Flat spot / stuttering 6 - 7.5K - ZX6R Forum
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 59 Old 10-21-2011, 06:55 AM Thread Starter
Squid
 
Join Date: Oct 2011
Location: Hampshire, UK
Posts: 25
Flat spot / stuttering 6 - 7.5K

Hi there,

Joined the forum as there seems to be a lot of useful information on here.

I have an issue with my ZX6R F3 (97)...

First issue was that between 6K and 7.5K i had a noticeable drop in power and the revs slowed down, it bogged slightly but once past that range it tore off. I had changed the manifold to a full stainless and fitted a stubby exhaust.

I would have thought it would be running a little lean after that but it is running really rich, the smell of the exhaust is very petroly (sic) and there is black soot like stuff on the exit of the exhaust.

I researched the problem and it pointed to the carbs being adjusted wrongly, i toop the caps off and looked at the needles but theyre not adjustable. I i was to shim them it would make them very very rich (i tested this).

I also cleaned the air filter a little as it was majorly bunged up but didnt clean it too much as i wasnt sure how clean it had to be. ?(It's a pipercross aftermarket one).

Since that i moved the exhaust further back up the pipe so that less of the link pipe was inside the can, figuring that if the stubby was making it run rich, making the exhaust system longer would lean it out. Which it appears to have done! I no longer have such a noticeable flat spot at that rev range, although I am now faced with another issue!

If i am on half throttle, cruising on a motorway or something, the bike slowly starts to bog, like someone has put way too much fuel into the carbs, it seems almost like the air pressure is dropping or maybe leaking and it's being starved of oxygen?

What should i look at next? I am thinking about taking the airbox off, really cleaning the filter out, putting it all back together again and being extra careful to make an airtight seal. I'll also look at the breather pipes / vacuum and make sure theyre all connected OK.

Any suggestions?!

I've been very thorough explaining looking at the length of this post!

TL;DR - My bikes running way too rich, no adjustable needles - what do?
chrsjcb is offline  
Sponsored Links
Advertisement
 
post #2 of 59 Old 10-21-2011, 06:58 AM
Pro Racer
 
Alex Gold's Avatar
 
Join Date: Dec 2010
Location: London, UK
Posts: 684

I Ride: 2003 B1H, green LED's baby!
Have you checked diaphragms for tears? I had similar symptoms from a not actually torn but wrongly installed (corner folded in) diaphragm.
Alex Gold is offline  
post #3 of 59 Old 10-21-2011, 07:01 AM Thread Starter
Squid
 
Join Date: Oct 2011
Location: Hampshire, UK
Posts: 25
Very good point, I may have not put them back together as carefully as I should have.

I will inspect this when I take the caps off again.

If it's not perfect i guess it would hinder the carb quite a lot!
chrsjcb is offline  
Sponsored Links
Advertisement
 
post #4 of 59 Old 10-21-2011, 11:09 AM
Team Green
 
Join Date: May 2011
Location: h
Posts: 96

I Ride: 2008 zx6r
time for a new bike
Dani3l is offline  
post #5 of 59 Old 10-21-2011, 11:48 AM
World Superbike Champion
 
zx6chris's Avatar
 
Join Date: Mar 2011
Location: weymouth dorset
Posts: 2,297

I Ride: whats left of a j1
Also check the needles my j1 was doing this and it was worn needles and wrong jets I for a set of carbs off eBay for 50 quid and it's cheaper than gettin a shop to sort them


its not what u know its who u know!!
zx6chris is offline  
post #6 of 59 Old 10-21-2011, 12:50 PM
Pro Racer
 
yoshi's Avatar
 
Join Date: Mar 2011
Location: Northampton UK
Posts: 818

I Ride: a 2006 zx6r
make sure you have fitted all the ram air bits on properly.

check the color of the plugs after a run in the 'dead' spot as it may just be one carb thats playing up.

************************************************** **

Formerly known as rotax81

My Facebook

Facebook


My Youtube Channel
yoshi is offline  
post #7 of 59 Old 10-22-2011, 03:34 PM Thread Starter
Squid
 
Join Date: Oct 2011
Location: Hampshire, UK
Posts: 25
I didn't notice it so much coming home earlier when I was on reserve.

