I can't solve overheating with modified busa. Help please

B

BoldPilot

Registered
Hi guys.
I have 2015 hayabusa with big bore kit. 84mm pistons with nikasil gen1 cylinder. I have cometic head gasket but i took off center layer of gasket for more compression. I using evans powersports r coolant and i m using motul 300v 10w-40 oil. When i hang around with low compression, low speeds, my Bike is super cool but when i start hitting gas it has no problem too but after then if i slow down little bit my Bike getting overheated and press the water from radiator to the water tank. I checked waterpump, it is perfect. I checked my thermostat and it was bended as open. Now i take off the thermostat. Will my problem fix? What is my problem? How can is fix overheating?

20230522_181409.jpg
 
RacingJake said:
The problem might be the thermostat being stuck open allowing coolant to flow too fast through the radiator and cannot cool fast enough.
I'd put a new thermostat in it and try it again.
Click to expand...
Good point, but that thermostat in the picture is damaged, looks like someone has bent it over to make it wide open permanently.
Bad move.
@BoldPilot
Welcome to the oRg.
First up, is the radiator cap faulty and bypassing coolant at a low pressure? That will lower the boiling point to 100degC
(with 15psi pressure in the system the boiling point is raised to 115degC or thereabouts.)
Is the plastic coolant bottle/tank filling up? this is evidence that the cap is bypassing the coolant and the coolant expansion is evidence of high temperature coolant.
If you don't have the equipment to test the rad cap, just buy a new one and go from there . . .
Go ahead and fit a new OEM suzuki thermostat back into the housing, then bleed the air from the cooling system.
Then let the engine idle a while until it gets up to temperature, high enough to switch the fan on (100degC). If the fan is NOT running at that temp, you need to find out why it won't switch on.
Unplugged?
Faulty thermo-switch in radiator?
fan blades obstructed?
Fan motor burnt out?
Bad wiring and connections burnt?
Bad ground wiring?
If the fan IS working normally, then check for a blocked or partially blocked radiator core.
If the core is flowing well, then fit a second fan and check for sufficient cooling.
If still overheating, maybe even fit a LARGER radiator?
If all these things don't fix the problem, then perhaps the cylinders are too close together after being bored out, and the heat dissapation is not enough anymore.
There is so many parts and requirements for an engine to cool sufficiently and there is a specific order of priorities to check it to make an accurate diagnosis of the fault.
 
Last edited:
greg3852 said:
Is your fan working? Do you have two fans? How about moving the whatchamacallit to the other side of the bike. Forgot the name of it. You can buy the lower thermostat thing so the fan comes in early too. Don’t mind me I don’t remember much.
Click to expand...

greg3852 said:
Is your fan working? Do you have two fans? How about moving the whatchamacallit to the other side of the bike. Forgot the name of it. You can buy the lower thermostat thing so the fan comes in early too. Don’t mind me I don’t remember much.
Click to expand...
Fans are working with no problem
 
Kiwi Rider said:
Good point, but that thermostat in the picture is damaged, looks like someone has bent it over to make it wide open permanently.
Bad move.
@BoldPilot
Welcome to the oRg.
First up, is the radiator cap faulty and bypassing coolant at a low pressure? That will lower the boiling point to 100degC
(with 15psi pressure in the system the boiling point is raised to 115degC or thereabouts.)
Is the plastic coolant bottle/tank filling up? this is evidence that the cap is bypassing the coolant and the coolant expansion is evidence of high temperature coolant.
If you don't have the equipment to test the rad cap, just buy a new one and go from there . . .
Go ahead and fit a new OEM suzuki thermostat back into the housing, then bleed the air from the cooling system.
Then let the engine idle a while until it gets up to temperature, high enough to switch the fan on (100degC). If the fan is NOT running at that temp, you need to find out why it won't switch on.
Unplugged?
Faulty thermo-switch in radiator?
fan blades obstructed?
Fan motor burnt out?
Bad wiring and connections burnt?
Bad ground wiring?
If the fan IS working normally, then check for a blocked or partially blocked radiator core.
If the core is flowing well, then fit a second fan and check for sufficient cooling.
If still overheating, maybe even fit a LARGER radiator?
If all these things don't fix the problem, then perhaps the cylinders are too close together after being bored out, and the heat dissapation is not enough anymore.
There is so many parts and requirements for an engine to cool sufficiently and there is a specific order of priorities to check it to make an accurate diagnosis of the fault.
Click to expand...
Fans are working with no problem. I complately took off the thermostat. I dont think that my radiator cap is broken but i Will test it
 
RacingJake said:
The problem might be the thermostat being stuck open allowing coolant to flow too fast through the radiator and cannot cool fast enough.
I'd put a new thermostat in it and try it again.
Click to expand...
Yes maybe. I hope that it is the problem. I took off the thermostat complately.
 
Dnyce said:
Big bores run hot, what’s the temp?. Let’s say it’s not mechanical.

Make sure there’s no air bubbles

Add a second fan on a switch, assuming the current fan does work.

To Jen the tune a bit

Add a high volume oil pump gear

Put a .043 head gasket in it
Click to expand...
There is no bubbles, fans are working well, i have high volume oil pump gear too. I like this compression rate because my Bike is so powerful right now. I dont want to put original gasket on it.
 
