Hello Guest User,

Please feel free to have a look around the forum but be aware that as an unregistered guest you can't see all of it and you can't post.

To access these 'Registered Users Only' areas simply register and login.

ZIA revs hanging when throttle is blipped

Need help restoring, building, or finding then try here.

Moderators: KeithZ1R, chrisu, paul doran, Taffus

Message
Author
User avatar
garybrez
Regular Poster
Posts: 34
Joined: 7th Apr 2013
Location: Sunderland

ZIA revs hanging when throttle is blipped

#1 PostAuthor: garybrez » Tue May 14, 2019 5:52 pm

Hi .. I have a Z1A fitted with VM26mm carbs a 4-1 and pod filters … the problem I have is the revs are slow to drop on throttle blip … idle speed is ok its just when the throttle is blipped to say mid range it seems slow to return back to idle..... checked advance retard seems ok … new cables fitted and have free motion …. carbs have been ultra sonic cleaned and I have fitted larger pilot jets ( should I have upped the main jet also ? ) checked slide heights and the shut off gap of the slide on each is ok … timing is strobed and is spot on ….

User avatar
Tonto
Custard Cream
Custard Cream
Posts: 563
Joined: 11th Jan 2012
Location: Lincoln - The Land That Time Forgot

Re: ZIA revs hanging when throttle is blipped

#2 PostAuthor: Tonto » Tue May 14, 2019 6:23 pm

Have you checked the inlet rubbers for cracks or air bleeds / leaks ? - revs hanging can be a typical symptom.
"Better to remain silent and be thought an idiot, than to open your mouth and remove any doubt" - Abraham Lincoln
Z900 A4 / ZRX1200R / Hodna CBXZ / H1F 500 Project / Z1000A1 Project / CBXZ Project

User avatar
garybrez
Regular Poster
Posts: 34
Joined: 7th Apr 2013
Location: Sunderland

Re: ZIA revs hanging when throttle is blipped

#3 PostAuthor: garybrez » Tue May 14, 2019 7:30 pm

I have not checked the inlet rubbers as they looked fairly new … I have read if you spray wd40 around the inlet rubber when the motor is idling the revs should go up if there is a poor seal

User avatar
zed1015
Hardcore
Hardcore
Posts: 2607
Joined: 2nd Nov 2005
Location: Somewhere between Scunny and Goole.

Re: ZIA revs hanging when throttle is blipped

#4 PostAuthor: zed1015 » Tue May 14, 2019 9:47 pm

New cables and hanging revs always usually points to not enough slack in the cables.
Try backing off the cable adjusters a couple of turns before doing anything else.

User avatar
garybrez
Regular Poster
Posts: 34
Joined: 7th Apr 2013
Location: Sunderland

Re: ZIA revs hanging when throttle is blipped

#5 PostAuthor: garybrez » Tue May 14, 2019 9:52 pm

Double checked cables … got play on both cables …. throttle action is loose

needaz1100r
ZedHead
ZedHead
Posts: 1025
Joined: 11th Sep 2012
Location: Reading
Contact:

Re: ZIA revs hanging when throttle is blipped

#6 PostAuthor: needaz1100r » Wed May 15, 2019 10:39 am

garybrez wrote:Double checked cables … got play on both cables …. throttle action is loose


You need to identify the cause, either slides not closing or some other way fuel/air is getting into the motor.

The return cable should be tight for this test, adjust the cables so that you can see the return cable get tight when you shut the throttle with the tickover correctly set, that way when you shut the throttle you are sure the slides shut.

If it still runs on then you most likely have an air leak, WD40 around the inlet, or easy start, CAN identify an air leak, but it is not conclusive, the behaviour of the engine is more so. Remember closing the throttle at higher revs creates far more vacuum than idling at tickover.
Cheers,

Mark.

User avatar
garybrez
Regular Poster
Posts: 34
Joined: 7th Apr 2013
Location: Sunderland

Re: ZIA revs hanging when throttle is blipped

#7 PostAuthor: garybrez » Wed May 15, 2019 6:18 pm

Latest ….. fired the bike up run it till steady idle …. sprayed wd40 around the inlet rubbers, engine speed remained at idle …… next removed both throttle cables, started the engine and operated the throttle cable pulley wheel by hand …….. engine speed still hangs until it slowly returns to idle

engz1b
Regular Poster
Posts: 83
Joined: 6th Dec 2016
Location: carmarthenshire ,wales

