Flat spot in the mid-range, only revs up at 1/8th throttle

[haroman666]

So... £800 later, and there's still shit going wrong. I'm at my wits end with this fucker.

So, I'd just cured a misfire problem, where i'd washed my bike and water was getting somewhere.
I'd had the carbs off, just to have a clean out, and make sure there was no water there. That was all fixed, but I had a bit of a flat spot in the mid-range.
I thought not too much of it as the bike was running and I just rode about with the intention of sorting out the "flat spot" in the near future.
Well fast forward a few days and i ran the tank very low, and she wouldn't run right at all, kept cutting out etc etc.
I was taking apart the bike to get the carbs off, took the fuel tap off the tank to have a ganders but ended up playing with the clutch/cable instead (Dont ask why, I just got side tracked).
Left the air box off overnight, went out this morning started her up (Without airbox) and she was running sweet as a nut. I knew I needed petrol so I quickly shoved the airbox on and hooned to the garage to stick a tenners worth of gogo juice in. Came back home, no flat spot, running as good as ever. Refitted the side panels and bolted the airbox properly, and went inside for 20mins. Came back out to go out and she wouldnt start... I knew she was flooded from cranking over, so waited a while and voila, she started again, but with the fucking flat spot again! I dont understand why she ran sweet as fuck for a trip to the garage and then go shitty again half an hour later!!

In any case, that's the back story; this is the bit that i'm asking: I've factory set the carbs, had them all apart (Floats/bowls, main jet out, taken out the lifters and jet needle) and cleaned where I can.
I stuck them back on hoping for improvement, but no change.
The revs pick up to 6k on slight throttle opening, but it bogs a bit, so if I back off, the revs will go up to 10k and if I open up a little more again it will go to up to near redline easily. If you WOT from the 10k mark it just bogs and nearly dies. if you WOT from idle, it gets to 4k and just bogs and wont go higher, but keeps running.

This sounds like fuel starvation in the mid-range, but I've cleaned the carbs and played with the adjustments about 10000 times now...
Any suggestions and help would be appreciated.
I reeeeally dont want to take it to the garage, but when my student loan comes in next week, I may have to.

TL;DR = Flat spot in the mid-range, How fix plz
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The mistresses: 2000 Honda CBR600f, 2000 Honda VTR1000

[bridlad]

It deffo sounds fuel related ,when you cleaned the carbs did you remove the emulsion tubes too? ,they often get overlooked when carbs are cleaned and from what you describe it is the mains where the problem lies they come into play for midrange and top end taking over from the pilots which take care of the lower rev range , if you didnt I would pull them down again and remove them and give them a thorough clean and double check everything else giving it all a good blow out .Once done rebuild the carbs and reset everything to factory settings this is provided you are running standard can and airbox .hth

[Budgetboy]

You might have water in your fuel tank (happens over time).

You could be getting a weak spark.. try turning your lights on HIGH beam and see if it gets worse.If it does its electrical.(lights will dim)

Another thing mate... if you have cleaned the carbs and set these all up, did you balance them?
I have had carbs in the past that have been cleaned or set up and they have been way out. Im not saying you have set them wrong but you might have.6k will be on the main jet btw...And are you sure all your needle valves are ok.Are your Air/fuel mix screws set.

Water in fuel sits at the bottom..Water will not ignite..lol Here a pic from when i done my ZX6R.This bike was sitting for 8-12 months.Stale fuel at top & water at bottom.
When you fitted your tank you slosed the fuel about mixing it.. left it 30 mins and was crap.. Could be water..if you see what i mean.

https://img689.imageshack.us/img689/2931/cleanzx6r012.jpg
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www.Mailorderrepairs.co.uk We service your Carburetor's, Calipers & Suspension for less Also Bike repairs undertaken.

[haroman666]

Ta for the replies guys!

Firstly i'm running standard can and filter, and as far as I know the carbs are still as standard.
I didn't remove the emulsifiers, but I did give them a good blow through. I wasn't really sure how to get them out to be honest. Might be worth me having a go i guess.

One thing I haven't done is balance them. I know it's probably the most important thing to "factory set" as such, but i've not got gauges and have never done them. When I get money (9 days and counting!) i'm investing in a set of gauges as i've wanted to balance the carbs since i've had the bike!

I did have a good look at the shape of the ends of the needles and all seems to be ordinary so i'm not convinced they're a problem.

Water was a thought of mine, so I ran the tank very low (Cant remember if I included this in my original post) and that was when it started cutting out etc. But then it ran really sweet on the ride to the garage :S I stuck in a tenners worth of fuel. I try to keep water off the bike as much as I can as I know creates problems, so i'm not too sure it's that.
And having said that water sits at the bottom, i would have thought it would have been mostly drawn through by now, as i've gone through 4 - 5 tanks since I washed her and she doesn't see the rain often at all.

