Tuning nitro engine

[teacherbloke]

Hello to everyone, i am new to rc model cars. I have a nitro 1/8 off road buggy that needs tuning. I have reset all screws for low speed, high speed and air gap. Nothing seems to work. It flys around the garden but will not idle correctly.

 

[TeknoJ]

This is what I learned from right here. Take the time to watch the full video and write some things down if needed.

 

[fstnd]

A video would be helpful. What do you mean with an "incorrect" idle, does it shut off, does it alternate? Resetting all screws to factory settings doesn't usually bring you the perfect tune. A too rich low speed needle could cause your engine to behave alright at higher speeds, while making your engine suffocate in fuel when releasing throttle

 

[Littlemotor]

This is what I learned from right here. Take the time to watch the full video and write some things down if needed.

^^^^THIS. Verbatim.

You will be EXTREMELY hard pressed to diagnose ANYTHING tuning related over a discussion forum. The absolute best thing to do is LEARN, and that’s impossible NOT to do with the JQ/Invisible Speed videos. Simply cannot be beat. Better than first hand from “the local nitro guy” imho too. 50 different answers, from 50 different people always includes a bunch of guesses, generalized answers, and most often-flat out terrible/incorrect advice from people that shouldn’t be giving any. Even on the off chance that someone who actually knows what they’re doing (and what YOU are doing), chimes in with the best (online) help/insight/coaching available-that help almost NEVER translates to the guy having all the trouble. This is the main reason I almost always just instruct people to invest some time into the Invisible Speed videos, and LEARN IT. Good luck sir, and keep us posted.

 

[CertifiedMike]

Welcome to RCTALK.COM!!!
You sound like you're close but fine tuning is still required as others mentioned.
No substitution for getting your hands dirty.

 

[jojobeans]

This is what I learned from right here. Take the time to watch the full video and write some things down if needed.

YES! And take notes!

For a quick and dirty run down, this video is by far the simplest guide I have ever found for the basics of tuning. But, it won’t teach you the more advanced stuff.

Biggest piece of advice… anytime you’re having a tuning issue you can’t figure out. Start over fresh. Reset the carb to factory settings in the manual and then start diagnosing. That’ll remove the human variable from any problems lol

 

[teacherbloke]

Thank you for your help. However after I watched the video I tried to get the engine going but it wouldn't start at all. It has never done that before. I can turn the engine by hand now and there is a definite rough spot at TDC with about a quarter of inch of play inside the engine. So I think it is curtains for the engine. Anybody know where I can get a new one please?

 

[Littlemotor]

Thank you for your help. However after I watched the video I tried to get the engine going but it wouldn't start at all. It has never done that before. I can turn the engine by hand now and there is a definite rough spot at TDC with about a quarter of inch of play inside the engine. So I think it is curtains for the engine. Anybody know where I can get a new one please?

Remove the backplate and LOOK at it.

What you are describing could very well be metal punch, and the feeling of “dwell” between the piston traveling up, and back down.

 

[teacherbloke]

I understand what you mean. I am used to petrol and diesel engines. If any one of them had the same play it would be a major rebuild!

 

[teacherbloke]

I understand what you mean. I am used to petrol and diesel engines. If any one of them had the same play it would be a major rebuild!

I will look at it tomorrow now, but thank you for quick reply.

 

[teacherbloke]

I will look at it tomorrow now, but thank you for quick reply.

Also, just a thought, doesn't turning it by hand mean loss of compression? I certainly couldn't do that before!

 

[Littlemotor]

Also, just a thought, doesn't turning it by hand mean loss of compression? I certainly couldn't do that before!

You need to watch that video. You’re basically telling us that you haven’t.. In order for anything to “translate well” over the internet, you’re going to need to understand some things-it’s apparent we are not there even after sharing the video..

 

[teacherbloke]

You need to watch that video. You’re basically telling us that you haven’t.. In order for anything to “translate well” over the internet, you’re going to need to understand some things-it’s apparent we are not there even after sharing the video..

