Looking for some input from you good folk as you are all knowledgeable and give realistic responses compared to other forums
Ive an issue with my GSF1200 Bandit – it's a 1999 Mk1 and it's got 16K on the clock
The issue I have is that number 4 cylinder is very very lean so much, so it is off the top of the scale on the Carbtune balancer
12& 3 are all running at even temperatures and they all look to be balanced well – N# 4 is barely warming up
Ive stripped the carbs cleaned as much as I can – replaced all the gaskets I can – the float levels are all set – changed plugs over between cylinders – removed the carb to block rubbers and no issued there – also diaphragm is not perished or worn
The bike was lying up, but I had the carbs ultrasonically cleaned last year
It is doing my head in bit on the plus side I can remove a set of carbs on in under 15 minutes
Your thoughts are appreciated
The only thing I can think of is maybe a subtle split in the carburetor mounting rubber thingy..
I know the splits can be quite difficult to spot sometimes when in situ..
Many years ago I owned a Honda CB750 Four (1969 model) and the only way I found the split was the flex the rubber when it was removed..
Hiya
@Del from what your describing it sounds deffinatly on the carb side somewhere as only affecting 1 (number 4) cylinder.
So my thoughts are simular to
@Speedy1959's .
You can check the inlet rubbers and manifold by spraying easystart onto them while the bikes at tick-over and listen to hear if the revs change as the fluid gets into any tiny splits (it's not totally conclusive) and can show up a problem there.
Good luck buddy
:cheers:
Hi , is it lean all the way through the rev range or only at the lower speeds , after a run are the plug colours consistent ? failing a vacuum leak it would have to be in the carb, are the emulsion tube holes clear? I have had them block and cause a lean condition but usually all the carbs have a similar problem and its a associated with the bike sitting for a time and with the current fuel tends to cause a white solid that blocks small holes. If you have ruled out a vacuum leak it would appear you need to go deeper into the carburettor.
Good Luck.
Horse
Del, is number 4 slide moving up with others? Does a splash of carby cleaner in that carb liven it up? Carby cleaner will prove its a fuel issue in that cylinder. Otherwise need to look at other reasons.
oh this thing is just taking the piss
had the carb rubbers off to check clean and renew the O-rings - no issues here the rubbers are all in good order no brittleness of cracks and all supple - Good I hear you cry
so while I'm here Ill try the compression - number 4 is 220 good I says - just to be sure try number 1 crank over and yip 220 so all good . . . . . . . . . . . . .hang on whats that oil doing all over the garage floor - ERSE I had removed the cam cover oil feed pipe to take off the rubbers - and now I have oil all over the floor the door and engine
checked the coil and I think number 4 & coil is breaking down - Fingers crossed gents
Sometimes it's a slippery slope to success :cheers:
It's a pain but the more you go through it the more things you can eliminate .
If you think it's coils swap 1-4 the problem should swop cylinders .
Then it must only be a plug lead rather than the coil but I'm not sure you can change just a lead .
Good luck buddy.
:cheers:
My pals bandit had running problems due to worn emulsion tubes / needles
@seth got a set of after market coils here and a stick coil conversion loom so one way or the other I'm sorted
@Bob had them all out and checked over and bikes only done 16K so don't think it'll be them but if the coil issue doesn't work Ill look at them mate cheers
Also Ive swapped all the components from carb 4 to carb 3 so if the issue moves its the components
cheers for the help chaps appreciated
Quote from: seth on Wednesday, 10 July 2019, 07:03 PM
It's a pain but the more you go through it the more things you can eliminate .
If you think it's coils swap 1-4 the problem should swop cylinders .
Then it must only be a plug lead rather than the coil but I'm not sure you can change just a lead .
Good luck buddy.
:cheers:
I assume they are like 14 coils, in that you could swap the coils & see if the fault follows the coil/plug lead.
