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Old 09-14-2008, 09:36 AM   #1
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Default Is my engine shot?

I have 2 1/2 gallons on my Associated 28Pro engine (came with RC8 RTR). Last time I ran it, it had it's normal power for about a minute or two, then began bogging, as if it was VERY rich. I put in a new glow plug and the exact same thing happened. It idles fine, just bogs and burbles when I give it full throttle. But if I let it sit and cool for a minute, the normal power comes back.

The only thing I can think of is that the piston/sleeve are worn out, and once the engine warms up and expands it loses compression. Any thoughts?

Thanks
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Old 09-14-2008, 09:45 AM   #2
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hows the compression spin the fly wheel or if u have a pull start then pull it slow if its low compression make shure your plug is tight and the
cooling head is tight if they r and u still have low compression then its shot
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Old 09-14-2008, 09:49 AM   #3
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When it bogs and gurgles, is it blowing lots of smoke? I would first try richening the top end 3 or 4 hours and see if that helps. Sounds like it might be a lean bog. The motor should still be good with only 2 gallons on it
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Old 09-14-2008, 10:13 AM   #4
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Originally Posted by porkey View Post
hows the compression spin the fly wheel or if u have a pull start then pull it slow if its low compression make shure your plug is tight and the
cooling head is tight if they r and u still have low compression then its shot
When it's warm I can spin the flywheel. It does feel like there is some compression there, although I'm not sure it's an adequate amount.
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Old 09-14-2008, 10:16 AM   #5
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Originally Posted by Adim_X View Post
When it bogs and gurgles, is it blowing lots of smoke? I would first try richening the top end 3 or 4 hours and see if that helps. Sounds like it might be a lean bog. The motor should still be good with only 2 gallons on it
No, not much smoke. It was just such a sudden and severe change from the way it was running 1 hour prior that I'm doubting it's a tuning issue. It went from running very well to all of a sudden barely moving when I hit full throttle.
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Old 09-14-2008, 10:51 AM   #6
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Sounds like a possible lean bog to me...
Hard to say via internet
Since you've got an RC8 - how's your tank? Air bubbles within the fuel line? AE's tank is a well known weak spot of this car (if not THE weak spot...)
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Old 09-14-2008, 11:11 AM   #7
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Not much smoke, tells me its lean, just remember your settings and richen the top a few hours. Just because it ran well an hour ago, doesnt mean it will run now. Its very hard to diagnose over the net, but it never hurts to try and richen the needle a bit.
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Old 09-14-2008, 11:49 AM   #8
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it could be shot. If it has power when it's cold that would be because the sleeve has cooled and contracted to form a good seal around piston. providing adequate compression for power. When it gets warm the sleeve expands revealing the loss of pinch and compression. There is not a mark gallon wise that signals an engines death. Many things can happen that we are unaware of on a forum that could mark the engines death.

Try the suggestions above hopefully its a lean bog.

Good Luck
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Old 09-14-2008, 11:54 AM   #9
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Quote:
Originally Posted by T$ View Post
When it's warm I can spin the flywheel. It does feel like there is some compression there, although I'm not sure it's an adequate amount.
is it ez to spin
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Old 09-14-2008, 01:20 PM   #10
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Just because it spins easy don't exactly mean it's worn out.
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Old 09-14-2008, 01:25 PM   #11
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If it is the same engine in my Thunder Tiger ST-1 (I think it is), then it will be easy to turn while warm. This does not mean it's shot it is just the way it is. Once you get up to running temps it runs leaner than right when it is cold, so I would richen the top end up like others have stated.
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Old 09-14-2008, 01:28 PM   #12
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Just because it spins easy don't exactly mean it's worn out.
when it cold and its ez to spin the fly wheel then yes the piston and sleeve and be shot
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Old 09-14-2008, 07:19 PM   #13
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I also have an RC8 and had the same identical issue you are having. Started out of the blue. My engine ran fine and then suddenly I started to lean bog at about 2 minutes. I changed absolutely everything, fuel lines, clutch, bearings, needles, carb, sealed everything etc.. The last thing I did was to buy an 808 tank and adapt it to my car. Wouldn't you know it, the problem went away.

If you want to trouble shoot to see if it is the tank with out buying a new one, try to borrow one from someone at your local track. It will take 5 minutes. First, take off your mounts and put a spacer underneath the mounts. Using slightly longer screws, reattached the mounts to the chassis but leave them loose. Then take the 808 tank and put it on the mounts using the clips. Afterwards, tighten the tank mounts up again, but not to tight. Just snug them up. That will be enough to run the car for 5 or 10 minutes. Put fuel and go.

Good luck!
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Old 09-14-2008, 07:37 PM   #14
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Pete is correct..
If you don't have the latest second generation white tank out then you might as well not bother tuning your engine.

Mugen tank, xray tank, and I believe a jammin tank all go in with little effort. I hand modified my ae tanks, but will probably try an 808 tank myself.
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Old 09-14-2008, 07:50 PM   #15
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Quote:
Originally Posted by jbrow1 View Post
Pete is correct..
If you don't have the latest second generation white tank out then you might as well not bother tuning your engine.

Mugen tank, xray tank, and I believe a jammin tank all go in with little effort. I hand modified my ae tanks, but will probably try an 808 tank myself.

Are you saying that the second generation white tank is good? I did receive one from Associated but haven't tried it yet. I'll give it a shot and see if that fixes it.

Thanks to everyone for the suggestions and feedback.
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