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cub missing

A

Anonymous-0

Well-known Member
Today I bought a new carb from dealer,put it on and still my cub won t run.I rechecked compression and spark on each cylinder,all good.At times it starts and runs smooth for a minuite, then sputters then stalls.It seems to start best with timing so far advanced the starter can barley turn it.Do you think it would sometimes run smooth if the cam gears are off?I pulled the distributor but there is a seal in the way to view marks.Could the gov be the problem?It seems to not have full range on throttle selector but I would not think it would not allow it to run. also I ve pulled the muffler. any ideas? thanks, Dick
 
if the cam gears are off, it will run bad all the time. i looked back a couple pages to see what else was going on with your cub, and i see the water in the exhaust post. if it runs good at times, then doesnt, i would re examine the ignition system and fuel system. disconnect fuel line from carb and let it run in a can for a few minutes to be sure you have good delivery and no sediment plugging stuff up. you have a new carb, so hopefully that is ok. do you have a mag or distributor ignition? recheck cap and rotor for damage, also re-check points and condenser. then wiggle distributor shaft side to side and check for worn bearings in the distributor. clean up all the electrical terminals if it is a distributor ignition. start at the dist and work back thru the coil, then to the ignition switch,then on to the battery power. try also running with the air cleaner tube removed from the carb, in case that is plugged up.
 
Are you sure there's a full stream of gas from your tank to the carburetor? If you're not sure pull the line at the carb a check the flow from the tank. If there's just a trickle you have blockage in the tank or gas line.

Bring No1 piston near the radiator to TDC on the compression stroke. Hold your thumb over the plug hole while a helper slowly hand cranks the engine until you feel pressure against your thumb. Have him keep cranking slowly while you keep your thumb over the plug hole until there's no pressure. Then look to see if the timing mark on the damper pulley is aligned with
the pointer. You can now install the distributor by rotating the rotor until it points to the No1 plug tower. Then reinstall the distributor. Then see if the engine will run ok. Hal
 
Thanks for the replies.I think since the plugs fire every hit with blue spark it should go.Iv e tried to time it with aligning #1 on compression stroke, but something is still wrong.My manual says there should be 2 marks on the pulley tdc and 16deg btdc, but I only see 1 mark.Thats where I ve been lining it up. But from there I ve twisted it each direction.I ve replaced several parts but keep coming back to the good spark at plugs and gas at the carb, with good compression.I ve been working at it over a month now and just can t seem to come up with the right answer. I m almost ready to haul it to the dealer and that will be a hard pill to swallow. Dick
 
Hold your hand over the throat of the carburetor while a helper makes an attempt to start the engine and see if there's good suction. Poor suction is an indication of low manifold vacuum. Could have a leak around the intake manifold or poor compression. Hal
 
Take the cap and rotor off. Check for play in the distributor shaft.

If the distributor bushings are badly worn the timing will be all over the place.
 
I took the cap off and I can wiggle it about 1/32in. is that too much? I got out my parts book and I don t see bushings, do you replace the whole shaft? Do you think this is the culprit? As I say it has good blue spark every time it cranks.Also it has suction and white smoke coming out the muffler.A couple weeks ago I was reving it up and down and it sounded pretty good, but now it barley starts and sputters. For gas I ve got the hood off and a 1 gallon plastic can mounted aboue the touch control so I don t think fuel is the problem as it has good flow of new gas.Also I ve replaced wiring harness and coil with no change. Maybee the distributor is bad. Thanks Dick
 
How long have you owned this Cub? I don't think the the cam gear can be off since the engine runs smooth at times. If there's a fuel filter in the gas line remove it and try starting
the engine. I still think you have a fuel problem. Do a compression check and compare the readings. Hal
 
I ve had it 3 months. At times I ve drove it up and down the street,thanks for the ideas. I still am missing something.I also changed head gaskets as my uncle told me to clean all the carbon buildup off. I pulled the exhaust manifold, didn t see anything obvious.I don t know what I m missing but I ll keep updating. Dick
 
Spray some starting fluid in the area where your intake manifold mates to the engine. Do this trying to make a start without using your choke.
If the engine fires you have a manifold leak. Hal
 
(quoted from post at 21:09:34 10/29/11) Spray some starting fluid in the area where your intake manifold mates to the engine. Do this trying to make a start without using your choke.
If the engine fires you have a manifold leak. Hal
Click to expand...
Check the needle valve at the sediment bowl. Open it up all the way then close one turn. Tighten the packing nut enough so the needle does not move from vibration.
 
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