Yamaha TRX850 Enthusiasts Forum

This may be a simple one... and I'm honestly hoping that the shop will have it all sorted before I even get a response to this...

I picked up the bike from the shop today (getting the new engine installed...) and only got about half way home before I looked down and saw that the temperature guage was right over into the red... I pulled over, shut the engine off and watched the guage go straight back down, checked for bubbles in the radiator... none I could see/feel... and cautiously set off again, only for the temp to spike straight back up!!!

I stopped again (this time at a servo, so I could actually spend a bit of time making sure it was ok... and figuring out just what the hell I should do!) and checked the radiator again, a bit too quickly, so I ended up with wet feet!!! So, I seem to be getting pressure... I felt the water, and it was barely lukewarm... I could even touch the block itself with bare hands... The guy at the shop reckons it might be an earthed out sender wire for the thermostat... I wondered if it might be a blockage in the radiator?

It was hinting at high temperatures before the engine was replaced, so I'm guessing that whatever it is is in the remaining, unreplaced parts... Any ideas on where to look? Ideas on what the problem is likely to be? Has anyone seen/heard of these sort of symptoms before?

I just want to get out and ride before we loose all the good weather!!!

Cheers...

The temp sender is in one of the two rad hoses above the engine under the tank. These two pipes connect to the water pump motor.

Its easy enough to check if your sender is working: take the tank off, or hinge it backwards, undo the temp sender unit (10 or 12mm brass-looking nut with wires in the middle iirc) from the rad pipe, whip it out and then put it in a cup of hot water and see if the gauge goes up as it should, with ignition on.

Or may be the water pump is not working, so the temp sender is in a pipe on the top of the engine in still water, therefore gets hotter than it should??

TRX motor generally runs quite cool, but on hot days can get rignt into the 'red' before the fan cuts in. Did the fan work?

Yup, fan kicked in normally... The car goes off the road this weekend so it'd be really nice to have the bike sorted!
If the radiator is pressurising though, wouldn't that suggest the pump is ok?

Check the shop haven't fitted the carb warmer and expansion pipes the wrong way round - the cooling system won't pressurise if they are and it'll overheat.

Definately got pressure in the system!!! lol... the puddle under my bike will attest to that one!!!

Got a call that they've found the problem... I'll update here when I find out what it is! Thanks for the suggestions!

If the pipes were the wrong way round you'd still get a puddle under the bike - the coolant pumps straight out the radiator, into the expansion tank - fills the tank and overflows to the deck.

Wasn't coming out the overflow... but I hadn't thought of that either way...

Turns out it was actually an issue in the unpacking of the new engine that resulted in a stray bit of rag where it REALLY shouldn't have been... One of those simple/stupid things I suppose, but no damage done and I got my coolant flushed for free!!!

Awesome ride home through the hills! It'll take a bit of getting used to, but I can see this bike being a hill lover already... even if only for the sound of those pipes!!!

Ah, the old "left-a-bit-of-rag-in-a-hole-in-the-engine" issue, its a common fault on the TRX, should have thought of it!
Glad you like the bike. They are perfect for hills and twisties!!

Got a problem with heat too.

I ride about 20k's on the highway and then have about 5k's stop&go through town to get home. Standing at the traffic lights the temp goes up quite quickly over 80 degrees and sometimes climbs to 100. It gets down pretty quickly once I am home or I get a few 100 meters of driving at 40km/h+. Is that normal? Oh and it's summer with outside temps of about 20-25 degrees. Oil is OK (semi synth) and coolant level is also OK. Haven't checked any more than that yet. Driving on highway open road is never an issue. Temps are all stable at about 65 degrees then no matter what the outside temp is.

Any ideas or am I just over sensitive and all this is plain normal?

Cheers Oliver

Same for me Oliver, im on the Gateway for about 30 kays at around 120kph, then off and on side road with lights and the temp will spike up to 80--90..not enough to bring the thermo fan on though.
Slow traffic riding will bring it down and nice and cool again for the park and switch off...queensland temps too

Was the guy who fitted your second engine qualified??? I am sorry to say but this is appalling if a tradesman has let the bike out of his shop with this very basic check not done!

Hey Alex

Thanks for that makes me relax a little. You talk about a fan and I read it somewhere else too. I havent opened that part of the TRX yet but from the outside I see no fan anywhere. Where does that sit and when does it come on? (as I haven't heard it either)

Cheers

the cooling fan sits in behind your radiator.
it is thermostatically switched at a preset temperature.
if it isn't coming on, you may have a faulty fan, faulty thermo switch, sticking thermostat or even a loose earth wire.
check your fuses as well.
cheers
fung

Thanks fung I'll have a look.

Had a look. How could I have missed that?!? Now I just need to see if it actually works.