What needs adjusting?

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Model T Ford Forum: Forum 2012: What needs adjusting?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Donald Rivard on Thursday, September 20, 2012 - 06:53 am:

I have a 15 Roadster I purchased to do a body off restoration on. It starts and runs great on battery and mag. so I wasn't planning any engine work. There is one problem though. Every time I shut it off in back fires (very loud when your in your garage). It doesn't seem to matter where I put the gas and spark levers when I shut it off. it still back fires. Has anyone else had this problem? What is the cure?
Thanks
Don


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Thursday, September 20, 2012 - 07:29 am:

Donald,

Could be a few things and a first stab at it is probably too much raw un-burned gas getting into the exhaust. When the air flow stops, the heat makes it go 'pop'.

Have you gotten through correct carb setting on lean/rich? Start car and let it smooth at idle with 'sticks' in the right place. Turn the bonnet needle valve on carb ccw 1/8 turn at a time until it just sputters, and then 1/8 cw back to smooth it out...Go for a ride and if it sounds starving at higher RPM open the needle valve 1/8 more cw and probably no more than 2 times. See if your backfire got better.

Another little trick once you know where the sweet spot is, is to bend the throttle cross rod , with the throttle stick all the way up so that the carb starves and conks out before turning the switch off...

Give both a try, it just may be your cure.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode Chehalis Washington on Thursday, September 20, 2012 - 11:20 am:

Maybe some carbon build up in the combustion chamber and exhaust valve. The carbon will get red hot and set off raw gas after the spark is turned off.

I like George's solution/work around. Just close down the air fuel mixture to starve it to death or maybe even better just turn off the gas feed to the carburetor. If it is going to set any time at all you should always shut the gas off that let the gas run out of the carb anyway.

Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Claverie on Thursday, September 20, 2012 - 11:27 am:

Good advice, George, but don't you have your CW and CCW backwards?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Wetherbee on Thursday, September 20, 2012 - 12:25 pm:

My apologies Don - that little car sat for a while and it is most likely too rich now that the old gas with stabil has been used up from the tank. If what George suggests does not work, a good cleaning of the carb with gumout may be needed.

Also - back off both levers before shutting down - try starving it and there will be less unburned gas to pop.

I've lost your number or I'd call with all this - if you need give me a call.

Mark


Top of pagePrevious messageNext messageBottom of page Link to this message  By Donald Rivard on Thursday, September 20, 2012 - 07:48 pm:

Thanks to everyone for the info. Starving the carb seems like the simple solution. I will set it up so I can almost stall it with the throttle right before I shut it down.
Don


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