4a084 trouble

[swampdoo]

n4wsp,
Thanks i will try that

[Papee]

What RPM are you running at cruise when this happens?

One way to prevent this is by not running a constant rpm, feather your throttle once in a while. If it is and icing problem, most of the time it will backfire then lose rpms. You can leave off the gas and idle for a a minute or so and it will pick back up again. I still have icing problems once in a while but not often. It mostly happens when I am running full throttle for a long length of time without feathering the throttle. The best fix I have found for the icing using a stock carb is to get the original rubber boot that comes off the carb and use it. This allows the use of the breather tube into the intake. I added a KN filter on the end and it works fine. I'm really not sure if I have had a problem since then.

Another reason for this may because of overheating. When I was running a power prop and pushed it hard it would heat up and act almost the same way. The difference being that it would not backfire, it would just start losing power. It would not shut down if I just let it idle for a while I could go back to running again. I think I was running around 3400 rpm with that prop.

I have a photo on here somewhere of the KN filter setup. I'll try to find it. Found it.


When you are running the boat look back at the carb. If there is a lot of moisture on the carb it is most likely Icing.

[swampdoo]

Papee
It doesnt matter what rpm i am at if it is anywhere above idle for a minute or two it does it and I have a pipe with a breather on the end of it and sometimes it backfires and sometimes it doesnt but when it does backfire it dies out if it dont it stays running and i believe there is moisture around it i have a buddy goin pick it up tomorrow to look at it some more i have a bowfishing tournament i wanna fish Jan 8 so I need to get this solved
Thanks, Cody

[Papee]

That doesn't sound like either icing or overheating. What gas tank are you using? Try running it with the cap off. I would also go back to the mechanical fuel pump, I'm not sure how that would work with an electric fuel pump, you may have fixed one problem but created another one. Just for elimination purposes I would go back to the stock pump. If the electric pump pressure is too high you may be sending fuel past the needle valve causing it to get too much gas. Don't give up, I'm sure it's something simple. You can give me a call if you want. 717 433 8937 I' just had surgery and I'm on pain meds so I may not answer right away. Just leave a message and I'll call you back. I know we can get it going as long as the carb is working correctly.

Another thing, I run a manual choke on mine set up with a choke lever/knob like you see on the old cars. Depending on the weather, sometimes I have to run with the choke partially on. Run the motor until your condition starts then try putting the choke on little by little. If it stalls you have plenty of gas but if it cleans out and runs better you need more gas. That carb isn't very adjustable so I just put on the hand choke and adjust it as needed for the conditons that day. Some days I don't need it and others I run it partially choked all day.

[swampdoo]

The pump i put on it is a 2.5 -3 psi pump and i have tried running it without the cap on. The choke just has a wire hooked to it and i can manually pull it I will maybe call you thursday im offshore at the moment
Thanks, Cody

[Papee]

OK, my guess is that you will find that putting the choke on part way will solve the problem providing the carb is adjusted right. My engine has that sweet spot with the choke, on just a little bit will give it better response and more top end rpm. This would most likely depend on what filer setup you are using and air flow restrictions caused by the filter.

[swampdoo]

I guess I will try that when i get home thanks again

[swampdoo]

still a no go the intake is condensating really bad i tried running a hose from the crankcase breather to the intake and it ran a while longer but did the same thing

[Duane Scarborough]

swampdoo,

Just to find out, why not rig up a carb heater similar to what Chuck suggested a few days ago.

Here's a link to help:

http://www.aircraftspruce.com/catalo...sheatmuffs.php

I'm not suggesting that you buy one of those, but use it as an idea to homebrew something.

It ain't got to be fancy to see if it helps. If it helps, then you can get fancy.

Good luck !

Duane

[swampdoo]

I was thinking of doin something like that well i will have to cause it is bad you can hardely touch the intake and carb it is so cold

[chuckitt]

When your intake makes the air so dense that it ices, you might need to drill out the main jet to the next .001. to richen it up a little. When we made cold air intakes for the 220 GPU, we had to go up 4 jet sizes on the main jets in the 2 barrell holley. Just remember, this makes more HP. It it improves but is still not good enough, drill another .001.
Thanks, Chuck

[Papee]

Sounds like none of the stuff we talked about on the phone helped. I've just never seen a motor/carb ice up that fast. What prop are you running?

[TEEJ]

Generally, a back fire requires unburned fuel to be reaching the exhaust side, where it explodes.

If its carb icing, the venturi gets so restricted, air can't flow through...so fuel is sprayed, but not enough air...but, typically, it is not relieved by just getting off the throttle...it needs time to defrost....and runs like crap until then...you had a seemingly swift recovery?

I HAVE seen the backfire itself jar ice loose though, which WOULD give a swift recovery.

If a butterfly sticks due to ice, etc...that can cause some issues.

Too high an octane can cause too slow a burn, which can result in unburned/still burning hydrocarbons being sent to the exhaust side.

