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Drawing air into the exhaust

A

Anonymous-0

Well-known Member
I am wondering what I did wrong. After rewiring my 49 Cub the exhaust is now drawing air in when I try and to turn it over. I know it is positive ground and think that I rewired it correctly. A different (from another CUb) distributor was put on with new wires, new plugs, the timing was set an the valves were adjusted also. The starter switch was also swapped out and a light switch was wired into the mix after not having one prior. So what would cause it not to start and draw air in through the manifold pipe. Thanks
 
Did you take your timing gears off?

Exhaust valves could be open on your downstroke. Check your timing marks, if they are correct, its turning backwards.
 
The starter will only turn one way. I converted my H to 12 volt negative ground and it turns right. Shouldn't matter if it is positive or negative ground.
The only think that would cause that, that I can think of, is the cam being in wrong. Good luck.
 
Is there an exhaust valve that is stuck open? I had a single cylinder marine engine that had a stuck exhaust valve and it sucked enough water (salt) back up the exhaust valve to fill the carburetor and contaminate the crankcase oil.
 
I do not know what you did, but two things strike me as important.
It should spin CW when standing in front of it looking at the radiator. (the fan blades pull air through the radiator, top of fan moves to the carb side. If it is spinning backwards, the only two things would be a starter from a power unit that should go on the engine side of the flywheel and face as they do in most cars which if put into the rear will spin it the wrong way, Or the starter motor has been disassembled and resoldered together wrong. All series wound motors run one way only no matter what the polarity. When manufactured, that direction is set. Jim
 
If it is turning backwards it is not getting oil to the engine parts. Oil pumps do not pump anything but air when turned the wrong direction. Jim
 
Great, thanks for the reply. One thing that David Bennett from Virginia told me late last night was he thinks that the valves might have been over tightened. Armed with all your responses I'll tackle the Cub Saturday morning and see if I can get her running again.
 
(quoted from post at 06:21:47 04/06/10) Great, thanks for the reply. One thing that David Bennett from Virginia told me late last night was he thinks that the valves might have been over tightened. Armed with all your responses I'll tackle the Cub Saturday morning and see if I can get her running again.
Click to expand...

Exactly! The exhaust valves are not closing completely. Go through the entire valve adjustment procedure again.
 
Yeah he does, too bad his Cubfest is this weekend because he said to call and he'd walk me through the steps. But I don't want to bother him while he's got 100 people over at his place.
 
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