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160 sounds/acts lean

Old 05-02-2008, 09:38 AM
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Default 160 sounds/acts lean

Hey Troy

I ran a 160 last night for the first time since a new case/bearings rebuild by Richard last summer. Had to prime the pump no surprise, first runs when new were like that. First startup at idle did not sustain the fuel flow ran out the "prime." Primed it again and started it at higher throttle setting this time it kept going. Coming up from lower throttle settings it sounded really good happy with amount of fuel. From previous experiences I'm advancing the throttle 1 notch at a time and listening carefully. I get to someplace between 1/3 and 1/2 and the sound changes with the next notch hmm sounds like it might be getting lean. One more notch and the sound changes more but no increase in RPM. Needle valve is already at 3 turns out... Do a shut down and turn the pump regulator screw in 1/8 turn. Repeat the startup and adjust three more times (now I have accumulated a half turn in on the screw). The RPMs at which it seems to get lean are getting higher but not able to get to full throttle. Ran out of daylight, time, knees and patience all about the same time. How far in can I go in on the regulator before bad things start to happen? The pump is the same part as before the "rebuild" the regulator screw is now below flush with the casting. From the sound, the vibration level, and the fact that the prop has moved close to 90 degrees from its original position lead me to believe it's going lean as the throttle is advanced. Occasional short lean periods for seemingly no reason led to having to get the new case and bearings. This is the same engine that I posted about last summer end play in the crank fore and aft front bearing had spun in the case. Everything is nice and tight now but it is not running right. Any ideas?

Will you be in the midwest this summer?

Old 05-02-2008, 11:03 AM
Troy Newman
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Default RE: 160 sounds/acts lean

richen the pump about 1/2 turn and try it.....

Run the engine at just about 4000rpm for about 5 min to make sure everything gets seated and broken in.
Don't go above the 4000rpm. Its just a high idle....Just let it run there.

If the engine is overheating a little this will make it lean. New bearings and new case can do that.

Next thing is there could be some crap in a fuel filter, in the lines are somewhere that is causing restriction. This will also make it act lean. Pull the HS needle and flush the needle seat....This can be done with fuel to the pump and just spinning the engine over with a starter, then close the fuel line off to the pump. You may need to put a towel up over the needle housing to prevent the raw fuel from spraying on your model. If there is any dirt or growth of crud in the HS needle seat it should flush right out.

Fuel filters are the same way they can gunk up and restrict flow. Flush them out good or replace them.

Troy Newman
Team YS

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