Are you using full choke? Might be worth trying it with the mixture screw's turned further out, go 1/4 turn at a time and try again.
Still nothing refers to “not starting by itself”. It’ll struggle to start, but starts nonetheless when you tip a little petrol down the carbs. The revs are high at around 4K when it starts then drops to idle after about 15-25 seconds. I’ve tried half turns, quarter turns and the revs will change, So I try adjust to what I believe it’s a nice idle then turn off to see if it will start by itself. Then it’s goes back to square one (not starting without the help of pouring petrol down the carbs). I’ve reset the mixture screws 1st time starting at 1.5 turns and then doing quarter turn there on. 2nd reset was from 2 turns going out from half turns. Then from half turns to quarter. I’ve noticed that when I get to about 3 and a fraction turns out, it dies. I may being doing something wrong, I’m unsure as it’s my first time fooking around with carbies. Is there anything else apart from the mixture and float level that may be effecting it? Sent from my iPhone using Tapatalk
When you say nothing - drops off idle and stalls - even when it's just idling the pump should click periodically. Won't start - once the carbs are well adjusted they need choke to start. BTW those measurements with the float height and fuel level are spot on Anything else been done to the carbs? keyster kits or anything else changed?
I have used full choke and it doesn’t really help all that much. Some times it will help get the engine running and most times it does nothing Sent from my iPhone using Tapatalk
The pump is working fine. I’ve held my hand on it to feel the pumping. I haven’t used any kits on it. Sent from my iPhone using Tapatalk
OK only other thing I can think of is the balance between the carbs - obviously it's not easy to keep running to do it with a carbtune or the like. So you can do it with a small drill bit - wind up the idle to get underneath either number carb 2 or 3, (forget which) - then adjust the others to the same. Once done wind the idle back down Is the airbox installed with the filter and lid?
Heres the 3 problems you have Its a 30 yr old bike Its an FZR250 3LN1 It has 4 inline carbys I have had one for 4 years and it still doesnt run 100% ... close but not perfect .... and I know what Im doing ... kinda This forum is full of 'inline 4' carby problem posts .... and they continue The carbys WILL need a full rebuild with Litetek kits and new emulsion tubes /needle jets and properly cleaned (especially jets and all orifices) as per the many posts/threads about on this subject But if its 'starting' from fuel chucked down the carby throats then lets go back to the beginning of the fuel delivery system .... Theres a vent in the cap that stops a vacuum forming as fuel leaves the tank Theres internal filters inside the tank where the fuel outlet is Theres o rings and such inside the fuel tap Theres should be a fuel filter running from the tap to the pump that is one directional First thing to do is to pull off the fuel hose at the carbys and turn on the pump (with a container under the hose end) and check for fuel flow Stick with it ... its worth it in the end ....
I’m having almost exactly the same problem with a 3LN3, however mine won’t start at all without fuel down the carbs. I’ve rebuilt carbs with keyster kits. I’ve checked fuel filter, tested pump and checked that fuel is filling each bowl on the carbs. Checked float heights and set mixture screws to 3 turns out. Might test a few changes to mixture screws. Would be very interested to hear the outcome of this one @Forky
I have the fuel tank off and just have a bottle connected to the fuel hose going into the pump. I might either get a replacement carb and piss this one off or get a new kit.. more leaning towards the new carbs Sent from my iPhone using Tapatalk
Ill repeat myself .... have u had the hose off the carbs to see if the pump is actually pumping? And Ill repeat myself once more ... new carbs ? ... what are they ?? .... EVERY set of carbs will need an overhaul and then adjusted/tuned when on the bike We had an FZR here and when we bought it were told 'mechanic had 'done' the carbs' ... yea done alright ... done a dodgy ..... they were untouched inside but had a nice coat of grey/silver paint on the bodys to look 'reconditioned '
Yes obviously I’ve checked the fuel pump. And I know you can’t get brand new spanking carb. It’s just my way of saying, I’ll get new carbs to the bike.. Sent from my iPhone using Tapatalk
We all know the frustration, so you're amongst friends who've been there done that. You've done a good job with the float heights, fuel level so you can rule that out... stick with it - perhaps check some basic things such as blocked/clogged jets. If you don't have compressed air to blow through them then some copper filaments out of some power cable is nice and soft to avoid damage and thin enough to get through the smaller ones which are the most likely candidates to be blocked. Depending on what you've done to them thus far, it's worth double checking anything you've done Most of the Fizzer carbs get litetek kits through them c/o @maelstrom and the full clean in the process, https://www.litetek.co/Carb_Kit_Yamaha_FZR250_3LN1.html Worn emulsion tubes and needles usually cause the most problems with chugging and refusal to rev at idle, but doesn't seem your problem, the fix is then keyster kits 2 for the inners https://www.motorcyclespareswarehouse.com.au/products/k-1205yku-ky-carb-repair-and-parts-kit and 2 for the outers https://www.motorcyclespareswarehouse.com.au/products/k-1205yks-ky-carb-repair-and-parts-kit
Just a quick update, I’ve pulled the carbs apart to inspect and clean one last time before I give up. Drained the fuel from the floats into a bowl and noticed there was a lot of **** in it that could have potentially blocked a jet or other. After a quick look, I’ve noticed the needles settings go 3,2,3,2. I’ve also noticed that two o rings on the diaphragm side are missing on 1&2 carb. Sent from my iPhone using Tapatalk
3&4 have the same size 102.5 and 1&2 are 90. The ones below it are all the same at 37.5 is this correct? Sent from my iPhone using Tapatalk
Check this post where I explained the two possible combinations for 3LN1 carbs https://www.2fiftycc.com/index.php?...settings-specs-3ln-3yx-zeal.9787/#post-112136
That's a mess - 1&4 should have 102.5 mains 2&3 should have 100 mains, but from your pic the mains are installed where the starter jets should be and vice versa Check this post https://www.2fiftycc.com/index.php?...8-26mm-carb-settings-specs-3ln-3yx-zeal.9787/