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Discussion Starter #1
Bike has been overheating. Seems to only happens after riding for a while or after riding hard. If I'm moving at a decent pace, it's fine. If I have to come to a stop and idle, the temp soars; I'm talking 240 plus and I've had it flash "hi."

Mods are slip on and bmc race filter.

Flushed the system and running Coolanol.
Just had the radiator acid cleaned and flushed, no leaks.
Fins are pretty straight and airflow is good. You can see through most of it.
Cap wasn't holding pressure so got a new one.
Changed the water pump.
Changed the thermostat last season.
Stock fan is working fine and no leaks anywhere in the system.
Got all the air burped out and it's holding a constant coolant level.

Wtf could it be? I'm at my whit's end with this issue.

Only thing I can think of is that the thermostat went bad again/ is faulty.
 

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Squid wannabe
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Well, i know this sounds stupid, but how is the oil?
 

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Thermostat failure, wrong or damaged spark plugs, or your bike is running lean from incorrect fuel pressure or some other issue.

When was the last time you changed your spark plugs, and did this problem appear when you installed your last set of spark plugs?

Do you have significant problems starting, like you have to try starting repeatedly before she starts, or you let her crank for several seconds before she starts?

You say you got all the air out, but did you double check the fluid level a day after you filled the radiator? There's always air trapped inside the cylinder head and it doesn't escape to the radiator until you've run the bike for a day.

Can you tell that the bike is running hot without looking at the temp reading, such as a noticeable drop in idle speed, odd running sounds or the frame gets uncomfortably hot?
 

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Discussion Starter #5
Hoses are connected correctly according to the service manual and the natural bends they have over time.
Oil is maybe a couple hundred miles old. Motul 300v and the level is fine.
 

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Discussion Starter #6
Thermostat failure, wrong or damaged spark plugs, or your bike is running lean from incorrect fuel pressure or some other issue.

When was the last time you changed your spark plugs, and did this problem appear when you installed your last set of spark plugs?

Do you have significant problems starting, like you have to try starting repeatedly before she starts, or you let her crank for several seconds before she starts?

You say you got all the air out, but did you double check the fluid level a day after you filled the radiator? There's always air trapped inside the cylinder head and it doesn't escape to the radiator until you've run the bike for a day.

Can you tell that the bike is running hot without looking at the temp reading, such as a noticeable drop in idle speed, odd running sounds or the frame gets uncomfortably hot?
Spark plugs were done last season and caused no problem.
The bike feels and rides fine, not like there is a fuel issue. It's starts up immediately. It is normal in every aspect, except it overheats when idling.
I've been through this before, and I know that running lean can make you run hot. This is NOT the problem. You're not going to overheat like crazy from being lean with a slip-on and air filter.
Yes, it actually is hot. The frame and ambient air near the motor get very hot.
When I say I got the air out, I mean over the course of three days riding to and from work, I had to add about a half a bottle to keep the level up. You could see air bubbles when it warmed up in the overflow reservoir.
On that note, when it gets up in the 220s to 240s, the fluid in the reservoir expands and looks like it boiling.
The idle doesn't change.

That being said, I think I have to bite the bullet and take out the thermostat and check it. I was trying to delay having to do that by seeing if anyone had any ideas.
It seems to me that the system is pretty straight forward. Radiator, coolant, hoses, thermostat, water pump. It has to be one of these components, and I've checked every one except the thermostat. I just can't believe it went bad in less than a year. It worked fine for a while after I changed it.

Thanks everyone. Let me know if you think of anything else.
 

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.......I had to add about a half a bottle to keep the level up. You could see air bubbles when it warmed up in the overflow reservoir.
On that note, when it gets up in the 220s to 240s, the fluid in the reservoir expands and looks like it boiling.
At this stage my bet is a bad cylinder head gasket. Sounds like it's leaking compresion towards the coolant circuit, thus heating it up and introducing air/gases into it which come out from the system as the bubbles you see at the coolant reservoir.
Another strong indication of an over presurized system due to compression leakage is that the radiator hoses expand and look like inflated.
 

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Discussion Starter #9
At this stage my bet is a bad cylinder head gasket. Sounds like it's leaking compresion towards the coolant circuit, thus heating it up and introducing air/gases into it which come out from the system as the bubbles you see at the coolant reservoir.
Another strong indication of an over presurized system due to compression leakage is that the radiator hoses expand and look like inflated.
Good info. I'll check the thermostat, and if it's ok I'll go this route.
 

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Discussion Starter #10
Just wanna close this thread.

Got the word from the shop that the motor is shot. Little to no compression and intermittent spark.

I ended up replacing the head gasket, but then couldn't get the bastard to start. Also had an issue with the clutch that never got sorted out; oh well.

Anyway, I will be parting everything out. Can't wait to buy a gen 4!
 

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when you say little to no compression did the bike start to feel funny? reason I ask is my gen 4 is doing the exact same thing coolant overflow tank fills with coolant and bubbles, yet the bike runs fine but extremely hot.

fan runs fine and kicks in at 95c
coolant moves fine through the system
cap pressure is fine

all started happening around the time I removed the front intake solenoid.

Soo hoping the engine isn't toast spent way to much on this bike for it to fail
 
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