2000 J1 6r running problem.... - ZX6R Forum
 
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post #1 of 9 Old 03-08-2009, 12:09 AM Thread Starter
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2000 J1 6r running problem....

hey guys,
Wondering if anyone can help me with diagnosing a running fault with my 6r, i am a car mechanic but fairly new to bikes...

right here goes
it idles fine, and free revs fine but if you wrap it out through the revs it starts to brake down (miss fire) around 8k and begins to clear again through the top end 11k to 14k up at these revs its a little hard to tell if its completely dropping on one cylinder or partially dropping more than 1...

how ever i have found that if i cruise along in 4th @ around 4k and open the throttle up but ride the brakes to prevent it accelerating (high load) it will begin to miss fire on one cylinder ie. running on three... let the brake off and it clears back to 4 Cyl's then as load increases back up around 8k begins to hesitate again...

also if you are down changing through the gears it sounds a bit missfirey occasionally

this has also gradually been getting worse.. at first it just felt surgy through the power band
but now is miss firing... and it seems to be worse once the bike is at full operating temp...

only things done to the bike is K&N filter, rs3 ti yoshi, carbs shimmed with washers (have now removed shims)

so far i have tryied
a valve clearance check, 3 were out of spec and were re shimmed... (not far out .03mm from min clearance)
have changed plugs
and have swapped coil packs from my other bike
remove shims from main jet needles.
checked all ram air ducting vac hoses etc... all ok
and so far no success

im starting to think its more a fuel delivery problem possibly fuel pump, partially blocked needle and seat/main jet etc...

next things to try i guess>>
compression check (seems ok, sounds even when cranking and pulls hard when it doesn't play up)
swap fuel pump
swap igniter module (if compatible other bike is a 636 AP1)
strip and clean carbs

its just strange how it doesn't do it every time and that it comes good in the top end...
anyway any help would be appreciated and anyone else that has had a similar problem and what it turned out to be..

cheers Allan.
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post #2 of 9 Old 03-08-2009, 06:07 AM
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I would have said coils as it's only one cylinder - is it always the same one? Could it be a timing issue?
Apart from that, fuel pump and filter / delivery.

Good luck, let us know what it is when you sort it

EDIT - Have you checked the pickup coil?

Is this your bike Al, or the mutant that you guys have been working on?

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Last edited by Mentok; 03-08-2009 at 06:42 AM.
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post #3 of 9 Old 03-08-2009, 02:00 PM
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The ONE thing I NEVER hear people say they've tried is cleaning the carbs.

Pull the carbs, remove the pilot mixture screw plug (air/fuel mixture screws plugs) so you can remove the mixture screws for cleaning, and disassemble the rest of the carb.

Get some CHEAP Wal-Mart brand carb cleaner spray and go to town on all the passages.

Eye up the butterflies, using the mixture holes in the throttle bores as a reference point.

Install the flat valves in different locations. (do NOT remove the valve seats at this time unless you are replacing the seals)

set mixture screws to 3.0 turns out, and do not use shims at this time.

Do not install airbox at this time. Assemble everything else. And test ride.

If running well, good. Tune as desired from here.

If same, or similar condition remains. Remove gas tank after motor gets to operating temp, and look down the throttle bores to see if any one of the carbs is leaking gas up through the metering rod port (emulsion tube) (it should not be pushing gas up). THIS IS A COMMON PROBLEM WITH SOME OF THE OLDER MIKUNI BIKES. Means that the float valve is bad.

Could also be dirty carbs, a loose metering rod (cap is not on completely), extremely dirty air cleaner (doubtful), clogged fuel filter, bad fuel pump, etc.

My guess is the carbs are dirty and maybe need a float valve or two.

It doesn't have to be the right tool; Just one that works.
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post #4 of 9 Old 03-08-2009, 02:14 PM Thread Starter
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no, i havent checked that yet but they would be the equivalent of a crank angle sensor on a car right? which would normally effect more than one cylinder?
not 100% up there with bike electrics, bit different to car stuff...

might go talk to the bike mechanic next door to work today, get a few more opinions make sure im looking in the right area.

and no its not my mongrel project bike, its running sweet, well it was until i started steeling coil packs and fuel pumps do diagnose this bike! haha!
this is my first bike "old betty" which had been great until now, originally i bought the mongrel bike as spares for betty, but then it turned into a project.... im my own worst enemy!
cheers al
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post #5 of 9 Old 03-08-2009, 02:29 PM
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I re-read your post and you say it clears up at higher revs? probably not spark then. Like you I've more experience with car mechanics, you may be better off listening to manley..

good luck and get going on that mongrel

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post #6 of 9 Old 03-09-2009, 07:15 PM
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Thanks Mentok.

Not saying it's just dirty carbs, but that is really the first and easiest thing to do, and GENERALLY it is the most common problem.

Give er a try. The J1's love fuel, and when they get starved they really hate it.

It doesn't have to be the right tool; Just one that works.
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post #7 of 9 Old 03-10-2009, 12:29 AM Thread Starter
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think its sorted!

hey thanks for the tip manley,

pulled it down and found one of the slides metering rod retainer had poped out causing cyl1 to run obscenely rich!

i also found that the diaphragms were a bit stretched and soft, bit like how rubber goes if its been soaked in oil. so i swapped the slides and diaphragms from the spare set of carbs i had lying around

anyway took it for a spin in the rain last night and it seems to be back to its normal self.

although the needle retainer cant have been my original problem as i de-shimmed it and must have stuffed up putting it back together when i did the valve clearance and plugs so thats where the initial fault must have lied
cheers al.
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post #8 of 9 Old 03-10-2009, 12:56 AM
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I think manley stole my thunder on this one. I would also relace any fuel filters on the bike, and since you'll have the tank off to clean your carbs, try pulling the screen filters out of the tank, and spray them out with some carb cleaner as well. You migh be supprised to see them all gunked up. Like manley said, they love fuel.
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post #9 of 9 Old 03-10-2009, 03:35 PM
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I just know these bikes too well.lol

I rode a 900 miles with a loose metering rod.

It doesn't have to be the right tool; Just one that works.
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