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2.5 Engine= JUNK!!!

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Old 04-28-2003, 09:23 PM
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POJack
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Default 2.5 Engine= JUNK!!!

Ok, I'm convinced this thing is a peice of crap. Yes it does provide great performance, but only when it is running. This thing cuts out on me after every 2-3 high speed passes. Today I was out with it and drained my starter battery on only a HALF TANK! Obviously, during the 2 year "reasearch and development" of the 2.5 engine, they didn't figure out a way to keep it from stalling ALL THE TIME. I'm going with the Sirio. I can't take the 2.5 anymore. Anyone with the Sirio? Does it cut out all the time like the 2.5?
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Old 04-28-2003, 09:27 PM
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Rob D
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Default 2.5 Engine= JUNK!!!

After the wonderful pro 15 i said id never buy anther traxxas unless it was cheep then i would get a real engine
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Old 04-28-2003, 09:29 PM
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Default 2.5 Engine= JUNK!!!

I also had the Pro .15 and it didn't cause me any problems with idle. I've tried everything on the 2.5 and it just dosn't want to stay running.
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Old 04-28-2003, 09:30 PM
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Default 2.5 Engine= JUNK!!!

jus sounds like u werent tuning it properly your the first person ive seen on these forums to have such problems and contiuned to have them with that engine, yah it does need work everyday to run it is picky, but come on, you cant expect nitro to be plug and play like USB ports or Electric ^_^ If you dont want the engine ill take it off your hands no prob. And get a better battery than those cheap 1500's they give u for the charger, it doesnt even have enough punch
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Old 04-28-2003, 09:40 PM
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Default 2.5 Engine= JUNK!!!

Originally posted by CaseyDDR
jus sounds like u werent tuning it properly your the first person ive seen on these forums to have such problems and contiuned to have them with that engine
Excuse me, but if you can find the last post where I've complained about this engine, let me know...You won't find any posts from me regarding the 2.5 because this is my first post regarding the 2.5 engine. I'm the 1'st person you've seen to have consistant problems with this engine???????? Obviously, your not paying attention to the posts. Just look up "2.5 problems" in the search field. Also, look at the Traxxas forums and do the same thing. Every day there are people complaining about the 2.5 stalling and no, it's not my tuning ability. I had the pro .15 with no probs and also an hpi rs43 with no probs.
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Old 04-28-2003, 09:44 PM
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Rob D
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Default 2.5 Engine= JUNK!!!

And dont forget the posts about it running hot all the time
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Old 04-28-2003, 09:53 PM
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Default 2.5 Engine= JUNK!!!

Well this helps me make up my mind... Hmmm.. should I go with the 2.5? Or the Sirio that my buddy at the LHS has for 200 with the pipe.... hmmmmmm.
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Old 04-28-2003, 09:56 PM
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Default Hey perculator

Definately go with the Sirio...It can't be any worse than the 2.5. I've read many forums that say it is more reliable. I'm not worried about the power increase, I'm just concerned about reliability.
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Old 04-28-2003, 10:07 PM
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Default 2.5 Engine= JUNK!!!

I'm having the stalling probs with my 2.5 as well, though not nearly as bad as it was. I believe it has something to do with vapor lock. Have any of you tried the longer piece of fuel line (pressure line) from the exhaust to the fuel tank? I installed a piece approx. 17-20 inches long, enough to make 2 loops (I just wrapped mine around the rear body mount on my Maxx. This helps the stalling problem. Mine still stalls ocassionally, but not nearly as much as it used to. Installing a Nova Pro head will help it run cooler as well. It's supposed to run up to 40% cooler with this head. Mine seems to run cooler with it.
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Old 04-28-2003, 10:12 PM
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Default 2.5 Engine= JUNK!!!

what does more tubing do? I have very short tubing on my car, and it never stalls.
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Old 04-28-2003, 10:14 PM
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Default 2.5 Engine= JUNK!!!

