ericbloodaxe Posted October 7, 2008 Share Posted October 7, 2008 ok i'm stuck........ my FZR400R circa 1989 keeps dying when the engine gets hot with no throttle responce.it's fine when cold a runs fine till the temp gets high then it dies....... best explanation i can give is that it gets starved of air when hot.. remove the air filter and cover still no joy....remove the complete air box and hey presto it burst into life .... so far i have check valve clearences .. all ok... ensured fuel pump is fine...... tried a set of carbs of a running bike to check mixtures etc...and still not resolution to the prob. checked inlet manifold rubbers .. ok... so i'm totally stuck don't know what to try next. so any help much appreciated Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 7, 2008 Moderator Share Posted October 7, 2008 Engines dying when hot can be pickup coils for electrnic ignition going open circuit or even the ignition coils themselves Cant explain the airbox phenomenon though, thats got me scratching my head, next time it dies can you check for sparks on pots 1&2 . Fuel starvation can also be a problem, if the fuel filter (wherever it is) is getting blocked. but i would only expect this symptom if you were running in 'Prime' position on your fuel tap! Im interested to know if youre running in prime position though (assuming there is one on your bike) Link to comment Share on other sites More sharing options...
ericbloodaxe Posted October 7, 2008 Author Share Posted October 7, 2008 no full tank of fresh fuel tried it on prime and reserve............. filters are clean so is petrol tank...... first thing i checked...... it's very odd... all the pick up coil etc are fine....being a sparks they've been tested hot and cold .... it's just very wierd had bikes for the last 30 years and cured all of them except this one...... i'm just wondering going off at a tangent that the stat is stuck closed and the engine is over heating causing mixture probs...i'll take it out tomorrow and see what happens. try anything once lol Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 7, 2008 Moderator Share Posted October 7, 2008 have you done the 'suck' test on you vacuum fuel tap and got a good flow of fuel? Link to comment Share on other sites More sharing options...
Parsley1000 Posted October 7, 2008 Share Posted October 7, 2008 Engines dying when hot can be pickup coils for electrnic ignition going open circuit or even the ignition coils themselves Cant explain the airbox phenomenon though, thats got me scratching my head, next time it dies can you check for sparks on pots 1&2 . Fuel starvation can also be a problem, if the fuel filter (wherever it is) is getting blocked. but i would only expect this symptom if you were running in 'Prime' position on your fuel tap! Im interested to know if youre running in prime position though (assuming there is one on your bike) Its the idle mixture , its too rich, it may just be a cloged air filter , if not then ,what you need to do is this, take the tank off ,to gain access to the carbs ,on the top of the carbs, where they join the intake rubbers, there are 4 screws , 1 on each carb, they are slightly lower than the suurface and made from brass, turn them all the way in,then unscrew them 1 and 1/2 turns out, if you still have probs turn in 1/2 a turn untill its ticks over ok, if you still have probs, then your idle jets are blocked, but thats very unlikely coz she runs when cold , its deffinately not coil or leads, coils either work or they dont, leads will play up when they are wet, plugs play up when they are under pressure ,pulling away, uphills ect, if you need any help just i.m me, Parsley Link to comment Share on other sites More sharing options...
Parsley1000 Posted October 7, 2008 Share Posted October 7, 2008 Its the idle mixture , its too rich, it may just be a cloged air filter , if not then ,what you need to do is this, take the tank off ,to gain access to the carbs ,on the top of the carbs, where they join the intake rubbers, there are 4 screws , 1 on each carb, they are slightly lower than the suurface and made from brass, turn them all the way in,then unscrew them 1 and 1/2 turns out, if you still have probs turn in 1/2 a turn untill its ticks over ok, if you still have probs, then your idle jets are blocked, but thats very unlikely coz she runs when cold , its deffinately not coil or leads, coils either work or they dont, leads will play up when they are wet, plugs play up when they are under pressure ,pulling away, uphills ect, if you need any help just i.m me, Parsley just thought of something else , has the bike ever been fitted with K&Ns or the like, it may have been up jetted, have a look at the plugs, are they black, thats a sign that she's running rich, if none of these, then try getting a compression test, um, have you tried adjusting the tick over , sometimes they do vibrate out,sometimes it the real obviouse things that get over looked,I once had a bike in my garage, bloke trailered it over to me & he said it wont start,its completely dead,it was nothing more sinister than the kill switch was off!! Link to comment Share on other sites More sharing options...