BoldPilot said:
(...) but after then if i slow down little bit my Bike getting overheated and press the water from radiator to the water tank.
Click to expand...

little tutoring in physics necessary ? :lol:
seems so, so .....
what does water when getting hot ? :rolleyes:

yesssssssssssss - it expands :shocked:

and by that the waterlevel in the expand tank rises a bit
usually 2 fingers (2 inches / 5 cm) high

so watchable at all at gen1s (and i suppose at gen2s too)

so if the level stops at a hight of 2-2.5 fingers higher than cool (full-level-mark) , that is absolutely normal - don´t worry - no danger in sight .

only if the level goes way over 2.5 fingers higher over full-level-mark
and perhaps along with bubbles in the tank
your head gasket is through and needs to be renewed / changed , means way over 14-16 h of work . (engine needs to be pulled)

______________________________

if bubbles in tank
my hint is to go back to standard bore size (81mm) and standard gasket
the big bore always causes issues - sometimes more , sometimes less .
for use of a turbo or compressor the big bore is pure nonsense !! - so my own experiances .
the meat between 2 cylinders is then soooooo small . that the head gasket is always a very high risk of blowing through, especially at these 3 points (wall of the cylinder 1 to 2, 2 to 3 and 3 to 4) .

next step , after blown through , the piston will scratch the cyl.-walls hard and the block is just scrap .

a new 81mm gen2 block incl. standard pistons with low milage (30-40000 km) can be bought - preowned ;) - for around 350-500 euro (at german ebay) + new head and new foot gaskets in sum ca. 120 € (euro)

then for more acceleration get a bigger rear sprocket (2-3 teeth more) and the engine will last (nearly) forever.
 
Hayabusa Wannabe said:
Welcome to the forum @BoldPilot.
Click to expand...
Thank you so much!
Berlin Germany said:
little tutoring in physics necessary ? :lol:
seems so, so .....
what does water when getting hot ? :rolleyes:

yesssssssssssss - it expands :shocked:

and by that the waterlevel in the expand tank rises a bit
usually 2 fingers (2 inches / 5 cm) high

so watchable at all at gen1s (and i suppose at gen2s too)

so if the level stops at a hight of 2-2.5 fingers higher than cool (full-level-mark) , that is absolutely normal - don´t worry - no danger in sight .

only if the level goes way over 2.5 fingers higher over full-level-mark
and perhaps along with bubbles in the tank
your head gasket is through and needs to be renewed / changed , means way over 14-16 h of work . (engine needs to be pulled)

______________________________

if bubbles in tank
my hint is to go back to standard bore size (81mm) and standard gasket
the big bore always causes issues - sometimes more , sometimes less .
for use of a turbo or compressor the big bore is pure nonsense !! - so my own experiances .
the meat between 2 cylinders is then soooooo small . that the head gasket is always a very high risk of blowing through, especially at these 3 points (wall of the cylinder 1 to 2, 2 to 3 and 3 to 4) .

next step , after blown through , the piston will scratch the cyl.-walls hard and the block is just scrap .

a new 81mm gen2 block incl. standard pistons with low milage (30-40000 km) can be bought - preowned ;) - for around 350-500 euro (at german ebay) + new head and new foot gaskets in sum ca. 120 € (euro)

then for more acceleration get a bigger rear sprocket (2-3 teeth more) and the engine will last (nearly) forever.
Click to expand...
Is there a solution with using in this setup with no problem?
 
What is the day time temperature where you are?

Depending on where you live, the last time I was in Turkey it was hot, hot enough for a highly modified engine like that to struggle to keep at temperature.....

Do you have any friends who own stock Hayabusas? Perhaps you can ask them if their stock bikes are running hot, it might just be the nature of the beast that was created......

@Kiwi Rider and @Berlin Germany are generally right on with their advice......
 
I daily ride my 1441 Gen 2 Busa. I've got wossner 13.5 Pistons, yoshimura cams, stock head gasket and base gasket, with light porting. I kept the oil cooler and the standard radiator setup. I could park in traffic, I can ride it fast, I can write it slow, and I have no problems with heat. It will start hot or cold doesn't matter.

I only had to get hot one time right after I built the engine and it was because I had air in the system. I had to warm up the engine a little bit, and loosen the screw on the radiator hose elbow going into the head. Some air came out and then a little bit of water and I tighten it up.

One important step is I tuned it by data logging it for about 20 rides and I have the air fuel ratio looking pretty good everywhere. Perhaps if I had it idling lean it might run hot I don't know.
 
Bumblebee said:
What is the day time temperature where you are?

Depending on where you live, the last time I was in Turkey it was hot, hot enough for a highly modified engine like that to struggle to keep at temperature.....

Do you have any friends who own stock Hayabusas? Perhaps you can ask them if their stock bikes are running hot, it might just be the nature of the beast that was created......

@Kiwi Rider and @Berlin Germany are generally right on with their advice......
Click to expand...
Normal day time temperature is about 25-35 °C in summer
 
Busa Quick said:
I daily ride my 1441 Gen 2 Busa. I've got wossner 13.5 Pistons, yoshimura cams, stock head gasket and base gasket, with light porting. I kept the oil cooler and the standard radiator setup. I could park in traffic, I can ride it fast, I can write it slow, and I have no problems with heat. It will start hot or cold doesn't matter.

I only had to get hot one time right after I built the engine and it was because I had air in the system. I had to warm up the engine a little bit, and loosen the screw on the radiator hose elbow going into the head. Some air came out and then a little bit of water and I tighten it up.

One important step is I tuned it by data logging it for about 20 rides and I have the air fuel ratio looking pretty good everywhere. Perhaps if I had it idling lean it might run hot I don't know.
Click to expand...
What is my problem ? I have same kit like you. Same kit same same cams everything same. I have only 1 difference, i took off center layer of head gasket. For 13.83 compression.
 
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