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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: matjas on March 25, 2024, 05:38:43 AM
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Hi
decided to start a new thread in hope this could help someone in the future. my second to me brick was running hot from the very beginning and would jump to fan cooling after 15 seconds of standing in traffic , also when in the mountains the temp needle would be past the middle when going up and well below middle when going down and engine braking. Same would apply to riding in the rain - the needle would drop to 1/3rd of the scale immediately.
The bike was returning good fuel economy though - at constant 110-120kmh, with side tragkorbs, it would never take more than 5liters of 95Pb 5% ethanol laced fuel.
My diagnosis, based on some logical thinking, was that the thermostat in my brick is not closing fully. Many here said: 'they all do that'.
I never liked the fact it would go so around the scale /many here said: 'they all do that' :D/ so bought another radiator with fan and thermostat from some poor old brick that got dissected, and also a new toyota thermostat and boiled all three thermostats - they all opened at the same time and the opening size was the same. So I decided to leave my original thermostat on the shelf together with the toyota one and use the one from the boneyard radiator. BUT...
mind - when I was taking my old/original thermostat from my radiator I noticed the rubber strip gasket that runs around the perimeter of the thermostat base had been taken off the ridge of the thermostat on the assembly and maybe 3cms of the circumference is without the gasket - this was causing the leak between the small and big circuits!!!
and - it is virtually IMPOSSIBLE to fit that bestard back without compromising this gasket as upon seating in the nest it wants to go off - so is the design. Moreover if youre unaware of that you will not see this happening and will just fit the two screw plug on and there it is.
I used some superglue on the gasket all around and attached it firmly to the thermostat ridge so it sits where it needs to be now when inserted into the radiator.
My brick now is ROCK STEADY on the scale - with temps of 10-15C it is in 1/3rd of the first below middle field and stays there no matter how I am riding once it gets to the operating temperature.
OFC I will see how it goes in the heat of the summer and with varying ride temps but I am absolutely sure I would never reach this temparature on the scale before.
So - if yours is going all around the scale have a look - maybe this rubber strip has been twisted as had been mine. It is VERY easy to do it when just fitting the thermostat in.
Cheers.
matjas
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103123
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Good information. It is important to get the thermostat installed properly because one of it's functions is to close off the radiator bypass.
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Thanks for sharing.