Motorcycle Repair: ct70 3-speed, carb settings, stock intake

Question
How do you tell if the engine is overheating? What should the temp be? Where to check? Is testing the oil good. I have a infrared ther. And I am totally confused about the sooty look on my spark plug. I believe it is running rich. I read try alot of plugs at different stages until you get it right. I just rebuilt it so I thought you weren't supposed to run it at full throttle for extended time. I heard ride it up a mile hill and check. If I am just riding in the yard should I use a hotter plug? Is some black okay or none. Are these bikes hard to adjust? Thanks Shirley  

Answer
How do you tell if the engine is overheating?
USUALLY THE PISTON WILL SEIZE MOMENTARILY
What should the temp be? OF WHAT? EVERYTHING HAS DIFFERENT TEMPERATURES TO IT.. OIL LESS THAN 300 DEGREES, THE EXHAUST TEMP WILL REGISTER UP INTO 1500 OR MORE....
Where to check? SEE MESSAGE BELOW IN SMALL PRINT
Is testing the oil good. CAN BE IF YOU ARE LOOKING FOR BURNT OIL, INDICATING OVERHEATING, BUT USUALLY THE PISTON WILL SEIZE FIRST.
I have a infrared ther. PROBABLY DON'T NEED IT. NICE TOY, THOUGH
And I am totally confused about the sooty look on my spark plug. I believe it is running rich. I read try alot of plugs at different stages until you get it right.
WITH A STOCK ENGINE, STOCK INTAKE/EXHAUST THE STANDARD PLUG WILL BE JUST FINE. THEY MADE CT70S FOR 10 YEARS WITH DIFFERENT CARBS, SO I DON'T KNOW WHAT TO TELL YOU ABOUT THE CARB SETTINGS. NEED SERIES, CARB NUMBER SERIES, YEAR OR SOMETHING MORE....

I just rebuilt it so I thought you weren't supposed to run it at full throttle for extended time. CORRECT, YOU NEED TO BREAK IN THE PISTON AND RINGS, GENTLY
I heard ride it up a mile hill and check. PROBABLY NOT
If I am just riding in the yard should I use a hotter plug? NO, IT ISN'T A RACE BIKE, IS IT?

Is some black okay or none. NONE WHEN IT IS DIALED IN CORRECTLY.

Are these bikes hard to adjust? NOT FOR ME, BUT I DON'T KNOW WHAT YOU KNOW ABOUT THEM OR YOUR EXPERIENCE WITH WORKING ON BIKES, MOTORS, CARBS, ETC.

Okay, Shirley....   Will try to get you on the right track without writing a book about it.

First, the engine needs to be checked to see if it is okay, mechanically. If the cylinder was rebored and new piston and rings fitted, then they need a gentle breakin for about 300-500 miles, varying loads and speeds, but NOT WFO for a mile at a time.

On reassembly, the cam timing is critical to engine performance. If you KNOW that it is right, then the compression should check out at around 150-175 psi. If it is way down below 150, either the valves are too tight (reset at .002" cold on compression stroke) and leaking, a piston ring is broken or damaged or the cam timing is off a tooth. Fix whatever it takes to get the compression back up to range again.

Once the cam timing/compression is correct, then you need to set the ignition timing. With a magneto system, the gap regulates the ignition timing (all engines, really), but there isn't any other timing adjustment other than the gap setting. The points need to just barely open when the F mark is aligned with the engine case mark.

NOW you can address the carburetion. The carb needs to be clean inside with no worn parts, like the slide needle or main jet. Idle mixture screw setting should be around 1 3/4 turns out from seated. Clip on the needle will be good around 2 or 3rd notch from the top of the needle. Again, it depends on the carb model number and year of the bike. Hopefully, they are all the same items from the factory. If you are putting a "bitsa" bike together, then you will have to fight your way through the settings until they work for your application.
C7-HS or C7-HA plug should be just fine if everything else is dialed in properly. If you have changed the air filter and/or exhaust, then the carb settings may be way off and you get to do more tuning until the bike runs properly through all rpm ranges and the plug is nice and toasty brown or white on the tip. Any kind of odd "pepper flakes" on the electrode are also signs of overheating, BTW.

On a new engine, the rings will not be seated properly, so the motor will use a little oil and smoke a little blue smoke, perhaps. If it does, the plug will show a bit oily and maybe a little black towards the tip.  Once it all breaks in, properly, then the plug should be clean all the time. Hopefully, you replaced the valve stem seals, if equipped.

"""" THE END"""

Bill Silver