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Traxxas 3.3 hard starting issue and idle issue

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Traxxas 3.3 hard starting issue and idle issue

Old 09-15-2010, 07:29 PM
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zone 5
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Default Traxxas 3.3 hard starting issue and idle issue

On my 3.3, when it sits overnight, it comes close to killing a fully charged battery in the starter. If you don't hold your finger over the exhaust to force fuel, it will not start. Once it is running, it seems to start correctly with a quick push of teh starter button.

Once its running, it runs fine, just as always. but when you come to a stop, using brakes either hard or gently 95% of the time it shuts off. when its running and brakes aren't on, it will not sit still. you have to have the brakes on to keep it stopped, and then it will usually shut off. when it shuts off, its a quick shut off, it doesn't try and run, just quits.

I've checked the piston and cylinder, and there is a pretty snug fit when I push it up/down. All fuel lines replaced. all bolts checked (head/carb etc) and are tight. idle is set with just less than 1mm. (adjusting it seems to do nothing) high and low screws are set back to stock at 4 and 1.5 turns out. running the Traxxas med glow plug and traxxas 20%. Throttle linkage does not move carb slide when brakes are put on. I even switched fuel tanks to a known good one and had the same issues. The engine has ~ 1 to 1.5 gallons run through it since new. It has run perfect until the last week or so, and nothing has been changed.

I'm guessing from reading these forums that there is an air leak, but I have no idea where to look for one, or how to find/fix it. So any suggestions, answers help are more than appreciated.
Old 09-15-2010, 07:43 PM
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alvinl
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Default RE: Traxxas 3.3 hard starting issue and idle issue

Priming the motor is normal. You can also remove the hose from the exhaust and blow in it to force fuel up to the carb. Then put the hose back on the exhaust. That will save your battery.
Old 09-15-2010, 08:15 PM
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kyntar
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Default RE: Traxxas 3.3 hard starting issue and idle issue

To seal an engine pull off carb. and place a small amount of silicone around it and re-install it. Pull backplate and place a small amount of silicone around it and re-install it. There pretty much sealed up. As far as tuning once truck is running and at operating temperature pinch off line right at carb. truck should run then idle up and die at about 3 seconds. If not richen or lean it by lsn till it does. Once that is set then make some high speed passes if it stalls at high rpm richen it upby the hsn, if not then lean it till it does and advance 1/8 turn. Once those are set then adjust idle. That should help.
Old 09-15-2010, 08:23 PM
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zone 5
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Default RE: Traxxas 3.3 hard starting issue and idle issue

Thanks!!! I didn't know where to seal it, so I appreciate the info. Have my project for tomorrow.

Am I assuming correctly that you think this is what the issue is?
Old 09-15-2010, 08:49 PM
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Default RE: Traxxas 3.3 hard starting issue and idle issue

I seal all my motors right off the bat. Even new they can have slight air leaks that can make tuning a problem once the engine starts to age. To start mine I cover the exhaust and spin the motor over with the cheezy start till fuel reaches carb. I then use a glow igniter instead of the cheezy start glow wire. My trucks fire right up everytime. It seems the EZ-Start just doesn't put out quite enough voltage to the glow plug for me.
Old 09-15-2010, 08:56 PM
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Default RE: Traxxas 3.3 hard starting issue and idle issue

I sort of had this exact same problem, only with a different engine. You would start it as as usual, and it would rev like normal with the igniter on the plug, but soon after taking it off the engine would just turn itself off, even on throttle. Changed the plug, problem solved. So all you need to do is get a new plug and that should stop the engine from just randomly quitting. But as for the crawling, all I can say to do is to either shorten the spring holding the clutch shoes, or get a tighter spring. That helped me when I was running the Traxxas engine, and I know that their carb sucks, it wont completely close up no matter what. Just have it set as closed as you can get it and leave it there. Also the low end might be a little too rich, causing it to shut off after sitting there for a while.
Old 09-16-2010, 09:26 AM
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zone 5
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Default RE: Traxxas 3.3 hard starting issue and idle issue

found the issue. Pulled the clutch bell, and the broken spring fell out. Duh. Will seal the engine up while its off the car.

Thanks for the info. I appreciate it!!!
Old 09-25-2010, 10:47 PM
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Default RE: Traxxas 3.3 hard starting issue and idle issue

try useing a LITTLE gasoline to prime it
Old 09-26-2010, 03:22 AM
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Default RE: Traxxas 3.3 hard starting issue and idle issue

-1 on that, theres a reason why you dont use gasoline in these engines. Just put a few drops (2-3) of fuel down the carb, spin the engine a few times, and it should start easier. The fuel should also be at the carb.
Old 09-26-2010, 07:59 AM
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thechap76
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Default RE: Traxxas 3.3 hard starting issue and idle issue

NO GAS!!!!!!! WOW NEVER HEARD THAT B4!!!!!! NO NO NO [:@]
Old 09-26-2010, 09:16 AM
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Default RE: Traxxas 3.3 hard starting issue and idle issue

I've been in R/C for over 12 years, and what I do to prime the engine is pull the pressure line off the muffler and blow through it until fuel reaches the carb and give it just a little bit more. Replace the pressure line, give it a start and (for me) it should start and run very quickly.

I've had half a dozen traxxas engines over the years and Since the newer generation of .15/.20 engines (2.5/3.3) have been out, I've found the front bearing tolerances between the inner bearing race and the crankshaft tends to be a little bit loose causing oil and/or air to leak. When I'm sealing the engine (since its all ripped apart anyway) I wipe the inner bearing surface (with crank removed) with denatured alcohol, as well as the surface of the crankshaft that rides against the bearing. Once its clean of all oil residue, I put a thin film of RTV (high temp orange or black) on that surface of the crank and stuff back in the engine. This prevents oil from slipping past the rear bearing trapping it between the two bearings and thus leaking out. I also put RTV silicone on the base of the carb, the backplate, and all of the fittings that screw into the carb. (the two hex screw plugs, and the top and bottom of the aluminum washers on the main needle assembly. Next I use some O-Ring lube (some guys use "green slime") on the needle o-rings. I use o-ring grease for Bostitch pneumatic nail guns which works just as well and is easier to find (hardware store). I've done this to all of my engines and have never had an air leak to date. Newer engines that dont have a lot of run time on them can still be finicky. Once you hit the 1 gallon mark, they should be running pretty consistently.

NOTE: RTV Silicone requires a 24hr cure time. If you run the engine before the RTV cures, the fuel moving through the engine can and sometimes will displace the silicone creating a leak anyway.

Just my 2ΒΆ
Tim

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