Need help with my troublesome first nitro truck

[Zombotomy]

Hello, this is my first nitro and I really need help. It's beyond frustrating. It's a hpi savage I believe it's a savage x, it has a hpi .21. 3.5 engine. I think it's the s25. I've been out 12 or 13 times and only gotten it to start 2 times and have yet to be able to get past 40 percent throttle. I've reset all the carb settings to factory with both lsn and hsn. I've used up 3 glow plugs, 2 new and I've verified it gets nice and hot before trying to start. I've tried leaning the needles and richening the needles. I tried pre hearing with a hair dryer. I'm using 25 percent nitro. I have a good losing ignitor that's always fully charged. I've only got it going 2 times.when I do it's super finicky, randomly stops a lot and then I have to restart, give it any gas when you start and it dies. The most recent time I had it going I had it going the fastest yet at 40 percent throttle which is still slow. It got warmer than it had before but randomly died and hasn't started since. Sometimes it sounds like it might but never actually does. I don't know what else to do at this point. Something has to be wrong. There is no way nitro guys are messing with starting this much, takes all the fun away from it. I hope I have enough info

 

[Suburban_Hooligan]

clogged fuel line or filter? vacuum leak?

 

[Zombotomy]

clogged fuel line or filter? vacuum leak?

No clogs in the fuel system. I get bubbles from the carb if that means anything. Not sure if there is a vacuum leak, not many spots to leak from.

 

[dustyroller]

Replace all hoses and O-rings, take apart and clean all slides and needles. Next would be the tank itself, take out and hook up to a small compressor with soapy water and check for bubbles.

 

[CertifiedMike]

Is your fuel new and fresh? What brand?

Is the return from the muffler to the fuel tank clear and connected?

Does the fuel tank hold pressure?

 

[Zombotomy]

Replace all hoses and O-rings, take apart and clean all slides and needles. Next would be the tank itself, take out and hook up to a small compressor with soapy water and check for bubbles.

Fuel lines are already new. I've never taken this full apart. Do I lube it when I put it back together? Only o ring I know is the carb where it attaches to the engine. Do I just blow air in a tank that has soap and water from the cap?

 

[rc dump]

Do I just blow air in a tank that has soap and water from the cap?

once the tank is clean just connect the fuel lines to the tank and blow into the pressure line while blocking the other line with your finger.
while blowing there should be no tank pressure loss and listen for leaks.

 

[Zombotomy]

Is your fuel new and fresh? What brand?

Is the return from the muffler to the fuel tank clear and connected?

Does the fuel tank hold pressure?

Fuel is only a couple months old. Just opened it for the first time a couple weeks ago. It's sidewinder brand 25 percent. Return tune is clear and connected. Not sure how to check if it holds pressure

 

[CertifiedMike]

The fuel tank will become pressurized once the motor is running. Its not high pressure or anything. It gives the fuel in the tank a bit of a push into the carb. It is timed so the pulse should jet fuel at the right time to get it into the carb, the cylinder.

The question is more about if your fuel tank is sealing correctly so that fuel pulse can work as its intended.

Nitro fuel goes bad over time. Keep it cool and out of the sun. Keep the bottle closed.

Bad fuel can cause all sorts of issues including similar to yours.

What # plug are you running? What brand?

I guess counterfeit plugs are a thing too. Did you buy them from China or at a hobby shop?



You installed new orings. Did you use green slime or appropiate lube when you installed them?
This is an extremely common mistake to not lube orings.

 

[Zombotomy]

The fuel tank will become pressurized once the motor is running. Its not high pressure or anything. It gives the fuel in the tank a bit of a push into the carb. It is timed so the pulse should jet fuel at the right time to get it into the carb, the cylinder.

The question is more about if your fuel tank is sealing correctly so that fuel pulse can work as its intended.

Nitro fuel goes bad over time. Keep it cool and out of the sun. Keep the bottle closed.

Bad fuel can cause all sorts of issues including similar to yours.

What # plug are you running? What brand?

