Thermostat Replacement On A Rc36

..can this be done without removing the carbs? I've heard that you can access it from the right side of the bike by removing the upper right hand fairing. Is this true? My bike has started over-heating and I believe this to be the thermostat.
Any help will be appreciated.
Cheers
Nate :huh:

I don't hav an answer, but overheating is typically not caused by bad thermostat. Just the opposite. Bad thermostat will cause the bike to run cold, b/c it is always open by default unless it heats up.
There are rare exceptions though, so don't rule it out completely. Just leave it as a last resort.
If you haven't done so already, try burping the system. Air will cause it to overheat.

Yes, no need to remove the carbs.
[image: Posted Image]

Yes, No need to remove anything to get at it except for the thermostat housing cover and to push aside a few small hoses. It would have been much easier for me though, if I didn't have to go around the pollution control air pump and hoses right in front of it on my CA 95 :angry: . It gave me some badly scraped knuckles, but I got it all done in about 20 minutes!
Plus one for the older VFRs on this maintenance item! :huh: I'm so glad i didn't have to go through the horrors of wrestling with those monster induction boots that hang on to carbs and throttle bodies like the "Kraken" itself!! :ohmy:

Beck
95 VFR

Thanks for the reply guys!
The bike suddenly started to run cool again (i was stuck in traffic and it was just over half way, then when I check a few minutes later it was just in the warm zone! something must have given!)

As I've already ordered the part I'll replace it (seeing as it's such an easy job!) and burp the system while I'm at it.

Next up is a carb balance (I've read that's an easy job on this bike, don't even have to remove the tank!)
What's all that bad press regarding the complexity of this bike making it hard to service!? LOL

Thanks for all your help guys! Much appreciated :biggrin:

Nate

[image: View Post]NateRC36, on Jan 9 2009, 09:15 PM, said:

Next up is a carb balance (I've read that's an easy job on this bike, don't even have to remove the tank!)
Well, I found the front adjuster (carb. 4) not so easy to get at.

[image: View Post]V4 Rosso, on Jan 9 2009, 11:04 PM, said:

[image: View Post]NateRC36, on Jan 9 2009, 09:15 PM, said:

Next up is a carb balance (I've read that's an easy job on this bike, don't even have to remove the tank!)
Well, I found the front adjuster (carb. 4) not so easy to get at.


I did the carb balance, I have burnt knuckles to prove it! The bike runs silky smooth now. I'm still having the over heating problem, just not as pronounced as before. The gauge still rises part the half-way mark even though it's winter and 2 degrees C out there!

I had a go at burping the radiator as advised, I took the cap off and let the bike run. The only thing that happened was the water began to gradually rise out of the radiator, no air bubbles of anything. The level in the expansion is spot on and hasn't gone up or down. Could this be the thermostat still? I've yet to swap it over, but from what I've read it should be running too cold not over-heating.
How would a faulty radiator cap affect the bike?

Sorry for all the Qs, it'll probably be something simple but before I resort to removing the complete cooling system I thought I'd ask you guys first.

Cheers
Nate :fing02:

Yeah, burned knuckles is adequate proof. :laugh:

In what does the overheating manifest itself, is it just the gauge showing it is past half way or the fan kicking in and staying on?
The coolant level in the expansion tank staying at a constant level is a good sign. I have to get myself a new one as the level rises as the engine heats up, which is OK, but doesn't get back to normal when all has cooled down again. So the radiator cap must have an air leak. I am not sure what will happen if the cap is stuck closed, I suppose it will eventually pop a leak in the radiator or one of the hoses, whatever has the weakest spot.

Does the radiator feel very hot, maybe the thermostat is stuck closed (although some people claim that can never happen).

[image: View Post]V4 Rosso, on Jan 19 2009, 07:00 PM, said:

Yeah, burned knuckles is adequate proof. :laugh:

In what does the overheating manifest itself, is it just the gauge showing it is past half way or the fan kicking in and staying on?

