Triumph Sprint ST 955i Overheating Problem

[noobRider]

Can't seem to get to the bottom of this. Advice welcome.

Months ago I had a low speed off and my radiator got a tiny crack. I got it repaired but ever since the bike has run hotter and gets very hot if you work it hard and then leave it standing or riding slowly. I have ridden it with the needle well into the red before I got it home. I have been topping it up with water over the summer, so it was losing water: I guess some was boiling and the crack had started leaking again.

It's now got a replacement radiator, which took ages to fill, because the coolant doesn't seem to want to get across it because the inflow and outflow are on the same sides.

It hasn't made any difference. The bike still runs hot. The fan comes on and cools the radiator but the engine stays hot, even though coolant is being pumped around. The water pump seems OK. When you open the drain plug at the bottom of the engine the coolant comes out so it doesn't look like there is an airlock. Thermostat fitted or not doesn't make any difference. The engine itself sounds fine and the bike rides fine. It's just not cooling properly.

Edit: Everything is standard on the bike. No while smoke from the exhaust. I think the head gasket is fine. No leaks.

Anyone got any ideas?
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Licence: Nov 2012, Bikes: Suzuki GN125, Moto Guzzi Strada 750, Triumph Sprint ST 955i x 2
AnPhonEh: I need plans, I need contingency plans also, I need back up contingency plans

[jaffa90]

Is it the correct radiator?
Is the coolant mixture 50/50 (distilled water)?
Is there more than one bleed screw?
Have you tried warming the engine up with the rad cap off and topped up until full?
Did you change the air filter, engine oil or fuel type after the off?

[noobRider]

[Polarbear]

From your description, presuming the new radiator is compatible there can be really only 2 things that could cause this. Air locking or water pump issues. I'd want a laser temp gun on the radiator inlet and outlet to tell me what the coolant is doing because I think it is a flow problem.

I take it there was no problem before the off and it was never right after that happened, with either radiator
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[Robby]

The radiator being slow to fill sounds odd. I would also suspect a flow problem.

Quick and dirty test is to take it off the bike and run a garden hose through it. If the water flow through nice and quick, no problem. If it's only dribbling out one end, you have a blockage.

[jaffa90]

Did the exhaust get damaged after the off?
If not and for piece of mind take it to a tuning specialist and check for a weak mixture or gas analyzer.

[Ariel Badger]

The problem started after the crash not after the rad change. This means that the problem is not the rad. Does the bike have a thermostatic valve, is the pump working, is the fan cutting in?
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[noobRider]

[temeluchus]

Diet coke is great for breaking up blockages.
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[Snowdonia Rider]

Faulty sensor?
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[Polarbear]

[noobRider]