Running too rich when hot - Losi 5T

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BHarris

RC Newbie
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Hello. Hopefully someone can give me a few pointers. My Losi 5T (29cc Dynamite) runs fine to begin with, but then gets extremely rich after reaching operating temperature. I then lean it up and it runs well for 2-5 minutes before richening up again. This cycle continues until the screw is almost all the way in. It's a bit crazy. It is basically new, so it's acted this was from the start. I have just replaced the carb (Walbro 990), new fuel lines, tank grommet and carb gaskets - I will run it again within a day or two to see if this helps, although an air leak should have made it run too lean. Hmm
 
I forgot to mention that I installed a new Bartalone pipe after the break-in. I run non-ethanol 94 octane (I'm in Germany) with Castor 927 premix at 28:1. Other than that It's stock.
 
I forgot to mention that I installed a new Bartalone pipe after the break-in. I run non-ethanol 94 octane (I'm in Germany) with Castor 927 premix at 28:1. Other than that It's stock.

I had never heard of that happening ,nor do I think that it is possible to just start changing like that ,once the carb, settings are set ,
it shouldnt change ,however ,it could be more pressure build up in the tank causing more fuel to be forced into the cylinder than
needed!

It sounds more like a tank pressure problem ,were the tank builds up too much pressure ,the tank needs to ventilate ,you may
need to replace the cap or add a secondary tank vent devise!....:cool:
 
It is a weird problem, but it's definitely happening. I replaced the grommet and the fuel hoses, so maybe that will take care of it. I am still using the stock tank cap and ventilator (assuming that the little thing is a ventilator).

Thanks for the response!
 
Odd situation since it's a 2 cycle gasoline engine. Normally these are problems only associated with the nitro engines. Hang in there, we've got several large scale guys who might be able to figure this out for you.
 
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