madmike Posted June 30, 2009 Report Share Posted June 30, 2009 hello... again... my CBR400 has had this strange little mishap a while but it rarely sorta happens see. If its idling at say 1500pm and i blip the throttle up to 3000(ish) it will drop back down to 1000 or even a little and sound like its abit to stop then it goes back up to 1500, sometimes though... it does cut out its done it once or twice when im in slow moving traffic, if i have the clutch in and then move foward about 1 car space (letting the clutch out ever so slighty) giving a little throttle it will drop and cut out... Or! drop to about 900 - 1000 rpm then back up to 1500, ive upped the idle to about 2000rpm and it sort of helps... Otherwise, the bike idle's fine and runs grreat... Any help appreciated! Link to comment Share on other sites More sharing options...
fran9r Posted June 30, 2009 Report Share Posted June 30, 2009 There's an air leak somewhere. Check the carb rubbers, then the carbs themselves -strip and clean, inspect everything, then balance them and try again. Link to comment Share on other sites More sharing options...
madmike Posted July 1, 2009 Author Report Share Posted July 1, 2009 Your sir are awesomeness! Link to comment Share on other sites More sharing options...
madmike Posted July 1, 2009 Author Report Share Posted July 1, 2009 right, had a look before, bottom of the air box (that attaches to the carbs) wasnt actually on properly or securely! so i attached all that properly, made sure it was all on and it still is abit iffy, gonna give the carbs a clean next week if possible, anyone recommend a good carb balancer? vacuum guage thingy? Cheers Link to comment Share on other sites More sharing options...
fran9r Posted July 1, 2009 Report Share Posted July 1, 2009 Morgan carbtune are supposed to be good...I'd check all the inlet rubbers are OK (no cracks or tears), the vacum pipe is in place, and the bolts on the other take off is sealed/secure. But a carb clean (any cleaner) is the real cure. I'd check any airbox seals are intact too. Link to comment Share on other sites More sharing options...
Mr.Pigdog Posted July 2, 2009 Report Share Posted July 2, 2009 My bro has a NC23-didn't run real good-it ended up being the reeeeeally small o rings that seal the mixture screws on the carbs.Quite pricey as i opted for a 'carb overhaul kit'from david silvers(think it was in the region of £11 per carb)in hindsight you might be able to source your own from a seal dealer kinda shop?? Link to comment Share on other sites More sharing options...
madmike Posted July 2, 2009 Author Report Share Posted July 2, 2009 ah ok, if the weather holds off today then ill have a proper good look over the carbs and report back, with photies! thanks for the help so far guys Link to comment Share on other sites More sharing options...
TheFlymo Posted July 2, 2009 Report Share Posted July 2, 2009 Morgan carbtune are supposed to be good...I'd check all the inlet rubbers are OK (no cracks or tears), the vacum pipe is in place, and the bolts on the other take off is sealed/secure. But a carb clean (any cleaner) is the real cure. I'd check any airbox seals are intact too. IMO avoid carbtunes like the plague. Impossible to calibrate, and if you test from a single vacuum source, the gauges are all over the place. I pinged this info to Morgan, and never got any reply. Rubbish bit of kit, the £50 is better spent on Ebay on a set of ordinary dial-type gauges. Link to comment Share on other sites More sharing options...
madmike Posted July 2, 2009 Author Report Share Posted July 2, 2009 Like these? Link to comment Share on other sites More sharing options...