That jar of fuel looks like Lemon curd! haha
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The mistresses: 2000 Honda CBR600f, 2000 Honda VTR1000

[bridlad]

If the emulsion tubes are blocked no amount of blowing and cleaning will clean them in situ ,they tap out ,use a drift nothing sharp tho I find a quarter inch drive etension bar from a socket set works well ,once float bowls and everything else is removed tap them out from the top of the carb nice and gentle like ,I bet you anything this is your problem ,the tube itself will have a series of holes running the length of it and some will be blocked stopping the correct amount of fuel through in the mid to top range ,use some very fine fuse wire to clear the blockages then give them a good blow out

[Budgetboy]

Water does not get into your tank by washing it mate. In hot & cold weather condensation builds up inside your tank.Over time this builds up at the bottom of your tank.If you hardly use reserve you wont notice it at all..
As you ride your bike the fuel sloshes about mixing the water with the fuel.
If the water goes into your carbs it will just sit there building up until it runs terrible.The water is heavier than fuel so wont draw up the jets as well as fuel.

Find the drain screw on your carbs.Then fing the drain outlet on each carb.Connect a hose to the drain out let and drain the fuel in the carb bowl into a glass jar (like i did for that photo)
Leave it for 30 mins-1 hour and check it. If you see water in the bottom then theres your problem.

If no water, its either your carbs or electrical.You need to balnce the carbs (get a Carbtune) i have one and they are A1.

If i had it im my shed i would have it sorted within an hour.Are you miles away from me (Norwich)
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www.Mailorderrepairs.co.uk We service your Carburetor's, Calipers & Suspension for less Also Bike repairs undertaken.

[haroman666]

Sounds like a piece of piss really... I'll give that a go tomorrow. Let you know how it goes...

And what I meant by washing it, was just inside the fuel cap, there's an overflow drain hole, which drains down a pipe into the carbs. I'm pretty sure water has got in there when I washed it.

And now doubt there's condensation in the tank. I've run it on reserve a little bit recently. And I have shaken the tank about like a cocktail barman, didn't make much difference tbh.

And cause i've had the carbs off several times in the last few days, i've drained them each time. Surely most water will have been mixed and drawn through, or drained out... And when I drained it into the jar today, fuel looked clean as ever...
I sure as hell hope it's not electrical, as i've just recently played with the electrics a whole load (New HT leads, full inspection of the ignition circuit, not long ago had to diagnose something on the charging circuit, had a new starter motor too). I'm convinced its fuel as it does rev high, but only on the tiniest amount of throttle and bogs if you give it anymore. Cant think of any issue with electrics where it would do that.

And i'm currently in Hatfield (just outside of N-London) so not really in a decent distance from you.

I definitely intend to balance them once i have some balance gauges, and hopefully that will make her run smoother too as well as helping sort this crap out
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The mistresses: 2000 Honda CBR600f, 2000 Honda VTR1000

[Budgetboy]

I think the hole in the fuel cap is your breather pipe mate (for the fuel tank). never seen a pipe go from the top of a tank to the carbs.
And water wont get in there as it is sealed by the rubber ring on your filler cap.Sounds like you panic allot lol..

Electrics can be a nightmare.
Some electrical things that can cause your problems are:-
Battery
Pick up coil
Coils
HT leads
Plugs
Wiring

have a fiddle and let me know..Glad to help out. And yes London is just too far away.. Ming you a van would have cost you less than £800 to deliver it to me to fix. lol
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www.Mailorderrepairs.co.uk We service your Carburetor's, Calipers & Suspension for less Also Bike repairs undertaken.

[haroman666]

Ahh the pipe goes from underneath the tank, but is linked with the drain hole in the top. See I spilled fuel down that drain hole earlier and it came out the bottom of the tank where that pipe goes on... Seems a tad silly design, as there's no seal around the outer rim of the cap to stop water going down that drain hole...

And yeah, i've had lots of fun with the electrics on this bike
Everything you list there has been replaced since i've owned the bike.

And it's been a bit of an ongoing project really. Unintentionally though... I wanted a decent runner as a first big bike but i've been lumped with the biggest chain of mechanical hurdles ever.
With each thing i fix, i hope it's the last, but I know deep down it's only a matter of a few days before the next problem. I want to her just running so I can get rid and find something a little more reliable.
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The mistresses: 2000 Honda CBR600f, 2000 Honda VTR1000

[Pete.]

Next time you have the carbs off drop the float levels a mm (in other words, when they are up-turned, make the distance from the float bowl sealing face to the top of the floats as you view them greater. This will lower the fuel level and lean out the fuelling a little.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[haroman666]

Did the emulsion tubes. Bike is running smooooth as now.

There didn't seem to be any visible crud come out of the holes in the tubes, but what I did, worked.

Bit of a pig to get started after it's been sat for the night but once's she's fired up and warm, revs pretty smoothly all the way through.

Thanks for your input guys! Much appreciatings.

On a side note; I took photo's and a video of doing the work on the carbs, only cause a guy on Banditforum needed assistance. But ima post up the "tutorial" if you fancy having a ganders.

Thanks again
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The mistresses: 2000 Honda CBR600f, 2000 Honda VTR1000

[bridlad]

Nice one glad ur sorted mate ,with the emulsion tubes there doesnt need to be much 'crud' to balls things up sometimes just a few specks you can hardly see,our lass had a bandit 400 many moons ago and it was always a hard starter when cold no matter what I did to it ,in the end I gave up and just made sure it was always on the optimate so it had plenty of juice to spin it up
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Wheels polished and painted £90 a pair all in ..........bargain!