Hot to touch crankcase/timing covers.

After successfully running a rebuilt motor for a few short road tests, I took the rear wheel off to fix/replace the speedo drive. Re-assembled and started but it ran really poorly and misfired under load. Further, it is now very difficult to start. Plugs are black so I leaned down the mixture 1/2 turn.

There is a solid spark & compression; not great 110 both sides but I've noticed that the crackcase and timing cover were extremely warm to touch. Too hot to touch actually. I'm pretty sure I can figure out the misfire but the temperature of these aluminum cases concerns me.

Does anyone know if these generally run that warm?

Thanks

BC

I completely rebuilt my motor two years ago, and yes with all new components not bedded in yet it ran "hot".

I kept the initial rides to under five miles to let the motor heat up and be allowed to cool down.

I noticed after some 300 miles that I did not feel as much heat, and yes the timing cover and crankcase do get very hot, the timing cover way too hot to more than just touch and the crankcase cooler.

I wouldn't be concerned about it, that heat off the cover is normal and built up very soon after startup.

I changed the initial oil and filter at 50 miles, 400 miles, and now every 1000 miles with castro 20-50 GTX dyno.

I had a very hot motor after a rebuild and I'm sure it had to do with carb settings. Needle set too low and float level low. Got hot enough that the timing cover would boil sweat.. scared me good. Double check your timing and carbs.

I have a 1973 750 Roadster that has never been rebuilt, runs so good that I haven't checked timing or valves in years (which equals maybe 4000 miles) and I only putt around town without revving wildly, and I have a hot timing cover too. Has new Amals (930's instead of 932's, happened to be the only pair on the shelf) and idles at about 1100 rpm at stop lights without having to blip the throttle. I want to tell myself that the hot engine is normal, and keep on riding as is?

I have never been able to put my fingers or hand on nearly any part of the engine after it's been run.

Dave
69S

Take your car out for a ride, just around the block or so. When you get home, pop the hood and try to lay your hand on the engine block. Now remember, this is a water cooled situation.

Just a perspective.

Clearly I'm not going to handle the cylinder blocks. Its the timing cover that seemed to be unusually warm given that the heat is generated well above that point. I can't see how the firing pistons would cause the timing cover/crank to heat up, and as such, it might be the crank bearings? Everything spins freely and there's no noise so I find it a little concerning. The Triumph 650 certainly never gets as hot as the Norton.

BC

The timing case is aluminum, and is attached to the barrels. Aluminum is a very good conductor of heat, as well as electricity. Touch the drive side crank case for comparison. I'm sure you'll find it's the same. But realize you can't hold your hand on anything above about 130 deg F. and that's not very hot.

Stillreel said:

Clearly I'm not going to handle the cylinder blocks. Its the timing cover that seemed to be unusually warm given that the heat is generated well above that point. I can't see how the firing pistons would cause the timing cover/crank to heat up, and as such, it might be the crank bearings? Everything spins freely and there's no noise so I find it a little concerning. The Triumph 650 certainly never gets as hot as the Norton.

BC

Click to expand...

Aluminum is a great thermal conductor. Too hot to touch is PERFECTLY NORMAL

Indeed , 90 degees , with grubby fingers , yyou can :lol: place he on it and count to ten , without burning them . ( not pressing ) Commando timing cover was about the count of two
after a few miles . With the oil breather system aft , the oil heat is going through there .

As Above , though . Id check and see ign. timing is correct on both , and read plugs , see theyre square tips on centre electrode 7 no molten deposits .Real Fuel used to burn
pale yellow on center insulator and chocolate brown on outer face , on a TRIUMPH . Norton was white , white & white . :mrgreen:

Useing 100 Octane fuel will make things better all round , running in . Cooler days preferable to a heat wave . Usually 500 miles for the first Oil Change , to remove the initial
debri from components seating . Let the throttle roam , and the speed a little , rather than sitting at one dead spot . I prefer to use 1/4 or less throttle for the first 500 miles.

Consider 2000 run in and 4000 loosened off to free running , but youd always whip the fingers away at the count of 2 or three , on the timing cover .