Is taking the whole carb set off a pain in the ass or is just a few screws / tubes? May as well get it all off and give them a service while I'm at it.
chrsjcb is offline  
post #8 of 59 Old 10-22-2011, 03:42 PM
World Superbike Champion
 
zx6chris's Avatar
 
Join Date: Mar 2011
Location: weymouth dorset
Posts: 2,297

I Ride: whats left of a j1
its not to bad once u have the air box off the 4 little allen key bolts are a bit tricky to get to but the carbs might just pull off. u have to take off the throttle cable and choke cable and a few pipes then ur away


its not what u know its who u know!!
zx6chris is offline  
post #9 of 59 Old 10-22-2011, 03:56 PM
Pro Racer
 
Alex Gold's Avatar
 
Join Date: Dec 2010
Location: London, UK
Posts: 684

I Ride: 2003 B1H, green LED's baby!
'Reserve' comment above would make me pull the fuel tap and check the filter on the main 'on' setting isn't partially blocked.
Alex Gold is offline  
post #10 of 59 Old 10-22-2011, 03:56 PM Thread Starter
Squid
 
Join Date: Oct 2011
Location: Hampshire, UK
Posts: 25
Once the airbox is off, i know there's two bolts that go through the carbs and the black casing on the top, do they have to be undone too?

Where are the 4 allen bolts you mentioned?

EDIT: Noted, will check the filter on the tap too... Could just be because i was doing 60 instead of 75 and sat at a different rev range.

EDIT2: Found this, really useful: http://www.themcdonalds.net/~themcdo...ors_on_a_ZX-6R

Cheers

Last edited by chrsjcb; 10-22-2011 at 04:04 PM.
chrsjcb is offline  
post #11 of 59 Old 10-22-2011, 04:08 PM
World Superbike Champion
 
zx6chris's Avatar
 
Join Date: Mar 2011
Location: weymouth dorset
Posts: 2,297

I Ride: whats left of a j1
Quote:
Originally Posted by chrsjcb View Post
Once the airbox is off, i know there's two bolts that go through the carbs and the black casing on the top, do they have to be undone too?

Where are the 4 allen bolts you mentioned?

EDIT: Noted, will check the filter on the tap too... Could just be because i was doing 60 instead of 75 and sat at a different rev range.

Cheers
no u dont need to take them long bots apart they are holding the 4 carbs together the 4 allenkey bolts are between the card and the cylinder head they a tucked right under the carbs on top of the rubber boots things


its not what u know its who u know!!
zx6chris is offline  
post #12 of 59 Old 10-22-2011, 04:37 PM
Post Master General
 
arron's Avatar
 
Join Date: Jul 2007
Location: melbourne
Posts: 11,637

I Ride: 1998 zx6r, 1999 sv650
Did you sync the carbs once you cleaned the carbs and filter?
Are the air mixture srews all the same turns out as well?




tinted screen, hel lines,intergrated tail light, rearset adjusters, K&N air filter, +4 advancer, -1 front, pazzo knock offs, ape cct, zip tie mod,07 shock + rear disk, 08 swingarm, vernhil rear line, 636 exhaust with dan moto cf can, Kleen air mod..

still lovin forever!
arron is offline  
post #13 of 59 Old 10-22-2011, 04:41 PM Thread Starter
Squid
 
Join Date: Oct 2011
Location: Hampshire, UK
Posts: 25
I'm still learning all of this so apologies....

I havent synced them as I havent had the carbs off yet, they looked fine when I took the caps off though.

Where is the air mixture screw on the carb? (noob, but learning)
chrsjcb is offline  
post #14 of 59 Old 10-22-2011, 04:48 PM
Post Master General
 
arron's Avatar
 
Join Date: Jul 2007
Location: melbourne
Posts: 11,637

I Ride: 1998 zx6r, 1999 sv650
You sync the carbs on the bike when its running..

https://zx6r.com/attachments/mechanic...loseup-3-4.jpg

this it the air screw..Some you have to drill the plug out and some you dont..Ther all set different turns out but ond and i have done it to 3 1/4 i think..

https://zx6r.com/mechanical-technical...carb-tune.html




tinted screen, hel lines,intergrated tail light, rearset adjusters, K&N air filter, +4 advancer, -1 front, pazzo knock offs, ape cct, zip tie mod,07 shock + rear disk, 08 swingarm, vernhil rear line, 636 exhaust with dan moto cf can, Kleen air mod..

still lovin forever!
arron is offline  
post #15 of 59 Old 10-22-2011, 05:04 PM Thread Starter
Squid
 
Join Date: Oct 2011
Location: Hampshire, UK
Posts: 25
I see what you mean, so those four screws control the air mixture in the carbs.

Scanning through the thread they should all be equal and if they're way off then that can cause performance issues...

I think that's going the be the first thing I look at after making sure my diaphragms are fine as the bike didnt have running issues until I changed the manifold.

I read what you posted, I'll put them at 3 turns out and see how it runs!
chrsjcb is offline  
Reply

  ZX6R Forum > ZX6R Forum > Mechanical and Technical

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
zzr1400 flat out scoobs Videos 1 01-24-2012 11:05 AM
Flat spot :confuses: zx6chris The ZX6R 17 08-17-2011 11:56 AM
Flat Rear Arlo_007 Motorcycle Talk 7 05-02-2011 09:12 AM
flat spot on front tire?? hocknscary87 The ZX6R 1 04-09-2009 08:34 PM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome