed99]

I have a throttle response question. Between OFF and 1/8 throttle, it seems like there is a delay and then she comes to life with a little snap. It is like there is play in that first part of the wrist twist. It can be a little scary on low speed corners when I try to give a small amount of throttle input...there is nothing there....then it snaps on.

Is this normal.....do I need to clarify more. I am hoping there is a non-PCII fix for this so I don't start another Holy War.

Thoughts?

If there is another post covering this very problem....let me know and we can scrap this one.

Thanks,

Rick

EDITTED: I have a '99 (Injected)....5600 miles

[Mithrandir]

Try looking at adjusting the throttle cables. Sounds like they're a bit loose. Normally just a lock nut and then finger tightened thread that adjusts the cable. IIRC the XX setup is a twin cable, so you want to check on the cable that opens when you twist the throttle open as the target for adjustment.

[SwampNut]

Yeah, all the FI models have this problem. Caused by a lean spot. Richening the mix helps it some, but it doesn't go away completely.

[GerardoXX]

:evil: That behavior is normal in the FI model, the PC commander solve pretty much this problem. :twisted:

[spEEdfrEEk]

Happens, to some degree, on most bikes with CV

carbs (judging from what I can gather).

It's certainly nothing I'd experienced on MX bikes

with direct cable-to-slide carbs..

:cool: TJ :cool:

[SwampNut]

I have not tried it with the PC. With the Techlusion TFI box, which affects ALL throttle positions and speeds, it was better. I'd characterize it as "half gone," along with the 5300 RPM flat spot which was nearly gone.

Unfortunately, Techlusion was never able to solve the problem of the too-smart FI on the XX. The bike sees the injectors staying open longer than they should, and generates an FI fault eventually.

[slowxx]

You can change you PC yourself from 0 to 11,000rpm.

It can make it run real good or real bad.

Try setting your idle past the lean spot about 2,000rpm

or so, that will help. :roll: I also helps low idle oil pressure.

[XX RATED]

I adjusted my throttle cables with the top cable (throttle open) having no play [0] - Honda recomends 1/8' play (I believe) but I like it tight.

I set the idle @ 1100 rpms.

With the throttle set as above, the PC-II & the Mig pipes, I have absolutly no flat spot at all!

No exageration - gospel - I swear!

[Obby]

I've have the 1/8 throttle delay issue too. It's right when i just begin to open open throttle...then surging power ('97 carb cal. model with dyno jet kit and dual micron exhaust). It wouldn't be such a big deal if the big bird didn't have so much torque.

[tvking]

I have the same problem. With the larger rear sprocket it's even worse. Just getting around an intersection in 1st gear can be more exciting than I'd like.

[bbirdxx2000]

Not to start a war but :cool: , I saved hudreds of dollars by have my Injectors (throttle boddies) synked while putting in a K & N at the same time. Problem solved :grin: , even got better gas mileage, best being 43 MPG, low fuel light went on at 210 miles :grin:

Harry

[SwampNut]

TB sync (or lack of) doesn't cause this problem. It causes surging at steady throttle and hunting at idle. If you didn't have those problems, sync did nothing. I've checked the sync (which Honda says should NEVER be adjusted, BTW) and it is perfect. Yet the off-idle problem persists, of course, since it is unrelated to sync.

Who did this unnecessary work, and where did they get the service procedure since there isn't one?

[bbirdxx2000]

My local shop, All I can tell you is that it made a slight differance, maybe combination with the K & N filter :cool:

Harry

[Speed99]

<Hanging out and reading your responses.>

I will try adjusting the cable first and see if that helps.

Richening the mix helps it some, but it doesn't go away completely.

How do I do this on the Bird? I have the Haynes manual, but not sure if it will tell me how to do it.

-Rick

[Andy1100]

Make sure the throttle cable is adjusted up, and make sure your chain is adjusted up too. That little bit of excess driveline slop can make a difference too!

[Pete in PA]

Hey Swampy, I've got a carb. model of course. Why don't FI throttle bodies need Synced. Carbs and FI both have 4 throttle plates hooked up mechanically. both subject to going out of sync. from wear/vibration and individual cylinder vacuum diffs.

Just want to understand.

[Mithrandir]

EFI systems can still be sync'd - ask anyone with an EFI v-twin like the RC51 or Mille. The sync is used to control the timing minutely of the fuel delivery at the injector level rather than the EFI. Over time the sensors do get dirty or just loose adjustment so you end up bringing them back to the right value. It's much more important in a big twin than an I-4.

And, to the others - on my bike I only get the off-throttle jerkiness while the bike is still cold. Once it's warmed up it's smooth as anything so I definitely think the problem is throttle cable or loose chain.

[SwampNut]

Why don't FI throttle bodies need Synced.

That's what Honda says, I don't know what they did that's so special. The screws are even sealed from the factory. The dealer manuals say "no service" and there are no TSB's on doing it. I measured vacuum on mine at around 40k miles and it was perfectly even.

I have yet to ride a XX that does not have this problem. You can minimize it with tight cables, tight chain, and a slightly higher idle, but it is there. I've had this argument a few times--guys swear THEIR bike doesn't do it, but it does.

[Andy1100]

Mine definately does it, but it has helped me keep better control of it to have the trottle cable less than 1/8 in of play, and to stay on top of the chain, keep it within specs....

[mickcbr1100]

Mith is correct in saying

EFI systems can still be sync'd - ask anyone with an EFI v-twin like the RC51 or Mille. The sync is used to control the timing minutely of the fuel delivery at the injector level rather than the EFI. Over time the sensors do get dirty or just loose adjustment so you end up bringing them back to the right value. It's much more important in a big twin than an I-4.  

And, to the others - on my bike I only get the off-throttle jerkiness while the bike is still cold. Once it's warmed up it's smooth as anything so I definitely think the problem is throttle cable or loose chain.

The Haynes manual does give the correct procedure for synchronising the FI starter valves stating "out of synch starter valves cause uneven idling when cold starting and warming the engine" which seems to cover the point raised by a few with FI when cold. It isnt too hard a job I use the Morgan carbtune manometer not found much of a variation but just do it for peace of mind.

[tomek]

FI on XX is a single throttle system and as such on/off throttle response will be questionable and jerky.It can be tune out to some degree by dumping more fuel ( richening ) in offending area of rpm/ % of throttle opening to make engine come on power softer but I don`t think it can be removed completely.

I understand that Yamaha`s and Suzuki`s dual throttle systems are much better in this regard.First gen FI Gixxer 750 had single throttle and had the same problem,later they "invented" second throttle just to cure it.

I really like Yamaha`s FI on new r1/r6 models,very simple and it works.

[SwampNut]

for synchronising the FI starter valves

But that's not what we're talking about. We're talking about synchronizing the throttle body butterfly valves. Totally different. The starter valves are out of play once the bike warms up even just a little bit.

[skybluebird]

Maybe it's an ignition mapping thing (for emissions?). My (UK) bike has absolutely no delay whatsoever. My dirt bike has this problem and I bleeding hate it, but the Bird's throttle response just couldn't be any better. Should be possible to adjust it out, then.

David

[SwampNut]

It is an emissions-related lean fuel condition.