Perhaps follow up on the suggestion that excess pressure might be forcing fuel to that stage for example, as that would be able to cause that symptom...as would inadequate spark, or, too rich a mixture, or, timing that was firing at a less efficient point in the process, etc.

If the timing is supposed to advance/retard with rpm/vacuum/mechanically, etc...its possible that a part of that feedback loop is malfunctioning....a vacuum leak or air bleed leak for example, or whatever the moral equivalent is for one of these engines.

If the carb has a float, or other means of sensing/regulating the fuel....perhaps it sticks once in a while.

If you have a manifold gauge on it while running at a constant RPM, and the manifold pressure drops while the RPM stays the same...that's typically icing for some situations, but a loss in power at the same RPM is a clue too.

And so forth.

Some people (I have no personal exp with them) swear by anti-carb icing additives like Silko and Gunk's M2616

I have never seen one of these engines, so, please forgive my potentially useless advice....but, I am familiar with engines in general...and when looking at a problem like this, this would be my thought process when trying to imagine WTF was going on.

[dak10]

no one hit on this but i found out that the primer ball was sucking flat and we all know what happens then, just a though i removed mine and my high speed bogging went away ,an if u r useing a ele. pump then y do u still have the fuel pump on the engine ? just an though, my solex will not go with a 170mm main jet but it will go like crazy with a 150mm

[Duane Scarborough]

no one hit on this but i found out that the primer ball was sucking flat and we all know what happens then, just a though i removed mine and my high speed bogging went away ,an if u r useing a ele. pump then y do u still have the fuel pump on the engine ? just an though, my solex will not go with a 170mm main jet but it will go like crazy with a 150mm

Ron,

I'm just thinking out loud now... (I know how dangerous that can be )

If you are still using the original engine mounted manual fuel pump, I can see that it might have a problem lifting gas up the about 3 or 4 foot distance to the carb. It wasn't intended for that. An electric fuel pump, mounted low (close to, or below the bottom of the gas tank) SHOULD not have that problem. All fuel pumps seem to better be at pushing than they are at pulling.

A collapsed primer ball seems to suggest that it was at least trying, but wasn't quiet up to the job.

Now, with an electric pump mounted low, I wouldn't think you'd even need the original engine mounted manual fuel pump.

Just something to think about...

Duane

[Papee]

He's using an electric fuel pump. He has no tach that is why I was asking about the prop. The only thing I can come up with is that is is running high rpms. What prop he is running may tell us more about the rpms he is getting.

[dak10]

cool but i think if it is iceing then there is water in the fuel it don't make sence to me in the cold states water is the problem and the carb that comes on the 084 is ok for now i have the solex and when i run wide open my manifold will condensate and almost freeze but the bogg is from no fuel or to much fuel just a thought i have ran mine as high as 4200 rpm and all i got was high head temp,not a fuel problem,my manual pump will pull fuel from the tank with no priming,,just trying to help

[Papee]

It sure is a head thumping problem, I talked to him on the phone about it. It has to be something simple. I'm not sure how each carb reacts, but I do know that if I run over 3400 with the stock carb for any distance it will ice up. I haven't had the problem since I put the stock boot on and have the breather tube hooked up then added the KN filter. I also don't run over 3200 rpms often. My prop won't allow me to go over 3200 unless I get some wind helping out.


When Mine ices it will backfire then run rough for a minute then idle right. I just idle for a few minutes then I can take off. Like I said, I've not had that problem lately. When I did I just made sure I didn't hold full throttle for an extended time or feathered the throttle when I had to make a long run. Here it's not hard because you are always on and off the gas because of rocks.

[dak10]

here is something i forgot to say the steel 3/16 fuel line from the pump is to small for what we demand i put a 5/16 rubber line from the pump to the carb,i do think at iceing came come from lean fuel,i said something to chuck but he thinks the line is good but look at all u have done the brass incert in the carb has a smaller hole then the fuel line does check it out i have 3/8 fuel line from the tank to the water sep,to the carb, no primer (i do have a primer on the fuel pump but i have not had to use it) and 5/16 to the carb remove the incert a barbed 5/16 fuel end will fit ,try that i did havn't had a fuel problem sence

[n4wsp]

here is something i forgot to say the steel 3/16 fuel line from the pump is to small for what we demand i put a 5/16 rubber line from the pump to the carb,i do think at iceing came come from lean fuel,i said something to chuck but he thinks the line is good but look at all u have done the brass incert in the carb has a smaller hole then the fuel line does check it out i have 3/8 fuel line from the tank to the water sep,to the carb, no primer (i do have a primer on the fuel pump but i have not had to use it) and 5/16 to the carb remove the incert a barbed 5/16 fuel end will fit ,try that i did havn't had a fuel problem sence

I did the same thing with the fuel line. I also raised the float level a little bit. never had any icing séance. Steve