5th gen overheating?

Hi all, there has been a lot said about VFR's running too hot.
I thought I would give my two bob's worth of experience and observations from my own bike.
I'll mention that my background is in airconditioning design and R & D, so I have a lot of experience in air flow and heat exchange.
It might not be motor mechanics, but general knowledge on heat transfer.

It all started the last few weeks now that the weather here has turned hot, mid 30's. By full summer it will be mid 40's.
It would hover around 84C when moving along at over 75km/h, but quickly climb to 98C or 104C, sometimes 112C in traffic or at a stand still waiting for lights to change.
If standing still it would get to 104C, then fan would kick in and drop to 98C. At speed it was never a problem but it would take longer then I would think normal to drop to 84C.
If moving slowly in stop start traffic, specially if started moving when bike around 100C, it would get much hotter very quickly sometimes reaching 112C in a matter of 30 seconds.
This worried me, I had done a full clean, flush and refill only about 8000k's/10 months ago (when I bought the bike) and thought it was all fine. Back then I found a very dirty system & a blocked line to the overflow tank.

Don't get me wrong, a hot running VFR does not worry me as much as it seems to do a lot of folks here. As long as the coolant isn't boiling, I'm not worried, it takes a lot higher temperatures to damage an engine. And good engine designs need very tight running temperatures to keep them working at their best.
The VFR has the added problem of having to keep a cool head with the badly positioned side radiators.
Only one has a fan, but I think this is for a reason.
I've noticed people here who have modified the fan to run the other way (blow out instead of suck in) and it seems to work better when you start moving but worse when standing still.
I think the reason for this is that its sucking very hot air from top of the engine instead of fresh air.
From what I can work out, the reason why there is only one fan is so when you start moving, the airflow is working against the fan side, but flowing well on the side with the radiator without a fan.
Hence why I don't think adding another fan to the right side is the answer.
I just don't think it is needed and it over complicates things.

Back to my problem, I decided to dismantle the cooling system and inspect.
To my surprise, the overflow line was blocked again. As soon as I pulled the fairing off I noticed the suction hose from the engine to the upper right side radiator was flat, as if it was sucking too hard.
I pulled off the overflow line and it sucked in a lot of air.
The coolant I pulled out was again dirty, I think a single flush and clean the last time wasn't enough.

This time I umblocked the overflow line, filled the system with water, closed all caps and went for a ride for 10 minutes and then stopped at home and let it idle until it reached 104C.
When it cooled enough I again drained it and repeated this two more times.
I then filled it with 50/50 Tektalloy Cool Gold and distilled water (not antifreeze as it is not needed here) and started the bike on the side stand and let it idle to heat up.
Make sure you use distilled water, as tap water has impurities and boils at a lower temperature.

The first thing I noticed was how long the bike took to get hot, it got to 78C quickly but didn't want to move from there.
There was a light breeze here and around 23C with no fairing on the bike and it seemed to not want to heat up.
I raised the idle to 2000rpm and watched.
The thermostat opened at 84C, when this happened it dropped quickly to 78C.
It then very slowly climbed to 101C and fan cut in, within 30 seconds it was back down to 89C and fan shut off again.

The most striking thing is just how much longer it takes to get hot, and how quickly it drops when fan starts.
I can now sit through a set of lights and only climb very slowly from 84C.


I'm now happy and all seems well, I'll just make sure I do a better clean and flush next time at least at the start of every summer.

It isn't that these bikes run too hot, it's that they need a very well maintained cooling system to work as designed.
And to those that still worry about a hot running VFR, switch to ambient temp. :kiwi-fruit:

 

Just a quick update to my previous post.
A few weeks after all the work, my right side radiator sprung a leak.
I decided to swap it with a 6th gen as they are two rows bigger and of better design.
It looked easy, and I only needed some slight modifications to make it work.
The 6th gen radiator is taller by two rows, so I needed to carefully cut the inner plastic for an air tight fit.
The lower position mounting pin is also further forward on the 6th gen, but a light hit with a rubber mallet and a bit of cutting of the plastic worked fine.
The top hose that holds the radiator cap is now too high (by two rows) so I cut off 25mm and re-installed.
I just went slow and used a white paint marker to trace where the radiator sat on the inside of the plastic surround and cut with a good pair of metal tin snips.
I think the left side is a bit harder as you have to work around the fan, but if it goes, I think I'll give it a go.
I'll see how it performs once it stops bloody raining here.
Three weeks ago it looked like we were going to lose the entire east coast to fires.
Now we are scraping fungus from our walls.
Go figure!!

 

Let us know how it works, haven't heard of this swap before.

 

Good info. Thanks for the post.

For those of you looking for some step by step directions, I've always found KC-10's thread to be helpful. Here it is.

http://vfrworld.com/forums/showthre...th-Gen?highlight=5th+Generation+Coolant+Flush

 

By popular demand, here are some pictures of 6th gen radiator install:
This is the finished product.


Here you can see the difference of size and design between the two.


You should be able to see that the top mounting tabs on the 5th gen are longer then the 6th gen, hence why the 6th gen sits higher when installed.


This is the locating pin bracket that sits further forward on the 6th gen radiator, a soft hit with a rubber mallet was all that was needed to realign it.


And here is where I had to cut the plastic of the inner fairing to suit the new radiator profile, it wasn't very hard, I just used a white paint marker to trace around the radiator and cut with a good pair of tin snips.


I cut away the inner plastic grille as I have mesh on the inside of the fairing.


I'm happy with the results, it comes down in temperature quicker now and runs more consistent at 78C.
I'll be doing the other side as soon as I find one at a reasonable price.

 

It's been a while since I did the mod, so I thought I would report on how it's going through this summer.
It has not been a significant change, but it is a bit better.
We had a couple of 39c days and it definitely cools quicker when you start moving. It still has the same problem when sitting in traffic, or moving under 80km/h, but it seems to take that bit longer before it gets over 98c.
I know there has been some reports on this forum on the VTR fan blade mod not helping that much, but I have a feeling that if I also replace the left side radiator and install the VTR fan, it might be marginally better.
I don't think it is ever going to be perfect, having radiators on the side requiring to move at speed to create that pressure differential at the radiator face for them to work correctly, was always a bad idea, and only seems to work if you are going over 80km/h, and doesn't work great until 100km/h and over.
I will mention that on one of my last rides I swapped with my mates Black Bird for a while, and the BB was definitely running hotter (92c) then the VFR which was holding 84c, so much for the front radiator being much better.
I just think today's bikes are designed to run hot.
On a side note, I've been experimenting with the front suspension, check out my new thread to get an opinion on my findings.