Re: ZIA revs hanging when throttle is blipped

#8 PostAuthor: engz1b » Wed May 15, 2019 6:37 pm

take tops off carbs and make sure the locking bolt on the lifting arms are done up, i have found some loose ones on a couple of bikes

needaz1100r
ZedHead
ZedHead
Posts: 1025
Joined: 11th Sep 2012
Location: Reading
Contact:

Re: ZIA revs hanging when throttle is blipped

#9 PostAuthor: needaz1100r » Thu May 16, 2019 6:37 am

garybrez wrote:Latest ….. fired the bike up run it till steady idle …. sprayed wd40 around the inlet rubbers, engine speed remained at idle …… next removed both throttle cables, started the engine and operated the throttle cable pulley wheel by hand …….. engine speed still hangs until it slowly returns to idle


Then provided you don't have a slide loose on the mechanism like engz1b says, you have an air leak. It doesn't matter that WD40 doesn't change it at tickover - it's not at tickover that you have the issue. I've just had one doing similar, the WD40 trick didn't work because it was only 1/4 running on that cylinder at tickover, because it didn't have enough vacuum at tickover to pull through the pilot circuit, but it did at higher revs.

Have you measured the exhaust temperatures while ticking over?
checked vacuum pull with the carbs off and your hand over the inlet manifolds?
checked vacuum pull with inlet manifolds off and your hand over the inlet stubs?
That's the best way I find to check definitively for an intake leak.

Do those things next...
Cheers,



Mark.

User avatar
z1bman
Hardcore
Hardcore
Posts: 4245
Joined: 3rd Mar 2010
Location: WORDSLEY WEST MIDLANDS

Re: ZIA revs hanging when throttle is blipped

#10 PostAuthor: z1bman » Thu May 16, 2019 9:11 pm

remove the tick over screw & see if the revs are still hanging if its ok without the tick over screw the slide heights will need to be set correctly

needaz1100r
ZedHead
ZedHead
Posts: 1025
Joined: 11th Sep 2012
Location: Reading
Contact:

Re: ZIA revs hanging when throttle is blipped

#11 PostAuthor: needaz1100r » Fri May 17, 2019 6:26 am

z1bman wrote:remove the tick over screw & see if the revs are still hanging if its ok without the tick over screw the slide heights will need to be set correctly


That would just give him a high tickover that he can't adjust, but that's not his problem. I read it that he can get a reasonable tickover, but when closing the throttle the revs don't instantly drop back to that tickover.
Cheers,



Mark.

User avatar
garybrez
Regular Poster
Posts: 34
Joined: 7th Apr 2013
Location: Sunderland

Re: ZIA revs hanging when throttle is blipped

#12 PostAuthor: garybrez » Fri May 17, 2019 5:03 pm

The idle speed is ok and is easy to adjust with the tick over screw, this was also a problem with idle speed until I fitted larger pilot jets, do you think I need to fit larger main jets also …. do you think mid range is too lean hence the revs hanging

Robw
Custard Cream
Custard Cream
Posts: 841
Joined: 8th Oct 2007
Location: Suffolk

Re: ZIA revs hanging when throttle is blipped

#13 PostAuthor: Robw » Fri May 17, 2019 6:14 pm

I have just had a similar problem. I had just rebuilt my engine after a rebore and fitted smaller idle jets and it kept on hanging, went through all the usual fault finding procedures and got no where. So I put the larger jets back in and it was fixed.
Rob
Z1000R/ZRX, RD 125LC, Zx7r , Endurance racer

User avatar
garybrez
Regular Poster
Posts: 34
Joined: 7th Apr 2013
Location: Sunderland

Re: ZIA revs hanging when throttle is blipped

#14 PostAuthor: garybrez » Fri May 17, 2019 7:36 pm

I already fitted larger pilot jets and idle speed is ok ……. I am contemplating fitting larger main jets as it seems lean mid range revs tend to hang

User avatar
garybrez
Regular Poster
Posts: 34
Joined: 7th Apr 2013
Location: Sunderland

Re: ZIA revs hanging when throttle is blipped

#15 PostAuthor: garybrez » Sun May 19, 2019 1:48 pm

Latest … pilot & main jets increased to 120 / 20 and lifted the needles a notch …. running better but still hanging on blip …. while the carbs were off I put my hand over each inlet rubber then turned the motor over, all kept a good vacuum until I removed my hand except, cyl 3.... I removed the inlet rubber on cyl 3 and still no vacuum ….. could this be the problem


Return to “Bike Help”

Who is online

Users browsing this forum: No registered users and 13 guests