Coose Posted July 2, 2009 Report Share Posted July 2, 2009 There's nowt wrong with my old-skool lethal mercury Carbtune - lust get rid of the air bubbles and keep it level! I've balanced carbs many a-time using a piece of 3/16" windscreen washer hose and an ear a la Pops Yoshimura. It works a treat and costs about a quid! Link to comment Share on other sites More sharing options...
madmike Posted July 2, 2009 Author Report Share Posted July 2, 2009 whats the best stuff.. or actually... how do you go aboot cleaning carbs properly? Link to comment Share on other sites More sharing options...
fran9r Posted July 2, 2009 Report Share Posted July 2, 2009 Take apart, then remove all jets -do one carb at a time, then you have the others for reference to see how it goes together! A set of workshop destructions will help, you can set all the tickover screws to the same...check the diaphram is ok, clean everything, then reasemble. If the jets are manky/blocked, then source new ones. If you poke anything in them to clean them, you will most likely damage them, making them larger than intended. I've used (admitedly a mates) carbtune with no issues, but get a quality set rather than dirt cheap. Carb cleaner can be from anywhere, just get a brand so you know it's quality. Link to comment Share on other sites More sharing options...
madmike Posted July 2, 2009 Author Report Share Posted July 2, 2009 Had a nose today but i havn't got a long screwdriver to get to all the tight seals, I can get the one on the left but the others look they have been knocked round, i might have some help on saturday... if not i might need to give Conica or TriGGer a nudge They have every tool for everything! so should be good to get some expertise doing it too! P.S! Thanks for all the help so far! Got the problem nailed... now to fix it eh! thanks guys! Link to comment Share on other sites More sharing options...
Mr.Pigdog Posted July 2, 2009 Report Share Posted July 2, 2009 Personally i wouldn't think of any other balancers than davida-but i bought mine on other bike mechanics recommendations-they warned me to steer clear of mercury ones BUT i have no experience of them.remove the whole carb bank and put them gently in a vice to remove the float bowls-remove all the jets but make sure you keep them all in order-i find a wire from a wire brush cleans idle jets out fine-i often soak them in a fluid called 'truck clean'overnight-i've tried the coke thing and the nail varnish remover but find the truckclean best so far.When it comes to diagnosing the airleak-it can halp to spray your wd40 around where the suspected airleak is as it can temporarily highlight the problem area in that the revs rise slightly.All i can say is work over a big piece of white paper or something so that its easy to see any small things you may happen to drop(seals or springs etc).Before removing the carb diaphragms move the slide up with a finger to see if they have a vacuum there--they can be fiddly to re install.Compressed air makes carb cleaning a whole lot easier btw Sorry just to add--my bro's mixture screws were/are very chewed up too--soak them in penetrant and heat the carb body up a little to make it easier!!remove clean and lube Link to comment Share on other sites More sharing options...
madmike Posted July 3, 2009 Author Report Share Posted July 3, 2009 Rightt! got the carbs off eventually, who ever put them on before me made a lovely job of making the screws fucking impossible to get to... took about 3hours to get them off!!! well, drained all the petrol out of them but now have a problem of opening the part where the float is in because... once again... the person before me has fucked the screws over nicely, they're nicely rounded off Link to comment Share on other sites More sharing options...
lorenzo Posted July 4, 2009 Report Share Posted July 4, 2009 the person before me has fucked the screws over nicely, they're nicely rounded off A bit of wd40 for them to soak in overnight, a bit of heat before you give them a twist, and then a bit of a journey round to Triggers when you fuck it all up. HTH Link to comment Share on other sites More sharing options...
madmike Posted July 5, 2009 Author Report Share Posted July 5, 2009 wow, thats exactly what happened! he has them atm! gonna get them out and im gonna guy some new ones, stainless too lol and whoever manged to destroy the screws put some of the float bowls on the wrong way too so i couldn't get to the draingage screws!! Link to comment Share on other sites More sharing options...
madmike Posted July 7, 2009 Author Report Share Posted July 7, 2009 well the float bowls had a fair amount of shite in them but im a little worried about removing the jets to clean them, should i be worried about any major problems it could cause if i fook up? ta. Link to comment Share on other sites More sharing options...
