Hi. I have an 86 VFR750 that I got about a month ago. After riding today I noticed a sound coming from underneath the seat that sounded like the coolant in the rear cylinder head was boiling. This is the first time I've heard this and it went away after about one minute after I shut it down. The temperature gage wasn't up there and the coolant is topped off. I'm wondering if that head gasket is blown but the bike seems to have plenty of power. I've had it hotter before in stop and go traffic and I haven't notied this. Has anyone else experienced this? The bike has the California emissions system on it so I'm wondering if there is some foul up with that but the noise was like a loud, runbling sound. Another thing I've noticed is that my left leg up by the seat really gets hot. It's hot enough that wearing shorts is pretty uncomfortable. Incidently this would be right by the head in question. Has anyone else experienced this? I'd like to ask other people about it before I look into a leak down test or something like that. Thanks
There's a skinny overflow hose between the radiator and the coolant overflow bottle. Your '86 is old enough that if this hose is original it's probably split. If it's split, then when the coolant cools and contracts and gets pulled back from the overflow to the radiator, it may not be able to suck the coolant back over; instead it may just pull air through the cracks in the hose. This would cause air in the cooling system and that might make noise. Plus it wouldn't cool the bike as well. I'd check this hose just on general principles.
i recently picked up an '85 VF1000R and i'm experiencing the same problem. after riding, i can hear the coolant boiling. i don't hear any sound like air being sucked through cracked hoses, just bubbling. i have not heard the fans turn on at all so i'm thinking that the thermostat is stuck and probably needs replacing. anyone? thanks!
