Overheating ans hot start problem... | GTAMotorcycle.com

Overheating ans hot start problem...

K

krrakt

Well-known member
Hey.

I have a 98 GSXR 750 that I have been working on and I'm stumped with this problem.
the bike starts cold no problem, once hot though the starter can barely turn the engine over if at all.
Also the bike is overheating, the cooling fan is working though.
So far I have changed the following;

1-Stator
2-Regulator/ rectifier
3-Starter
4-Battery

I have checked all the circuits by removing each fuse one at a time and trying to start the bike when it is hot. It makes no difference.
I have also checked all my connectors for corrosion and they are fine.
I believe this is an electrical problem but I'm really not sure at this point, I have replaced everything I can think of that could cause this problem.
Any suggestions are appreciated.
 
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Many moons ago I had a bike that did not start when hot. It was the batt. Something about the plates expanding just enough when hot to "short" (or something like that). When the batt cooled down it started no problem. So start (no pun intended) with the simple things. Borrow a batt and try it when the bike is hot....or just swap it in and ride and try it that way.

***edit***
nevermind...mis read your post. Batt already changed.
 
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So the fan works fine, no mention on cooling system troubleshooting and you think an electrical problem......
I am assuming it is liquid cooled and if so, check the cooling system.... (Rad, thermostat, etc) if the bike is overheating and work back from there.

Thats my best guess.
 
Thanks guys,
I did replace the thermostat and the battery is brand new.
I checked the battery being the issue by putting booster cables on it and it still barely turns over when hot, definitely not nearly fast enough to start the engine.
Yes, liquid cooled in line 4 motor.
Any further suggestions?
 
Had a similar problem, bike would sputter until it died and wouldn't start until it cooled down again. For me, that was a simple fix...p/u coil. Agree with Riceburner....start with the simple things first. I am not a big believer in replacing parts until you get it right. Had a no start on my bike in the spring, took apart the starter button and cleaned the contacts...got lucky! Battery was dead too, took it to the shop and they said it was toast as it wouldn't hold a charge. Was able to bring it back to life and have not had a problem with it since. Good luck and keep the shiny side up!
 
Hey,

I have a parts bike so its easy to replace whatever I want with only my time being invested.

The bike does not die when its running and just runs a little hot unless standing still or in heavy traffic, that's when it overheats.
 
It's fuel injected,

How does timing advance effect hot starting, Any links to info on that?

Anything else it could be?
 
Do you happen to have the Factory Service Manual?
 
DJM said:
Do you happen to have the Factory Service Manual?
Click to expand...

Yes, I have the manual.
It says nothing about my issue that I have not tried. All my voltage readings are correct from stator to rectifier to battery to starter cold and hot.
I want to figure the starting problem first, as If I'm losing voltage when the engine is hot (not overheated, just warm) That may cause the overheating by slowing the cooling fans.
There is no air in the rad, I just flushed it to make sure.
 
The fans are kicking in at 105*c as they should and the thermostat is brand new.
 
On cars, I've seen starters that don't work when hot (just before they stopped working entirely). Can you get to the leads attached to the starter and apply 12V directly to the starter using jumper cables?

What about a clutch problem? Slipping clutch would make a ton of heat that would annoy the cooling and dragging clutch would upset the starter as the hot clutch expands and tightens up? Just a thought.

Edit:
Do you have a rear stand? try putting the bike in gear and turning it over using the rear tire when cold/hot (ignition off). See if the engine is harder to turn when hot, this may still be a mechanical problem.
 
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Grey Ghost Why would the motor be binding when warm? I have push started this bike more than a few times when it would not start and it did seem very hard to turn the engine over (get rear tire traction) when the bike is warm but I have never push started it cold so I cant really compare.
The starter is new and the old one was fine from what I can see anyway.
 
Voltage means **** all. It's all about current. Apply power directly to the starter when it refuses to crank, see if that makes any difference. If it does, than apply power to battery and try it.
 
krrakt said:
Grey Ghost Why would the motor be binding when warm? I have push started this bike more than a few times when it would not start and it did seem very hard to turn the engine over (get rear tire traction) when the bike is warm but I have never push started it cold so I cant really compare.
The starter is new and the old one was fine from what I can see anyway.
Click to expand...

I am far from a mechanic, so I can't help you much with the details. Obviously things expand when hot, this can create problems if tolerances were already tight.

Do you normally start the bike with the clutch lever pulled in? If not, try that when it's hot next time and see if it makes a difference.

When you are push starting, I find second gear much easier than first. I don't know if butt feel will be good enough to pick out the difference between hot and cold, there are lots of things happening while you are trying to push start, that's why I'd try and raise the rear wheel and spin the motor over by hand with the transmission in its highest gear (5 or 6).
 
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Check your starter motor itself.
 
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