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Overheating Yamaha dt125r

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Rjgk2012
Two Stroke Sniffer



Joined: 17 May 2020
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PostPosted: 14:00 - 31 Jul 2020    Post subject: Overheating Yamaha dt125r Reply with quote
Hi guys, I just bought a 2003 Yamaha dt125r and it is great fun but I've noticed that after about 2 minutes of riding the temperature gauge starts to touch the red line and stays there, but it rarely enters the red. I changed the coolant and the stuff that came out looked grey, I'll attach a photo. I found a small but of silicone in there which is presumably from a DIY gasket. The coolant level doesn't seem to get lower with time. The cylinder gets very hot whereas the radiator stays cool enough to touch but still quite hot. This is my first liquid cooled bike but after a bit of research I'm thinking it's the thermostat? Please let me know what you think the issue is and what I should do. Thanks.
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droog
Spanner Monkey



Joined: 03 Dec 2019
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PostPosted: 14:40 - 31 Jul 2020    Post subject: Reply with quote
Assuming coolant levels are correct and there is no leakage in the system:

From your description tt could be the thermostat - it could also be an airlock in the cooling system.

Before you test the thermostat I would eliminate the possibility of an airlock by removing the rad cap and giving the bike a few blips of the throttle to circulate the coolant and remove any potential trapped air in the system.

If this does not fix it then testing the thermostat is your next option.
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Robby
Dirty Old Man



Joined: 16 May 2002
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PostPosted: 14:49 - 31 Jul 2020    Post subject: Reply with quote
Seeing as you found a bit of silicon, I would checking the water pump and rad for more of it blocking something.
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redeem ouzzer
World Chat Champion



Joined: 06 Oct 2015
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PostPosted: 14:52 - 31 Jul 2020    Post subject: Reply with quote
Is this the rebuilt bike you've just bought?

Stuck thermostat a possibility but I have grave doubts over the ability of anyone who uses silicone sealant when rebuilding a DTR lump to of made a decent job of the rest of the engine.
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jaffa90
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Joined: 06 Apr 2016
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PostPosted: 17:04 - 31 Jul 2020    Post subject: Reply with quote
""" temperature gauge starts to touch the red line and stays there, but it rarely enters the red.""""
What is the problem with your bike?
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Rjgk2012
Two Stroke Sniffer



Joined: 17 May 2020
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PostPosted: 18:05 - 31 Jul 2020    Post subject: Reply with quote
jaffa90 wrote:
""" temperature gauge starts to touch the red line and stays there, but it rarely enters the red.""""
What is the problem with your bike?
I don't know why I said rarely, it does it quite often but doesn't go far into the red. I've been told the needle should sit about half way into the green, have I been misinformed? Hopefully you're right and there's nothing wrong.
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Riejufixing
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Joined: 24 Jun 2018
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PostPosted: 18:13 - 31 Jul 2020    Post subject: Re: Overheating Yamaha dt125r Reply with quote
Rjgk2012 wrote:
I changed the coolant and the stuff that came out looked grey ... I'm thinking it's the thermostat?

Drain the coolant, rinse it out and see what comes out if anything. Test the thermostat with hot water. Refill the system and measure how much it takes, it should take what the manual says, if not you might have an airlock.
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steve the grease
Crazy Courier



Joined: 26 Jan 2018
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PostPosted: 18:48 - 31 Jul 2020    Post subject: Re: Overheating Yamaha dt125r Reply with quote
Riejufixing wrote:
Rjgk2012 wrote:
I changed the coolant and the stuff that came out looked grey ... I'm thinking it's the thermostat?

Drain the coolant, rinse it out and see what comes out if anything. Test the thermostat with hot water. Refill the system and measure how much it takes, it should take what the manual says, if not you might have an airlock.


To test the thermostat , take it out and hang it it on a bit of wire and stick it in a pan of hot water.
Bang the water on the stove and start heating it up, from time to time lift the stat out of the water. Before the water boils the disk in the the thermostat should move, opening a way for water to pass through. If it hasn't opened by the time the water has boiled , it's Donald. It's either a duff stat or an airlock. (99% of the time)
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iooi
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Joined: 14 Jan 2007
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PostPosted: 20:43 - 31 Jul 2020    Post subject: Reply with quote
Remove pipes from radiator.
Stick a hose pipe in radiator inlet pipe and flush a lot of water through. Do it in reverse is a good way of getting rid or any stuck crap.
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Rjgk2012
Two Stroke Sniffer



Joined: 17 May 2020
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PostPosted: 22:17 - 31 Jul 2020    Post subject: Reply with quote
Forced wrote:
Is this the rebuilt bike you've just bought?