ericbloodaxe Posted October 7, 2008 Author Share Posted October 7, 2008 just thought of something else , has the bike ever been fitted with K&Ns or the like, it may have been up jetted, have a look at the plugs, are they black, thats a sign that she's running rich, if none of these, then try getting a compression test, um, have you tried adjusting the tick over , sometimes they do vibrate out,sometimes it the real obviouse things that get over looked,I once had a bike in my garage, bloke trailered it over to me & he said it wont start,its completely dead,it was nothing more sinister than the kill switch was off!! lmao.......... i know it's not the carbs as i have a set off a good running bike which came straight off one bike and on th mine and still the same problem occurs i did say it's a strange problem........... Link to comment Share on other sites More sharing options...
yoda Posted October 7, 2008 Share Posted October 7, 2008 The most obvious answer Eric, is that you are getting a fuel vapour lock when the bike is hot. It must be common to all carbs otherwise it would still run and its not electrics as they heat up quickly and the bike runs. So you must examine your fuel feed pipe and see where its getting hot. Link to comment Share on other sites More sharing options...
ericbloodaxe Posted October 7, 2008 Author Share Posted October 7, 2008 The most obvious answer Eric, is that you are getting a fuel vapour lock when the bike is hot. It must be common to all carbs otherwise it would still run and its not electrics as they heat up quickly and the bike runs. So you must examine your fuel feed pipe and see where its getting hot. Hmmmm..... i not sure about that as at the moment the tank is at the side of the bike and the fuel feed pipe is clear of everything so i can't envisage that is the problem..but i will have a look ....... Link to comment Share on other sites More sharing options...
Parsley1000 Posted October 7, 2008 Share Posted October 7, 2008 The most obvious answer Eric, is that you are getting a fuel vapour lock when the bike is hot. It must be common to all carbs otherwise it would still run and its not electrics as they heat up quickly and the bike runs. So you must examine your fuel feed pipe and see where its getting hot. most obvious , ok, but it wont be that,if a set of carbs you know are ok & still you are having probs, you need to get compression test done, i know you siad the inlet rubbers are ok, but how did you check ? its not always poss to do a visual check, run the bike with the tank off , ues a long petol pipe, tank must be conected or it'll run lean, then put plenty of oil on each inlet rubber,in turn , if you get smoke out of the exhaust then that inlet had a split, or if you are in the Norwich area bring it to my work shop , ive been trading for 16 years, i have all sorts of diagnostic equiptment, Link to comment Share on other sites More sharing options...
yoda Posted October 7, 2008 Share Posted October 7, 2008 most obvious , ok, but it wont be that,if a set of carbs you know are ok & still you are having probs, you need to get compression test done, i know you siad the inlet rubbers are ok, but how did you check ? its not always poss to do a visual check, run the bike with the tank off , ues a long petol pipe, tank must be conected or it'll run lean, then put plenty of oil on each inlet rubber,in turn , if you get smoke out of the exhaust then that inlet had a split, or if you are in the Norwich area bring it to my work shop , ive been trading for 16 years, i have all sorts of diagnostic equiptment, You are talking out of your backside. If you change the carbs and it still happens then its not the carbs. Link to comment Share on other sites More sharing options...
Parsley1000 Posted October 7, 2008 Share Posted October 7, 2008 You are talking out of your backside. If you change the carbs and it still happens then its not the carbs. thats right ,that's why i think it could be inlet rubbers or compression, one more thing i just thought, on the inlets there are blanking rubbers, they are for carb vacuum gauges,they sometimes brake down & let air in, when a bike with CV carbs is at tick over,the butterflys are amost shut,there then is a very lagre vacuum in the inlet rubbers ,if there is a very small spit it will pull air though that spit,but haveing a good old think, its more than likely to be cloged air filter, that will make it run rich, & you did say she run ok with the fillter out and air box off,or you could say fu** it & fit some K&Ns !!!!!!! make life a lot easyer when you need to take carbs off, Link to comment Share on other sites More sharing options...
