Help FZR250 3LN3 carb problem.

Recieved the seals. Thank you Blair, took a while, but better late than never.



Anyway, adjusted fuel level a bit, but as expected, not enough. Rised fuel level another bit and almost good.
There was an lean spot at about 4.000 - 6.000 rpm so I raised the needles one notch.
Now she has fuel enough, perhaps a bit too much. Dunno.

The bike starts good now when cold with choke and soon I am going to drive around and see how she handles on the street.

 

Drove around and pickup from closed throttle is still a tad too lean. I am not happy with it.

So I dropped the needle one notch to original place and raised fuel level a bit. Result was a tad better but not perfect.
Finally I turned the mixture screw one turn more out and now it became like it should be.
I noticed that one carb fuel level differs from the rest, so I am going te fix that.
Measure A/F again and than I hope it is finished.

In the mean time, I have removed and installed the carbs hundreds of times now. If there is ever going te be an competition in removing 3LN carbs, I think I make a good chance

 

Started with base settings: 3 turns out.

I did probably read My67xr work, but I don't know what you are referring too?

 

Good to hear people are able to receive oem setting.

The first time, years ago, when the engine quit running, I started cleaning carbs etc. When that did not help, I changed fuel level by bending the float lever a little. Since that moment, oem setting is useless, I am afraid.
Oem setting is only achieveable with stock floats, without messing with the lever at all.

So, for me, the only way to get a nice running engine is measuring fuel level, measure A/F, listen and test the bike.

Anyway, I tried to get oem level and measure like described. But I am getting nuts how to do that. Where do I measure exactly? In the middle? Side? Top? Left? Right? So, for me, to dumb to measure float level, I simply measure fuel level and see what happens.

It was too late last night to finish, but first impression, with an pretty high fuel level and the mixture screw a tad more than oem, she did sound really nice and idle was good too. I had a big grin on my face.
I am eager to build her up and go for a drive.

 

Ruckusman, thanks for your excellent answer an patience.

Anyway, on my bike it did not work.
Setting the carbs in oem way was creating a lean spot. The only way to tackle that, was lifting fuel level a bit and 3/4 turn more out for the mixture screw.
Installed everything now, but I did not have the time to test on the road.

For chronology:
In 2016 the engine quit running.
Found this site, Blair and Keyster: bike running again.
Swappet float needle, emulsion pipe and needle, new gaskets and an overall clean up.
But she never ran like I hoped. Cold start was bad too.
So, this winter I decided to get me some oem emulsion pipes and needles and try to get her better running.
Unfortunately, emulsion pipes available, needles not!
So, swapped emulsion pipes and installed the old oem Mikuni needles.
Hmm, engine would not rev anymore passed ± 6000 rpm. And blipping the throttle was not good either. Measured with an wide band A/F analyzer = lean spot.
Swapped the old Mikuni needle with the Keyster one.
Nothing changes.
Raised fuel level: tiny bit richer and better running.
But still not good enough.
Swapped the needles again and Mikuni's back in the carbs.
No changes.
So, raised needles one notch (= 0,5 mm?).
Now, pretty good. Took her for a spin, measured A/F, pretty rich, but good.
But still, I was not satisfied with throttle pickup.
So, turned out the mixture screw a little. That went better.
Finally, dropped the needle in the stock middle position, raised fuel level a bit and mixture screw set at 3¾ out.
Tested, measured and listened. She runs good, aggressive on the throttle, but pretty rich.
Better rich than sorry.

Okay, just a afternoon test drive on the streets left to do, I am curious.

Checking fuel level:


Connecting sensor:


Idle A/F:


Checking temp headers (not easy to shoot left with the gun and right with the camera, simultaneously):

 

Bummer, drove around and still no good, so I pulled the carbs again. These things are driving me crazy.

Adjust everything to exact stock settings and started the bike. Still no good, so actually, it must be something else. So perhaps an air leak?
So I sprayed some brake cleaner between the carbs and the intake rubbers. The engine started to idle lower and finally stalls... hmmm... not good.

Nothing to see on the carbs and the intake rubbers are good too, at least no visible damage.
So, what to do? I notice that intake rubbers are still available (I think), but they cost a fortune.

Tips anyone, before I burn my wallet?

 

Yes I can. See pic earlier taken:


I do believe in "better rich than sorry". I have seen several melted pistons due to a lean mixture. Not good, my 3S-GTE piston:




Anyway, about my carbs. I will remove a boot and take a close look and see if there is anything unusual. I saw that Ali is selling FZR250 boots from BJMOTO for fearly cheap, anyone any experience with those?

A vacuum leak could explain why the engine stalls sometimes and not an steady idle.
I am sure the carbs are clean and all settings and jets are oem specs. There must be something else wrong.
Keep you posted!

 

Okay, this one:



And this one:





But that is cheating too. First one is from Aprilia SX125 and second one from Aprilia RS250, both two stroke.

Too be honest, I tested A/F with the MC22 and the MC22 is much more richer than the FZR. Stock MC22, except the bolt on (loud = open) muffler.

 

Removed one boot for an close inspection. Nothing wrong with it, seals good to the head and fits perfect to the carb.
I am afraid it is not in the boots.
Probably have to replace the throttle shaft seals. Bummer :-(.
Find me some JIS tools and a small dremel and an rebuild kit, Blair?

This evening I will try to discover some more about the vacuum leaking.