Stuck thermostat a possibility but I have grave doubts over the ability of anyone who uses silicone sealant when rebuilding a DTR lump to of made a decent job of the rest of the engine.
Yes it has had the top end rebuilt but I believe that's it. Everything else seems to be working so far but I suppose time will tell.
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Rjgk2012
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Joined: 17 May 2020
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PostPosted: 22:23 - 31 Jul 2020    Post subject: Re: Overheating Yamaha dt125r Reply with quote
steve the grease wrote:

To test the thermostat , take it out and hang it it on a bit of wire and stick it in a pan of hot water.
Bang the water on the stove and start heating it up, from time to time lift the stat out of the water. Before the water boils the disk in the the thermostat should move, opening a way for water to pass through. If it hasn't opened by the time the water has boiled , it's Donald. It's either a duff stat or an airlock. (99% of the time)

Thanks, I'll try this tomorrow. A new thermostat is only about £20 so not bad really.
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jaffa90
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Joined: 06 Apr 2016
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PostPosted: 23:21 - 31 Jul 2020    Post subject: Reply with quote
Rjgk2012 wrote:
jaffa90 wrote:
""" temperature gauge starts to touch the red line and stays there, but it rarely enters the red.""""
What is the problem with your bike?
I don't know why I said rarely, it does it quite often but doesn't go far into the red. I've been told the needle should sit about half way into the green, have I been misinformed? Hopefully you're right and there's nothing wrong.

What makes you think that the temperature gauge is correct?
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Nobby the Bastard
Harley Gaydar



Joined: 16 Aug 2013
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PostPosted: 10:28 - 01 Aug 2020    Post subject: Reply with quote
The easiest way to find out if it's the thermostat is just take it out and go for a ride.

If it still gets too hot it's not the thermostat.
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Rjgk2012
Two Stroke Sniffer



Joined: 17 May 2020
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PostPosted: 22:16 - 02 Aug 2020    Post subject: Re: Overheating Yamaha dt125r Reply with quote
So I tested the thermostat and it worked but there was a small bit of silicone stuck in the small hole in it, I don't see why this will make much difference. The water pump was also working fine and I believe there are no air locks, I measured the fluid that went in and it seemed correct. I put in some decent coolant and it seems to stay away from the red zone now but realistically it was probably just the recent hot weather. I'm gonna leave it at that for now unless it starts to frequently go back into the red zone. There are other issues with this bike that I need to pay attention to and i'll start new threads for them if I need any assistance. I've got a faulty clutch which causes me trouble when trying to get moving as it doesn't fully disengage and I've got a leaky carb which will hopefully be simple to fix but I'm struggling to find the cause so far. I'll spend some time trying to figure it all out and start a new thread if necessary, thanks for the help.
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jaffa90
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PostPosted: 00:24 - 03 Aug 2020    Post subject: Reply with quote
""" starts to touch the red line and stays there""
""" doesn't go far into the red. ""
"" I'm gonna leave it at that for now unless it starts to frequently go back into the red zone. ""

Make your mind up, i think you are the problem!
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jeffyjeff
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PostPosted: 02:59 - 03 Aug 2020    Post subject: Re: Overheating Yamaha dt125r Reply with quote
Rjgk2012 wrote:
So I tested the thermostat and it worked but there was a small bit of silicone stuck in the small hole in it, I don't see why this will make much difference.

That small hole in the thermostat is for de-aeration (removal of air) of the coolant. You might have unknowingly found and corrected your problem when you inspected the 'stat.
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Rjgk2012
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Joined: 17 May 2020
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PostPosted: 17:53 - 05 Aug 2020    Post subject: Re: Overheating Yamaha dt125r Reply with quote
jeffyjeff wrote:
Rjgk2012 wrote:
So I tested the thermostat and it worked but there was a small bit of silicone stuck in the small hole in it, I don't see why this will make much difference.

