Hey to everyone here.

I have been having issues with this motor for the passed 6 months, seemed to happen about half way through runin and now I am just trying to figure out what is wrong. I will start with the problem,
whenever I take the plane out for the day the first time I start the engine the tuning is MILES off. It idles perfect but the second it transitions to the high end needle it dies, so I was at first thinking 'maybe I need to let it warm more' so after leaving it sit for around a minute or two I try and boom no go still. So I ritchen it all out until it decides to run on both needles (Pig ritch mind you) then tune the motor back to peak, from there I have tried leaving it at peak tuning, ritchening it to just below peak, and going just a touch further than peak to see if maybe I am just too ritch (I know its not a good idea, but I was trying everything) For the rest of that day all the transitions are fine, tuning is fine and everything seems to be a okay. Then I come back the next week and same thing again, having to do the tune dance again.

Its a 10-15 litre old motor, running a cannister muffler (although the problem existed on the standard muffler). My fuel mixture is 32:1 Petrolium oil (Once this bottle empties in the next few flights I am going synthetic) I pull the whole carby apart every second month and clean the filters, double check alignments of all the valves and float needle. It doesn't feel like an air leak as the idle is perfect, could it be a bad carby? Its a standard DLE 30 carb (Tillotson ?sp?) and I have been tempted to just get a walbro and be done with it.

Any help would be greatly appreciated, this motor has been close to flying without a plane for a while now.<br type="_moz" />

Sounds as though the metering diaphragm has become stiff in the carburetor?

It would be good to put a new diaphragm in it. I understand that the Walbro WAT style repair kits work in this carb.

Sounds a bit like a air leak still.
No signs of black stuff coming from the front bearing??
Are you using the plug supplied with the engine, or a CM6

I originally thought of air leaks as well, the motor runs clean with no visable oil leakige from any bearing or metal to metal connection, the rubber diaphram is still rather soft as I take it out and check it every cleaup of the carb. I will go grab a rebuild kit from the chainsaw joint (they sell the actual carbies as well, at a stupid price though) but it doesn't feel so much like that. I am using a CM6, first thing I did when I got the engine was throw the heap of metal they call a 'spark plug' into the bin and get an NGK. I run the CDI with a LiFe thats been dropped by a UBEC, voltage testing under 3 amp loads show no signs of visual voltage loss to remove that factor.

I do admit the diaphram sounds hard by description but leaving the engine running to warm has no effect, even if it was hard wouldn't it soften up after a bit of fuel flow and return to normal during the warming phase?<br type="_moz" />

Once the Diaphragms get a little hard, they get very frustrating with different tunes of the needle every time you run it and sudden stoppages.

kk, I have pulled the cowl off to just have a quick look to look for anything air related, the gaskets are intact with no marks, the diaphram isn't what I would call hard but it does have a stiffish feel to it, there are no black marks where oil has been or ever was outside of the motor.

I am going to put a new diaphram in it and see what happens, I will open this thread back up after my next flight which wont be for 2 weeks, keeping my fingers crossed this is the issue. I knew a hard diaphram could cause issues but I wouldn't have called this one 'hard' by any means, hope it IS the issue however.

A club member has an old 30 with the side carb. It would run fine on the taxi and flight but the second the plane touches the landing strip, it would quit. I mean, like someone threw the switch to OFF. He ordered the rear carb conversion kit and has not had a bit of trouble since.