Hi all I've read through various threads on carb tuning for these bikes and am a little confused so I'll be as clear as I can. The bike is a 91 FZR250 with the 3LN3 engine, bike has quite high k's. Long story short, top end was shagged. Barrel has been re sleeved with new pistons and rings, valves reshimmed to acheive proper clearance. The cards have been rebuilt, but we noticed that the 2 inner carbs, namely cylinders 2 and 3 have different jets. #100 and #42.5 as opposed to #97.5 and #40 on the outer cylinders 1&4. Does this sound right? The carby kit also had different needles also. Without any real solid info we opted to leave the float heights as they were. The bike struggles to start, requires choke to get it to fire almost every time and idles erratically. We have identified leaking manifold boots, new ones on the way. If anyone could shine some light on the float height procedure or any other useful info that would be awesome. Cheers
From memory I think that is correct. The leaking boots are a problem. Get new airbox ones while you're there, they're cheap (suzuki item I think along with carb diaphragms). Once the manifolds are sorted, set the pilots (2.5 turns to start with and adjust by ear/exhaust temperature after) and balance the carbs. Have you done the valve clearances and cam chain? Tensioners usually pretty reliable.
No worries, thankyou. Yes valve clearances are set. Cam chain appears to be in reasonable condition, tensioner comes out less than halfway when bolted in so I'm inclined to think the chain/tensioner is okay. All the guides appear in good condition too.
https://2fiftycc.com/index.php?threads/mikuni-bdst-28-26mm-carb-settings-specs-3ln-3yx-zeal.9787/ https://2fiftycc.com/index.php?threads/carb-fuel-level-everyones-favourite.3254/ https://2fiftycc.com/index.php?threads/suzuki-diaphragm-replacement-fzr-3ln-bdst-carburetor.8851/ Check these o rings were installed and that the pilot merge chamber was cleaned https://www.litetek.co/Guide_MikuniPilotMergeChamber.html Pilot screw configuration correct? https://2fiftycc.com/index.php?threads/fzr250-cam-chain-tensioner.3336/
Those main jets are backwards - the larger jets go on the outer carbs because the intake air is cooler/denser and requires more fuel - some confusion occurred because the keyster kits for these FZR250 carbs came with those main jets in the incorrect boxes - inner carbs -v- outer carbs The different starter jets is a bit of a mystery, but if working with what you have, put the #40 on the inner carbs Heaps of info on this page as linked by @GreyImport - especially the last post as it explains what to do if you have either/or/or both 5CT7/5CT9 needles, both work with the correct settings https://www.2fiftycc.com/index.php?...8-26mm-carb-settings-specs-3ln-3yx-zeal.9787/ BTW, you won't get it running properly with leaking manifold rubbers - set everything to where is should be and wait for them to arrive