I guess counterfeit plugs are a thing too. Did you buy them from China or at a hobby shop?



You installed new orings. Did you use green slime or appropiate lube when you installed them?
This is an extremely common mistake to not lube orings.

I haven't replaced any o rings yet. Can I lube with white lithium grease? I don't know what green slime is. Beside glow plug number it's just a picture. Got 2 of them from the hobby shop hsp brand. They said I have 2 options turbo or no turbo. My engine doesn't have turbo so I took non turbo.

 

[CertifiedMike]

Ok. My guess is your orings are junk. It sounds like the engine wants to run but its not getting the right mix.
You need to use a silicone based lube that allows the oring to slide. If not, it will twist and bunch up. You'll have another leak.
White lube is not good for this job imo.

Got a link to the plugs you bought?

 

[Zombotomy]

Ok. My guess is your orings are junk. It sounds like the engine wants to run but its not getting the right mix.
You need to use a silicone based lube that allows the oring to slide. If not, it will twist and bunch up. You'll have another leak.
White lube is not good for this job imo.

Got a link to the plugs you bought?

I'll replace all o rings and fuel line again just in case. My work has a compressor I can test the tank tomorrow. The glow plug has n4 written on it. Do I lube any other parts in the carb or engine after I take it apart?

 

[CertifiedMike]

You will only need to take off the carb and remove the needles from the carb to replace orings. Its not a major overhaul or anything.
There won't really be other pieces to lube.

You should be able to blow into 1 fuel line with your mouth while you block the other line with your finger, blow into the tank and be able to tell if you have a leak.

You might need to hold the fuel cap down too.

Maybe use fresh hose for this test.

I will try to find some info about your plug to see if its correct.
Wrong plug can cause all this too.

 

[Zombotomy]

Tank holds pressure and cap is good. This is the hobby store near me, the one I got my current plugs doesn't have online inventory for me to show you. Not sure what the differences are

 

[ohsnap]

Reading your description, two possibilities came to my mind as the odds-on bets.
1. Vacuum leak (as previously mentioned).
You could also try something like Lucky 7 engine sealant, which can be applied externally to seal
the components (carb to throat / crankcase cover to crankcase).
This won't address a leaking front bearing, but then again, neither will an o-ring.

2. Dead engine. It's an old model - maybe well used with little or no compression.
If things don't get better, I would check the compression at some point.
BTW - The S-25 is a .25 (4.1) engine and the early release engine blocks were still cast with 3.5 on the side.
The S-25 shares the same block with the original 21BB engine (a .21), and if yours has 3.5 on the side and if you have a carburetor
with only LSN and HSN needles (no mid-range needle to adjust), there's a good chance that's what you have.
The 21BB engine came with 3 needle carbs.

But let's hope that your issue is neither of the above and see if we can get it running.
Well, there's a third thought - your carb settings...
Reset the needles to factory settings and don't play with the LSN until you get it running.
You may not need to adjust the LSN beyond the factory setting. But that's another day...

The S-25 manual states that the factory settings are...
HSN - 4.5 turns out from fully closed
LSN - 3 turns out from fully closed

I would then lean the HSN (clockwise) 1.5 turns.
The manual for the S-25 says, "After break-in, the needle setting can range from 2 1/2 to 3 from fully closed depending on humidity, elevation, fuel, and glow plug."
HSN is now 3 turns out from fully closed.

Try starting it now.

Do you have a temp gauge?
If so, what is it reading (aiming for the glow plug) when you had it running?

Glow plugs:
You have the right style (standard) for your engine.
HSP N4 glow plug - Personally, I would avoid these like the plague. YMMV

Buy yourself some good plugs like OS #8's or McCoy #9 glow plugs.
My buddy had so many issues with N4's that he chucked them into the trash and went back to OS and McCoy.
My opinion - They (the N4's) are cheap for a reason.

Fuel:
I've never had problems with Sidewinder and always found it to be a decent brand.
You can save a buck or two and use 20% and be fine.

