FZR - Sluggish throttle

[Magua]

I've noticed it before but figured I was in the wrong gear or something but today while on the motorway, around 70k's I guess, I twisted the throttle a fair amount and the engine just lost all power for a few seconds and sort of gurgled before the power connected again in a big way pulling the bike foward. I've noticed it more recently as I've gotten used to the bike and have been trying to ring out more power. It doesn't allways happen, but everyknow and then you ring the throttle and it gurgles away to itself again. I'm going to take a guess and say airfilter, not allowing in enough air. Any ideas?

[Slingshot]

Sounds like it's hungry for fuel rather than air.

Have you had the carbs off lately?

The float levels may have gone out of adjustment which means the bowls on the bottom of the carbs may not be filling to the correct level. If this is the problem then when you open the throttle, the vacuum that is created trys to suck heaps of fuel through and if the bowls aren't full enough that when you get your problem.
This could also be caused by crap around you needle valves, same as above, the fuel enters the bowls via the needle valves and if there's crap around them it may be blocking the flow.

Let me know if you're thinking about looking at it yourself and I'll post some pointers.

[Slingshot]

Thought I might post some photos so it shows what I was talking about:

The 1st photo is of the carbs looking from the airbox side. The bit at the bottom is the fuel bowl. Think of this as the cistern on your toilet, imagine that you hold your finger on the flush button, the cistern will obviously start to empty out into the bowl but they also start to re-fill. Same principle with your carbs except they should be able to fill faster than they can empty. I think in your case they're emptying before they can fill.

Second photo is of the inside of the bowl. The orange thingy is the float. The brass bits are the jets. Top right part of the orange thingy is where the floats connect to the needle valve.

[erik]

Sounds similar to what my bike does. Sometimes when I'm accelerating and opening the throttle, it gets to a point where it kinda dies a bit and the bike slows. I've tried removing the airfilter (temporarily), which seemed to improve things a bit, so if we're talking about the same thing, you might be right that it's the airfilter. My airfilter is apparently fairly clean, so I haven't replaced it. I just live with the problem and work around it.

[Slingshot]

The key here is...does it do it if you quickly open the throttle AND if you slowly open the throttle OR only one or the other??

[Stevo]

My FiZzeR does the same thing. I thought when I opened it up it was sort of flooding, but maybe slingshot is right and it is just starving:spudwhat: I get around it by dropping an extra gear (sometimes two) when pulling out to pass so it is already revving plenty when I am pulling out to pass.

Nothing worse than pulling out to pass and have the thing boggdown before it gets it's wind up and rockets off. Most of the time it only does it for me if I am doing less than 11000 revs. Keep them up is what I say! It also does not seem to do it so much if already accelerating and just wind it open as much as when cruising and I just open it up to feed it the fat, that is when it really bogs itself down!!

One day I while get myself a rocket on wheels and my prob will be solved.........

[Slingshot]

One day I while get myself a rocket on wheels and my prob will be solved.........

Just pull ya carbs off and give them a good clean. You could even leave them on and just get some carb cleaner, all you'd need to do is take the airbox off and spray the cleaner into the carbs while the engine is running.

You will get better results if you strip them down.

The other possibility is that one of the jets is blocked, if I remember correctly these carbs normally have 3 jets per carb. Different ones are used for different revs, if it's always happening at a particular rev range then the corresponding jet may be blocked.

[vifferman]

The other possibility is that one of the jets is blocked, if I remember correctly these carbs normally have 3 jets per carb. Different ones are used for different revs, if it's always happening at a particular rev range then the corresponding jet may be blocked.

I'll try and dig out a carb analysing test I used to have, that helped you to work out whether the bike was running lean or rich, and what needed tweaking (idle jet, main jet, etc.) to fix it.

If it was running fine, and now it's not, and nothing's been changed on the bike, then it's relatively easy: some cleaning is required.

[Magua]

If it was running fine, and now it's not, and nothing's been changed on the bike, then it's relatively easy: some cleaning is required.

It's been doing this since I bought it but like I said, at the time I just thought I was in the wrong gear. Maybe I'll get at those carburators soon but all the seals around the top of them are cracked. If I was to pull them out and these were to tear of fall apart, where could I get more? Yamaha?

[vifferman]

It's been doing this since I bought it but like I said, at the time I just thought I was in the wrong gear. Maybe I'll get at those carburators soon but all the seals around the top of them are cracked. If I was to pull them out and these were to tear of fall apart, where could I get more? Yamaha?

If the seals are cracked, then airleaks may be likely. OEM seals from Yamaha will likely cost an arm and a leg, and your left nut, so wreckers would be a better bet.

Here are some handy links, but I'm sure there's lots more stuff on the web that's helpful if you choose the right keywords.

http://www.motocross.com/motoprof/moto/mcycle/carb101/carb101.html

http://www.nightrider.com/biketech/carbadjust.htm

http://www.eric-gorr.com/techarticles/carbtuning.html

http://www.snowvalley.20m.com/bikes/jets.htm

[Magua]

Thanks firestormer, but I'm going to finish replacing the filters (air and fuel) before I move onto anything more complicated. From the looks of it, I'd rather get someone else to work on the carbs for me.

[Stevo]

Sounds like an interesting problem esp if the Zeal gets it too! Fooking Yamahahaha. Must get me a Honda!!!!

Let us know Magua if you have any luck meddling around and what you think the problem is........... Ta

[Artifice]

can you get her on a dyno with a fuel analyzer?
costs $60 down here but can help no end to finding out the problem.
i suggest you take firestormer up on his offer.
you know it could just be built up crud around the filter of your fuel tank.