Another Overheat Mystery

Crow

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Anyone able to shed some light on this one as it’s doing my head in? :D

Stock 1999 Busa with 4/1 exhaust system, was running fine until I took it off the road 3 years ago.

Have just put it back on the road: whole new front braking system and I’ve binned the PAIR, capped the pipes and ports.

Didn’t burp the cooling system when I put the rad back on, so it overheated a mile from home on a test ride.

Got called a fair few names, told to burp it. Burped it, filled rad and reservoir (latter to half way between L and F). Rocked bike, squeezed pipes a few times, saw bubbles, topped up. Let stand, topped up (50/50 water / concentrate).

Went for a spin, seemed better. 5 miles later I pulled up at some lights and the temp needle started rising fast, straight into red. Killed engine, but it kept rising until the temp warning light came on.

Shat myself, let cool, limped home. Get back and the reservoir is bubbling like a volcano, spewed coolant all over, emptied bottle.

Noticed that fan doesn’t come on until the temp needle hits red, so installed a manual switch. Went out for 5 miles with the fan on constantly and, as soon as I got back and killed the engine, the reservoir starts bubbling and pukes half of the bottle.

Went out today, refilled system and left rad cap off, then fired it up. Within 5 mins the temp was at 2/3. Killed engine, let sit for 30 mins, turned on power and temp needle immediately goes into red without starting engine.

Left it an hour, came back, needle did the same, fires it up, needle dropped, then after 10 mins it overheats and the reservoir is bubbling like a witch’s cauldron.

The rad cap is blistered, it has been ever since I got it, see pic, but is this sufficient to cause the problems I’m seeing?

Have I missed something after the PAIR valve mod?

CDBBA35A-2252-495C-97BD-01FCE6ADFE4A.jpeg
 
Nah, didn’t think so.

Replaced the cap, bled system and, although it’s not boiling the bottle any more (step forward), it’s still overheating.

Fired it up, ran it for 10 mins on advanced tickover (2,000RPM) and it went straight into the red.

Interestingly, I noticed that the wires for the fan switch I had installed were getting red hot.

Any ideas guys?
 
Have you removed your thermostat completely to test its opening, or ran without it completely? also red hot wires? sounds like you have a short somewhere
 
No, I’ve not removed the thermostat yet, that’s the next job. First off I’m going to perform a proper flush of the coolant system and refresh everything, then do an oil change (just for the hell of it).

Then the thermostat is coming out.

Think you’re right about the wiring short, going to have to trace that.

And thanks for your reply btw, apart from sixpack and one or two others who have been really helpful, I had just about given up on getting any serious advice from here.
 
"First off I’m going to perform a proper flush of the coolant system and refresh everything, then do an oil change (just for the hell of it)."
To be able to flush the system, the thermostat MUST come out FIRST.
The thermostat is the FIRST thing to look at/replace.
When a thermostat is overheated (in this case due to NOT bleeding the air from the system BEFORE you went for a ride) it is virtually guaranteed to be damaged, in this instance it will be jammed shut, causing no flow/no cooling and the symptoms you have described.
Now, when you "burp" the system AFTER replacing the thermostat, if you see a constant stream of bubble coming up to the top of the radiator, either the head gasket is damaged and leaking combustion gases into the coolant, OR, the cyl head is no longer flat and/or cracked from overheating.
There is other possibilties to look at.
These are unlikely, but must be checked before assuming the cyl head gasket or head is damaged.
1)Make sure the water pump is working and the coolant has adequate flow.
2)Be sure the radiator has full flow also, any blockage there will cause over heating also.
3) Check the Thermoswitch in the radiator for correct operation
4)Check the fan motor is working by powering it up directly from a 12v source.

I hope this helps, and I hope your motor is still ok.
 
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Thanks man.

TBH that is my concern, that the head is damaged and this is going to become a money pit.

I’ve got the thermostat out, going to test it tonight.
 
Thanks man.

TBH that is my concern, that the head is damaged and this is going to become a money pit.


I’ve got the thermostat out, going to test it tonight.
Is the thermostat open or closed?
When you test it be sure to have a temp gauge in the pot and bring the temp up slowly taking note of the opening temp... That is if it opens at all.
If it's wide open when cold, you most likely have a damaged head or blown head gasket ... Or both.
Good luck mate, let us know the outcome!
 
