• Welcome to the Two Wheeled Texans community! Feel free to hang out and lurk as long as you like. However, we would like to encourage you to register so that you can join the community and use the numerous features on the site. After registering, don't forget to post up an introduction!

1990 GSXR 750 Not Starting

Joined
Nov 2, 2005
Messages
5
Reaction score
0
I recently took off the carbs on my 1990 gsxr 750 to check them out and see if they needed cleaning or anything, which they didnt... looked as if the carbs had been rebuilt within 1000 miles... the idle problem i was having was just because of a misadjusted idle screw, which i plan to fix, if i can get the bike to start... once i put the carbs back on the bike and hooked up all the various vacuum hoses and fuel lines and such, the bike just won't start... I've pulled out the spark plugs and cleaned them off, tested the spark coming through the wires (which was good), checked if there was fuel in the bowls of the carbs, which there is, put new fuel in it in case the fuel that was in it was bad (which wasn't likely since its only a couple weeks old) and completely recharged the battery... I am stumped as to why it won't start... all I did to the bike was pull of the carbs and check them out and I pulled off the air filter (which is a K&N) and cleaned and re-oiled it... I've also tried using starter fluid, but then the bike starts and runs erratically until the fluid is burned off then it dies again... a friend of mine thinks its the spark, but I dont see how that can be it... The Clymer manual I have says that a cause for troublesome starting could be the oil? I've got a new case of oil to put in the bike, but I wanted to get it warmed up and such before I changed it... I can't even think of what to try next... any ideas??

I live in College Station and any help would be much appreciated...

-Daniel
 
so the starter is working but, the bike isint firing? you have checked the fuel lines to make sure they are working properly right?

check here

has a section just for bikes like yours and the people there are pretty helpfull
 
Last edited:
Check the following in this order
Fuel delivery:
Unscrew fuel bowl drains to see if gas is getting into Fuel bowls When motor is turned over
If no fuel there:
Check vacuum line, Disconect it from carbs disconnect gas line and see if pulling a vacuum on vacuum line will open petcock and allow gas to flow out of fuel line
Check fuel lines, vent tubes,to make sure they are where they belong Not reversed, some of these bikes have 2 of each located closely to each other
Next check float level has it been moved during diassembly
Next are the needles attached to the float correctly?

If there is fuel in float bowls then fuel delivery is'nt the problem.
Remember it takes 3 things to make an engine run
Air Fuel mixture
Compression
Ignition
check them one at a time
Good luck
SRAD
 
Welcome to the web site, Daniel.

Sorry that your first contact is about bike trouble, but you should find some help here (2 posts already). There may even be someone locally.

Good luck and check out the activities in the BCS ans surrounding area once you get 'er back up and running.

Just an additional thought - I assume that the bike was running before you took the carbs off. If so, I would venture a fuel problem - make sure you reconnected the tank line & that it is not clogged...
 
Last edited:
You said you've got fuel in the float bowls, so I don't think lack of fuel is your problem. You've knocked something out of whack while working on it. Maybe you disconnected a wire to the coils or spark plugs while removing and replacing the tank. Does the exhaust smell like raw gas when you are cranking and cranking it? I'm not sure how the emergency engine cutoff works on that buike, but some will let a bike crank but not deliver spark to the plugs (I prefer the type that makes everything go dead so it is easier to find). Did you bump that to off while working on the bike?

How far did you get into the carbs? If you merely opened the float bowls, declared them clean and bolted them back up, you probably didn't change anything. BUt if you took out jets and possibly failed to reinsert one correctly, you may not be getting proper fuel delivery. Is there any chance you put the carbs on backwards?

My guess is it is something electrical. Pull a spark plug cap or two, stick a fresh plug in the cap and ground it on the bike so you can check for spark while cranking it. If no spark, that is where you want to focus your attention.
 
zero4o3 said:
so the starter is working but, the bike isint firing? you have checked the fuel lines to make sure they are working properly right?

check here

has a section just for bikes like yours and the people there are pretty helpfull

Already posted there... nothing i've tried has worked... I think it has to be some kind of huge vacuum leak, but I really dont know enough to really know what the problem is...

here's the thread tho...

http://www.gixxer.com/ubbthreads/showflat.php?Cat=0&Number=1880450&page=0&vc=#Post1880450

I haven't had much time with tests and the Corps and everything to work on it, especially since i really dont know what i'm doing...

Any Ideas?

-Daniel
 
:tab Unless you simply can't afford to, I would take it to a local private shop and have it diagnosed. Some shops will do that, assuming you pay them for their time, even if you wind up doing the final repair yourself. Although, my experience is that it is cheaper for me to just pay them to do it once they have it apart than for me to spend the time messing with it.
 
It sounds like it is flooded, your drowning the spark with fuel, the starter fluid is highly volital and is hard to drown. Check to see that your cables are working properly at the carbs, this is throttle and choke. look to see if they move when you twist 'em. pull a spark plug, plug it into its wire and lay it against the motor. Does it spark? Does it spark blue? (yes) was it wet when you pulled it out?
 
It can't be flooding because I'll try to start it for a little bit, then wait a few hours and try again, so even if it did flood then it would have plenty of time to dry out and such before i tried it again... the spark plugs have a nice big blue spark, they should too, considering i just bought them a couple weeks ago...
 
pull the plugs and make a liar out of me! I dare you. You have to pull them after you try to start it, this lets you know if you (1) have fuel (2) have to much fuel or no spark. It is not uncommon to put bad plugs in, they get damaged through various means. Basicly you are inspecting each component of the fuel and ignition to verify its correct operation." What if" type of thing, you didn't say if the choke (enricher circuit) was operating or if the slides are working.

This is tough to diagnose a problem like this across the internet. They may sound like dumb questions but you have to cover all the basic stuff.
 
Last edited:
I have pulled all the plugs after every time i've tried to crank it. They only get wet fouled if I try to crank it for a while and it doesn't work. As far as I know, the slides and everything work fine and the choke does work. I didnt really get into the botom of the carbs when I took 'em off, I more-so just checked out the diaphragms and such. But yes, after I crank on it for a while, the plugs do get wet-fouled, but after i just crank on it for a minute or so they're finee and dandy, still shiney like new without any gas on 'em...

I know this is really hard to do over the internet, especially when everything is being relayed through me and I really dont know much about bikes. I have worked on cars for years, but bikes are whole different monster. I still really dont understand how the fuel lines work and such without a fuel pump, just doesn't make sense to me...

-Daniel
 
Well, did you "adjust" any thing? There is a cable for setting the idle speed, it is located under the right side of the carb bank. Is it set to the idle adjustment stop. If you move this stop you should see that the throttle cable also moves it. Adjust this in and out and look for the throttle linkage to move. twist the throttle and observe the linkage, does it move in the full range. Some throttles have a return cable some use a spring on the linkage.Does the linkage return after you twist the throttle? The enricher knob, is it returning to fully closed after you pull it on? Check your full lines to make sure they have not been pinched, crimped, squeeshed by something. It is gravity fed. You can prop the tank up with the seat off. I have creased lines putting them back on just like folding a garden hose, twisted and pinched. Same with vacum lines.
 
Doesn't sound like spark to any great degree.
Normally, if they'll easily start with starter fluid, but not w/o, then you know you have decent compression and ignition and timing. Pretty much leaves carburation.

If you can limp it along with starterfluid til it warms up a bit and then it runs normally on gas, then it's likely the choke circuit.

If it will run on gas at higher rpms, but not low, then it is likely the idle jet, or a plugged idle air bleed, or a vac leak.

Something didn't get assembled the reverse of disassembly.
Butterflies and slides both return normally, and not binding? Same for choke? Plugs wet? Plug color?
Any firing at all? On any cylinder? All plugs look the same?
Plug wires going to correct cylinders?
 
Did you forget to light a few candles, dance around the bike and chant? :-P
 
Tourmeister said:
Did you forget to light a few candles, dance around the bike and chant? :-P

****.. that must be it, I'll have to try that tonight :nana:

As far as I know everything was put together the exact reverse of dissasembly... I didnt mess with any of the complicated parts, I basically just pulled out the diaphragms and such and put them back in and just sprayed everything else down liberally in carb cleaner... the only parts i really took apart was the top side of the carbs...
 
As DaveC mentioned above, it may be that your idle speed is adjusted too low. Tried twisting the throttle a little while starting it on ether?
 
Ok, Ill throw my 2 cents in.

You mention that you just oiled your K&N. Take the air filter off completely (open carbs) and try to start it. If you overoil the filter it will be really really hard to start as it is not getting any air. If you take the filter off and it starts then just clean the filter and lightly oil it. While you have the filter off make sure that ....
1. The slides open when you twist the throttle and
2. They close when you let go.
3. While holding the slides open push up on the needle valve body. You should feel a bit of resistance and they should close quickly but no too quickly ;-) . Basically if it slams shut then you have a leak to the backside of your diaphragm that you need to find. Seeing that you took the tops of the carbs off I would guess that you pinched a diaphragm putting it back togther.


You also mention that you got it to start, it shot up to 7-11k and then died. Who knows? I would guess that you have the throttle twisted wide open (check while the air filter is off). Maybe you have the throttle cables reversed although I would think that would be tough to do.

Good luck and keep us posted. Did you ever mention where you are located?
 
HEy if u want to sell ur bike or the motor let me know. plz...
 
and u didn't or returned your idle mixure screws back as they were? It's a real Pain if u have them off too much. excess or not enough air
Michael
 
Back
Top