nitrojimbo

When I'm running my LST ona high speed pass for tuning, then bring it in to tune it, it revs real high and creeps forward faster than if it was just the idle speed screw. I have no idea whats wrong with it. I checked for linkage, idle screw, air leaks, and tuning. They're all good but I have no idea why it revs so hi. So could you guys throw out some ideas for me, or if you know what the problem is tell me. I just hope that God will let my engine run the way it's supposed to. Oh, btw I'm using traxxas top fuel 33%.

SAVAGEJIM

Sounds like a carb leaking air. (Or air seeping into the engine where it is not supposed to be).

I do not know what troubleshooting remedies you have already done, but please bear with me as I mention them. Ignore what you have already done, but if there is something I mention that you have not yet done, try it to see if your problem goes away.

Lets start with simplest.
Rip off all of the fuel lines and replace them all with brand new lines.
Totally replace you fuel tank with a brand new one.
Check your engine for any cracks, loose bits, etc.
Make sure your exhaust has a good coupling on it; actually, rip off teh one on their now and install a brand new coupling .
Check teh gasket nipple on the engine's exhaust nozzle, make sure the manifold goes on such taht no air leaks.

Now for the more harder.
Dismount the engine, disassemble it completly.
Clean everything thoroughly
Inspect all the parts, replace anything that is bad.
Check the block and back plate for cracks, inside and out.
Rassemble the major parts (crank, conrod, pisotn, sleeve). do not install teh carb yet.
As you reassemble the engine, put RTV on the engine, like on where the backplate and engine block interface. Dont put RTV on the head or head button, make sure you haev teh right abount of head shims, they will prevent air leaks on their own.
Now the carb:
Take out the needles. Replace all the o-rings, use Associated Green Slime on the new o-rings.
Look at the needle tips very carefully. If they are bad, replace the needle(s)
Inspect teh holes teh needles go into, make sure they are free of debris and other obstructions.
Reassemble the carb, use RTV on the neck that mounts onto teh block. Put RTV also on the clamping screw taht secures the car to teh block, DONOT OVERTIGHTEN!
Let RTV cure
Next day, try to start and tune.

If all this fails, call axial to warranty the engine. The fault is in manufacturing, not you carelessness or abuse.

nitrojimbo

Hey thanks man. I'll get on it tonight since I'm on winter break(I'm in the 8th grade). I'll get back to you tomarrow moring.

HerrSavage

nitrojimbo. Turn your electronics on - radio and truck. Give gas and brake over and over, fast, slow, etc.. Is it catching or jerking or anything unusual like that??

Are all the screws in tight - backplate, cooling head, etc??

What fuel are your running? And what plug? How much fuel does the engine have through it?

No offense Jim, but I'm skeptical he needs to totally disassemble his engine, carb, etc...

OK, maybe seal the backplate and carb throat - but he can do that without even taking the engine out.

nitrojimbo

I'm running traxxas top fuel 33%, McCoy 59 plug. I got about half gallon through it.

mentorman

My Feedback: (2)

I would replce the fuel lines first, and richen the botom end. If symtoms dont improve, then I would seal the carb base and back plate.

HerrSavage

If he's running %33 fuel, maybe he needs to remove a shim? Or add one?? I don't know which... But I hear people talking about adding or removing shims with high nitro content fuel all the time..

nitrojimbo

Well, I would need to add one for higher nitro content, but 1 less shim that I want wouldn't cause it to run so erratically.

helivaguy

he would need to add 1 shim fir that 33%,you could add 1 shim and still use 20% and this will help topend hi-speed runs.
personally imho i think 30% is a waste of money.
also he could be using the wrong plug and pipe and the carb neck and backplate should be sealed also,but i still think it has a bad bearing.
mc59 i beleive is a short plug,he should be using a mc8 long plug.

HerrSavage

I had a pretty leaky bearing in my Axial 28RR, and after researching how to replace it, decided that was too much hassle.. So I just put a big washer behind the collet, and it ran fine like a top for a good 3-4 more gallons til I sold it..

He said there's no leakage from behind the flywheel though..

[sm=confused.gif]

nitrojimbo

I'm sure it's a bearing leak because when I checked for air leaks, I heard a little whining sound indicating a leak near the flywheel.

mentorman

My Feedback: (2)

I think what you are hearing is the bearing just getting noisy because it is going bad. And it wont always leak, beacuse it is sucking air in, causing your leaning issue when the carb closes at idle. I hear this is common with Axial and many others aparently.

nitrojimbo

So do I replace the bearing? Also, I hear the whining sound when I blow in on the fuel line into the carb when I'm checking for air leaks. You know like plugging the carb hole and exhaust outlet and blow into the engine?

mentorman

My Feedback: (2)

If it is still in warranty I would send it back to them saying that its leaking fuel all over from the front, otherwise you could do it yourself if you know the size.

nitrojimbo

Yeah I should send it back. But what if they ask what fuel I'm using cause I'm using 33% even though the warranty only covers 20-30%.

ridgerunner1

Hey nitrojimbo the size bearing you need for the front is 7mmx19mmx6mm, I had the same trouble with my motor ran great but i couldn't get the idle was always to high or to low never just right and this happened only after a gallon, I took off my engine and i had a lot of fuel under it in fact i think i saw a flee doing the back stroke...lol anyway after replacing mine i have had no more trouble idles nice now, Check with a hoddy shop close by and see if they have a bearing puller installer if so they may do it for you or you can do the oven thing, One other thing look at you mid needle make sure it's flush for some reson they tend to move on there own during running i sealed my mid needle so it wouldn't move.

race raider

what did use to seal the needle

ridgerunner1

I used high- temp rtv silicone gasket maker.

mentorman

My Feedback: (2)

33% or any other percentage has nothing to do with your problem anyways. And if you are thinking about doing it yourself, be prepared to pull the crank out, which is no big deal really. But call Axial or email them first and see what they say. Its a factory defect.

nitrojimbo

No what I'm saying is that the Axial warranty only covers 20-30% fuels. Any percentage over that breaks the warranty.

nitrojimbo

Also, do I have to type 1800 before their customer service number because everytime I try to call the line is busy.......maybe because there's so many problems with these engines?

vtec.

im having a problem with the acial motor from my Robitronics protos. has a slight Bog problem but after i give it throttle little by little its okay.