500 Two-Stroke Tech

I drove my RD 500 with low RPM till 7000 at 4°C and the temperature was still 74-78 °C.
After I drove her them with 10 000rpm the temperature went not down, only the coolant fluid run out.
Looks like too much pressure inside the system.
No thermostat assembled.
Assembled is GP radiator. They say 10-15% more cooling power.

I changed the coolant filling part and assembled one from Aprilia. Also 0.9 bar. Refilled the radiator.
Same problem.
I removed the water pipe at the water pump and radiator. Only 600ml water came out.
Does anybody knows something like this?
In the manual is written from 1.95 litre, but I was only able to fill in 1,5litre.
Is in wrong written in the manual, or something wrong with my RD?
Or is based on the situation, that the lower cylinders are still filled with water?

3XV wrote:I drove my RD 500 with low RPM till 7000 at 4°C and the temperature was still 74-78 °C.
After I drove her them with 10 000rpm the temperature went not down, only the coolant fluid run out.
Looks like too much pressure inside the system.
No thermostat assembled.
Assembled is GP radiator. They say 10-15% more cooling power.

I changed the coolant filling part and assembled one from Aprilia. Also 0.9 bar. Refilled the radiator.
Same problem.
I removed the water pipe at the water pump and radiator. Only 600ml water came out.
Does anybody knows something like this?
In the manual is written from 1.95 litre, but I was only able to fill in 1,5litre.
Is in wrong written in the manual, or something wrong with my RD?
Or is based on the situation, that the lower cylinders are still filled with water?

Could be your water pump seal has gone. Check for coolant in the gearbox oil.

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Hm,
sound at the first view not so logic.

If the sealing ring is defect, the pressure in the cooling system should be less.

But the water is flowing out at high rpm from the drain hose of the reservoir.
The smaller reservoir what I use gets over flooded after 500m at 10 000 rpm.

I think more about a defect cylinder head sealing.
But I don´t like to disassemble the cylinder head, if it is not needed.

3XV wrote:Hm,
sound at the first view not so logic.

If the sealing ring is defect, the pressure in the cooling system should be less.

But the water is flowing out at high rpm from the drain hose of the reservoir.
The smaller reservoir what I use gets over flooded after 500m at 10 000 rpm.

I think more about a defect cylinder head sealing.
But I don´t like to disassemble the cylinder head, if it is not needed.

Yes. With that extra information, it does sound like a head gasket has blown.

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You can make a pressure test of the cooling system.

Apply some pressure to the system and wait - if the pressure drops you have a leak.
Check after the test if the crankcase is full of water (head gasket)

Thanks for the info,
but I do not have this tool.
And I´m also not a fan in filling my cylinder with water.

A manometer instead the radiator cap would be better to see, if overpressure will get produced.
I also do not have such a manometer.

So I need to remove the cylinder head.

But I´m still searching for somebody, who could give me the information about the water amount.

The cylinder head gasket is gone at the upper left cylinder.

Lucky me, no water in the cylinder.

That looks like a crappy aftermarket gasket set.
The OEM Yamaha head gasket is black and expensive but it works.