Are we still talking about a lean condition? I will be very interested to learn how a coil creates a lean burn issue, I would believe that a weak coil will give a cylinder non firing condition under maximum load and maybe slight uneven running but I can not understand how it ends up lean. Maybe slight incomplete combustion ( a stretch ) but not lean , Have been wrong thousands of times before and stranger things have probably happened,
Hope you find the fault soon,
Horse
Hi
@horse - the issue of the bike being lean was due to the carb balancer on N#4 being off the scale when I tried to balance carbs after refitting (I hate carbs as much as I hate electric string) - now Ive had the carbs on and off several times stripped and cleaned everything I could get too and decided to check other things as I wait for more parts to arrive - such as compression and then spark basically checking everything - compression isn't an issue so while in the vicinity thought check spark and that is how I found out 1&4 were not sparking as half as well as 2&3 - I am hoping I get this effin bike sorted as its starting to really fuk me off
hope this explains my thought process a bit
Great Del , I was just a little confused (not hard for the elderly) when the lean issue turned to a spark problem, generally weak spark will usually manifest itself with peak combustion pressure and if its alright there ( WO throttle at low and above speeds) the spark quality should not be a problem elsewhere anyway sounds like after all the work you have been forced to do it will run sweet as for some time to come,
Have a good weekend
Horse
Well I think I may have sorted the bastardin thing out - new coils (clutching at straws now) and emulsion tubes (again trying everything) and still No4 not running - so carbs back off and stripped again (this is at least the 6th time) - so as Im checking everything over I notice No4 butterfly not lever as the rest - after investigation I discover a very small spring missing from the linkage - onto Fowlers and identifying the part number I fell over at the price (nearly £12.00 delivered) - fitted carbs balanced and ticking over - a few other things to sort and think that will be it
thanks for all the input fellas
Del
Being a dodgy bodging twat I'd have been looking for an old pen to nick the spring out of & cut to size. That worked when I lost a similar spring off the side of a carb on my RF600.
With that spring missing from the carb linkage you were correct in saying that you couldn't balance the carbs..Nightmare!
Bandit carbs aren't too bad to get in and out once you get used to them..Main tip is remove throttle cables from twist grip end and NOT from the carbs themselves.
Glad you're sorted now.
PS. Make sure you leave fuel tap on Run position and not Prime. If either the tap diaphragm or carb float valves are worn it can end up leaking fuel into engine and causing it to "Hydrolock" which isn't good! It's a common problem with bandits.
Bandit carbs? Nightmare? ..... definitely, or am I blaming the carbs for a bigger issue?
I had flooding like you wouldn't believe but new O rings & float adjustment sorted that with the carbs. So I start the bike without the air filter & it idles beautifully. Give it a rev & the slides are all working well but then it starts to backfire & blow smoke according to my son who was watching. I didn't see the smoke but I suspect it was black from over fuelling as at that time fuel started pouring out of the breather in to the air box. It appears I have some serious blow by.
I wonder how hard it is to fit a 1402 lump in to a Bandit frame?
Why would blow by make the carbs flood?
In my (limited) experience, a quick check for blow by is to unscrew the oil cap. If it's blown off with the engine running then you've got blow by. I worked on a CG 125 once that'd lift the cap about 3" at idle (the dipstick kept it in line) and blow it several foot away when revved.
It wont be blow by. Guarantee it'll be a stuck float. Bandit carbs can be a total ball ache at times.
Just to eliminate fuel tap diaphragm fault..Pull the feed pipe off the tap and no fuel should flow in the Run position. If it drips or flows fuel you'll need a rebuild seal kit.
The fuel is gravity fed from a can attached to my vacuum gauges. The carbs aren't flooding. The fuel is entering the air box via the breather tube at a rapid rate.
Quote from: Snapey on Sunday, 27 October 2019, 02:32 AM
The fuel is gravity fed from a can attached to my vacuum gauges. The carbs aren't flooding. The fuel is entering the air box via the breather tube at a rapid rate.
I had the same issue the other day - the float was jammed and not shutting the fuel off and was pissing out of the black pipe as well as spitting back through the carbs into the air filter box - carbs off and as Froudy says there not hard to remove - stripped cleaned and rest the float heights added missing spring - mixture screws set at 2 turns was a mare to get idling and grey smoke everywhere but after balancing the carbs its running as sweet as
Quote from: Snapey on Sunday, 27 October 2019, 02:32 AM
The fuel is gravity fed from a can attached to my vacuum gauges. The carbs aren't flooding. The fuel is entering the air box via the breather tube at a rapid rate.
If that's the case, then one or more float valves aren't seated properly.
Yup, I'd go with needles not seating properly too, it's all that makes sense.
Thanks for the feedback fellas. Now I've got a manual to go by hopefully I'll get it right this time.
The tiniest bit of dirt will stop them seating, good luck.
Out of interest, i`ve just sold my mint, 12000mls standard K3 1200, following a nightmarish 3 months trying to get it to run properly again following an 18month lay-up in my (heated) garage. I`d left fuel in the tank & carbs which everyone i spoke to suggested that to be the problem. Having stripped out the carbs to find they were as clean as new inside and all the seals were fine i refitted them to find a fuel leak! Being lazy i didn`t bother replacing the gaskets. Big mistake. So off they came again! Following the rebuild the bike still ran really badly at low revs to a point it was dangerous.
In the knowledge that the carbs were perfect, it dawned on me that the problem was elsewhere. A change of plugs didn`t help so i checked the HT leads - in fact i removed the caps and snipped 5mm off each in case any had started corroding. Eureka, the bike ran like new from that point......in real terms, a five minute fix!
My point being, check out the simple stuff before spending hours looking for a problem that doesn`t exist!!
Issue sorted ... I hope once the repair kits are fitted.
No wonder the breather was spewing fuel in to the air box. It had nowhere else to go because the sump was full of it from the carburettors flooding. I filled a 10L bucket plus over a litre spilled from an engine that has a 4.5L oil capacity. That's a pretty serious flush that will need a few oil changes to clear. Hopefully that fuel & oil mix hasn't damaged the motor.
I fitted a few O rings I had but they're probably not petrol friendly so repair kits are on order that I hope will end my woes. One lesson I've learnt from this is to know where 'reserve' and 'prime' are on the petcock. I thought I had it on 'reserve' but being on 'prime' the leaking carbs allowed fuel to enter the sump. Shame they're not like my Hondas where the fuel escapes via an overflow pipe if flooding & you can see it so you know of the problem.
@Snapey This is such a common occurrence on Bandits. It comes up nearly every day on the fb Bandit pages I'm on. Its vital to keep the fuel tap on Run and not Prime or Reserve. Even if the fuel tap is on Run, if the tap diaphragm springs a leak, coupled with faulty/dirty or worn float valves it will dump the contents of the fuel tank into the engine as yours did. If you don't spot this and try starting it while hydro locked it can twist the crank and destroy the engine.
Just drain the fuel oil mix from the sump and leave sump and filler cap open for a couple of days to clear it. Fit new oil filter and fresh oil and it should be fine.
A lot of carbs have an O ring around the needle seat they crack and the fuel bypasses the float needle on the outside causing flooding. the needle seats are push in retained by a clip.
Quote from: Irish in Oz on Monday, 28 October 2019, 07:20 PM
A lot of carbs have an O ring around the needle seat they crack and the fuel bypasses the float needle on the outside causing flooding. the needle seats are push in retained by a clip.
I suspected that was the main cause Jeff so I put new ones in there and on the plastic bit too but I doubt they're petrol tolerant. They stopped the flooding but there's still a very slight loss of fuel. At least I know what the problem is so I can confidently start the restoration knowing the carby kits will stop the flooding..
Pete, it is the first thing I do on any vintage bike I rebuild, I even had problems with the Katana running the CR carbs and that was the reason for erratic idling, it's a common problem in all the manufacturers all models as they don't make the carburettor's or fuel taps.