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Re: [TriumphTrophy] Popping at low RPM

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  • Samuel Crider
    Eric, My best guess is the popping is caused by an overly lean fuel condition over a extended time. Likely the beginning stages of burnt valves. Once the lean
    Message 1 of 9 , Apr 10, 2013


      My best guess is the popping is  caused by an overly lean fuel condition over a extended time. Likely the beginning stages of burnt valves. Once the lean condition is corrected it seems to self heal. Richer fuel mixture provides the byproducts to fill the tiny leaking voids in the valve seats over time. Anyway, that's the only half logical puzzle of events I can dream up to explain my gals behavior.

      One thing I forget to mention before is to check the tee screens. These are located inside the carb tees where the fuel lines connect. Mine were already missing and I never replaced them. Instead opting for the proper fuel line filters. So while your in there make sure they are clean as they can cause lean conditions as well.

      Enjoy the ride!


      On Apr 10, 2013 3:30 AM, "Eric Tomosky" <etomosky@...> wrote:

      Thanks Samuel. Just hearing that it can be overcome is helpful and the step by step maintenance list is invaluable. Thanks again, very much appreciated. 

      Eric Tomosky AIA

      On Apr 8, 2013, at 4:36 PM, Samuel Crider <dieseldude1@...> wrote:


      I also had all the same issues for the first six months of ownership. Completely clean the tank and petcock assembly. Reseal it with a light film of hilomar upon assembly. Replace the small o-rings under the carb to top caps. Replace the vacuum line to the petcock with the same size fuel line. If you still have the oem vacuum fuel venting network consider gutting it and just capping the other vacuum ports. Leaving the carb vents open to the atmosphere. If you have the means adjust the valves and sync the carbs before reinstalling the tank. Test the petcock by adding a gallon of fuel and gently sucking on the new vacuum hose. It should turn the fuel flow on and off with only a light suction. Once you get her reassembled this should cure the 1/4 tank syndrome and any related lean running issues. Providing your floats are set correctly and the carbs are completely unclogged. As for the popping mine slowly disappeared over a period of six months of daily use.

      Best of luck,

      96 BBBB PB
      New Orleans

      On Apr 8, 2013 6:27 AM, "etomosky@..." <etomosky@...> wrote:
      Hi everyone,
      I found a 2000 1200 with a little under 1400 miles on it.  Since picking her up last fall the carburetors have been cleaned and synced (twice) the spark plugs have been changed,two valve guides were reamed out and those two valves replaced (they had hit the pistons, a new crank shaft position sensor was installed, new coils were installed and battery was fitted, in addition to a new air box.  A mouse had used the original air box for a condo, poor little guys.

      I've checked the battery and charging system with a multimeter, and all the parts that generate apark seem to be working as they should: none the less, below 2000 RPM the bike sputters and pops like a popcorn popper. When I ride, the bike generally performs well (more on that momentarily)no popping while travelling but it does start back up at stop lights and while idling.  It pulls well at all speeds until it stalls from fuel starvation symptoms.  I am waiting for some parts:  roll over valve and fuel lines; before taking the bike apart again and will report out if I've been able to eliminate the fuel starvation issues.

      When the bike starts there is some whitish smoke until things warm up then it burns clear.  I have noticed that my eyes burn while letting the bike warm up and letting it run to try and diagnose the issue.  This is much better than the black smoke that came out of the bike when I first got it, prior to changing the air box and the coils.

      I am wondering if anyone can offer any suggestions on what might be the source of the popping.  Thanks in advance.

      I am in upstate New York, run ethanol free 91 octane, as much as I can, and have changed all the fluids prior to taking her out a little bit last fall.  She sat through the winter with her battery tended in a heated garage.


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