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Rough idle on newly rebuilt 270

capnandy

New member
Guy's, last summer we pulled and had rebuilt starboard 270. Reinstalled, it has a rough idle. Tried timing it out with no success and rebuilt Qjet. Is it time for a new carb and what kind is best. Also what CFM?
 
what does "no success" mean wrt "timing it out; you couldn't set the initial timing?

If you can't set the timing, leave the rest of the adjustments alone. You'll wind up making so many changes, you won't know what worked and what didn't.
 
Ignition Problems:

1. Warm the motor and idle it at 1,000 t0 1,500 rpms.

2. Using insulated gloves and pliers, pull one wire at a time from the distributor cap then replace it.

3. If the motor slowed noticeably, that is good. If it did not, note the wire position and continue on.

4. If TWO wires did nothing, interchange them and see if that helps.

If you had just one cylinder that did not respond, replace its plug and wire then try the above again.


Carb Problems:

1. Warm the motor and idle it all the way down.

2. Gently turn each idle mixture screw all the way in and note what happens: If the motor keeps running--and picks up, even--the carb is flooding. If it slows and dies, then the carb is okay.

Try the above and get back to me.

Jeff
 
Will try that jeff thanks. As for timing I think we had it perfect. That engine runs great when crusing but idle is rough. Will try those carb adjustment steps.
 
In addition to what Jeff said, you can really set the idle adj. perfect with a cheap vacuum gauge. Start with both screws at 3 turns out, hook up vacuum gauge, and slowly adjust screws evenly in and out noting the effects on the gauge. You want the most vacuum possible.
 
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