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carb popping Ford 8n

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scott

01-24-2004 17:01:49




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The problem Im having is after the tractor starts it pops back through the carb. It does this at idle as well as full throttle. All the tune up parts are new including new carb. Gaps are set correct on plugs and points. Checked and double checked them. Im thinking maybe a stuck valve?? Any Help or ideas
Thanks




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Ron

01-24-2004 22:05:48




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 Re: carb popping Ford 8n in reply to scott, 01-24-2004 17:01:49  
I have seen two different types of valve-lifters in these.. The "Domed" ones can "peen down" and spread out, and stick... the newer ones are not domed, and don't cause that problem.. I don't know that is your problem, but I have run across this..



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Mike

01-24-2004 20:01:41




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 Re: carb popping Ford 8n in reply to scott, 01-24-2004 17:01:49  
Haven't seen whether the popping is constant or if it sometimes does run right. The firing sequence on these is different than most 4 cylinders, if my memory serves me right. If it runs okay sometimes, might be electrical or fuel, not mechanical.



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Don Wadge

01-24-2004 19:22:47




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 Re: carb popping Ford 8n in reply to scott, 01-24-2004 17:01:49  
Was the popping the reason for the tune-up. Maybe you are not getting furl freely to the carb. An engine will pop back through the intake when it is starved for fuel. Not familiar with the 8n but if it has an adjustable needle valve maybe it is set too lean. If this tractor has been sitting a long time there is the possibility of a sticky valve(s) which would bother at high rpm but would likely clean up after 30 minutes of running as long as the valve is operating and not stuck open. If it was stuck open you would certainly know it. If it was just a poor valve I don't think it would pop at higher rpm. I'd look more to a fuel problem than anything and I would double check the timing. You would have to be a long way off for it to do this but it is possible.

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Scott

01-24-2004 19:28:49




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 Re: Re: carb popping Ford 8n in reply to Don Wadge, 01-24-2004 19:22:47  
The tractor had been sitting not ran in about 3 1/2 years The popping it spits back out a little smoke also as I dont have the tube hooked back up yet that goes to the air box



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Don Wadge

01-25-2004 07:14:24




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 Re: Re: Re: carb popping Ford 8n in reply to Scott, 01-24-2004 19:28:49  
Well, it sounds like there is the possibility of a sticking valve. I think I would check to make sure you are getting gas freely to the carburetor and I would double check the float level as well as making sure there is no dirt obstructing the jet or needle valve as the case may be just to eliminate this possibility. Then I would take off the valve covers and check to see that all valve lifters are going back down and see if all valves are going back down. If this is all good I would start the tractor up and spray WD40 on the valve stems and lifters with the tractor running. I'm not sure how long you can do this as I do not know how much oil will come out with the covers off. I have done this with overhead valve engines and it works well. If this is sticky valve(s) or lifter(s) it will clean up with a bit of running. Another thing you can do is put about 1/2 a gallon of WD40 in th oil and run it for a while. This will help clean up your rings as well.

I did this with an old unstyled A John Deere we found several years ago. It was seized when we got it and we managed to get it unstuck but it barely had enough compression to start and ran poorly so we put about 2/3 WD40 in the crankcase and let it run. It just got better and better. Then we drained it and put good oil back in. It then had not bad compression and after a period of time just of normal playing around (wasn't being used for work) it would bounce like a new tractor.

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Jerry/MT

01-24-2004 18:44:51




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 Re: carb popping Ford 8n in reply to scott, 01-24-2004 17:01:49  
Chance's are it's a sticky valve if it's poping through the carb. Those L head engines were prone to that. A little Marvel Mystery Oil on the valve train and about a pint to a full tank of gas was the method my neighbor used on his 9N and he said it cured a chronic problem for him. Hope you are using detergent oils. They should help prevent that problem.



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Scott

01-24-2004 19:07:42




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 Re: Re: carb popping Ford 8n in reply to Jerry/MT, 01-24-2004 18:44:51  
What do I need to do to correct this and free up the valve if stuck.Not stupid but dont know alot about these motors



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Jerry/MT

01-24-2004 19:40:11




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 Re: Re: Re: carb popping Ford 8n in reply to Scott, 01-24-2004 19:07:42  
Yeah, I would, 'cuz if you don't, your tractor will run like a three legged dog. I believe your engine is a "valve in block" type. Take the side plates off to where you can see the valves. Have someone crank it over for you to see which one is sticking. Verify by pulling the plug on that cylinder. I will probably be fouled. Squirt some carb or brake cleaner up the valve stem to the guide to try to disolve the accumulated varnish and gum. In the worst case, you may have to take off the head and remove the valve. When you get it free, add some Marvel Mystery oil to your crankcase per the instructions on the can and 1/2 pint to a tankful of gas and run her that way. While you're in there check the valve clearances and adjust as necessary.
Hope this helps.

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old

01-24-2004 17:10:34




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 Re: carb popping Ford 8n in reply to scott, 01-24-2004 17:01:49  
Could be a valve, or you might have it to lean which can cause it to back fire some. If its to lean it can also burn valves and with this unleaded gas its better to run a little rich then to lean



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