Hi! First time post... I have a 1990 FZR250 i recently obtained. Runs sweetly EXCEPT the 120km/10L consumption... I had an '89 FZR 3ln that did 180km/10L but did NOT start sweetly, and was also aggressively written off... Good spare parts though! ANWYAY - It had a slight leak in the fuel tap - FIXED Set jet needle to 5th clip and reset mixture screws to 3 turns out (black plugs and exhaust now basically gone, still easy to start cold and great power, doesn't overheat so seems like a good mixture, but thinking I should have done this AFTER cleaning carbs and balancing?? Because might push it a little lean afterwards...) Going to clean carbs with carb cleaner and compressed air Going to check and reset FUEL LEVEL (not float height) to 10.5mm above line One day I'll bother checking the valve clearances but it runs so nice and starts so well in all temperatures I'm not convinced this is a problem... Spark plugs are new, voltage is fine, tyres pumped bearings goodetc etc... Going to check and possibly swap the rear sprocket with my old bikes - seemed to rev lower at 100km/h - 8k vs 9k. Going to check and set synchronisation of carbs - and here's my problem I have constructed the homebrew carb sync tool (4m of clear 4mm tube and a little oil) but WHERE DO I PLUMB THE VACUUM FROM? I've looked through the site and I havn't looked in depth on the bike yet but it's easier if someone just tells me This is what I thought was a reasonably comprehensive list of things to check for high fuel consumption. There are a few things I havn't mentioned, and I havn't used a tank after the changes I've made so not sure if it's made a difference. But I will let you all know what happens! If anyone can throw in some more things to check, go for it. See what I can get outta this machine! Happy riding! P.S - how do you insert smilies?
Ignore me! First post and ALMOST a waste of time... So you tap the vacuum from the silver allen key screws that are on the intake manifold... makes sense really! http://www.fzr250.com/viewtopic.php?t=1702 here's the link it took me a week and 2 seconds after my post to find... Still, any further ideas for fuel consumption lemme know! Give those dam CBR boys a run for their money.. literally...
Ok here's what I've done so far and the results if anyone is interested, to try increase my fuel economy from 12km/l... Cleaned the carbs. They were dirty. Ran fuel system cleaner through it (1 tank of gas). Fixed leaky petcock (fuel tank switch/reserve switch/fuel selector... whatever it's called) Reset idle mixture screws to 3 turns out. All main jet needles are now equal values (in theory 2&3 should run slightly richer for cooling but no problems so far). It appears someone fiddled with them. Cylinders 1&3 and 2&4 were different sizes. Removed extra plastic screw-off bit on airbox. I am now up to 14.1km/l, and the bike no longer: Smells of fuel after being parked Cuts out when applying choke when it's cold - it acts like a normal choke system should! Maybe its rich. Seems great to me! No smoke, no plug fouling (they are now in great condition). Runs as hot (reads about 1/5th up the temp gauge now vs just under 1/2) Needs >6000rpm to pull away - can pull away with about 3k or something now. Much better anyway! Surges when cruising below 6500rpm. I can cruise at 50-60km/h at 4000rpm perfectly smoothly if i want to! Has a low top speed.... What's next? Change sprocket size to get 8000 at 100km/h from 9200ish. Balance carbs - it needs it! Slightly erratic idle. So far SUCCESS!!! Can't wait for further improvements... I'll keep you posted.
Good that you have resolved a few issues I must have missed your previous postings... Been working some odd shifts and not always had time to read posts. What jet sizes did you have originally..??? The main jet sizes according to the spec sheet says #100's go in carb 2 & 3, #102.5 go in carb 1 & 4. I presume that a leaner mix in the centre would compensate for the higher temperatures found there, being hotter the fuel will burn faster and from what I have read, a lean mix burns slower because the fuel molecules are more widely spaced. So it all balances out. Keep posting <!-- s --><img src="{SMILIES_PATH}/icon_biggrin.gif" alt="" title="Very Happy" /><!-- s -->
Late reply apologies... The jets were the standard sizes you mentioned. What I changed was the main jet needles - I put the circlip on the notch furthest away from the point (leanest setting - maybe a little severe), and changed them all to 5CT7 size (on cylinders 1 and 3 they were 5CT9 or something... seemed wierd to have them different on those cylinders instead of 2 and 3). I also find my bike runs better in general, and has better consumption on 91 octane fuel. It hates 95, and doesn't mind 98. One problem... I feel, even though the temperature is fine, the spark plugs are great, bike runs well and the fuel consumption is better, I may have made it run a bit lean... It backfires a little on deceleration. Why does this occur with a lean mixture? And is this a major problem (realising backfiring is explosions in the exhaust system?..) Could backfiring be caused by unbalanced carbs? Still to do- Balance the carbs Change rear sprocket P.S - there's probably a more suitable name for this thread "experimenting with fzr tuning" or something... admins feel free to change it accordingly.