Have you removed your thermostat completely to test its opening, or ran without it completely? also red hot wires? sounds like you have a short somewhere
The wires to the switch you put in that are getting hot may be too light to carry the current load, those fans draw a lot of current.
 
Bad news. I don’t have a thermometer, so can’t take a precise reading, but I put the thermostat in a pot and began bringing to boil. It opens and closes freely.

Tomorrow I will go get a thermometer and take the numbers, but things aren’t looking good here...
 
Bad news. I don’t have a thermometer, so can’t take a precise reading, but I put the thermostat in a pot and began bringing to boil. It opens and closes freely.

Tomorrow I will go get a thermometer and take the numbers, but things aren’t looking good here...
Don't worry, just put a good thermostat back in the system and try again to bleed the air out, or even no thermostat at all, then see how fast the temp rises, if head is damaged or gasket blown it will rise fast, you'll then know for sure.
 
I'd also get the fan issue taken care of. At 2000 rpm with no air moving across the radiator it will get hot.

How hot, how quickly?

I’m now about 90% certain that my bike is dead, but am still groping around for any hope...

The problem I have is that I can’t risk taking it too far in case it overheats and leaves me stranded, so I’ve just been testing it on tickover (advanced, 2000RPM).

Standing still, the temp steadily rises into the red after 10 mins, then the overheat light will come on if left another minute. The fan isn’t working (I’ll rewire that later), but still...

Can I ask, if you left yours standing, how quickly does the temp rise? At what point on the temp gauge does your fan kick in?

Really appreciate you guys’ time and advice here. A month ago I was all excited about getting my bike back on the road and being up in the mountains on it. Now I’m starting to feel despair :(
 
Thanks for the idea, but being based in the U.K., postage would be prohibitive and any problems would be a nightmare to resolve.

Without advertising anyone here, I do perhaps have one hope. Bought a fan off a guy in Goole through eBay, he breaks Hayabusas. First time I spoke to him, he listened to my problems, called another engineer he knows, called me back, offered advice and then (when I suggested replacing radiator) says, “If yours isn’t leaking, then I doubt it’s that. I’ve just broken 5 g1 Hayabusas, but don’t want to sell you anything you don’t need. Let me know what parts you suspect and I’ll lend them to you. If they fix your problem, you can buy them. If not, send them back. No charge.”

I’ve only spoken to this guy once, he charged me £10 for a fan and wanted £50 for a rad, “But it really is a bit poop. It would do the job though.”, so he’s not going to suddenly shaft anyone on price.

I’ve got a feeling I’m going to be calling this guy back, but I still bet I’m looking at £1,000 for the full rebuild. Not sure I’d trust myself to do it myself.
 
Thanks for the idea, but being based in the U.K., postage would be prohibitive and any problems would be a nightmare to resolve.

Without advertising anyone here, I do perhaps have one hope. Bought a fan off a guy in Goole through eBay, he breaks Hayabusas. First time I spoke to him, he listened to my problems, called another engineer he knows, called me back, offered advice and then (when I suggested replacing radiator) says, “If yours isn’t leaking, then I doubt it’s that. I’ve just broken 5 g1 Hayabusas, but don’t want to sell you anything you don’t need. Let me know what parts you suspect and I’ll lend them to you. If they fix your problem, you can buy them. If not, send them back. No charge.”

I’ve only spoken to this guy once, he charged me £10 for a fan and wanted £50 for a rad, “But it really is a bit poop. It would do the job though.”, so he’s not going to suddenly shaft anyone on price.

I’ve got a feeling I’m going to be calling this guy back, but I still bet I’m looking at £1,000 for the full rebuild. Not sure I’d trust myself to do it myself.
u could take the head off... see the damage... u might get lucky.... and a ported head and some decent cams is a GREAT upgrade..... if u need a new head anyhow
 
Standing still, the temp steadily rises into the red after 10 mins, then the overheat light will come on if left another minute. The fan isn’t working (I’ll rewire that later), but still...
If I started my Hayabusa on a warm day and let it idle at 1200 rpm the fans would turn on after 7-8 minutes.
 
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