Havent had any problems with mine. It is my first nitro rc car and I know very little about keeping them running but it has worked fine for me. I have almost 4 gallons of fuel through it and it still runs fine, starts and idles great.
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Old 04-28-2003, 10:16 PM
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Default longer tubing

I read something about this helping with vapor lock...I'll give it a try and see if it works...
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Old 04-28-2003, 10:18 PM
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Default Re: longer tubing

Originally posted by POJack
I read something about this helping with vapor lock...I'll give it a try and see if it works...
lol another newb question, whats vapor lock ^_^
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Old 04-29-2003, 12:37 AM
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Default 2.5 Engine= JUNK!!!

Vapor lock is when the amount of air or exhaust is too great in the cylinder. When it gets compressed it is too much for the piston to compress all the way enough to start it's down stroke cycle. Therefore the piston reaches a point where it stops traveling up the cylinder and it stalls the engine.

Hydro lock is the same situation but with a liquid mixture. Such as too much fuel or oil left in the cylinder. Hydro lock is MUCH more common than vapor lock in R/C two strokes.

Both situations can cause the piston to crack, the connecting rod to bend or the head gaskets to blow out. Or all of the above at once.

To cure it you have to loosen the glow plug and let the extra pressure escape. Then readjust the fuel/air mixture.
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Old 04-29-2003, 01:01 AM
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Default 2.5 Engine= JUNK!!!

uh, actually vapor lock is when the vapor pressure is too high. when heated, gas forms a vapor, and the older style fuel systems in cars were pull instead of todays push systems. hard for a diaphram pump to pull vapors. hence the term vaporlock. i guess it can happen in r/c cars, if the fuel gets hot enough...
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Old 04-29-2003, 01:11 AM
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Default 2.5 Engine= JUNK!!!

That is true. But these are Two Stroke engines. Most two strokes are pull type fuel delivery systems also. So I'm not incorrect in explaining.

Both definitions of different vapor locks are true.

I'm guessing using vapor lock as the word for my definition is incorrect, and I can't think if what it is technically called, but they get my point.
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Old 04-29-2003, 01:20 AM
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Default 2.5 Engine= JUNK!!!

To eliminate vapor-lock, reroute the fuel (not the pressure) line away from any heat source. If you are going to lengthen the fuel line (to reduce starvation when the car is flipped) make sure it is away from the cylinder and/or the exhaust system.
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Old 04-29-2003, 01:28 AM
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Default 2.5 Engine= JUNK!!!

Vapor Lock is a joke!

Longer hose's, are going to do what? nothing, not a thing! Why would a longer hose make it not vapor lock, it wouldn't! It would give it more resistance??????????

Hello......, isn't that what the vapor lock is doing (if that were the Case, and its not), yep lets add to the non existent problem!

News at 11:
If your engine is new, its set wrong, if its got a few gallons of fuel through it, its shot!


Richard Newman
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Old 04-29-2003, 01:35 AM
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Default 2.5 Engine= JUNK!!!

My buddies maxx has this very same problem.It will start fine and run fine for about 1/2 a tank and then it starts stalling and it gets hot and doesn't want to start again.The two of us have tried everything to get this thing running right and nothing has worked and it's not just my tuning ability either,even the guys at both of our local hobby shops couldn't do it either.If someone finds a way to tune this thing perfectly please let me know because this has been pissing me off since he got the truck and I feel bad because I recommended it to him.
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Old 04-29-2003, 01:49 AM
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Default 2.5 Engine= JUNK!!!

If this truck is new: adj the top end first, then adj the idle screw, where its almost going into gear, then set the low end, and finally set the idle from there again.

MAKE SURE YOUR TRANSMITTER IS NOT EFFECTING THE CARB ON BRAKING AND REVERSE,if it is, your wasting your time. Resolve this
so the transmitter doesn't kill or alter the engine rpm.

I live way down south: my settings are 3-3/4 out on the high end, and 3/4 out on the low end, go RICH from these settings if your north of me.



If its not new, your engine is toast! I just went through this with Traxxas. Totally pissed!

