So I took my F3 for a dino and they got it to kick out another extra 8hp which is quite cool.

I know have a problem which we haven't been able to solve. When the bike idles for a while (like at a traffic light) it sometimes have a flat spot when you pull away but only when it's hot. If you give it a quick ref before you pull away it's fine.
I've had the bike back twice and they can't find the problem. The mechanic thought that the needles on the carbs were set to rich and that the bike is flooding when you pull away
The way he explained to me is that the bike peculates when it's hot and idling. This means the fuel pushes thru the main jets and when you pull away it floods.

Anyway they opened it up and the needles I have is stock so they aren't adjustable
He just suggested thet I set the idling higher and drive it like that which means it will probably idle at 2000rpm.
He also suggested that I must considder getting a after market carb kit with adjustable needles.

I'm not happy at all because since the bike is stock it should be running fine and I shouldn't need to do any mods.

Does anyone have any suggestions on this or should I maybe go for the carb kit?

 

peculates...?? never heard that word before....I think he's messing with you. Fuel doesn't "push" up into the carb unless the float height is off. Fuel is sucked into the throat by the air passing over the holes. At idle, NO fuel is coming from the main jet circuit as the slide is more or less completely closed, even at light throttle it is.

Sounds to me like the fuel screws are set too fat....or the pilot jet is oversized. Without know what has been changed, or what your mods are, I have to talk in generalities. If you rev it before pulling away and thats better, the needles are not rich.

A jet kit won't solve running problems....they usually create even more as they were meant for the track.

 

I've already had the bike three times back to the shop and they can't solve it. Each time leaving there three days at a time. This is quite a drag because it's my only transport.
I've decided to write of the money I had to pay (the bike wasn't doing this before the service) and try and solve the problem myself.

As I was mentioning in a previous thread. It was heavy on juice so I opened the carbs and found that it had the main jets for the 97/98 F3s so I swapped them back to the smaller ones which the 95/96 models use. This only brought conumption down slightly.

I must mention that after I did this it had the same kind of flat spot but not so bad and it was a bit higher up in the refs.

I know the jetting in the carbs is standard because I compared the sizes with those specified in the book and apparantly this gye didn't do any rejetting he only adjusted.
Some one was mentioning that you can adjust the needles by shimming. How would I know if this was done on my bike. Is there washer on the needles from the factory or only clips?

You said that my fuel screw are to fat (please elaborate). The way I understand it, those are air correction screws and the more you open them the more air comes into the engine when idling.(Please correct me if I'm wrong)
So should I tighten them or loosen them?
Then of course do you know any tricks of doing this without taking of the carbs (I had a shortenned screwdriver for my old bike but theres no way I'll be able to fit it in there.

I almost dropped the bike this morning because of this stupid problem so I must fix it asp!

 

Yeah....people call it the air screw, idle mixture screw etc etc....but you know the screw I am referring to...its opening amount controls fuel. Make sure that is stock...probably 2 turns out from seated or 2 1/2 max...I don't have my manual handy to look it up....I've seen some way out like 4 1/2, and it will cause what you describe.

These screws sometimes have a cap over them. If so, you drill a small hole through them, just barely poking through so you don't damage the screw behind it. Then use a wood/sheet metal type screw to tighten into that hole in the cap you just made....twist and pull on the screw with a pliers to pull the cap out....don't pry to the side...you can bust that tower off the carb....and then you will be sad.

If your fuel consumption is high with stock parts, I would check the float height. Again, I don't have my manual handy so can't tell you what it is. But, what you do is put a clear tube on the drain spout for the carb....then hold the open end of that tube up. Open the drain screw on the carb and that tube will fill up to the height that is in the float bowl....you might need to turn the bike on and start it so the fuel pump fills the carbs up. You need to check each of the four carbs as they all have their own float. Bike needs to be sitting level as well.

If you don't have a manual...get one. I bought a CD on ebay that was a scanned in one...was like $5. If this continues to be an issue, a cheap alternative might be buying another rack of stock carbs....they go like $50 on ebay.

Good luck,
JB

 

So I checked my carbs:
135 & 138 main jets
40 pilots
Pilot Screws 2 turns
According to the manual this is stock for a 95'
Seems like stock none adjustable main needles without any washers
I tried 1.5 turns on the screws but it didn't make much difference so I tried the other direction to 2.5 turns and that made the flat spot on pull away even worse.
This bring me to one conclusion and that is that it's running to rich but the problem isn't with the pilot screws so... I give up.
Is there any difference between the 95/96 main needles and the 97/98 main needles because when I got the bike it was jetted 138 and 140 (97/98 jetting) maybe the needles are different to the 95/96.
I don't know. If anyone has suggestion on what to do or test that would be nice.
One of my friends have an old F2 set of carbs are they any good. Can I use any of the parts?

 

So I tried something else. I've gone down to 1 turn on the pilot screws.
This has greatly improved the flat spot (although it's still there) and the flat spot is also slightly lower in the refs but I can feel I've lost some power in the lower range.
[align=left]I think this proves that it's definitely a mixture problem and that changing the turns on the screws is just putting a bandaid on another problem.
[/align]Is there anything else you can adjust on these carbs?
The only other thing I can think of is that the float needles are leaking but those needles are quite expensive so it doesn't help just to replace them if I'm not sure that this is the problem