125sm radiator leak + overheating

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brought my bike in for fluids maintenance and general check up.
was told that radiator was almost empty and that cap might need replacing soon.

on the way home got sprayed with radiator fluid. found out that the hose that loops through the frame connecting left to right got torn, possibly due to over tightened clamp.
replaced the hose, replaced the clamps, topped off the coolant. notice that some coolant shows between the fins on the right radiator. i'm guessing a leak somewhere.
took it for a spin and 10 minutes into riding the overheat light came on. limped back home. cooled down, check the coolant level. its still full. definitely leaks somewhere slowly though.

why would it over heat if the coolant is still at the full level?
the shop mechanic said he went over the whole cooling system and there were no issues other than it needed to be flushed out several times.
cap turned out ok as well, the rubber spacer was either not put on correctly or slid off during cap removal.

is the leak causing some suction problems?
anyway to fix the leak without replacing the whole radiator?

[DAVID THOMPSON]

you may have had a big air bubble some where in the system after a fresh fill up of fluid..
that will make one get hot ....
run it some short trips and see if it works out
and an old timers stop leak is
fine powered ginger
yes the kind you use to flavor chicken
and other stuff when cooking
just a pinch but not till your sure its leaking
it comes out the small hole and dries hard when it hits the air


dave

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this sounds encouraging. thanks David.

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so it doesn't look like the radiator is leaking at all. the coolant i found between the fins on the grille were probably there from a spill and were really taking their time evaporating.
i took the bike out 3 times so far, and each time about 10 minutes into riding the light goes on.
both times it happened as i was switching into 5th gear. 1st time when i downshifted again the light went off.
other times it stayed on. these were trial runs so i was always within 2 minutes of home.

i'm at a loss what to suspect next.

thoughts?

[TSiarz]

are you sure it's over heating?
it may be some electrical fault

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i am fairly certain that its over heating. the right fender gets hotter than before, even in these cooler temperatures. my knee actually feels the heat difference.
also once i stop the engine the fan blows like crazy for good 10 minutes before the overheat light goes out. also, when i open the cap there is usually some coolant in the reservoir suggesting that it probably boils in there.

[basser23]

possible water pump...check to see if there is flow...not sure about the 125,on the 660 there is a drain screw,see if ya have coolant to the pump.if there is a air pocket,this can cause this to happen cause no coolant can flow

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i've laid the bike on the side pegs hoping that if there is any air bubble, it would move.
how noticeable should the swirling of the coolant be to indicate a working water pump?
is it supposed to start and run with the engine or is there some simes pattern to its operation?
i opened the cap and started the engine. as far as i can see the coolant stays still.

[DAVID THOMPSON]

there is a gear that drives it behind the right side case behind and below the oil filter
drain oil required to see if it still has teeth and turns
dave

pictures in shop manual do not show much
i have a motor that is partly apart and can take some pictures if needed

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ok i believe the pump is working. with the radiator cap open, i started the bike and revved the throttle. i saw movement, and at higher rpms i even got some of it spitting out. suction is definitely there.
so the question remains whats behind the over heating?


while the bike was on the side (trying to get the air bubble out) i looked over the hoses closer and came across this one with a crack on it.

[DAVID THOMPSON]

think that's the crankcase breather to air box venting

fix that before you blow oil all over the place
its not much oil but will gets messy if left undone
dave

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could that have any play with the overheating light?
i checked the oil level and its perfectly up after the recent change.

[DAVID THOMPSON]

take a different temp reading device and see what the water temp is running
you may have a defective temp sensor
dave

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thanks dave.

i dont think its a faulty temp sensor because the coolant starts to boil out of the vent tube as well.
i was never able to figure out the issue, so i just kept on starting it every couple of weekends, running it till it get hot again to prevent carb clogging.

last weekend i noticed a crack on the hose that goes from the air filter box to the engine.
could this some how cause overheating?

i plan to replace the hose as soon as i find the right size, but in the meantime i was thinking of sealing the crack using this tape.
http://www.amazon.com/F4-Tape-Self-fusi ... _pr_sims_i

thoughts?