Engine runs intermidently when under load,fine at idle or in neutral. Has a clean carb, good gas flow, clean air, and new plug, almost feels like like governer at 5mph and above

Fuel starved, carb should have an idle adjustment which sounds like it is fine. Look for the second adjustment

Hey Fred, I AM SOOOOO JEALOUS!!! My teenage years Saturday nights were spent in a 64 Fairlane...(4 speed - 390 - WOW!!)..
Any way.. your carb needs some TLC, a valve clearance setting-get a qualified pro to do this!!), new spark plugs (wires maybe) .. a new air filter.... mainly the carb needs a QUALIFIED PROFESSIONAL to clean and set it once you have put in the plugs/air filter.. This will eliminate possible rough idle issues and give the mechanic peace of mind when he is adjusting the carb.
Good luck...

Hi Wendi:
If the engine runs fine except when you don't have your foot on the gas, maybe the idle stop needs to be adjusted. With the engine off, have someone step on the gas pedal while you look at the linkage at the carb. There should be a plate with a screw in it that keeps the butterfly valve from closing completely. This can be adjusted with the engine running. (SAFETY FIRST - MOVING PARTS CAN BITE)
If the engine will only run at not nice too high RPM, chances are that the idle jet in the carb is plugged, and a carb cleaning and possibly overhaul may be needed.

Fresh gas.new fuel filter and fuel lines and clean carb and screen and make sure your diaphrams are good, preset your jets 1-1/2 and run and fine tune once you get it going, also check your exhaust port and screen for being plugged

I am not sure if the bike is a 650 or 1100 but in either case it sounds like a fuel issue or and air leak. When the carbs were off for re-jetting did they get cleaned? The slow circuit controls to about 2000 rpm and it sounds similar to your problem.

The first thing to look at is the carb synchronization. If the front cylinder is lagging, it can give the same symptoms. I do not think that the exhaust is a factor because the front is cold when running.

Spray some WD 40 at all the intake manifold area when the bike is running and see if the idle changes. the idle will change and push some smoke out of the exhast if the intake is leaking.

If both of these check good I would pull the carbs back off and clean the slow circuits out completely. This is delicate work and shoud be done by and experienced tech.

If I can help some more just send message.

I hope that his helps. Steve

The Tecumseh snow motors are notorious for idling rough. Especially the last few years of production. Most service techs just say "live with it" But there are a couple of things you can do to help.
It is not a carb adjustment issue. It's usually a fuel, clean carb issue.
First, use a premium grade fuel without ethanol and a fuel stabilizer. This will give you the best fuel mix.
Second, Remove the carburetor shield and clean the inside and outside of the carb with carb cleaner. Even though you can't see the carb usually, they do get varnish build up and cleaning it will help some.
Third, Put the recommended amount of fuel system cleaner in the gas. I use Sea Foam brand. Over a tank full or two you will notice a difference in how the engine idles.
Fourth, Use a high quality spark plug and use a new one every year. Make sure the gap is correct.
Good Luck! Feel free to as any other questions you may have. Don't forget to rate this answer!

sounds like the carb is gummed up from the old gas you will need to clean and rebuild te carb(this is a easy job)...good luck

If 2 stroke check crank seals, check plug cap for proper resistance,check for good fuel flow to carb.Spark should jump at least a 1/4" gap,NOT JUST the .030 or plug gap.

Reving in neutral does not mean the same thing as under load. If you need to pull 4500rpm under load and for an instant the load was gone, you would probably overrev to 6500. With the cover off and motor not running move the throttle to full forward. Look at your carbs and see if the throttle plates are wide open. If they are not all wide open take it back to the dealer. The throttle adjustment is off. You need the full range of travel from idle to topend.