Gregorious77 Posted July 7, 2009 Report Share Posted July 7, 2009 its as simple as unscrewing them cleaning them through with carb cleaner or compressed air and screwing them back in. clean all the holes in the carb out too while they are out. DO NOT poke anythin in the jets as this can fook them up as they have precise holes in them. Link to comment Share on other sites More sharing options...
fran9r Posted July 7, 2009 Report Share Posted July 7, 2009 If the jets are at all manky, just replace with new. It's a cheap job for guaranteed spot on jetting. Link to comment Share on other sites More sharing options...
madmike Posted July 8, 2009 Author Report Share Posted July 8, 2009 Right! its nice and sunny so im off in the garden to get them all cleaned! Going to spend all day cleaning them and then putting the bike back together! Thanks for all the help guys! ill report back later with any news! Link to comment Share on other sites More sharing options...
madmike Posted July 8, 2009 Author Report Share Posted July 8, 2009 Rightttttt! Carbs all cleaned! back on... slight problem... the bike is only running on 3 cylinders now! well it sounds and pulls god awful Im all out of motivation now so ill take the carbs back off tomorrow and check each one... again Link to comment Share on other sites More sharing options...
Mr.Pigdog Posted July 8, 2009 Report Share Posted July 8, 2009 Is it just at idle that its running on 3?try giving it some revs(like over 5,000rpm)if its low revs it indicates blocked idle jets--the most common as smallest diameter holes-believe me when i say a small piece of wire is good to clean so long as youre not too forcefull-im a bike mechanic not an internet mecchy.400's are VERY delicate when it comes to carburretion.Did you alter float heights at all?checked fuel filter too as you say float bowls were full of crud?fuel pumps do go on these bikes too i might add.Just to add-whilst you're buggering about with the carbs-re check you have the mixtures set to standard(assuming you have a standard air filter and exhaust system on it)as revs hanging up is a classic sign of mixture wrong-common for people to chop and change silencer etc.also if you can prop the tank outta the way and spray combustible stuff down the inlets to idnetify which cyclinder isnt igniting correctly(sometimes you can just feel the exhaust header pipes to see which one isn't warming up so quick) Link to comment Share on other sites More sharing options...
madmike Posted July 8, 2009 Author Report Share Posted July 8, 2009 Well... its actually running on 4! BUT... When ive put the jets back in I havn't done it properly i believe, or they're not in right... it seems fine at certain RPM... like it rides ok 6,000+(ish) but low revs is a BIATCH... TriGGer is gonna have a professional nose around on friday! so without a doubt the problem will be properly identified! Link to comment Share on other sites More sharing options...
fran9r Posted July 8, 2009 Report Share Posted July 8, 2009 believe me when i say a small piece of wire is good to clean so long as youre not too forcefull-im a bike mechanic not an internet mecchy. If it's an original keihin or mikuni it's been flow tested to check...bunging bits of wire up them will VERY likely screw them up. Clean yes, but not the original flow capacity. Link to comment Share on other sites More sharing options...
madmike Posted July 8, 2009 Author Report Share Posted July 8, 2009 on a side note... the fuel filter (at least thats what i think it is) had the mitsubishi logo on Link to comment Share on other sites More sharing options...
madmike Posted July 10, 2009 Author Report Share Posted July 10, 2009 RIGHT! the header of this post is TriGGer And Conica Are Gods!! :pb2: A little trip to the meadows' humble home and removed the carbs with trigger, set all adjustment jets to the same amount and found 2 air leaks in the same cylinder! 1) The 4 vacuum valve thingys that stick out from the cylinders have covers on... well... 1 actually didnt at all! AIR LEAK! ... fixed with a make shift tube and screw on the end... 2) The rubber to hold the carbs to the cylinders had a slight crack... AIR LEAK! fixed with some glue Needless to say the bike is running amazing, need to order some new rubber housings though for the bottom of the carbs of course... but... the bike is running better than ever! Big thanks to TriGGer and Conica! :beerchug: Link to comment Share on other sites More sharing options...
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