how hot is too hot, air cooled engines

[duzatun]

heres a question i was asked and couldnot answer
a mate of mine has a 500 four and had been out riding when he got home he said he put spit on his finger and wiped it on the top fin of the head and it sizzled do you think its running too  hot he asked, i didnt think so in my opinion as these are air cooled and this got me thinking how do you know if your bike is running to hot

[Bryanj]

They do get hot and unfortunately you only find out its too hot when it locks up

[SteveD CB500K0]

Under normal running conditions they will not overheat. In the late 70's I was going to Silverstone for the British GP (no dual carriageways in those days). It was a baking hot day and we queued three abreast down a country lane to get into the bike entrance. I was on a CB550K3 which ran leaner than most bikes of the day. I could tell that it was overheating as the heat that was coming off the engine was just stupendous! It also smelled "hot" (like an oven that you haven't used for a while)

I turned the engine off and pushed (as did quite a few others)

So in answer to your question "How hot can they get" the answer is "Bloody hot!"

[matthewmosse]

On the 500/4s the cluches and gearbox start misbehaving badly if they get too hot, try fitting a sidecar and driving thru Hereford center at rush hour in summer, suddenly stopping and having an ice cream seems a really good idea.

[dritchy]

In the land down under when summer days reach 40 degrees in the shade and if you have to stop you look for shade, thats just so your petrol doesnt boil in the tank! Air cooled runs hot, very hot "I have some pretty good burns on my inside leg to prove it!" You wouldnt want to stop every 1/4 mile for a set of lights, as the clutch does start to feel a bit slippy and grippy and the motors top end seem to ping a bit too much for any sane motorcyclists liking.

 I have travelled some long country miles in this kind of heat with little or no problems at a constant speed and with not too many quick stop starts. Avoiding the city riding in this heat is probablly shrewd, yet in saying that sometimes you dont have a choice.

 My Honda has yet to melt from this kind of riding. After 4 hours riding in these conditions, then stopping and turning her of she didnt want to start again, atleast not straight away. I presume due to oil level as the red light was on? and of course I needed to go again a.s.a.p, I gave about enough time to have two cold beers and fill the oil up 100ml and of we went again this time two up?

 I have tryed my best to see how hot, too hot is and honestlly I dont think under normal conditions you will. As long as air is flowing through and around the motor of any heat? its when this air stops that the heat transfers very quicklly to the lower motor which retains it and need I go farther.

 It would be a very nasty experiment to sacrifice a motor for the satisfaction of knowing exactlly how hot is too hot. Maybe Honda did these tests? that would make good reading. 

[JonnyB]

I love our language  - "It also smelled "hot"", but I know what you mean, as long as you're moving forward, it generally isn't a problem, it's being sat in traffic and only move a couple of inches an hour.

I remember once, when we used to have hot summers, on an early Yam 350LC - in black leather (me not the bike), sat in traffic in the middle of town, I had to pull over and cool off because it was just to unconforable having somthing that hot between your legs.

[clive]

back in '76, for those that can't remember it was a hot summer , i had a cb750 dresda k1, when stuck in traffic or crawling along at 30mph it used to spit out of the carbs and stop, after about 15min i could start it up and go through the same sequence again unless i was on an open road doing 50+, a friend suggested fitting an oil cooler, which i did and the problem was cured

[duzatun]

well dritchy being in down under  myself i know exactly what your talking about on top if the heat the humidity is a killer and i have had the old clutch probs through heat with the 750 fours but this is the 1st 550 ive owned and it suprised me the amount of sting she has i guess as long as you get home in the end alls good