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Low rpms on 318

F

frank

Member
" heres the story, just rebuil

" heres the story, just rebuilt twin 318s, drives and trans. first run out of the shop she ran up to 3700 rpm( only did it momentarily until breakin). after 10 hours tried it again and she got up there momentarily then fell to 3100 and now cant get through 3000 rpm and occasionally backfires. Fuel lines are new, all fuel filters new, coil new, points rotor new, carbs rebuilt and cleaned, flame arrestors cleaned thoroughly. any ideas "
 
"BOTH engines simultaneously?

"BOTH engines simultaneously? First, make sure your props aren't fouled. If not, concentrate on the fuel system. The backfiring is a clue that they may be starving for fuel or that your fuel is contaminated.

If we're talking one of the two engines, I would first check timing and advance with a timing light to determine if your ignition system is working properly. Next, concentrate on fuel and carb setup. Check for vacuum leaks in the intake.

You might even swap carbs to see if the other engine now exhibits the same problem. Installing new fuel system pieces can often introduce dirt, which then will clog filters. Check'em out.

"
 
props are good. ran both off

props are good. ran both off seperate tanks of fuel to no benefit. it is hard to tell if both engines are weak or if one is carrying the other. i believe that that is the case. im leaning toward some type of electrical/ground problem but am not sure where to start
 
" Frank, I had this same probl

" Frank, I had this same problem with my 318. It ended up being my floats in the carb not adjusted properly.I was using Carter AFB carb and had to raise the float just slightly to get more fuel. Also is this a straight drive or V drive set up ? If it is straight drives are you using a wedge block at the carb base ? "
 
they are v drives dont know

they are v drives dont know if this is relevant but when engines are hot they are difficult to restart. if i try within a few minutes of turning off the engines they start right up but if i wait 10 minutes plus they are hard to start
 
"Frank, this sounds like vapo

"Frank, this sounds like vapor lock. Fuel boiling out of the float bowls from engine heat. Low float levels as Dennis mentioned and/or internal leaks in the carbs would make this worse.

Try this: when the hot engines won't start normally, CAREFULLY shoot a little fuel down a carb. Leave engine hatches open and ventilate the area. An ounce of fuel should do it. If the engine catches and runs for a second, your engines are fuel starved for one or more of the above reasons.

"
 
Check timing. and rev the engi

Check timing. and rev the engine check the timing at about 2500rpm
 
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