Parsley1000 Posted October 7, 2008 Share Posted October 7, 2008 thats right ,that's why i think it could be inlet rubbers or compression, one more thing i just thought, on the inlets there are blanking rubbers, they are for carb vacuum gauges,they sometimes brake down & let air in, when a bike with CV carbs is at tick over,the butterflys are amost shut,there then is a very lagre vacuum in the inlet rubbers ,if there is a very small spit it will pull air though that spit,but haveing a good old think, its more than likely to be cloged air filter, that will make it run rich, & you did say she run ok with the fillter out and air box off,or you could say fu** it & fit some K&Ns !!!!!!! make life a lot easyer when you need to take carbs off, well if i was talking from my back side,then so be it, ive done ok from it, i have 3 blokes working for me, 4 hols a year, 750i BMW, and BMW M5, not bad for talking shit Link to comment Share on other sites More sharing options...
ericbloodaxe Posted October 8, 2008 Author Share Posted October 8, 2008 well if i was talking from my back side,then so be it, ive done ok from it, i have 3 blokes working for me, 4 hols a year, 750i BMW, and BMW M5, not bad for talking shit indeed lol............ right then......how about this........... keep the airbox on...remove the balancing screws...... and that brings it back to life well nearly life the revs pick up a bit slower but it does rev... and i get throttle responce.... god damn thing i just about give up with the damn thing.....lol wish i'd never sold my TL1000S......didn't handle but never let me down..lmao Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 8, 2008 Moderator Share Posted October 8, 2008 lmao.......... i know it's not the carbs as i have a set off a good running bike which came straight off one bike and on th mine and still the same problem occurs i did say it's a strange problem........... have you done the 'suck' test on you vacuum fuel tap and got a good flow of fuel? Ok if its not the carbs, did you check the fuel delivery to them? Link to comment Share on other sites More sharing options...
ericbloodaxe Posted October 8, 2008 Author Share Posted October 8, 2008 Ok if its not the carbs, did you check the fuel delivery to them? yes i thought i cracked it when i found thre feul pump would not push fuel to the cards under pressure...this has now been cured and the tank...fuel tap filter and pump are alll fine and in good working order......... the carbs are in good working order as they are off a good working bike and he is running on my original set with no problems.......... so to as why mine will not run with the air box attached is just a mystery..... and removing the balance screws will make it run though not properly with the airbox on and the airbox off ..and off it goes this is the strangest thing i've ever come across in 30 years of biking and i've had some odd-balls....lol Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 8, 2008 Moderator Share Posted October 8, 2008 and the airbox off ..and off it goes this is the strangest thing i've ever come across in 30 years of biking and i've had some odd-balls....lol Me too, its boggling, I know its a daft question and that you will have done this already, but im gonna ask anyway Can you see unobstructed passage from all the carb manifold connections to the air box and unobstructed passage from air inlet to air box?? Link to comment Share on other sites More sharing options...
NoTimeToPlay Posted October 8, 2008 Share Posted October 8, 2008 Me too, its boggling, I know its a daft question and that you will have done this already, but im gonna ask anyway Can you see unobstructed passage from all the carb manifold connections to the air box and unobstructed passage from air inlet to air box?? I cannot offer anything other than sympathy because I have a similar problem with my 10yr old 10,000 miles SJ600. Simply waiting for it to cool (typically 20 minutes) after cutting out makes it good for another 50 or so miles except in traffic when 7 miles is the best between cutting outs. I am not entirely convinced it is simply temperature related because it does much the same in the wet - slightly more annoying! I hope these symptoms may help with your diagnosis too. Link to comment Share on other sites More sharing options...
ericbloodaxe Posted October 8, 2008 Author Share Posted October 8, 2008 Me too, its boggling, I know its a daft question and that you will have done this already, but im gonna ask anyway Can you see unobstructed passage from all the carb manifold connections to the air box and unobstructed passage from air inlet to air box?? latest update........... put it all back together......... without the airbox...and went for a spinn.upto 4k revs it's fine the thats your lot under load..guess to be expected do to the mixture being screwed with no airbox....... on the paddock stand it will rev freely with no load on the engine..... but hey ho......... i think i'll buy a 600 engine and stuff it in......be more fun lol still the mystery continues............. wonder if a dose of C4 would help it....... Link to comment Share on other sites More sharing options...
ericbloodaxe Posted October 8, 2008 Author Share Posted October 8, 2008 what has been done so far......... fuel tank cleaned.all fuel filters cleaned..petrol pump check and all ok run with air box split to view carbs still the same.new airbox rubbers fitted no change replaced carbs with a good set off a running bike.my old ones are on my mates and are fine. still no change checked that manifold rubber are ok.......... they hold a good vacuum on inlet no air leakage check thro' electrical system coils generator.. all to spec....new plugs and plug caps fitted new regulator fitted new battery fitted remove thermostat to check to see if it opens at correct temp run engine from cold and revs freely till the temp gets up remove air box when fault occurs.revs freely when no load road test with airbox of struggles to get above 5k.but i'm guessing thats a mixture prob with no airbox on so can you think of anything else i've missed Link to comment Share on other sites More sharing options...
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