Topic: SOHC 750 - How to judge for overheating

[neil10]

How to judge for overheating    thks

[troppo]

i`ll be waiting on the answers to this one too

[736cc]

  On a new motor, rings not sealing and not allowing heat to be radiated from combustion or an oil lube problem. Overheating a mechanically sound air-cooled motor will happen if its not air-cooled sufficiently, as in idling excessively, stop and go traffic on a hot day, full-throttle miles on end. No or low oil level will also do it. Clutch is the 1st to complain, obvious heat pouring off the motor the 2nd, increased mechanical noise another symptom.  When oil starts pouring out of unwanted places, its likely the motor mating surfaces have warped (I hate when that happens).
  Basically it won't overheat if you avoid causing it. Thats a stout motor w/ one of the best reliability records ever. I've never had a CB750 overheat on me, and we're talking over 100,000 miles and I don't baby them.

[SteveD CB500F]

It's happened to me twice.

Once on my 550K3 queuing to get into the British (bike) GP in 1978. Smoke from the engine breather was the main symptom. As it started coming out from under the seat, my mate shouted "your bike's on fire!" Me and the GF off in a nanosecond! I caught it before it nipped up thank goodness.
I think Roberts beat Sheene that year 

Second time was recently on my '72 500. A very slow 6 mile ride in first gear slipping the clutch. It was a charity toy run and you just had to go with the flow. Most guys were there on watercooled bikes.  The clutch overheated and grabbed badly. It became almost impossible to ride and I had to stop and let it cool down.



BTW Neil10 - I've edited the title of the thread; you may get a better response.

Steve

[andy750]

If the cam cover is red hot then its probably overheating! You may have your timing over-advanced  -this happened to me on my K2. Timing was way advanced and as a result my engine was red hot. I could feel it on my face while sitting on the bike! Hot!

And sitting in traffic at Laconia, NH with 100,000 other bikers in traffic on a very hot day dosent help your bike much either 

Good luck in sorting it out!
cheers
Andy

[736cc]

  Detonation (pinging) becomes obvious when rolling on the throttle.

[neil10]

this is my first air coled engine for 30 years  so I feel the engine and i'm saying to my self this engine is hot. Maybe it's just me

[merc2dogs]

 I keep an industrial type dial thermometer on my bike, one of those with the long spike and the dial, normally monitot the oil temps on long hauls.  sometimes they're used in cooking for checking roasts turkeys etc, Just dip it into the tank when I stop for whatever reason, oil temp generally stays between 180 to 210 degrees, I assume it's a fair indicator of safe temps.
 I'ts well within the 'safe' temp range of watercooled bikes, I have seen hotter, both on mine and water cooled bikes, though with no ill effects being noticed.

Air cooled Volkswagon head temps are acceptable at over 350 degrees, oil temps for them are good at 210 or so, I'd assume the same would carry over to other air cooled engines.

 If concerned, there is a pretty nice little cylender head temp gauge made for VW that should be easily mountanble on the sohc.  Been out of bugs for a while, so can't give a name/source.


Ken

[neil10]

thks ken thats a good idea thermometer in oil

[Jonesy]

  Detonation (pinging) becomes obvious when rolling on the throttle.

Yup. A warning sign is when it starts to sound like marbles rolling around in the top of the engine when you give it throttle under load. That tells me I need to find a nice, clear stretch of pavement and "breeze it out", as they say...

[dustyc]

You could also use an infrared thermometer http://www.maxtool.com/index/Digital_Infrared_Non-Contact_Thermometers.asp

[neil10]

 just neeed  to judge what temp is correct the first time then i''ll know. Maybe kitchen shop for thermometer   thks guys

[Tower]

Turkey thermometer    If someone asks...just esplain..your bike doubles as a deep frier    Drumstick?

[dustyc]

Here's a thread about measuring the oil temp.

http://forums.sohc4.net/index.php?topic=11697.0

[PxTx]

I would like to second the mention of the advanced ignition causing the engine to run hot.  I had a 550 that had the mechanical advance locked up.  Bike ran fine, but after long trips, the oil light would come on at idle.  Later found the problem and resolved the oil light issue.