Sorry but that video said nothing about loss of compression. It was a very comprehensive video about tuning, my engine failed to start when I tried it today. The glow plug was ok, I was able to turn it by hand certainly couldn't before, the compression was way too high for that! Something has failed internally and caused the lack of compression! I will look probably tomorrow now, but thank you for your input.

 

[Littlemotor]

Sorry but that video said nothing about loss of compression. It was a very comprehensive video about tuning, my engine failed to start when I tried it today. The glow plug was ok, I was able to turn it by hand certainly couldn't before, the compression was way too high for that! Something has failed internally and caused the lack of compression! I will look probably tomorrow now, but thank you for your input.

It sure talks about pinch (and absolutely compression thereafter as they go hand in hand in the conversation) -Which leads me to my next question-did you make sure to bring your piston to BDC after each run-especially the last one? This is rule number one with a nitro glow 2smoke engine..

 

[teacherbloke]

It sure talks about pinch (and absolutely compression thereafter as they go hand in hand in the conversation) -Which leads me to my next question-did you make sure to bring your piston to BDC after each run-especially the last one? This is rule number one with a nitro glow 2smoke engine..

As the instructions I have been given i used some after run oil through the carburettor and turn it over a few times to get it through the engine before storage. Done this every time.

 

[Littlemotor]

As the instructions I have been given i used some after run oil through the carburettor and turn it over a few times to get it through the engine before storage. Done this every time.

Not at all what I’m asking. This is also covered repeatedly in the video as it’s THE single most important requirement of these specific engines. The SECOND you shut the vehicle off, it is absolutely IMPERATIVE that you bring the piston to BDC. Otherwise-due to the profile of the sleeve (JQ talks about this when covering pinch, and compression because the sleeve profile is TAPERED) when the engine cools-the sleeve will cool around the piston, thereby effectively stretching it to the point where you will lose all compression completely. This can happen in less than 5-10 minutes depending on the engine. It is not a case where it “can” happen, it WILL happen if you do not return the piston to BDC each and everytime you shut down the engine. It’s one of the basic fundamentals of nitro surface RC. This is nothing to do with storage, nor ARO.

 

[CertifiedMike]

Seems like a teardown for inspection is needed here.

 

[teacherbloke]

I will watch the video again. Although what you say does make sense. The clearances are very tight for obvious reasons. the makers don't mention any of this in their instructions. It is useful for future reference. So I will need a new sleeve and piston to restore compression then. Any idea where to get one please?

 

[Littlemotor]

I will watch the video again. Although what you say does make sense. The clearances are very tight for obvious reasons. the makers don't mention any of this in their instructions. It is useful for future reference. So I will need a new sleeve and piston to restore compression then. Any idea where to get one please?

Any decent online hobby shop.

You need to tear it down and diagnose what’s going on before just whipping out the credit card imo, however. Metal pinch goes away during/after break-in. It’s very difficult to know if you’ve lost that, lost compression, or lost BOTH when talking over the internet.

You say you “could not turn it over by hand” before, but you “can now”.. And you’re saying you’ve got no compression, but if you’re saying you’ve got no “compression” based on the loss of mechanical pinch compared to the FAR less resistance felt in rotating the engine NOW, then you may very well have only lost PINCH, which is normal. A simple way to make sure we are all on the same page is to remove the engine from the vehicle, hold it by the flywheel, and rotate the crank until you feel resistance, then let go of the crankcase. This is referred to as the “flop test”. If it “flops over”, then you’ve lost compression. If not-then you’ve simply lost metal pinch.

These engines are DESIGNED to wear in, and this is the reason for pinch.

As with full-size passenger vehicle engines-proper diagnosis is required. Let’s not just throw parts at it, or start looking for a replacement without inspection, and properly diagnosing what issues may be present.

Would also be helpful to know what vehicle, and engine you have, as well as photos, and video of what you’ve got going on.