When I bought it, I didn't know it would get that hot. I changed the coolant, but the problem remained. Even riding on regular roads it gets near to red temp area.
Today I went to the forest and it was quite muddy and rough and after every 200 meters the temperature was on red again. My friend who has a DT, didn't have such a problem, his temp barely reached over half the green area.
Engine was obviously overheated and radiator/cap were hot as hell.
What should I check in the coolant system in order to discover/fix this pain-in-the-ass problem, planning to go on some offroading next weekend.
it may be the thermostat,water pump,water pump gasket failing that it could be the head gasket is the fluid level dropping ?,you dont want to be running it that hot or it will heat sieze
check the gearbox window for the oil level and see if the oil looks like hair conditioner?
-- Edited by bykerbaz on Monday 1st of June 2009 07:32:27 AM
I unscrewed the top of the water pump (plastic circling thingy under there, am I right lol) , and it was clean and moving well. Also the gasket there seemed to be fine and not leaking.
Where is the thermostat located?
Is it possible that the head gasket is causing this problem, even without major loss of fluid?
When I run my bike, it makes a weird noise in the radiator area, like shhhhing. But I think it's from the heat, cause coolant seems to be getting really hot.
I wont ride it until I fix that problem.
*Edit: I just ran it for only 10 minutes and cylinder and powervalve got very hot for such a small amount of time. I opened the radiator cap while running cold and the fluid level was the same, also it was not bubbling or jumping out of the radiator.
-- Edited by marko727 on Monday 1st of June 2009 02:08:55 PM
the thermostat sits on top of the head,just follow the big top hose from the radiator to the head the thermostat is located underneath where this hose goes on to if i remember right there are 3 screws to undo to get to it
if the thermostat isnt opening it would cause the problem you are having
if you take the metal thermostat out (it looks a bit like a flying saucer) and dip it into some boiling water in a jug them watch to see if it opens up,if it dosnt then its knackard
if all is well on the thermostat then take the top and bottom hose off the radiator and stick a hose pipe in one of the open ends and turn it on this will clear out any ****e that may be blocking the system
also check the fins on your radiator that they are not clogged up with mud and debris which would cause the air not to pass through
do the thermostat first though m8 from what youve just said i would put my money on it being the culprit
Alright, I took the thermostat out. 3 screws held the top (am I right?) of thermostat. I boiled some water, dipped the thermostat into the water and it opened a bit on the top.
There was also coolant underneath the thermostat when I took it out, so I'm guessing that can't be the problem?
Coolant also reaches the water pump because when I unscrewed the top of the waterpump, some coolant got out from there.
The back of the radiator isn't in a good shape, the lower part. Imma add photograph later.
I tried to run it before and watched what happened. First the cylinder got hot, then the radiator as well. Also the radiator started steaming a bit, maybe from the colder air surrounding it.
What else can I do to fix the cooling system?
Edit*Should I put back the thermostat or try to run without it?
-- Edited by marko727 on Tuesday 2nd of June 2009 01:56:39 PM
Another update. I ran the bike without the thermostat and with the thermostat and there was basically no difference, it got hot in less than 10 minutes. I'm pretty sure the water pump is fine.
That leaves me with what..? I'm getting desperate :/
I understand it's difficult. Water pump is a plastic circling thingy (with a top on it) on the kickstarter side, I really couldn't miss it lol.
I ran it when standing still. But I think it shouldn't get so hot in few minutes, I mean it was quarter past half the green area in 7-8 minutes.
As I said before, radiator seems to be a bit damaged on the back side. Lower part of fins are a bit bent, like it has been washed with pressurized water. Front part of radiator seems fine.
Imma ask the obvious questions then.. how much costs the head gasket and how much costs the radiator? Coolant SEEMS to be circling the bike, I dont know why it gets so hot. Damn! lol.
i sell a full gasket kit in my shop for 20 pounds which has all the gaskets needed to rebuild the head and bottom end
i also have a used radiator if your interested i will have to check the condition of it as i havent seen it for a while and i can take a picture if you want me to
Sounds like what it was doing on my bike. The head gasket was leaking badly and water was just pouring into the cylinder lol. Changed that and it was fine.
Are you absolutely sure that it is overheating? A 125 engine does get very very hot to touch when its been running. If the water pump is running fine and you have no thermostat fitted it is virtually impossible to overheat. Does it blow any steam out of the header tank? Losing any water? Do not rely on the temp gauge as the gauge can be faulty or the temp sender in the head is faulty
Are you absolutely sure that it is overheating? A 125 engine does get very very hot to touch when its been running. If the water pump is running fine and you have no thermostat fitted it is virtually impossible to overheat. Does it blow any steam out of the header tank? Losing any water? Do not rely on the temp gauge as the gauge can be faulty or the temp sender in the head is faulty
I compared my bike to my friend's, who has the same model. We ran our bikes for like 10 minutes, his temp gauge was barely on quarter, mine was quarter past half. I carefully touched the cylinder heads, radiators and mine were CLEARLY hotter (I know the real cooling starts when driving, but this was just a little test). I will open the cylinder head this weekend, it makes a strange noise in that area (like "shhhhing", I wanna know what's going on there - could it be the head gasket? I've been thinking of buying a new one, I don't know what else to check anymore). After finding out my thermostat was ok, I put it back, cause it was working.
Yes, the radiator is steaming when I drive it a bit, and then stop. But then again, so does my friend's. And no, I don't seem to be losing any coolant.
And I am sure it gets too hot, after driving a short while, I cannot touch the radiator cap, because it's insanely hot. When it's a bit warmer weather, it sits on the line of overheating if not driven fast enough to cool it down a bit.
Maybe there's an air gap somewhere in the cooling system? Is it possible to vent it? Maybe there's some dirt inside the cooling system? Head gasket? I don't even know where to start anymore, lol.
I don't wanna take it to Yamaha, they will charge me to death with their insane prices. (aka new radiator = 735 Euros)
But if water was getting into the top end your bike wouldnt run at all as water cant be compressed so im not convinced its the gasket either as this happened to me once ad it wouldnt start at all.
What are the other options then? I'm rather suspicious though, cylinder makes a weird SHHHHHING noise, like air or coolant or something is getting near it. Today was quite a cold evening and my bike still got hot, fast. Imma update what head gasket change will bring me soon.
Another thing, when I was topping up coolant, I remember I CLEARLY filled the expansion tank to maximum. Today I installed all the new bearings and I discovered the expansion tank was just filled at about minimum level. This must be the head gasket.
I have tried my friend's radiator cap (same model), but it was not the problem. On Saturday I ordered a new head gasket from Yamaha, it'll arrive on Thursday. Then I'll open the cylinder head and see what's going on.
I'm fawked, damnit. Changed the head gasket AND found out the real reason.. at least I think I did. Piston has two little broken pieces out of it at the side, on top of the piston.. how could I put it, there's like a melted little convexity on top, with a diameter of like 5 millimetres, few millimetres deep. Which is weird, cause my bike moves very well and doesn't show any signs of flaws. I don't know what the hell did my bike went through with its last owner. Soon I'll give it a new heart and hope it'll be fixed. I wont ride it till I fix, just to preserve the cylinder, it costs like 500 Euros. Thanks for all the help guys, I really appreciate it.
