Needle jet/needle damaged, in need of help/advice

[callum93]

Hello! I've got a bit of a bummer here. got a 91 zxr400l that has always had carb issues. got a micron system, re-jetted to 92 jets, adjustable needles likely from a kit and that's about it. the rest is fairly standard. I have the coolant/ anti-freeze carbs that have coolant lines going in and out. So basically it started running like toad all of a sudden where it dropped to somewhere in the region of 2 or 3 cylinders and wanted to die on me unless the revs were kept up. turned it off and it was a bugger to start needing a lot of coaxing but would start. thing is that when it started, you could tell something was bad as you could hold the throttle wide open and it wouldn't go past 1k rpm. let the throttle go and it died. Thought id blown a gasket and did a compression test which yielded interesting results but bear in mind this was done cold as it would not start. highest compression was 75psi cold so figured something was up. did a valve check and adjustment as 7 valves were out of spec and got it all back together recently. since I had the carbs off and knew nearly every problem with this bike was related to them, I stripped, examined and cleaned them for about the 5th time so they really didn't need it. However i found a slightly bent needle in one carb although I wasn't sure if I bent it putting it back in or if it was like that when i took it out as i only noticed it after a few fiddly attempts at getting that spring over the needle etc. I straightened it out rolling it on glass and now you can't see any bend at all, looks straight as chuck norris. put it all back together having a eurika moment as that was the culprit of the revs not rising, so I guess I just answered my own doubts as to me bending it or not. got the bike stated off a bottle feed and was amazed it started as battery drained 3 times before it got going. it idled great and revved as it should. Happy face:) Only happy until it didn't start the next day:/ I took the tank and airbox off again, as I put it back together after it started, and examined the carbs as i hit the starter. Long story short(which it's not as this is a long story so is ironically used) I noticed one carb was leaking a constant dribble of fuel into the engine when the starter was held basically helping to flood the number 2 cylinder. What I have discovered is the needle jet which the needle slides in and out of, is damaged and is slightly oval'd, presumably allowing fuel past it. I cant replace this part as it is not sold and probably cant fix it so I don't really now what to do. A bit confused as until this problem, the bike was running fine for months so I don't know why it has suddenly presented such a problem:S I will include pics of the part that is damaged and hopefully somebody can offer advice or maybe point to something I have missed as this damage has been on the carb for a while as i did notice it a while back but presented no issue. I'm wondering if maybe its worth getting new needles in the event there is a slight bend still in one of them which is causing fuel to leak through as i don't think the part that's damaged should affect things too much. I dunno, wrote too much, will add pics cheers:)

[callum93]

In short if you can't be bothered reading all that which i don't blame you, what is likely the cause of fuel leaking past the needle on one carb chamber? Do you think it is the damage to the needle jet that is pictured or do you think it is the needle itself? I will be swapping the needle over with another one from the carbs to do a leak test and see but if it is the case that it is leaking due to the pictured damage, how should i go about trying to remedy this? cheers

Also does anyone know how to remove the brass piece pictured?

And finally, if the culprit is just the needle and the damaged brass piece is not affecting anything, does anybody know where I can get a new/used needle to replace it? If anyone has a spare, I would easy buy it:) Thanks

[banner001]

damage to the needle will be obvious, post a pic of the four, also post your bike year and the info on the needles, I.e. N77S.

The damage is to the end of the needle jet and doesn't look like it will affect performance too much, the needles can sometimes wear the hole in the middle of the jet into an oval shape, if this happens you will exhibit rich idle and rich midrange symptoms.

As for removing it, I'm not sure you can, I would get a set from ebay and keep yours as a set of spare parts.

[Ewetea]

If fuel is dribbling into the no.2 cylinder when the starter button is depressed, it sounds as though the valve attached to the float is not closing the delivery port. That could be because the valve tip is worn, or the to which it is attached is bent, allowing the float to ride very high and permit too much fuel into the bowl. Try swapping the float and valve with another carb and see if the problem transfers to the other carb. When you depress the starter button it applies 12V to the pump to charge the carbs with fuel.
The manual details the setting for the float of 11mm above the face of the carb when the bowl is removed. Reference to the appropriate section in the "manuals" icon will make this clear. Also, if the float is depressed against the valve and then released, it should spring back (there is a spring inside the float valve). A tired spring will permit the float to ride higher than normal under pump pressure.
Sets of carbs appear regularly on e-bay for reasonable prices, and it would probably save a lot of time to just buy some, and use your existing set for spares.