That small hole in the thermostat is for de-aeration (removal of air) of the coolant. You might have unknowingly found and corrected your problem when you inspected the 'stat.

That's interesting, well it's running a lot cooler now so perhaps that did make a difference.
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Riejufixing
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Joined: 24 Jun 2018
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PostPosted: 18:46 - 05 Aug 2020    Post subject: Re: Overheating Yamaha dt125r Reply with quote
Rjgk2012 wrote:
So I tested the thermostat and it worked but there was a small bit of silicone stuck in the small hole in it, I don't see why this will make much difference.

What if no hot water was able to get to the thermostat? It might take a long time to warm the thermostat up enough for it to open... Manufacturers don't go making expensive holes in things without reason Smile

Did you find any other rubbish coming out when you flushed out the system, by the way?
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Rjgk2012
Two Stroke Sniffer



Joined: 17 May 2020
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PostPosted: 20:12 - 05 Aug 2020    Post subject: Re: Overheating Yamaha dt125r Reply with quote
Riejufixing wrote:
Rjgk2012 wrote:
So I tested the thermostat and it worked but there was a small bit of silicone stuck in the small hole in it, I don't see why this will make much difference.

What if no hot water was able to get to the thermostat? It might take a long time to warm the thermostat up enough for it to open... Manufacturers don't go making expensive holes in things without reason Smile

Did you find any other rubbish coming out when you flushed out the system, by the way?
A couple of other small bits of silicone came out, a previous owner had obviously replaced the water pump gasket with pure silicone and a bit too much of it, replacing that gasket is on my list of things to do. My main priority now is the clutch, I think I'm going to start a new thread for that today as I'm not very knowledgeable about clutches and it's being a pain, stalling my bike when I put it in gear with the clutch lever all the way in. Other than that I bloody love this bike.
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Riejufixing
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Joined: 24 Jun 2018
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PostPosted: 20:28 - 05 Aug 2020    Post subject: Re: Overheating Yamaha dt125r Reply with quote
Rjgk2012 wrote:
My main priority now is the clutch, I think I'm going to start a new thread for that today as I'm not very knowledgeable about clutches and it's being a pain, stalling my bike when I put it in gear with the clutch lever all the way in. Other than that I bloody love this bike.

You could try a (Google) serch like this:

dtr 125 clutch disengage site:bikechatforums.com

which throws out a few results. You could even leave out the "dtr" for general information.
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xX-Alex-Xx
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PostPosted: 22:38 - 05 Aug 2020    Post subject: Reply with quote
You sure it’s an issue with the clutch and not something as simple as a poorly adjusted lever? How much free play do you have? Could also be the side stand switch cutting the engine.
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Rjgk2012
Two Stroke Sniffer



Joined: 17 May 2020
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PostPosted: 22:50 - 05 Aug 2020    Post subject: Reply with quote
xX-Alex-Xx wrote:
You sure it’s an issue with the clutch and not something as simple as a poorly adjusted lever? How much free play do you have? Could also be the side stand switch cutting the engine.
Fairly certain it's the clutch, I've tried adjusting the lever, tightening it and giving it free play, and from my understanding the side stand would kill the engine but not cause the bike to jolt forwards like mine does.
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jaffa90
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Joined: 06 Apr 2016
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PostPosted: 23:20 - 05 Aug 2020    Post subject: Reply with quote
It could be the incorrect engine oil not suitable for wet clutches.
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Nobby the Bastard
Harley Gaydar



Joined: 16 Aug 2013
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PostPosted: 23:27 - 05 Aug 2020    Post subject: Reply with quote
jaffa90 wrote:
It could be the incorrect engine oil not suitable for wet clutches.


The only thing that I can thing of with oil fucking the clutch is it slipping due to additives.

What does the mightly mind of seedless90 think is making the clutch too grabby due to the oil?
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
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Rjgk2012
Two Stroke Sniffer



Joined: 17 May 2020
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PostPosted: 23:33 - 05 Aug 2020    Post subject: Reply with quote
jaffa90 wrote:
It could be the incorrect engine oil not suitable for wet clutches.
I just replaced the oil yesterday with Castrol 10w30, suitable for wet clutches, but the problem persists. After a bit of reading I'm thinking there's grooves in the clutch basket.
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