Author Topic: VM38 Jetting Invader 440.... close to giving up on Econojet.  (Read 3602 times)

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F500-92

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VM38 Jetting Invader 440.... close to giving up on Econojet.
« on: January 14, 2018, 02:51:04 PM »
I've done everything I possibly can to get these carbs working correctly and I still cant get the thing to idle.

Replaced crank seals in the original motor.
Got a rebuilt 440 with low hours from a friend.  Yes 2 different motors.
went through the carbs 3 times. ran wire through all passages to clean them out.
Replaced the Pilot Jet and Main (150) jet with new ones. 
New Jet O rings
Rebuilt fuel pump.
Replaced all fuel lines.
New Pulse line
Replaced fuel filter

It still runs exactly the same no matter what I do the air screws even . Won't idle. Slide helps a bit but i think its masking an issue.   

I have a 3 sets of VM38's that I know are good and a lot of jets and needles on hand.  What would be a good starting point in a VM38 for an invader 440?   And any other tips to get these econojet carbs working correctly?

Interceptor398

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Re: VM38 Jetting Invader 440.... close to giving up on Econojet.
« Reply #1 on: January 14, 2018, 08:30:17 PM »
79 Invader 44 carbs should be marked 36/72. Main jet is 150,  pilot is 30 and the power jet is 120RRT.  Air screw is 1 1/2 turn out,  idle screw is 6 turns and idle speed is 3000.  Is the plunger sucking air??  Do you see any air bubble in the gas lines when it is running?? Bubbles in the gas line is a big one!  Swapping in a known to be good set of carbs is not a real big deal and would help narrow down the issue.

F500-92

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Re: VM38 Jetting Invader 440.... close to giving up on Econojet.
« Reply #2 on: January 15, 2018, 07:45:54 AM »
idle screw is 6 turns.
This is the bit I was getting wrong.  I was turning 3 turns IN from when the idle screw touched the slide.   I just checked the manual again and it says 3 turns out from coil bind. 

kawhead

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Re: VM38 Jetting Invader 440.... close to giving up on Econojet.
« Reply #3 on: January 15, 2018, 08:23:40 AM »
power jet and vm carbs have the same idle circuit, imo the carbs aren,t the issue[2 different motors],if I were to try the 38s ...300 mains,35 pilots, same needle/n jet etc.imo...hold engine at lowest rpm possible w throttle, pull one plug wire at a time to find the affected cyl.

F500-92

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Re: VM38 Jetting Invader 440.... close to giving up on Econojet.
« Reply #4 on: January 15, 2018, 04:08:03 PM »
runs great once I got the idle screws set right.  4.5 turns out from coil bind.  Still a little bog when I mash on the throttle from idle though.  Will playing around with the air screw help that. 

jimvw57

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Re: VM38 Jetting Invader 440.... close to giving up on Econojet.
« Reply #5 on: January 19, 2018, 03:43:42 PM »
Idle on an Invader is quite high, around 3,000 rpm. If it is set lower, it will bog. Also balancing the carbs makes a world of difference. there is a simple tool you can make to do this and it works quite well.

The air screws ca get damaged and allow too much air in at 2 1/2 turns, I have had carbs that ran best at 1/4 turn as the holes get reamed out from using wire to clean them.