Put new carb on 86 cr 80 ran fine 4 10 minutes then quit changed spark plug and gas still nothing. has spark dont know how hot also changed manifold appeared to be dry rotting still nothing. even attemped dumping gas down the spark plug inlet nothing

Chcek stuck or loose choke flaps and integrity of carb manifold gasket. Check the ignition coil cable (connected to the spark plug). The kill switch wires should not any crack that may touch the chassis ground.

Hi Lennard:
Cars and trucks section but CR80 sounds like a motorcycle. right?
You need two basic things:
1) Spark - pull the spark plug, connect the lead, hold against the head, and spin it over. Spark shoulld be hot and blue.
2) Fuel - Drain tank and fill with fresh gas
Drain and flush carb
If it has a filter, make sure that fuel is flowing through it.
Try a "normal" start........... choke, kick over 5 times. If no start, remove plug and check for fuel in cylinder. Wet plug means no spark. Dry plug means no fuel.
If dry plug try priming the carb (give it a squirt of gas with choke off)
It should try to start.
To let me know how you're doing, reply as a comment on this post.
Cheers.

If you have compression then the first thing you check is for spark. If you have spark then you move on to the fuel system. You will have to pull off hoses at a couple of points to see if gas is at the carb and further along. If it is the carb then a simple carb kit will work.

Spray starter into the carb intake with no choke, if she runs for a few seconds then you know its fuel starvation
clean jets & airways & blow through with compressed air

try a new spark plug. if u fowl out a plug some time they will not fire under compression.2 strokes need. fuel,fire and air, very simple engines.it is possible crank seal are bad .that doesn't allow the engine to create vacuum in the crank case.thus fuel and air will not make it to combustion chamber.

hi
if you have a good compression,a strong enough blue spark and carburetion for the fuel air mixture try priming the engine(put small amount of gas in the spark plug hole)then start the engine.If the engine runs only the gas you put inside the cilinder there is a carburetion problem to find and fix.
let me know regards savumihai71

need to gap plug correct

Check the rectifier.

It can be quite a things - a blocked air filter or a blocked exhaust. To clean the exhaust, unbolt it from the manifold, hold it vertical and hit on the side until no more soot comes out. Changing the air filter should be pretty straightforward. If the spark plug bottom end is black then you have the fuel mixture too rich and you should lessen the flow of fuel.

Based on the information given, I think you may have a hole in the top of the piston. It sounds like pre-ignition, ( AKA detonation and engine knock ). Pull the cylinder head and check the piston and cylinder head. Sometimes the top outer edge of the piston disintegrates due to the heat. Replace the piston and rings and remove the carbon from the head. Be sure you run 32/1 mix on gas and oil. That's 4oz two stroke oil per gallon of gas. Only use premium gas.

Remove and clean the carb. Be sure the carb mount bolts and carb manifold bolts are tight. An air leak will cause the engine to run hot.

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