Bike overheating

G

GG221

New member
My bike is overheating easily. Radiator will be smoking after even a mellow hill climb. I let the bike cool down and check the radiator is full, but I can see a thin film of what I think might be oil on top, but not positive. It is not very milky like heavily contaminated oil, but maybe there is a small amount. When I change my transmission oil it does not look very milky at all.

Any ideas?

2018 XC 300
 
GG221 said:
My bike is overheating easily. Radiator will be smoking after even a mellow hill climb. I let the bike cool down and check the radiator is full, but I can see a thin film of what I think might be oil on top, but not positive. It is not very milky like heavily contaminated oil, but maybe there is a small amount. When I change my transmission oil it does not look very milky at all.

Any ideas?

2018 XC 300
Click to expand...

Your water pump shaft seal may be leaking. Pull the impeller off and inspect the seal and shaft
 
Today I looked in the radiator and it looks dry. I added about 1 cup of coolant and it was full again started the bike and I can see that the pump is working. It looks to me like the steam or smoke is coming off the header pipe. Maybe it is just a leak somewhere?
 
It is a new issue. I think jetting is good.
Sounds to me like i should replace the head o-rings and the water pump shaft seal.
Any other parts I need to order along with the pump shaft seal?
 
If the gear oil is not milky then pump seal should be fine. If you do have to replace the seal check the shaft. Mine got a groove in it. Was quite cheap.

I have a bung with a shrader (tyre) valve in it. You could glue one into a piece of plastic or drill and tap. This bung is radiator hose size. Put a plain bung in other hose and put a radiator in a bucket of water and a couple pumps with a bicycle pump. You'll quickly find a leak or prove it as a good part.

If they both prove fine and you swap a cap over then yeah I'd replace the head o-rings.
 
Steam from the pipe is quite common as on many bikes the overflow hose ends somewhere near, often above, the pipe. The coolant then drips on the hot pipe causing the steam.

Let the bike run and check if water/coolant drips on the pipe. If so try to find from where. I bet it comes from the overflow hose...
 
When the bike is cold unscreew the radiator cap and put you finger so you seal good with your finger..if you feel presure or hissing sound whe you stuck out you finger then is head gasket problem.
 
Doc Brown said:
Steam from the pipe is quite common as on many bikes the overflow hose ends somewhere near, often above, the pipe. The coolant then drips on the hot pipe causing the steam.

Let the bike run and check if water/coolant drips on the pipe. If so try to find from where. I bet it comes from the overflow hose...
Click to expand...

It'll be the rad cap. My 2018 model wouldn't seal from new and same issues.

As pressure builds with temp it would push coolant past the cap and out the overflow that vents directly onto the exhaust.

Over filling the rads will also purge some coolant out as there is no expansion tank on these models, so expect a bit initially too. Usually coolant just over the fins is the right place.

I put the cap from my 2013 on and no more issues. My dealer knows of at least one other he changed under warranty!
 
Jakobi said:
It'll be the rad cap. My 2018 model wouldn't seal from new and same issues.

As pressure builds with temp it would push coolant past the cap and out the overflow that vents directly onto the exhaust.

Over filling the rads will also purge some coolant out as there is no expansion tank on these models, so expect a bit initially too. Usually coolant just over the fins is the right place.

I put the cap from my 2013 on and no more issues. My dealer knows of at least one other he changed under warranty!
Click to expand...

This is exactly what I was thinking. Install a 1.8 bar KTM cap and see if the p0roblem goes away. You can see if the cap has a sealing issue if you inspect the rubber seal: discoloration or uneven wear is a sign that the cap is bad (or the sealing surface is uneven). Much faster, cheaper, and easier to swap the cap before cracking open the top end for new o rings.
 
As coolant heats it expands. If you fill the radiator to the top, unless you have an overflow tank the extra volume purges out of the cap. My bikes both run with the coolant right at the top of the fins when looking inside the radiator. If I top them off they will purge the excess to that point.
These bikes run pretty cool so maybe you just never actually got it very hot prior to experiencing this.
 
Jakobi said:
It'll be the rad cap. My 2018 model wouldn't seal from new and same issues.

As pressure builds with temp it would push coolant past the cap and out the overflow that vents directly onto the exhaust.

Over filling the rads will also purge some coolant out as there is no expansion tank on these models, so expect a bit initially too. Usually coolant just over the fins is the right place.

I put the cap from my 2013 on and no more issues. My dealer knows of at least one other he changed under warranty!
Click to expand...

Agree 100%. My 2018 rad cap wasn't sealing either causing the coolant to overflow. New cap and all was good. Seems the OEM caps come from China. Not only those from Gassers, I had the very same problem on some Kato's too. Fortunately they don't cost a fortune. Funny thing is that they are often defective on brand new bikes...

pscook said:
This is exactly what I was thinking. Install a 1.8 bar KTM cap and see if the p0roblem goes away.
Click to expand...

GasGas uses a 1.8bar cap ex factory. Not all KTM caps fit, they have changed them to a new design from 2017 onwards...
 
When installing new head o-rings should I lube them at all or just put them straight out of the package to the cylinder head?
 
All the ones I've gotten are a bit small so need a stretch which is a bit 'Bush' but they were fine afterwards.
 
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