Thermostat/radiator temps

I have a suspicion of a partially stuck open thermostat.

So, tell me chaps; from cold startup does your right radiator upper half get warm before the thermo opens? Up to 45C it's cold, gets a bit lukewarm at around 55C and at about 63C it's 'hot' to the touch. The thermo opens properly at 80C because the left rad suddenly gets hot and temp drops a couple of degrees then comes back up a few times. To my mind it shouldn't get hot at all till the thermo opens?

She sits at 78C within a mile or so of riding at 40-50mph. I noticed this morning that once I hit the motorway doing 80mph the temp dropped to 75C and came back up once speed dropped.

Fan kicks in normally at 106C and turns off at 96C or so.

My mpg figures are quite low but for the 22 mile daily round trip journey she does including 50% town crawling aren't entirely surprising. In the warmer weather a few months ago mpg figures were quite respectable in the high 30's (UK MPG not US)

I see plenty of anecdotal evidence along the lines of 'mine sits at 78 normal riding'. That's not really what I'm pertaining to, it's mainly the cold startup right rad temps.

 

There is a small breather hose running from the thermostat housing to the right radiator which is always open (and is there to stop the thermostat air-locking). I would say that getting some heat from here at the top of the right radiator sounds plausible, and my bike does the same small temperature drop at 80 when the thermostat properly opens and pushes the cold fluid from the radiators. I can't say I've ever noticed my right radiator heating at all before this happens, but I generally can't access the top of the radiator with the fairing on.

The temperature of my VFR usually sits around 77-78 when moving, 75 is not far from that and probably within the range of accuracy of the sensor. The only way to know for sure whether the thermostat is healthy is to remove it for inspection which is a few hours of "fun", and your bike sounds pretty close to normal to me so unless there was a good reason, I would leave it alone.

 

I'm wondering if I have an issue with my thermostat.

How long does a VFR800 vtec take to warm up with an air temp of 15°C? I have to drive mine on a dual carriage way for at least 10miles before it warms up to 90°.

The bike will get warm and the fans kick in at 103° but was wondering how long it should take or is the thermostat sticking or slow to close?

First post on here, great website

Cheers

 

You are describing pretty normal temperature fluctuation.

My fan Kicks on around 107c
fan turns off around 99c
thermostat opens 78c
My bike sits at 83c on a normal day under normal opperation (not sitting in traffic.)

I replaced the thermostat last year. It was stuck open and would run as low as 63c while under way on a cool day.

 

The thermostat should be open by around 80C, and I would expect it to get there within a couple of miles. Whether it then gets to 90C would depend on how you are moving in traffic. On a steady run (no traffic lights) my bike would rarely get to much over 82, no matter how hard I cane it or how long I ride.

Edit: beaten by Jim!

 

Thank you Big_Jim59 and Cadbury64, very much appreciate your quick response.

Looks like I don't have anything to worry about. I was thinking it was running rich and this may have been the problem. Only get about 110 miles a tank but if it's not warming up by the time I've got to work it won't give me many miles.
Doesn't feel smooth in acceleration and feels like it's running rich so will check over it this weekend.

Not had bike long so still getting used to it's ways

Cheers again

 

110 miles a tank doesn't sound right. I get around 210-220 mile for 4.5 gallon fill-up with my 5th Gen VFR.

 

Same here. If you're not getting minimum 30 mpg, something is indeed wrong. I'm getting over 40 in combined city/country riding, including segments of an indicated 85mph (we of course know how optimistic that is) on interstates.

ginger, what generation of VFR are you riding?

 

I suspect it's a 6th, 7th or 8th as he mentioned Vtec..

However, on my daily commute of 3 miles some weeks I don't even get 100 miles to a tank... but I can promise it's warm when it gets there - lol. And my bike runs perfectly.

I like having vtec as it ensures I use it...

 

These are the same temperature ranges that I see on my bike. Looks about right to me.

 

Being a 2004 I think its a 6th Gen.

My travel to work is 10 miles so is this fuel consumption out of the ordinary then?

 

Short hops like that are bound to use more fuel.

Yes you have a 6th gen, 2002 to 2012, 7th gen is the 1200, 8th gen is the 2014-current 800.


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Cheers matey

 

Well I think I may have solved my issue but need a new tank full of petrol to properly test it, but man what a different bike!

I bought a Morgan Carbtune and syncronised the starter valves and already I can feel it runs way better. One of the valves were so out of sync with the others I'm guessing the engine was working hard to compensate it. Now it purrs like never before and sounds so different too.

I would recommend the Carbtube if no one has ever use one or got one and really easy to do too.

Will keep you posted on how the next tank full does for mileage.

Cheers again for all your help