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Subject: Backfires

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Cal Sexsmith    Posted 10-17-2018 at 20:05:35 [URL] [DELETE]        [Reply] [Email]  
  • Backfires
  • I have a 1948 8N with front mount distributor and converted to 12 volts about 3 years ago. Put on a new carburetor two years ago. It has been starting and running reasonably well since the new carb. It wasn't used during the month of September. I tried starting it in early October and it took a long time to get going but finally started. I ran it for about 15 minutes, although it seemed to be running rough, and then it stalled and wouldn't re-start. I left it for a bit and tried again, I flooded it so I pulled out the plugs and cleaned them. It then started but was almost continuously backfiring. I put in new plugs and the problem remained. It also seems to be flooding very easily. Any ideas?

    Tim Daley(MI)    Posted 10-18-2018 at 03:27:37 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Backfires
  • It could be a fuel/carb issue, or, it could be an electrical issue. Did you do any tweaking to carb when you installed it? They are not pre-set out of the box. Many of us prefer to rebuild the original M/S TSX 241 carb, they are better than any new, aftermarket one sold today. You say it is switched over to 12 volts. Details needed. Do you have an alternator too? 1 wire or 3 wire? Is the Voltage Regulator in the circuit? Is he OEM Ballast Resistor wired correctly? Is the 6V coil used? If so, is there an in-line 1-OHM ceramic resistor in the circuit? Carb may need adjusting, or, wiring is wrong and/or shorted out. Sometimes an electrical short will cause misfiring/backfiring. Here's a document from our HOW-TO's forum/ELECTRICAL, on all the correct ways to wire these N's whether if 6V/POS GRN or 12V/NEG GRN. 99.98% of all non-starting/poorly running issues are due to incorrect wiring jobs, and the majority of those are due to some sort of 12V switchover job. Fouling plugs indicates it is getting fuel. When was the last time you did a tune-up?

    Tim Daley(MI)

    Cal Sexsmith    Posted 10-18-2018 at 15:15:41 [URL] [DELETE]        [Reply] [Email]  
  • Re: Backfires
  • I did some basic adjustments to the carb after it was installed and has been running fine for almost two years since then. The 12 volt conversion was with a kit that included a single wire alternator, new coil and wiring harness. Voltage regulator disconnected and a new ignition switch and plug wires installed at the same time. Long time since the last tune up.

    I got it started today but it runs rough and stalls out quite quickly, I did notice that gas was dripping from the carb after some time which makes me wonder if it is a carburetor problem.

    Tony C    Posted 10-18-2018 at 16:08:56 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Backfires
  • Assuming the fuel is good I'd start by tapping on the carb body. If that works, the needle valve is probably leaking, dirty or? Re-adjust the carb. It's not rocket science. If that doesn't work clean out and kit the carb. It too is a simple job.

    If you are unsure of the procedures check Kevin LaRues' tutorial here(?) or just2ns.
    PLenty of pictures and detailed step by step instructions. If you kit it, make sure the body of the needle valve is fully seated in the carb body and the gasket is in straight. Chase the threads in the carb body to make sure. Gas can find its way through the smallest gap. THe needle valve can appear seated but be a little proud. The gasket sealing it is pretty small.

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