GSX650F Strange misfire - Suzuki GSX-R Motorcycle Forums Gixxer.com

 
LinkBack Thread Tools Display Modes
post #1 of 5 (permalink) Old 07-25-2017, 03:39 AM Thread Starter
Squid
 
Join Date: Jul 2017
Posts: 2
GSX650F Strange misfire

Hey guys,
I apologize if this is not the right place for this but i assume there is probably not much difference between a gsx f and 600R
Bike 08 GSX650f
Im experiencing a rather strange misfire which occurs mainly at higher loads and RPM.
The misfire tends to happen at 80% - 100% throttle, and is that bad that you will not accelerate
if you use slightly less throttle than where the misfire occurs you can rev it out to the rev limiter cleanly.
And the interesting thing is, say you cruise along in 1st gear at 6k, snap throttle open and it starts to break down. You can flick the kill switch on off and then get straight back onto the throttle and it will pull clean. After a variable amount of time the miss will return.

Ive replaced the voltage rectifier
Fuel Pump
Coilpacks
menthol369 is offline  
Sponsored Links
Advertisement
 
post #2 of 5 (permalink) Old 07-25-2017, 06:01 AM
I know things... A lot of things.
 
Join Date: Feb 2015
Motorcycle: GSXR 750 K4
Posts: 2,966
Re: GSX650F Strange misfire

Quote:
Originally Posted by menthol369 View Post
I apologize if this is not the right place for this but i assume there is probably not much difference between a gsx f and 600R
Bike 08 GSX650f
I'm not so sure about that, as I've never laid eyes on a GSX-F service manual, so what follows will be general comments.

Quote:
Originally Posted by menthol369 View Post
Im experiencing a rather strange misfire which occurs mainly at higher loads and RPM.
The misfire tends to happen at 80% - 100% throttle, and is that bad that you will not accelerate
if you use slightly less throttle than where the misfire occurs you can rev it out to the rev limiter cleanly.
Up until here, this behavior is not very strange. It sounds like a textbook case of fuel starvation, probably due to a blocked fuel filter or injectors. Note that, although you mention having replaced the pump, if that means just the motor itself and not the whole assembly, then chances are you haven't replaced the filter. At least on a GSX-R you wouldn't have.

Quote:
Originally Posted by menthol369 View Post
And the interesting thing is, say you cruise along in 1st gear at 6k, snap throttle open and it starts to break down. You can flick the kill switch on off and then get straight back onto the throttle and it will pull clean. After a variable amount of time the miss will return.
This is more strange. If after cycling the kill switch, you open the throttle as much as before, at the same engine speed as before, and don't get any misfire any more, then that doesn't fit into the fuel starvation theory. It would point to a faulty kill switch, but that would cause trouble all the time, not at higher engine loads only. I therefore suspect this observation is not entirely correct. Perhaps you don't open the throttle as much after flicking the switch, or the engine speed has dropped in the meantime?

Quote:
Originally Posted by menthol369 View Post
Ive replaced the voltage rectifier
Fuel Pump
Coilpacks
Since replacing these has obviously had no effect, I'd recommend reinstalling the OEM parts, especially if they were replaced with cheap aftermarket parts.
dpapavas is offline  
post #3 of 5 (permalink) Old 07-25-2017, 08:24 AM Thread Starter
Squid
 
Join Date: Jul 2017
Posts: 2
Re: GSX650F Strange misfire

Thanks for your reply

I forgot to mention that when i replaced the pump the problem got a little better, i did some further research and found that theres a filter in the upper half of the fuel pump assembly that houses the fuel reg.
I cleaned it out as best i could and went for a ride and so far the problem has gone away.

I assume flicking the ign let it prime the rail to pressure again so it would run ok for one pull.
menthol369 is offline  
Sponsored Links
Advertisement
 
post #4 of 5 (permalink) Old 07-25-2017, 09:25 AM
Expert
 
maniac1886's Avatar
 
Join Date: Jan 2016
Location: Flint, Mi
Posts: 2,061
Garage
Re: GSX650F Strange misfire

I would find a manual and perform a fuel flow test to make sure the pump is pushing enough juice through the lines. Also, you may want to have a close look at the fuel line routing, and condition. Sometimws, especially if replaced with non oem, fuel lines can break down and kink more easily.
maniac1886 is offline  
post #5 of 5 (permalink) Old 07-25-2017, 10:05 AM
I know things... A lot of things.
 
Join Date: Feb 2015
Motorcycle: GSXR 750 K4
Posts: 2,966
Re: GSX650F Strange misfire

Quote:
Originally Posted by menthol369 View Post
I assume flicking the ign let it prime the rail to pressure again so it would run ok for one pull.
Yes, that sounds plausible, if the improvement is for one pull and depending on the way the ECU operates during a moving reset. The on-reset pump prime generally amounts to activation of the pump for a few seconds and this normally happens before you start the engine, but I'm not sure the ECU actively prevents firing of the injectors or plugs during priming; I think it's just that one usually just chooses not to crank the motor, until all the whirring has ceased.

If the bike is moving during reset, I'd assume the engine to start, as soon as the ECU boots up, thus preventing any priming, but I haven't actually ever tried that. When you tried it, was the throttle entirely unresponsive during priming, as if the engine wasn't firing at all?
dpapavas is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Suzuki GSX-R Motorcycle Forums Gixxer.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome