Slight overheating issue

[kev64]

On general riding, fast, steady, cruising I get no problem, in fact the gauge only gets up to the first mark
when im in traffic iin towns, slow moving/stop/start the coolant temp starts to creep up quite quickly, when im tuning up in a layby (im still experimenting with 2 different sets of carbs so this is quite often)
my coolant temp goes above halfway,, the fan comes on the right side coz I can here it kick in when tuning (not sure about the left)
Also with the fan running the temp still doesn't really go down. Is this common ? or maybe its a thermostat issue ?
The engine returns to normal quickly when im back on the move

This problem seams to have started after I changed the coolant a couple of months ago
Rechecked the coolant level and all is well

PS I changed the coolant expansion tank to a coolant bottle (half filled with coolant)
The pipe from the rad goes to the bottom of the bottle, always covered with coolant
and the overflow pipe is at the top of the bottle

[8541Hawk]

When was the last time you changed the radiator cap?

I would try swapping in a new one as the first step as a bad cap is the most common cause of minor overheating issues

[lloydie]

Have you looked in the rad to make sure it's topped up .
What your describing is normal to me and my storm .


Sent from my iPhone using Tapatalk

[kev64]

Might look into changing the cap then, the coolant level was ok when I checked, however,
that was well over a month or so ago

Just wondered if this was common on these engines to get hot/overheat quickly

Ill either check the level again or just ride fast !!!

[Cadbury64]

I agree that what you're describing sounds pretty normal for Hondas with side mounted radiators. BTW there is only a single fan fitted, to the RHS radiator. The fan should only come on when the engine is really hot (98-102C) and should switch off at 93-97C. That is a fair way above "normal" operating temperature which is controlled by the theromstat beginning to open at 73-77C, which is probably where the bike would sit when you've got a bit of cooling airflow through the rads due to movement.

My VFR800 uses the same set-up and has a digital temp gauge, and I can hammer on this as hard on the open road as I like and it barely gets above 80, but slow right down through traffic lights, stops signs etc and it gets up to 100 pretty quick and then the fan starts up.

If you had a thermostat failure (and I know my VTR has this, I've got a new one on order) then the bike will be slow to warm up, the radiators will feel hot almost immediately after starting up. The thermostat should stay closed until 73C, which means all the coolant is circulating round the engine only (not the radiators) so that it gets to operating temp quickly. Once that temp is exceeded the thermostat opens to allow the flow through the radiators so that the coolant doesn't overheat. Thermostats usually fail in an "open" position, so might restrict coolant flow a tiny bit but I doubt you'd notice that.

If you've got a radiator cap failure you will lose pressure in the cooling system and that can allow the coolant to boil and give high temps, but I suspect you'd see an issue with the coolant expansion tank overflowing if that happened.

[kev64]

Cheers for the info, will check my rads next time I start up

[VTRDark]

Cadbury64 I couldn't have put it better myself

(:-})

[Cadbury64]

Here's what a failed thermostat looks like; that open space between the top flange and the sealing disc on top of the spring should be closed when cold (and no, my garage wasn't above 73C when I took this picture!).



All you VTR owners should be very grateful that Honda put the thermostat in a semi-accessible position. On a VFR it is buried right at the bottom of the V, you need to pull out the airbox and throttle bodies, along with more assorted hoses, sensors and wires than you could shake a pointed stick at. And then you still need to pull the thermostat housing completely out of the bike to get at the bolts.