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Subject: 8N Performance degrades when warmed up

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Rick    Posted 04-20-2017 at 21:32:20 [URL] [DELETE]        [Reply] [Email]  
  • 8N Performance degrades when warmed up
  • I just installed a Pertronix electronic ignition (still 6 volt though) and it started right up and idled great and ran smooth when revved up. The best it has run in years. I was mowing uphill in 3rd gear if you can believe that. Then as it got up to temp the performance began to degrade some. What's odd is that it was fluctuating from terrible to not so bad and back again. When going uphill with PTO engaged I would have to downshift to 2nd or 1st but it would still go uphill in reverse, which I'm not mistaken is a higher gear than 2nd? Nyway, pun intended, I was still able to finish mowing the field I was working on, it didn't seem to run as smooth as when cold, sounded like it was starving for gas here and there then would clear up and missing or sputtering to a minor extent. I just replaced the plug wires at the same time so maybe one of the crimped fittings is not a great connection. The timing is also another possibility, but why would it run good when first started and then not so good when hot? So how do you adjust timing when running? You'd have to be crazy to reach in there and adjust the distributor (front mounted)while running. So what do you do, shut it off and trial and error the timing? Any Idea's on this would be appreciated.

    36 coupe    Posted 05-14-2017 at 05:59:05 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8N Performance degrades when warmed up
  • I set the timing on the center mark on the distributor.Air vent to fuel tank could be dirty.Heat could be a factor.Vapor lock happens.Fuel screens may have dirt in them.Dull mower knives need extra power.Try another brand of gas.Rusty gas lines or an inline fuel made for a 6 hp mower.A coil can get weak when hot.On a standard ignition the condenser is suspect....3358

    Rick    Posted 05-14-2017 at 07:58:57 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8N Performance degrades when warmed up
  • Here is the update on what I discovered. After all the suggestions I started with draining the gas tank and checking the fuel path from point A to the carb. I did find a very small piece of debris in the top of the float bowl assembly. It made a small difference when I compared the fuel flow before and after I removed it from the fuel line before it attached to the carb. The big difference was coming out of the bottom of the carb when I removed the plug. The flow was noticeably slower. I knew when I put the after market carb on that the linkage did not give me full throttle with this carb. If I manually pulled on the linkage I would get an extra 15% or so of power so as I stated before I ordered a rebuild kit for the original carb. Do not buy the kit from e-bay that comes from India, at least 5 of the threads on the different parts did not fit. Fortunately when I broke it down it didn't need a thing, I cleaned and checked it but it was good to go. When I installed it back on the tractor it ran great as before but when it warmed up it never degraded. So problem solved and I would have to conclude that the problem was related to fuel flow through the aftermarket carb. It doesn't make sense to me that it ran great before it warmed up, the fuel flow should have affected it no matter the temp of the engine. But the results don't lead to any other conclusion. Thanks everyone who contributed with suggestions.

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