Richard Newman







Originally posted by Rex2342
My buddies maxx has this very same problem.It will start fine and run fine for about 1/2 a tank and then it starts stalling and it gets hot and doesn't want to start again.The two of us have tried everything to get this thing running right and nothing has worked and it's not just my tuning ability either,even the guys at both of our local hobby shops couldn't do it either.If someone finds a way to tune this thing perfectly please let me know because this has been pissing me off since he got the truck and I feel bad because I recommended it to him.
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Old 04-29-2003, 02:05 AM
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Default 2.5 Engine= JUNK!!!

If adding the extra length doesn't accomplish anything as you say it wouldn't, then why are so many people solving, or at least drastically reducing the problem by adding the extra pressure line? It has drastically reduced the problem on my Maxx, and I've heard of people completely resolving this issue with the extra line. I can tell you it isn't a problem you're going to get rid of with tuning. I spent countless hours trying to get rid of it tuning mine, and it can't be tuned away. The extra pressure line definitely helps.
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Old 04-29-2003, 02:38 AM
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Default 2.5 Engine= JUNK!!!

Originally posted by Rex2342
My buddies maxx has this very same problem.It will start fine and run fine for about 1/2 a tank and then it starts stalling and it gets hot and doesn't want to start again.The two of us have tried everything to get this thing running right and nothing has worked and it's not just my tuning ability either,even the guys at both of our local hobby shops couldn't do it either.If someone finds a way to tune this thing perfectly please let me know because this has been pissing me off since he got the truck and I feel bad because I recommended it to him.
Your friends piston and sleeve are shot already it seems but I have no idea how old it is since you didn't say. The piston and sleeve fit fine when the engine is cold, but as soon as it gets hot (half tank) the tolerances loosen up and the piston cannot stay tight ot the cylinder wall anymore. Thus causing a leak and the engine dies. Replace the piston and sleeve and break it in right. Then always run it rich to be safe.

If this engine is new and broken in correctly, then there could be a leak in the pressure or fuel line. If the pressure in the tank is not enough because of a leak then when it reaches half a tank and the exhaust cannot pressurize the tnak enough it will choke off. Many times the primer button has a leak around it and causes fuel starvation to the engine.

OR of the pressure is too high (short line and new engine) it will flood the engine with fuel at times and choke it off.

BUT MOST of the time all these engine problems come from poor tuning plain and simple. And that can only be fixed with practice and fine tuning over and over again until it's right and you learn to find the sweet spot for your excat engine. No two engines ever run alike.
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Old 04-29-2003, 02:43 AM
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Default 2.5 Engine= JUNK!!!

That may or may not be the problem. Mine was doing the same thing after running just 10 tanks of fuel through it. I know my piston's not shot. I followed the break-in procedure to the letter. Adding the longer pressure line definitely helps with this problem.
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Old 04-29-2003, 02:52 AM
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Default 2.5 Engine= JUNK!!!

Originally posted by eletrick
If this truck is new: adj the top end first, then adj the idle screw, where its almost going into gear, then set the low end, and finally set the idle from there again.

MAKE SURE YOUR TRANSMITTER IS NOT EFFECTING THE CARB ON BRAKING AND REVERSE,if it is, your wasting your time. Resolve this
so the transmitter doesn't kill or alter the engine rpm.

I live way down south: my settings are 3-3/4 out on the high end, and 3/4 out on the low end, go RICH from these settings if your north of me.



If its not new, your engine is toast! I just went through this with Traxxas. Totally pissed!

Richard Newman
actually RC Nitro said to do the high speed first, then low, then idle.. And your saying if ur engine has a couple gallons through it, its shot? you know absolutely nothing then. I know ppl with 4-5 gallons through there engine and its still running strong.
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Old 04-29-2003, 02:54 AM
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Default 2.5 Engine= JUNK!!!

FYI.............

Vapor lock is when the fuel in the line or delivery system boils and creates gas or "vapor" pockets in the delivery sytem which in turn starves the engine of fuel as they (the vapor pockets) enter the carb, causing it to stall. This will also cause hard restarting problems. Its not unusual to waste two battery packs on the Ol' EZ start trying to get it up and running again. The only way to prevent this is to route your fuel supply line away from the engine and always run it a bit rich. Running extra exhaust pressure line does nothing. The 2.5 is a VERY tempermental engine to tune and once it gets lean its real hard to reel it back in.
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