GSXR400 Problems 1991 GK76A

[xXxKillDogxXx]

Okay so ive been fixing little things on my gsxr recently however i still havnt managed to get it reliable its forever cutting out, not starting or firing on 3 instead of 4 cylinders.

Heres all the symptoms:

If it does start, it will not idle and if it cuts out you cannot start it again thats with it running on 3 cylinders
Cylinders #1 #2 #4 will fire however if you spray brake cleaner down the vacume nipple on carb 3 it then fires up #3.

There is a strong spark on all 4 cylinders, and nothing changes when you swap plugs from each cylinders, its still number 3 that wont fire.

Compression is #1 150 *Approx*, #2 150 *Approx*, #3 150 *Approx*, #4 125*Approx*
(Ill fix number 4 later cause it should still run perfectly fine like that and ive never had problems with number #4, apart from i replaced the HT CAP cause it was faulty)

If you spray brake cleaner into the airbox when the bike wont start, it will pop and shoot flames as if the timing is out, however when it does start the bike revs and runs perfect apart from the missing cylinder of course.

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Causes:

I thought maybe it could have been a float assembly issue however ive changed the float, and the pin, and the main jet seal.

Changed the vacuum slider and cleaned all the carbs with carb cleaner and compressed air.

Maybe a possible air leak however nothing so far has been found and the exhaust is full sealed not blowing at all.

I do have jap stailess downpipes and a Danmoto endcan so maybe i need to richen the mixture however i thought it should run 1.5 turns out on the carbs fine and then i can fine tune from there with it running.

Just incase this is the cause my timing is set to 19 pins between the marks at the top im pretty sure im correct however im starting to doute my self on this bike and everything ive done with it now so if someone could confirm this i would be great full.


Thanks to anyone that contributes with the helping of solving my issues with this bike its much appreciated !

[thunderace]

So it looks like you're not getting fuel into #3. If I were you I'd be stripping the carbs again and making sure nothing has gotten into one of the fuel ways and is blocking it on #3.

[xXxKillDogxXx]

Thats the exact same conclusion we came to also, however they should be perfectly clean, and it should run on 3 still.

And it still dont explain why it will never start if it dies out :S

[xXxKillDogxXx]

i swapped the leads over and #2 stopped firing tested the coil and had no resistance on secondary, bought a new coil now have it firing on 1 2 and 4 but not 3 which is seriously wierd... gotta be the carb but it was running fine before i just dont get it tbh

[ben2306]

i swapped the leads over and #2 stopped firing tested the coil and had no resistance on secondary, bought a new coil now have it firing on 1 2 and 4 but not 3 which is seriously wierd... gotta be the carb but it was running fine before i just dont get it tbh

ever checked your (pulse coil aka pickup coil aka pulse gen assembly)? i'm just suggesting, hoping to help. as i had problems starting before when its hot, it even cut off 1/2way when riding. after changing it. problem no longer appear.

[xXxKillDogxXx]

thats what i started thinking tonight aswell bud, cant find one for shit thought gonna see if i can maybe test mine some how i dunno...

[ben2306]

my mech tested it with multi meter if i'm not wrong. but i don't know how. hope it helps.

[xXxKillDogxXx]

okay well ill try and test mine tomorrow, you know the bar that runs through the coil pack does that need the earth on both ends cause only one side of the bar is earth the other end has the bolt snapped off and on most the bar is straight through so as long as one end is earth it should be enough correct?

[xXxKillDogxXx]

ther was a air leak on the vacuum pipe so when it got synced it wasnt right when we retested it was miles out causing a miss fire cause there was no fuel, now we have to sort the unstable idle which we think is the mixture o rings so gotta get some of variables unless i can find the other set i ordered off him for the first set of carbs

[ben2306]

hope you get it sorted out soon. do update here. will be useful info.