VFR750F Overheating

GaryWright670... · L Plate Warrior Joined: 16 Oct 2023 Karma :

My beloved Honda VFR 750F 1992 is overheating. Please can anyone tell me what might be the cause or at least tell me what I should check first. Accessing the thermostat seems a very major dismantling job. But before I do that what else might be the cause? Question

Thanks

(PS This is my first posting to this forum Smile

jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

Hi, what tells you it`s overheating?

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

Does it have any coolant in the radiator and expansion bottle?

Is the radiator fan kicking in when it gets hot?

jeffyjeff · World Chat Champion Joined: 02 May 2020 Karma :

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

In what circumatances is it overheating?

On most older VFRs of that era, the radiator itself can be in a bit of a grungy state. Is it clean and are the cooling fins mostly clear and straight? Likewise the oil cooler. The oil cooler lines are also fairly out in the open, they are known for corrosion (which would cause a significant oil leak) but they are succeptable to damage or pinching too.

When was the coolant last changed? Was it drained properly via both the drain screw on the bottom of the water pump and the two drain screws on the front of the barrels? If it's not been done for a while, might be worth draining it to see if it's full of grunge and giving it a flush through. You'd going to need to remove some parts to get in about the filler cap and such anyway so it's worth doing while you're in there, then you know the system is clean and full of coolant. I generally drain it then stick a hose in the filler cap and trickle water through it slowly for a while. Then I fill it with water, run it up to temperastre and drain it a couple of times. The process of doing this might throw something up anyway.

The thermostat is a major suspect though. It's a bit of a pain in the arse to get at. You should be able to fiddle it out if you remove the right hand side panel and the coolant hose on the right side, then you can reach through the frame and undo the bolts to get the lid off. You may need to be inventive with small ratchet spanners and 1/4" sockets. Here's roughly what you're looking at with the airbox and carbs removed (at which point it's easy), this is a later model than yours but still an RC36 so it should all be very similar. It is possible to do with the carbs in place though but there is a lot of stuff in the way.
https://lh3.googleusercontent.com/pw/ADCreHeC7XEGAiGtmHBCacAY_IN2c-Xja0DvTMLac7i64uf-HSy2PnbHR_4H5r00zN3vfiDqCNKGKbf_yQa9b5gBZ2RLJwU8LypuDIpR3lGmCMIcdJhWOTblldPB-jkPF_oBkljQTIfmIrXjtLGn3rbCwZok=w1547-h870-s-no
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jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

Sounds like the O.P. has heat stroke? Crying or Very sad