broken down 1993 gsx600f firing on two cylinders

[airz1988]

Quote

1993 gsx600f firing on cylinder 1 and 2 only!!! 3 and 4 are stone cold!!!

the problem started THURSDAY (4 days ago), i was at work and all this horrible rain covered my bike which is running on k and n air filters (there is only 2 filters as they supply 2 carbs each) i think rain may have been sucked into the carbs or may have made its way in while the bike was stood? either way, on my way home i lost power completely, pulled up at the side of the road and discovered ONE of the cyclinders (number 3) was cold. i got on the bike and somehow made my way home with the bike making a right noise. i installed a new spark plug without checking the spark and replaced the leads and it seemed to have sorted the problem.

i finished work FRIDAY and started the bike with the choke on and started to warm her up and realised the problem had come back. i had no choice but to ride it home and set off on my way. the problem seemed to have cleared itself and continued to use it through the day and everything was fine, no problem at all.

SATURDAY (yesterday) i started the bike again to nip out and pick up something from town and discovered it had come back, the cylinder was cold again. i took the ht leads off and checked the spark for each lead and they were all fine. i swapped them around too see if they would make cylinder number 3 fire again but no joy. the leads worked fine on each of the other 3 cylinders, making me realise it wasnt an ignition issue, so i started the bike again and realised cylinder number 4 was down too, meaning the bike is only starting and running on cylinder 1 and 2. 3 and 4 are cold.

i removed the fuel tank completely and checked the fuel tap and checked the fuel filter and appears to be fine.

i re-fitted the tank, fuel lines and vacuum pipe.

i checked the fuel lines and none are split or blocked so i know fuel is reaching the carbs. there is one hose going to the center of the left pair of carbs and there is another hose supplying the right pair of carbs.

i removed the tank again, took the air filters off and checked inside the filters and boots to the carbs and all is ok.

i refitted the filters to prevent anything getting into the carbs.

i removed the carbs and drained the fuel, opened the tops up, checked the insides and all is nice and clean, so i put the tops back on.

i removed the bottoms and cleaned the pilot jets, checked the needles, checked the float assembly and cleaned the float chamber, then put the bottoms back on.

i put the carbs back on the bike and put the fuel tank back on and set the tap to prime to put fuel back in the carbs, then set the fuel tap to the "on" position.

i opened the drain screw on each of the carbs one after the other and each hole is letting sufficient fuel drain out, meaning fuel is reaching the carbs.

i turned the bike over and it is still happening. cylinder 3 and 4 is cold. it obviously runs terrible and backfires really loud and cuts out when on idle. i now wont be able to make it into work tomorrow because of this. i really need it sorting asap. next thing to try is to spray wd40 into the carb throats to see if it will help the cylinders fire up

i am not mechanically minded and really need advice on where i should have started and what to check first and what i do next? i thought it would be a simple fix as it happened then seemed to have sorted itself out and was running full power and everything was ok. then it went wrong again over night. it was fine when i parked up. next day, probe was back again. here again is what i did in order.

1. checked sparks-all ok
2. checked and swapped leads to rule out faulty leads-all ok (lead positions are ok)
3. visually checked coil packs and lead positions-all ok
4. checked fuel lines and vacuum line-all ok
5. removed fuel tap and checked fuel filter and tap mechanism-all ok
6. removed and checked air filters-all ok
7. removed carbs, took to pieces, found dirt build up in float chamber, cleaned chamber and cleaned jets-all ok
8. replaced everything in its correct place, fired it up and still no change.

 

 

[Fula28]

Swap coils see if it transfers over, just because it sparks does not rule out breaking down coil pack! We have all been here before at some time. Also those diaphragm fuel taps on gsxf are shite,bThey fail too a quick rebuild kit from tourmax £15 will be in order. 

[airz1988]

checked the fuel tap and there is enough fuel going through mate, the cylinders that are not firing are number 3 and 4 which are both on seperate coil packs so i dont think swapping coil packs will make any difference, i will definately try it in the morning tho just to rule it out

 

[jameskat]

Try the WD40, see if it is ignition or fuel. When you say the bike was making a right noise, what do you mean?

[airz1988]

the noise it was making on my way home it was sort of like a rev-limiter but not quite, in 6th gear i was probably travelling at around 50mph and wouldnt go anymore. felt and sounded horrible.

 

[jameskat]

Try WD40, swap spark plugs around (some dodgy plugs about) at the same time have a look at colour of the plugs and if they are wet. 

[teltwosheds]

Mine used to do that till I balanced the carbs. No 3&4 are  still slow to fire up if I start it on the side stand (just my observation) 

[martyngsxr]

id be interested to know weather swapping out the original coils worked as i have roughly the same problem starts on all four then when gets warm drops a cylinder at low revs going to change coils when i can to see if this cures the problem 

[airz1988]

BOOOOOM SO HAPPY!!!!! I swapped lead 3 and 4 by mistake as soon as I spotted it earlier I was praying that was the cause and it was!! Just been out on her for an hour and a half and it all runs as it did before, or does it??? Seems to have developed a strange knocking sound  

[airz1988]

Also, when I put it on choke to get it warmed up all the cylinders were scalding hot but number 4 was only warm??? Any ideas? 

[airz1988]