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People running bike carbs, whats your throttle tip in like?
dmrider_10 - 6/10/14 at 01:51 PM

2.0l I4 from an RS2000 with ZX6R bike carbs

I know my AFRs are all good etc and the car pulls well. But If I'm going from the overrun back onto the throttle theres a slight hesitation and its very slightly jerky unless you apply the throttle VERY gently. This is more of a problem when driving slowly around town than when giving it some.

On a mappable injection car, this would be cured by adjusting acceleration enrichment, but on carbs????

whitestu - 6/10/14 at 02:27 PM

I can't say I have the same problem on mine with ZX6 Carbs.

Is it actually a problem wiht the carbs or could it be the throttle linkage / pedal travel being too sensitive?


Stu

[Edited on 6/10/14 by whitestu]

MikeRJ - 6/10/14 at 02:44 PM

Sounds like your pilot jets may be a little on the small side.

dmrider_10 - 6/10/14 at 02:46 PM

No it's deo not a linkage/cable issue or anything. It's a throttle "tip in" issue. I'm wondering if it's the ratio of pedal travel and throttle opening? As in it's too aggressive?

whitestu - 6/10/14 at 02:49 PM

quote:

No it's deo not a linkage/cable issue or anything. It's a throttle "tip in" issue. I'm wondering if it's the ratio of pedal travel and throttle opening? As in it's too aggressive?


Sorry - that's what I meant by the linkage / pedal.

Stu

dmrider_10 - 6/10/14 at 02:53 PM

Ah right I thought you meant sticking etc.

In that case, how far into your pedal travel is your throttle fully open? Have you kept the standard cable "cam" on the carbs?

19sac65 - 6/10/14 at 02:58 PM

Ive heard some suffering this because the slides are opening too wide too quickly due to a car engine creating way more vac than a bike does
The fix is to close up the hole (s) in the diaphragm
Happens occasionaly on mine if ime aggresive with it at low rpm

whitestu - 6/10/14 at 03:39 PM

Yes, the cam on the carbs is standard.

I moved the point where the pedal connects to the cable closer to the pivot though to make it a bit less sensitive.

Stu

BaileyPerformance - 6/10/14 at 06:14 PM

quote:
Originally posted by 19sac65
Ive heard some suffering this because the slides are opening too wide too quickly due to a car engine creating way more vac than a bike does
The fix is to close up the hole (s) in the diaphragm
Happens occasionaly on mine if ime aggresive with it at low rpm


Yes, we have seen this issue and a way around it is as 19sac65 suggests

Also, the springs can be changed for some heaver versions slowing the the response of the slides, a fast acting slide causes a lean mixture when the throttle is snapped open, is its damped by a heavy spring or close up the hole it enriches the mixture. If it was an SU you would put heaver oil in the dashpot to correct the issue

Regarding jetting, what AFR to you see at very light throttle, light load?

www.facebook.com/baileyperformance

sjmatthews - 6/10/14 at 09:17 PM

I had a hesitation when going back onto throttle or when using very light throttle. The occasional spit back confirmed a lean spot which I cured by fitting a couple of washers under my needles. See here...

Needles...

coozer - 7/10/14 at 11:31 AM

I moved the cable further away from the pivot point on the pedal and that smoothed out the action but made the travel a lot longer. It was jerky with the short throw on the throttle.

monsterob - 7/10/14 at 11:42 AM

not had mine driving :-(

Jenko - 8/10/14 at 02:47 PM

I think also this can also be caused by the AFR being too lean between fully closed throttle and very light throttle load.