Hey,
The gauge rises to just over the halfway point and the fan kicks in, I'm pretty lost as to what it could be!
Nate :blink:

Ha, just edited my previous post:
Does the radiator feel very hot, maybe the thermostat is stuck closed (although some people claim that can never happen)?

The fan kicking in is not out of the ordianary, even during winter. Mine stays on for a few secs when e.g. waiting at a stoplight, and shuts of when I get moving again.

[image: View Post]V4 Rosso, on Jan 19 2009, 07:14 PM, said:

Ha, just edited my previous post:
Does the radiator feel very hot, maybe the thermostat is stuck closed (although some people claim that can never happen)?

The fan kicking in is not out of the ordianary, even during winter. Mine stays on for a few secs when e.g. waiting at a stoplight, and shuts of when I get moving again.

Hey sorry about the late reply, been busy with work.
I took the bike out again today, it gets two thirds up the scale after half hour of traffic riding even in the freezing cold. This doesn't seem normal to me however I've never owned a V-four engined bike before so I cannot draw comparison. The level on the expansion stays constant and there are no leaks anywhere on the system and there appears to be good pressure at the coolant pump. The only thing I could think it could be is either the rad cap or as you say the thermostat. I have a thermostat sitting indoors so I'll stick that in first and take it from there.
Thanks for all your advice, been a big help! :ph34r:

'Tis Fixed :lurk:
It turned out to be really simple, the thermostat was installed the wrong way by the previous owner! It's surprising just how much difference turning it around has made to the cooling system, now heats up to one third in heavy traffic, fan has yet to come on! This is what I expected in freezing conditions, even in heavy traffic!

Thanks for all your help people, much appreciated!

Next on my list is to sort the seat plastics out, as they rattle and vibrate like hell! I'm chatting to Thurn motorsports, they said they'd do me a deal on the one-piece back end with twin spot tail lights.

Nate :lurk:

You mean it was installed upside down, with the wax unit facing upwards :lurk:

[image: View Post]V4 Rosso, on Jan 29 2009, 07:00 PM, said:

You mean it was installed upside down, with the wax unit facing upwards :lurk:

No the small hole was facing towards the rear of the bike as opposed to the front!

Hey all it's me again.
The bike's started to run hot again, now I've replace the thermostat, burped the radiator, topped off the coolant and all seems ok. There's no visible leaks anywhere and the expansion chamber stays constant.

My question is this.. what sort of running temps are the norm for a '94 VFR 750?? Bearing in mind it was like 3 degrees C outside, my bike warms up to just over halfway within half hour of stop start riding then the fan will kick in, the highest it's got is two thirds up the scale on the temp gauge. This seems excessively hot to me, but then i've never owned a V-four motorcycle, only air cooled v-twins, inline fours and a parallel twin.

Could I suspect the oil? What with it being colder would using a lower viscosity oil make much of an impact in running temps and heat up times?

Thanks in advance for your help

Nate :cool:

The illustrations below maybe helpfull to see how hot your VFR is really running. The first pic shows the position of the temp gauge needle with the temp sensor replaced by resistors with a fixed value. The graph below that shows the resistance of the temp sensor in relation to the temp of the cooling fluid in which the sensor is submerged. As you can see the temp sensor is of the type NTC or Negative Temperature Coefficient Thermistor.
During normal riding the temp of my VFR is about 80C (which is as it should be as the thermostat opens at 82C), so the needle of the tempgauge is somewhere between that shown in the pics marked 42 Ohm & 56 Ohm. When stopped at e.g. a traffic light the temp sometimes rises fairly quickly to over 100C (24Ohm) even with the outside temp being below freezing. The outside temp should not have that much of an impact on the cooling temp, that is what the thermostat is for after all.

Note that the temp gauge seen in the pic below is that of a 3rd gen, not a fourth gen like yours. The temp sensor used in both the 3rd and 4th gen VFR is the same item.
[image: Posted Image]
[image: Posted Image]

Wow thank you so much!
Turns out it isn't that bad then, it was running quite hotter than the images before but now it's normal.
That was a huge help, now I can stop worrying about the bike and just get on with riding it! :biggrin:
Nate :cool: