Help FZR250 3LN3 carb problem.

Those illustrations are very good - for reference the 3LN series needles are 2.515mm diameter - the emulsion tube hole diameters (n-8) are 2.590mm so that 0.075mm - yep you read that right seventy five thousandths of a millimetre clearance past the widest part of the needle.

It doesn't take much wear to affect the amount of motion lotion coming up that tube at idle and screwing things up...

 

From memory, the emulsion tubes were done and solved the chugging problem at that time..but I don't think a Litetek kit was done on those carbs..

 

Sweet good to know! Thanks @Grasshopper

 

I have a lot of parts left over from 4 sets of keyster kits if you're interested. Includes jets, needles, emulsion, float valves etc. All brand new. Only really missing some of the seals and a few bits and pieces like needle clips. PM me, will move them on cheaply (they're $50 PER CARB otherwise, what a rip!)

 

Hey!!

If anyone still interested (@maelstrom ) I’ve changed the pilot merge chamber o-rings and no success.

Good news is now the problem is happening constantly, rather than intermittently. (Throttle very unresponsive and boggin down in low revs, struggles to build revs). Thought it could have been diaphragms but they are all good.

Will rebuild carbs tomorrow with new jets and emulsion tubes and see if that fixes it!

 

Emulsion tubes should suffice and probably a good first test so you can narrow down the cause to a single element.

Which jets do you have replacements for BTW?

 

I have bought rebuild kits, so will be able to do everything I think. @GreyImport i cleaned and blew out with compressed air.

Could it be blocked jets causing this?

Needles I wasn’t sure what to look for, they look fine only a few marks on them. (Pictures attached!) Will check emulsion tubes for wear after replacing.

 

Mine were all different! See attached...

Does anyone know where the jet air bleed is? Can’t find it, but my kit has a new one.

 

If you put a razor blade against those needles and held it up to the light I wonder if there is wear there to be seen.

It's ambiguous from the pictures if there's a little bit of soot on the needles making them look worn, or they are in fact worn, or perhaps both.

This has me wondering if there is wear there, then perhaps it's symptomatic of the hole through the slide being worn and accelerating the wear on the replacement needles and emulsion tubes

 

No luck with the rebuild kits, bike still isn't starting. Set fuel mixture screws to 1.75 turns out.

Will try some more tinkering through the week, perhaps check fuel pump. I have put new plugs in yesterday, any other suggestions?

 

Excuse my lethargy at not re-reading the whole thread. it's a quick solution to read the fuel height with the carbs on the bike
check
https://2fiftycc.com/index.php?threads/my-fizzer.872/page-32#post-15537

Now some thing I didn't think of originally was clear fuel resistant silicone tubing should be available at a mower shop for simplicity - there is no real need for the syringe two pen lines will suffice

That will rule in or rule out fuel supply.

Now don't know if you mentioned it not starting previously, that could be spark related, I notice you replaced plugs, someone else will have to chime in here if problematic clutch and/or side stand and/or neutral gear switches can cut the spark. It's just been too long for me and mine isn't running ATM to be able to check

 

Checked fuel heights, all good.

Found one pin on the coils slightly loose, tightened up and went to start, still not starting.

Bike started with a little fuel dropped into each cylinder, and no more lazy throttle (previous problem). This leads me to think problem was intermittent as coil drops in and out, leading to bike running on 2 cylinders.

However, bike not starting, have checked spark and air flow, tested fuel pump, set float heights and bench tested bowls filling up. Any suggestions what to try next??? Thinking ignition timing? Any guides on how to test this??

Thanks all!