Author Topic: Need Help with FL250 Idle  (Read 145 times)

fl250newbie

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Need Help with FL250 Idle
« on: June 05, 2021, 09:20:46 AM »
Newb here with the fl250 and stock carb and airbox and fuel system.  I have one that starts easily with the throttle or no throttle and revs all through the range, plenty of power.  What I cannot get is the idle right.  I have to turn in the slide screw until it stops to get it to idle and when it does idle, it is rough and it seems to hunt or raise and lower on it's own.  It is not consistent.   I adjust the air/fuel screw and it barely does anything.  I checked the fuel flow and I am not getting 4.5 oz/10 sec so I am rebuilding it.  Still does this with an auxiliary gravity fuel tank as well.  I have new motor mounts, new fuel lines, new fuel filter, new clamps,  new NGK coil.    What am I missing here?   I've torn apart the carb and made sure the ports are clear.  I am about to get a VM28 carb if this doesn't work out. 

fl250newbie

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Re: Need Help with FL250 Idle
« Reply #1 on: June 05, 2021, 05:34:41 PM »
Some new info.  I double-checked the jets and compared them to a rebuild kit.  The pilot, the slow jet was slightly clogged because I could see more light in the new jet in the kit.  I swapped that one in.  It ran better but still not right.  The plug is black and fuel-covered.  The air/fuel screw does not work well and the throttle stop screw still has to be bottomed out for it to idle roughly.  It revs up fine, holds rpms and runs great but once the RPM's come down it dies.  It will not slow down to an idle.  Next step I am going to pull the airbox and see if fuel is spitting out the back, I think its too much fuel.  I checked the float level and one side measured at 19.xx mm and the other was 17.xx, so the float was slightly bent.  I fixed that and still no improvement.   I am convinced the carb is pushing too much fuel because when the fuel in the fuel line runs out, the mix seems to get leaner and the engine starts to rev on its own until it completely runs out of fuel. 

LiveWire

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Re: Need Help with FL250 Idle
« Reply #2 on: June 06, 2021, 10:49:52 AM »
When you ran the gravity tank, what did you do with the fuel pump?

fl250newbie

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Re: Need Help with FL250 Idle
« Reply #3 on: June 06, 2021, 05:46:25 PM »
I routed the fuel line right to the carb, no fuel pump.  It runs the same way, with gravity or with a fuel pump.  I can see the fuel pump working fine, pulses and pumps fuel.  About 2-3 oz/ 10 sec.   What I do notice is, when I run just a fuel line gravity feeding the carb.  A small amount of fuel so it doesn't overwhelm the float needle, it runs rough idle but then I can tell when it is running out of fuel because it revs up and smooths out until it finally dies.  It is as if it leans out into the proper mix ratio.  I am not sure what this means, where should I be looking?  Obviously, it seems like the float level/too much gas is getting in but I've checked this.   
« Last Edit: June 06, 2021, 05:49:35 PM by fl250newbie »

LiveWire

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Re: Need Help with FL250 Idle
« Reply #4 on: June 07, 2021, 06:13:48 AM »
I asked because a leaking diaphragm in the pump allows fuel to be directly sucked into the crank case making it run very rich. If you are capping off the the pulse line when not using the pump, then that would not be the issue. FYI, the screw is an air bleed. Threaded out bleeds more air into the idle circuit. In is richer. It is the opposite of what many people think it is. Total adjustment is very small. Large changes need to be done with the slow jet.

The raise and lower part in your first post screams air leak to me. Air leaks are not consistent. They also make it go lean though. If you just bought the machine, maybe someone tried to fix lean with a larger jet.

fl250newbie

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Re: Need Help with FL250 Idle
« Reply #5 on: June 07, 2021, 03:18:36 PM »
I will rebuild the pump as soon as my kit comes in.  I also suspect an air leak at the crank seals, I will try the spray the seals trick to see if it changes the idle.  Can't check the flywheel side without pressure testing it so.  I also still think my pilot passage is blocked with junk.  I am going to carb spray it all out soon and see what that does. 

fl250newbie

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Re: Need Help with FL250 Idle
« Reply #6 on: June 11, 2021, 02:04:19 PM »
I got my rebuild kit for the pump today and I will do it tomorrow.  We have made some progress today though.  I thought about it and I was convinced the slow/pilot jet was giving me issues.  The reasoning for this is it will not idle without the throttle slide screw all the way in.  This tells me it has a fuel problem at the pilot jet.  I tore the carb back apart and sprayed all the passages with carb/brake clean into a white container.  The amount of fine dirt the came out was shocking, this teaches me that simply blowing out the passages with air after an ultrasonic clean is not good enough.   It ran smoother and the slide screw was at least 1.5 turns from bottoming out. 

fl250newbie

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Re: Need Help with FL250 Idle
« Reply #7 on: June 12, 2021, 07:44:58 AM »
I am looking into how to replace crank seals, how effective is doing this while the engine is still in place?  I don't want to ruin anything. 
« Last Edit: June 12, 2021, 08:08:20 AM by fl250newbie »

LiveWire

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Re: Need Help with FL250 Idle
« Reply #8 on: June 12, 2021, 09:41:46 AM »
I have never done an engine in place, but have done without splitting cases. You might be able to do in place. I drove 2 self taping screws into the seal. I then used 2 pair of vie grips to yank out. Put grease on the inside of the seal to lube until the fuel gets there, press in. Ideal would be some sort of thick wall tube but I just did with a block and tapped lightly on each side then the other watching that it was fairly straight. Once it gets to the case, the block will flush it up with that.