Engine Temperature

Just throwing this out for comments, all appreciated. Had my VF for nearly 5 years now and only just had a thought when out last Sunday about engine/coolant temperature. Except when in heavy traffic in town, stop start etc, my temp gauge never rises above rest. I seem to recall many years ago a car mechanic friend telling me that ideally the needle should be mid gauge for the engine to run at it’s designed temperature. Don’t have any problems, fans come on in slow traffic but when out on a clearish run needle is back down to rest almost. Bike runs really well, if a bit heavy on fuel consumption. Anyone got any thoughts?

hi rodger, if i go out for a leisurely ride my temp gauge normally stays just into the thick part of the gauge, the fans normally come on about three quaters of the way up, especially if you get in stop start trafic, i have fitted a fan over-ride switch which i normally flick on at train crossings ect if i know im going to be stood a while,
Years ago when i used to commute from barnsley to chesterfield (50% A roads and 50% motorway), i would normally get about 36mpg,
sounds like your bike is running as it should, or maybe a little on the cool side, personally i would deffinatly prefure one running cool than hot.

Sounds like your thermostat is stuck in the open position. Your friend was correct, they should run around the middle of the gauge, otherwise if the motor is being cooled too much, the pistons are trying to expand to operating clearances in a cylinder that cannot expand due to lack of heat, particularly when you ride a bit hard. I agree with vfpete, not as bad as running too hot, but not good for the motor either since it causes premature wear.
You could start by first checking the thermostat, then the temp sender with a known good one, just to eliminate the cheap, easy and most common causes first. Then maybe consider fitting the Subaru fan sensor to kick those fans in earlier.

VF’s run hot anyway,Very marginal on the cooling,the rear pots always hotter.My 3 1000’s and the two 500’s race into the top of the temp gauge as soon as you hit stop start traffic.Change the thermostat and put a VF400 sender unit in for the fans as it come on 10 deg’s cooler than the 1000’s.

Thanks guys for all the advice, will follow up with results, though as weather is crap at moment it may be next spring :slight_smile:

Thats interesting coz mine runs just out of the green colour and right where the wide band starts. I,ve had the thermostat out ( easy job ) but no obvious fault and the fans work if I leave it sitting at idle. If it aint broke …


yes a couple of interesting points, i hadn’t really considered the ware factor of a engine running too cool, but its food for thought and well explained tony,
been going to fit the vf400 fan switch for ages, but never seem to get round to ordering it, i only normally remember when i’m sat on the bike and my knees start to get warm, so thanks for the reminder crooky, ill add it to the list of other jobs this winter.

Yeah it’s the same principle (but to a lesser extent)of cold siezing a two stroke, happens when the local kid racer starts his bike when cold and revs the snot out of it up and down the street to “warm it up”, the piston gets hot quicker than the cylinder and expands until it siezes due to lack of clearance.
Of course a four stroke has better lubrication and does not heat up as quickly, but it is also used over much longer distances and kilometres/miles so the little bit of wear caused becomes a problem over 20,000 kms instead of 200 metres. Same principle though.

Pete, have you thought that the “warm feeling on your knees” when riding might be you should have stopped at the services before you got that bad ?[:D]


no lol[:D]… i always wear my rubber incontinence pants when i go out on the vf coz it frightens the poo out of me going round corners [:D]