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Feb 1st 2017, 03:22 PM   #1
 
  Jan 2016
  Tigard

GSXR won't start hot, starts cold no problem

Having a strange problem that's been getting worse for a few months now, and now it's bad enough to need some attention.

2007 GSX-R750 (original owner)

Symptoms: When I try to start the bike hot (such as after I've stopped to get gas), it turns over very slowly 4 or 5 times and then usually starts up. Recently, it has refused to start at all a couple times. The sound is like it is struggling to turn over, much like a bad battery would sound. However, If i wait an hour or two, let the bike cool down, then try to start it, it starts right up with no hesitation or struggling at all.

I've checked the battery and charging systems - all checks out well. 12.4 volts at the battery when off, 14.x volts when running at 5k RPM. The battery is a Yuasa lead/acid battery purchased by me about 3 years ago. Also, last year, I replaced both the stator and the rectifier/regulator - both stock pieces were bad within a short time from each other. Given the voltages I'm seeing, it appears these components are working fine.

Some online searching has pointed me to the starting motor. I'm in the process of getting that taken off to hopefully get it tested somewhere. Will an auto parts shop test this for me? Being off a bike?

Any other suggestions or things to look at?

Thanks.
Feb 3rd 2017, 10:10 AM   #2
 
  Jan 2016
  Oregon

  2017 Kaw Ninja 1000 ABS (Z1000SX)
Well!

Hard to imagine a hot start problem in the weather we're having..

3 components required for starting: Fuel, Spark, Cranking.

Bad fuel? Ethanol? How old is it?
Clogged injector?

Bad Coil? Bad plug? Coil connections good? I had an intermittent coil problem recently. Those suckers are expensive!

Battery good? Starter motor?

Possible vapor lock? Fuel line overheating? Try braided steel fuel line?

Anyway if nothing works, I recommend Motosport Hillsboro. Not cheap, but good work never is. Might save you $$ with a fast diagnosis and the right fix, the first time!
Feb 3rd 2017, 11:20 AM   #3
 Suzuki Stevo's Avatar
 
  Jan 2016
  Seattle ,Wa

  Burgman 400, TW200, Boulevard M50 & C90T, 2018 Indian Scout 1131
Pull the tank and make sure the coils are snapped all the way onto the plugs...had a similar problem with my GSXF and that cured it.
Feb 3rd 2017, 01:03 PM   #4
 MarvTravis's Avatar
 
  Jan 2016
  Kirkland, WA

  Kawasaki ZX-14
If the symptom is that the engine turns over slowly, it's NOT due to coils, spark plugs, clogged injector, fuel delivery system, bad fuel, tank vent, vapor lock, fuel line, etc.

It's more likely a poor electrical connection in the circuitry to the starter motor or with the starter motor itself. You may have a marginal connection at the battery, at the ground connection to the frame, at the starter motor relay, or within the starter motor. Clean and refurbish the battery and ground connections.

I once had the very same symptom you're having. I found that the flexible woven wires associated with the carbon brushes within the starter motor itself were frayed, and only the few remaining strands were conducting power to the starter motor. Replacing the carbon brushes restored adequate power to the starter motor. You can open the starter motor and see if it's as simple as replacing the brushes.
Rusty Nail likes this.
Feb 3rd 2017, 02:19 PM   #5
 cgt1229's Avatar
 
  Feb 2016
  Bellingham

  Suzuki
If the starter motor brushes are worn, I've ordered a kit for my old bike at
stockers.com Including the plate the brushes attached was about 25 bucks.
The commutator could be dirty too which's easy to polish up when looking at the brushes.
Feb 3rd 2017, 05:14 PM   #6
 Josh's Avatar
 
  Jul 2016
  The Couv

Are you giving the fuel pump a chance to pressurize the system before starting?

Turn on the key, flip the engine on switch and you should hear the fuel pump go ERRRRRRR for a second or two, wait for it to finish before attempting to start.
Feb 3rd 2017, 05:46 PM   #7
 Scribbles's Avatar
 
  Jan 2016
  NW

Quote:
I've checked the battery and charging systems - all checks out well. 12.4 volts at the battery when off, 14.x volts
12.4 seems a little low for a fully charged battery, it would be better if you got 12.6-12.7 volts.

