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47 cub wont start help

C

casefrank

Member
OK I"m lost here, Just finished putting new ring in her as the old ones we colapased. Had been bored .030 over Did valves too. Has nice blue spark from the mag. Set timming this AM and she Started and ran this AM for a few minutes then ran out of gas. Put new gas in and now will not start, run or stay running. Good engine turn over has 120 psi on the cylinders and 25 lbs oil psi, pulled carb off and cleaned it Had it rebuilt by Motec Eng. a few months ago, found little dirt cleaned everything, and made sure that each opening is open by spraying carb cleaner in each one, and put it back on. Now it hits and misses and puffs black smoke, starts to run but only for 5-10 seconds. Applying the choke doesn"t do any good. Pulled the main jet out and it had good clean fuel in the carb.
Any one know how big the fuel inlet valve hole sould be look alfull small to me. Have goveanor disconnected as it is another challange.
Please tell me it"s some dumb thing I"m doing
Thanks Frank
 
Sounds like your engine is flooding from too much gas. Check for dirt under the float's needle valve. Shake that float to make sure it isn't full of gas from a leak. Hal
 
Nothing jumps out at me - but black smoke sounds like it's getting plenty of gas into the cylinders - if not too much - just not burning properly.

(I'm assuming you've tried this without the air cleaner attached - and ruled that out for blockage - if not - try that first.)

My first guess would be that you're flooding - but typically once you get it to start after flooding they usually stay running ok.

Does the carb drip gas at all?

Could also be a weird combination of flooding - and restricted fuel from the tank. Make sure you have a solid stream TO the carburetor.

Also sounds ignition related - where you get fuel but it doesn't burn right - but assuming all those components were good to begin with - as in it used to run fine?

Might want to at least go over everything on that side - clean your points - make sure your cap is dry, etc.

Not sure about adjusting valve lash on a cub - but if it's something you can do - I'd recheck that.
 
Probably got some crud in it when it ran out of gas.

If you guys would do as I do and put a 2" standpipe in the tank outlet and make a fuel screen boot over it you would have no more fuel problems.
 
Well today I checked the spark by turnning her over by hand all plugs sparked I then thurned her over by the starter and had spark at all plugs Put the plugs back in and put hand over carb to see if their was valcum had good suction thruned gas on as she started right up but only ran for 2-3 minutes before she flooded out gas was pooring out of the choke area.
Got the gas to stop but then whe would not start again. I did give her a name Franks Nightmare
Thanks frank
 
I think the outfit that rebuilt your carburetor did a shoddy job unless some dirt from your gas tank is under the float needle valve. That's what keeps the gas at the same level. It may have a hole causing the float to sink and starts flooding. Hal
 
yeah - definitely sounds like your floats/float valve.

If it's dripping, the floats aren't closing the gas off into the carb.

Generally there are 4 things that can cause that.

1st the easiest - the floats are sticking in place. A few sharp raps on the side of the carb from something not too solid (like a screwdriver handle) usually frees them.

2nd - floats have a leak. If you've just had it professionaly rebuilt - one would hope that's not the issue.

3rd - Junk in the float valve - you might get by with blowing a little compressed air or carb cleaner through the gas inlet. But likely you need to remove the floats/valve and wipe it down.

4th - floats aren't adjusted properly - again one would hope that's not the problem since it was just rebuilt.
 
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