[callum93]

Thanks for your replies, I did alter the float hight recently to 11mm (which is a bugger to do btw) as I had fuel coming out the overflow pipes so I lowered the height so it wouldnt do that. However, the heights seemed about right so only did tiny alterations in the direction I needed to lower fuel level incthe bowls and it seems to have stopped the overflow issue. What I would like to know is whether the needle acts as a seal to prevent fuel going into the carbs as if not then I will look into the floats a bit more but if the needle should seal off fuel then its likely the small damage. Im thinking maybe the float needle potentialy coukd play foul here as the damage has been there for a while and only now I see, to have a problem indicating it may be something else. Float needle tips look new so unless its the spring then I dunno, will remove and clean them and also the float needle seats and see if there is anything to fault there. Also will try swapping things around as you say and see if the problem moves. Will let you know the results, thanks a lot

[Ewetea]

Firstly, I didn't put the smilie in my reply, I typed the word "tongue" which I assume the system recognised as a smilie. (so that may appear as a smilie too!)
Anyway, the float valve should be pushed on to the seat sufficiently firmly by the rising of the float to prevent more fuel flowing into the bowl. If the conical end is smooth, with only a seat witness, then it's probably OK. If there is a step on it, it's suspect. As I said, when the float is pushed down into the bowl and released, it should spring back smartly. If it does it half-heartedly then the spring in the valve is tired, and needs replacing. 12V is applied to the fuel pump while the starter button is depressed. Once the bike is running the voltage drops to just provide fuel as it is required. So the pump will be trying its hardest during starting, and that's when weak seats will permit excess fuel.

[callum93]

Hey thanks for that, yeah wondered about the smiley haha! I think after further examination your right by saying there is something up with the float seals. The needle tips are all fine but what I have discovered is the removable seats they go into may be the problem. Will confirm this later tonight as have swapped seats around and expect the leak to follow due to the O ring being flattened on it. I believe fuel may be leaking past the O ring on the seat and into the carb with the fuel pump pumping fuel straight into the engine. I wondered if anyone could tell me how to jump/bypass the fuel pump relay to allow me to test this without loading the carbs back on the bike. Just need to know which 2 of 4 wires to conect together to get the pump to work without starting the bike, cheers

[callum93]

Update to my last post, Ewetea was spot on and I have now confirmed the cause of the fuel leak. A little bitty O ring on the float needle seat has worn over time and has shrunk allowing fuel to leak past the float needle when the pump is pumping fuel. I bypassed the fuel relay to fill the floats after moving the seat from the suspect to another carb bowl and the leak moved with the seat. Where the float needle would seal the bowls, fuel was able to go around the outside due to a bad O ring resulting in flooding of that carb and ultimately the connected cylinder. So that is the solution to your bike randomyly flooding all of a sudden! Replace those rings! Thanks again, now time for a smilie

Note: as a sidenote, the problem came from the O ring mentioned and not from the damage pictured so if anyone has damage like I do, its likely not your problem as banner stated.

[Top-shaggy]

My L9 had a flat spot at just short if 4000 rpm which had gradually got worse to the point I had to do something about it.

The cause was the same perished O ring ..

viewtopic.php?f=32&t=16284

[Ewetea]

Well done. It's nice to hear a successful conclusion. Comments can be made by others, but ultimately it is the guy with the problem who has to sort it. You did well to grind out the result.

[callum93]

Cheers, nearly bought your black zxr off you on ebay Ewetea, know what was wrong with it?

[Ewetea]

Well spotted! I don't know what was wrong with it and didn't have the time or enthusiasm to investigate - too busy assembling another L1 in the conservatory! I also needed money to cover the cost of a new central heating boiler The guy who bought it used to import ZXR's from Japan, so had loads of spares and bike knowledge to sort it.

[Paul RF]

Just out of interest does anyone know what size those O rings are, internal diameter and CSA ( cross sectional area)? Would be good to know, I can then order some before it strip the carbs.
Thanks