I suggest having the battery load tested. Free at many places that sell batteries. If the battery tests good, then move on to MarvTravis' suggestions.
Feb 5th 2017, 08:46 AM   #8
 MarvTravis's Avatar
 
  Jan 2016
  Kirkland, WA

  Kawasaki ZX-14
Yes, by all means, have the battery load-tested to determine it's healthy. If it's three years old, and has not been kept on a battery tender, that could well be the cause of your symptoms.

Do let us know the final resolution.
Zoomie likes this.
May 6th 2017, 08:03 PM   #9
Boe
 
  Apr 2017
  king county

Sounds like a loose ground wire
May 6th 2017, 08:32 PM   #10
 TREX600's Avatar
 
  Jan 2016
  Custer, WA

  Suzuki 09 GSXR 1000 Suzuki 09 DRZ 400SM 1970 Yamaha 250 DT1 Enduro
Quote:
Originally Posted by Scribbles
12.4 seems a little low for a fully charged battery, it would be better if you got 12.6-12.7 volts.

I suggest having the battery load tested. Free at many places that sell batteries. If the battery tests good, then move on to MarvTravis' suggestions.
I agree 12.6-12.7
Thumperpilot likes this.
May 6th 2017, 08:43 PM   #11
 Dubnut's Avatar
 
  Apr 2016
  My Garage

One last question.
How many miles are on the machine, and have the valve clearances been checked?

Ok.. Two...

.02
dragracer1951 likes this.
May 8th 2017, 08:54 AM   #12
 MarvTravis's Avatar
 
  Jan 2016
  Kirkland, WA

  Kawasaki ZX-14
Quote:
Originally Posted by camaro322hp
Having a strange problem that's been getting worse for a few months now, and now it's bad enough to need some attention.

2007 GSX-R750 (original owner)

Symptoms: When I try to start the bike hot (such as after I've stopped to get gas), it turns over very slowly 4 or 5 times and then usually starts up. Recently, it has refused to start at all a couple times. The sound is like it is struggling to turn over, much like a bad battery would sound. However, If i wait an hour or two, let the bike cool down, then try to start it, it starts right up with no hesitation or struggling at all.

Thanks.
Did you resolve your issue and, if so, what was finally determined be the cause?
May 8th 2017, 09:51 PM   #13
 Zoomie's Avatar
 
  Jan 2016
  Kirkland

+1 with MarvTravis
12.4v on a three year old battery?
And, weak, corroded connections can create similar issues. But you'll clean all those up when you install your new battery, right? ��
May 8th 2017, 10:09 PM   #14
 Zoomie's Avatar
 
  Jan 2016
  Kirkland

@ MarvTravis and cgt1229, alright, so how old, and technical, are you guys, that you clean commutators and replace starter brushes?
Unless it's a rare, hard to find starter, it's ebay and PayPal (did I spell those right?) and the bike is back on the road. I'm learning (or trying) to love modern tech and the interwebz.
Eh, I'm lying, I've used emery cloth, a hacksaw blade, and a growler, too.
May 9th 2017, 06:46 AM   #15
 SilvieFox's Avatar
 
  Jan 2016
  welches, Oregon

  2008 Kawasaki Versys (Sylvester), 1972 Suzuki RV90 (vanvan), 1981 Honda TwinStar (Bobber),yamaha 225
Quote:
Originally Posted by Zoomie
@ MarvTravis and cgt1229, alright, so how old, and technical, are you guys, that you clean commutators and replace starter brushes?
Unless it's a rare, hard to find starter, it's ebay and PayPal (did I spell those right?) and the bike is back on the road. I'm learning (or trying) to love modern tech and the interwebz.
Eh, I'm lying, I've used emery cloth, a hacksaw blade, and a growler, too.
if somethings broke, fix it till it isnt.. or till its so broke noone will ever even know what it was, then you go on fleabay and get a replacement
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