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K7 GSXR 750 starting problems

10K views 40 replies 7 participants last post by  avalon173 
#1 ·
My GSXR 750 won't start at the moment and here is a small story and what I've done so far. And my apologies if this has been discussed somewhere, I couldn't find anything similar to my current situation. I took it out after it sat for a week or so and it ran fine. It sat for about a month and I decided I should take it out to keep everything in shape. It sputtered around a little bit during low RPMs but improved as I rode, I assumed the filter was getting clogged. I parked it and it sat for another month or so, took it out again and I got about 2 miles down the road and it just shut off, as if it had run out of gas. Tried to start it again and it wouldn't so I trailered it back to my place. It wouldn't start at all so I decided to take the tank off, pull the pump out and clean the filter. The filter wasn't as dirty as I had expected but I cleaned it up, put everything back together, drained the gas and put new in. It still won't start, it'll crank but it just keeps acting like it doesn't have gas. You can hear the pump turn on and run for a bit as soon as you turn the bike on. I'm going to check to make sure it's actually pumping gas out. I don't have any pressure gauges or anything so I'm assuming I could just take the fuel line off the bottom of the pump to see if gas is at least coming out. I wanted to go ahead and ask you guys and gals if it is pumping gas, where should I go from there? Thanks for all the help!


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#2 ·
You have to jump the pump, it won't operate disconnected. You can see if there is flow and measure it. I forget the amount, check the manual. You can't check pressure without the connector and gauge. It won't mean much. I had a bad pump that was able to put out more than enough gas, just not much pressure.
 
#4 ·
Random thought for those who may have slightly more mechanical knowledge than myself. The battery had gotten weak from me trying to start it, is there a possibility that, after cleaning the filter, there still isn't enough power to keep the pump going and to create the pressure it needs?


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#6 ·
So the pump is pushing out gas really well. When I try to start it it turns over and acts like it's trying to start, if I roll on the throttle a little you can hear it firing and trying to start. Rolling on the throttle clearly means I'm giving it more gas, and it actually tries to start when I'm on the throttle a little, so I'm going to guess the pump isn't generating enough pressure as Ernie said before. If you or anyone else thinks different let me know. Thanks.


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#9 ·
+1 to what ErnieM said. If the battery is half-drained it might be a able to turn the motor over, just not fast enough for it to start, especially cold. You could try measuring battery voltage with ignition off and how much it drops while cranking to see what condition the battery's in, but if you have access to an external charger, just put it on and see if it helps.
 
#14 ·
At idle? High beams on? What is your battery voltage at 5k?
 
#15 ·
It won't start so I honestly couldn't answer those questions, I just went to check it again, it's been about 12 hours since I took the charger off and it's at 12.9. I didn't check with high beams on, don't know if that would help determine anything without it running.


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#16 ·
Ok, well that should be enough to start it.

So you have fuel, and you have voltage. Do you have spark? Are the coils good? And are the spark plugs clean?
 
#17 ·
The motor turns fine and a motor only needs a few things to run lol. Fuel, compression, air, and spark. I'm thinking the next things to check are the plugs and air filter. I'm honestly hoping it's not compression, I'll be in trouble if that's the case. The last time I rode it was going fine, sputtered a time or two, then just died and hasn't started since so my fear is loss of compression


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#18 ·
I apologize in advance. I haven't slept in almost 36 hours, so my advice might be a bit off.
 
#24 ·
Quick question, and hopefully the answer isn't what I'm dreading. If I pull a coil pack, place my hand over the hole, and try to start the bike should I still feel air moving even if the bike doesn't start? In terms of compression.


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#25 ·
If the spark plug is out, yes.

Do a compression test.
 
#26 ·
Ahhh lol, I missed a key part I didn't take the plug out. Other than feeling for compression in an empty plug hole I don't have any other way to test for compression. It started raining on me and I don't have anyway to work on it inside so I covered it up and came inside. Guess I was feeling rushed trying to do at least one quick test lol


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#29 ·
You don't start it while doing a compression test, you just crank it.

Do a search, there are tons of videos and instructions on how to do a compression test if you haven't done one before. It isn't difficult.
 
#30 ·
You sure you didn't disconnect something when you replaced the air filter?

I had similar symptoms when my air filter was clogged and my filter looked very similar as well. I could get the bike to start by giving it over 1/2 throttle, but it barely ran and shut off immediately when I released the throttle.

New filter and all is well.
 
#33 ·
Changed the plugs, same result. My landlord comes over "What's wrong with that Japanese thing?" [emoji58] he's a Harley person, walks over looks at it, walks away comes back with starter fluid, sprays in the intake and it starts right up. I did noticed while we were trying to start it that no fuel was going from the rails to the intake. Problem solved, I've got the flow, just not the pressure. If I'd have done my pressure test right I'd have saved myself some time. But on the plus side, the air filter and plugs needed changed anyway. Thanks for all of your help ladies and gentlemen. I feel like an idiot now lol


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#38 ·
I also have a K7 750. Are you throwing any error codes? Is the bike all stock or has it been modded.....pipe,power commander,etc? I had some problems with mine that got worse over the course of a year. Everybody was baffled by it. I checked everything,sensors,plugs,filters,full tune up. It turned out to be that the previous owner installed the power commander on the secondary injectors,not the primaries. I am glad I double checked his lame ass install. Bike runs perfect now. So if you are modded in anyway I would look there first.
 
#39 ·
It had an aftermarket Jardine exhaust on it, but I replaced it with stock and ran better than it ever had. I'm not aware of any power commander, I'm assuming I'd have seen it by now with as much as I've taken apart but I could be wrong.


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#40 ·
Got my profile working again.........

Hi.

Take a bottlecap with a bit of fuel and drop it down the throttle body of each cylinder. If it starts for a moment, do it again while the pump is connected and look down the throttle bodies to see if the injectors are actually spraying.

What do you consider to be the fuel filter? The black or white plastic part the pump sits on or the plastic mesh on the bottom?

You must flush the black or red part reverse and forward a few times using 3bar water, then blow dry and try again.

After all this, chances are that you loosened some dirt in the fuel system and got your injectors blocked.

You can clean injectors yourselves, but that is only to do if you see that the above is taken care of.
 
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