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digger9

Joined:

Feb 11

Posts: 5

digger9 says:

Advice on dyno run...

Hey all,
I had a dyno run done on my 98 zx6r yester as I thought it was running bit rich and getting poor mpg. Turns out it is rich through mid range.
Not the guys at bigcc seemed to think there was nothing wrong with the jets etc maybe just a clean up and setup, but wanted £200 for the privilage...
I dont mind doing the work myself just thought id get a second,third...opinion.
So what do you guys recon? clean carbs jets etc and balance? maybe a stage 1 dynojet kit and balance?(has a full yosh system on it)
Cheers :biggrin:

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  • Posted 4 years ago (15 May 2011 08:42)

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jaffa90

Joined:

Mar 09

Posts: 8894

jaffa90 says:

jets

Nothing wrong with the jets on a 13 year bike how do they know?:shock: You may find the needles and jets are in good condition and just lower the needles one notch.Running the bike leaner after all these years may cause further problems with the extra heat.How is the bike when cold? Does it need a lot of choke to warm up? Are you satisfied with the top end power?What is your spark plug condition? Also what M.P.G. are you talking?

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eatcs01

Joined:

Aug 02

Posts: 3265

eatcs01 says:

Dyno

Take it to a better dyno shop.

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smidget

Joined:

Nov 07

Posts: 2419

smidget says:

diggers

When was the engine last serviced? 


What is the condition of the air cleaner?

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digger9

Joined:

Feb 11

Posts: 5

digger9 says:

jets

cheers for the help guys, the bike had the engine stripped right down last year to have shims, timing chain etc checked, so the engine is solid, when cold can be a little lagged just off idle but nothing major, peak power im pretty happy with (dont need a rocketship but a couple more can never hurt :wink:) and im geting about 110 miles to a tank...
the plugs and filter were fine at time engine checked but to be honest not checked since (done bout 1k since no more). was hoping to strip it down once and do it all together.
Next sun i am planning on spending a day trying to sort it, i have got hold of a carb balancer. so what would be the suggestions? where do i start? not sure wether to buy a new set of jets etc so can change them anyway while cleaning the carbs, or just try to clean, balance, get the mixture right and go from there.
Sorry I seem bit vague, this is my first time trying this and any advice will just make it bit easier:biggrin:

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digger9

Joined:

Feb 11

Posts: 5

digger9 says:

jets again

Cheers for replys any help really appreciated, my first time tackling this so anything to make it easier... Like say im planning on stripping her down next sun, check plugs, filter, clean carbs, then balance (have a carb balancer here), lean it off maybe and adjust air/fuel mixture see if that helps.
If it was you what would you be doing? is it worth changing the jets etc while in there, or is it easy to tell if they are damaged/ worn? tempted just to buy a stage 1 dynojet kit and fit as know will have right jets and good ones too then, but if i dont need to spend the money why do it...
thanks again

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smoto5

Joined:

Mar 09

Posts: 4548

smoto5 says:

A few things to think about here,

1) Did the dyno operators seem to know what they are talking about? Anybody else around you could ask about it?

2) Is it possible the bike has been set up with a different pipe on, either race or road? Is it possible the bike has been fitted with a K and N filter at some time? is it a standard airfilter in there or aftermarket, if not KandN then one of the other performance makes? (putting standard back in when jetted or Dynojetted for a KnN may make for rich mix)
3) Unlikely to wear out any jets apart from needle jets (emulsion tube) and it's accompanying needle. This may happen after many miles, the Yamaha five valve per cylinder twins (supertenere xtz750, TDM850) were known for that for example.
4) adjusting the mixture (air/fuel) screws will only influence running at tickover and small throttle openings up to about eighth throttle, then the cutout in the throttle slide starts to take over, it may be possible on CV type carbs that the springs are not right stiffness altering the point at which the slide lifts and the response.
That's about all I can think of at the moment! Be sure you know what you are doing before ripping carbs apart, it's easy to start blaming carbs before you've checked everything else, and it's easy to make the problems worse!

[This Reply has been modified by the Author]

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eatcs01

Joined:

Aug 02

Posts: 3265

eatcs01 says:

zx6r

My 1999 ZZR600 E7 makes 95bhp at the rear wheel. There's still more to come from your ZX6R

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jaffa90

Joined:

Mar 09

Posts: 8894

jaffa90 says:

carbs

Sounds like your going to strip the carbs,check what has been mentioned by all,also the floats and heights as well as the pilot jets and main jet size.Come back with what you find. 

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digger9

Joined:

Feb 11

Posts: 5

digger9 says:

so the results...

Well this is how it went, stripped bike, cleaned air filter etc, tested carb balance which was a little off but not bad, stripped and cleaned carbs which were mucky but no major signs of wear or damage. So adjusted the needle settings (just by one groove to lean her slightly). reasembled, rebalanced to get them just right. finished putting togther... time for test ride... 1/2 mile done bike dies, eventually starts again... less than 1/2 mile bike dies... curse, shout kick kerb few times... realise fuel tap still off... kick self try again. Bike riding 100% better, no stuttering, much more responsive right through range and no flat spots, no signs of overheating, big smiles all round! Will see how effects fuel economy as we go!
Only slight issue to arrise not is when i pull cluch lever to change gear or hold in (say at lights in first) neutral light comes on. must of knocked something, anyway job for another day along with checking valve timing etc, may as well check it all now... thanks all for your help

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