Bike losing coolant and oil on roadtrip - please help me :(

[Garfield]

Mike,

Hope you made it home safe by now !?

I listened to the video sound too and I agree with Michael, to me it does not sound like a loose cam chain - you would definitely hear that at idle speed.

[ItchyMike]

Hey guys, we got home safely! Thanks for all your feedback.

So now we're going to unpack the bags and take care of pending daily affairs and probably will disassemble the bike on Friday to explore the thermostat theory ( and check some other things mentioned on this thread ).

I will post an update as soon as I have news.

I just hope the engine is not damaged beyond ( a very expensive ) repair. I really love this bike.

ps: head gasket seems fine, I think:

https://ufile.io/5cocu4bz

[ItchyMike]

occam's razor (the simplest explanation is usually correct) - so I'm in for a defective radiator gauge since all other options are extremely rare

This is the first thing I will check! It is certainly preferable to try everything that's simple before disassembling anything.

A stupid question perhaps... but without a gauge cap and not having any other means to monitor the temperature, and not being sure if the temp light works, is it "OK" and more or less accurate to stick a sensor like this in the top of the head ( secured with a metal bracelet ) and see if it gets too hot while I do some tests?

https://www.amazon.com/RioRand-high-pre ... B00KGSBGP4

I've got a spare one lying around.

[scrambler]

occam's razor (the simplest explanation is usually correct) - so I'm in for a defective radiator gauge since all other options are extremely rare

This is the first thing I will check! It is certainly preferable to try everything that's simple before disassembling anything.

A stupid question perhaps... but without a gauge cap and not having any other means to monitor the temperature, and not being sure if the temp light works, is it "OK" and more or less accurate to stick a sensor like this in the top of the head ( secured with a metal bracelet ) and see if it gets too hot while I do some tests?

good to hear that you made it home. maybe its possible to stick a sensor into the fins of the radiator?



I recommend Trail Tech temperature gauge or speedometer https://forum.nx250.de/viewtopic.php?f ... 2098#p2098
I'm off now to the annual NX250 meeting and will be back on monday.

[ItchyMike]

Cool stuff!

Thanks for the great info as always.

I should have read that a long time ago.

If the problem turns out to be the radiator cap then I will be a big idiot that just went looking for trouble.

We'll soon find out, we are going to do a little testing soon and post back the results.

Have a wonderful and safe trip.

[ItchyMike]

Ok, so we switched the caps ( same cap in both bikes ).

My bike did not overheat now, but now my brother needs to do a short test with my cap on his and see the temp differences.

So, everything points to a defective cap, and a very experienced mechanic had a listen to the engine and he suspects there's damage done to the connecting rod bearing.

Remember kids, don't be an idiot like me and always pay attention to uncle Michael's advices!

[ItchyMike]

Well, the plot thickens...

After I posted the above, my brother went to do a test with the cap I had in my bike and had no excessive temperature, no coolant spill, no different temperatures on his bike.

What was different when I tested his cap is that I had no fairings in the bike and it was early in the morning, so perhaps airflow through the whole bike was bigger an the problem did not manifest itself. I just did about 15 km and did not drive it hard. More interesting is, he drove his bike like he stole it ( real hard ) with my radiator cap and still had no problems and no temps past 80 degrees celsius in the gauge in open road.

Certainly I don't want to make this the quest of a lifetime ( it's a 30 year old bike and I have no idea of what happened with it for the past 28 years, and the previous owner said that it had a gasket job before), but just for the sake of knowledge, it would be interesting to know what's wrong so it doesn't happen to anyone else.

What we know/observed/got so far:

- both bikes cooling fans engage at around 100 degree celcius in the gauge ( confirmed without any doubt ).
- both bikes have the same oil filter ( KN-112, with no anti-return valve, contrary to the OEM filter, but that doesn't seem to be a problem ).
- both bikes have the same radiator cap brand, bought at the same time( which we swapped for testing ).
- both bikes have the same oil ( Motul 7100 ), changed at the same time, from the same container.
- My problem started to happen after I did 100KM of open road between 100-110 km/h ( no full throttle for more than a few seconds for short periods ). My bike started to rattle a bit from somewhere after that. My brother's bike had to problem at all and went happily through all the journey.
- Someone at a Honda dealer suggested a tensioner problem ( doesn't explain the coolant/oil/spill/excessive heat ). I would rule that out, but I am just an amateur.
- Any cap on his bike's radiator is much more harder to tight than in my mine ( cooling system pressure problem could still be an explanation, but the cap doesn't seem to be the cause of that in this case, and the cap in my radiator doesn't feel loose, only easier to put in place ).
- My brother's bike starts much better than mine ( valve's not correctly adjusted causing engine overheating )?
- Another mechanic suggested a possible connecting rod bearing failure based on the noise ( maybe that problem was present in my bike before before and just got worse over time )?

[Nikolajsen]

This is strange
New ideas

Radiator clocked (or almost clocked)
Water pump failure (don't know what drives it)

[scrambler]

- ….. the previous owner said that it had a gasket job before …

Ok, that little piece of info would have been crucial to know The rule of the bullet proofed head gasket applies only if nobody screwed with it. Knowing that a blown gasket is not unlikely because of a poorly done job.
With that info

Any cap on his bike's radiator is much more harder to tight than in my mine … the cap in my radiator doesn't feel loose, only easier to put in place

I can imagine what happened.
The filler neck of the radiator is often ruined because the little security screw is overlooked. With a bended neck the radiator is also loosing coolant, just like an untight radiator cap. The previous owner discovered the loss of coolant and thought it’s due to a blown gasket.
So I would first check the filler neck. It’s made of very soft aluminium, so it can be easily straightened out with a piece of wood and a hammer.

NX250 radiator neck.jpg

I don’t think the noise is caused by the con rods bearings, sounds more like the piston. If you decide to replace the head gasket I would recommend also pulling the cylinder. Then you can check the piston and the upper con rod bearing.
That your bike won’t start easily is likely a carb issue – but on the other hand, if someone did a bad job on the head gasket maybe he also misadjusted the valve play, who knows.

[ItchyMike]

Thanks guys, I will revisit this matter later and when I have news I will post info ( can take a while since I have other pending matters ).

I would also rule out the water pump, because unless the previous owner had a bad job in it, I have seen the one in the disassembled engine and I would dare to say there is nothing that can go wrong with it ( It's the simplest form of waterpump, just a one piece-propeller-gear driven by the engine ).