Was the bottle new or old?
If it was old and sealed and you were the first person to open it, it really should not matter.
I've used (sealed (good brand)) fuel that was 20 years old, with no issues (I had a stockpile of fuel and took a hiatus from the hobby).
I would not race it, but it was OK for play.

If it was previously opened, there's a good chance that some of the nitro/alcohol content evaporated.
At least that's my theory...
If that's the case, buy a new bottle.
I've also tested this situation and found the fuel to be lacking... (oil heavy / down on power).

 

[Zombotomy]

Reading your description, two possibilities came to my mind as the odds-on bets.
1. Vacuum leak (as previously mentioned).
You could also try something like Lucky 7 engine sealant, which can be applied externally to seal
the components (carb to throat / crankcase cover to crankcase).
This won't address a leaking front bearing, but then again, neither will an o-ring.

2. Dead engine. It's an old model - maybe well used with little or no compression.
If things don't get better, I would check the compression at some point.
BTW - The S-25 is a .25 (4.1) engine and the early release engine blocks were still cast with 3.5 on the side.
The S-25 shares the same block with the original 21BB engine (a .21), and if yours has 3.5 on the side and if you have a carburetor
with only LSN and HSN needles (no mid-range needle to adjust), there's a good chance that's what you have.
The 21BB engine came with 3 needle carbs.

But let's hope that your issue is neither of the above and see if we can get it running.
Well, there's a third thought - your carb settings...
Reset the needles to factory settings and don't play with the LSN until you get it running.
You may not need to adjust the LSN beyond the factory setting. But that's another day...

The S-25 manual states that the factory settings are...
HSN - 4.5 turns out from fully closed
LSN - 3 turns out from fully closed

I would then lean the HSN (clockwise) 1.5 turns.
The manual for the S-25 says, "After break-in, the needle setting can range from 2 1/2 to 3 from fully closed depending on humidity, elevation, fuel, and glow plug."
HSN is now 3 turns out from fully closed.

Try starting it now.

Do you have a temp gauge?
If so, what is it reading (aiming for the glow plug) when you had it running?

Glow plugs:
You have the right style (standard) for your engine.
HSP N4 glow plug - Personally, I would avoid these like the plague. YMMV

Buy yourself some good plugs like OS #8's or McCoy #9 glow plugs.
My buddy had so many issues with N4's that he chucked them into the trash and went back to OS and McCoy.
My opinion - They (the N4's) are cheap for a reason.

Fuel:
I've never had problems with Sidewinder and always found it to be a decent brand.
You can save a buck or two and use 20% and be fine.

Was the bottle new or old?
If it was old and sealed and you were the first person to open it, it really should not matter.
I've used (sealed (good brand)) fuel that was 20 years old, with no issues (I had a stockpile of fuel and took a hiatus from the hobby).
I would not race it, but it was OK for play.

If it was previously opened, there's a good chance that some of the nitro/alcohol content evaporated.
At least that's my theory...
If that's the case, buy a new bottle.
I've also tested this situation and found the fuel to be lacking... (oil heavy / down on power).

I think I found the issue. Saw a small chunk out of this area if the carb, after that half of it just broke off. I suppose only fix is replacing the entire body?
Also I can't find what factory setting is for the idle screw. It is the 3.5 engine. All the videos I saw from you said that hsn and lan are both flush with their housings to go to factory.

 

[dustyroller]

An extra measure make sure the nipple on the pipe is clear to pressurize the tank too. I’ve had bugs come in and never come back out. That crack may have been your leak.

 

[Zombotomy]

An extra measure make sure the nipple on the pipe is clear to pressurize the tank too. I’ve had bugs come in and never come back out. That crack may have been your leak.

I found the air leak

 

[dustyroller]

Right on, now I see the whole thing, it looked like just a chip but that would definitely be a problem.

 

[Zombotomy]

Right on, now I see the whole thing, it looked like just a chip but that would definitely be a problem.

It was a chip but also a hairline fracture across the whole thing. Hard to find part now