I'm Pulling My Hair Out!

[SpontaniousCombustion]

Hello and thank you for taking the time to read this post. I have tried to attach necessary images and videos to this post to explain myself as best as possible. VIDEO:

A while ago I got my father old Protech Promax 1/6 scale nitro RC car out from the shed it had been sitting in for a good while (years). I cleaned it up and got it running with my little knowledge of Nitro RC cars. All was well and everything was going good, I purchased a new remote control for the car and was ready to begin tuning it!

This is where it all went... in the opposite direction shall we say haha. So I watched a few YouTube videos about tuning a nitro RC car and familiarized myself with the basics. I started to tune my old Protech Promax when I noticed that the carb doesn't have a low speed needle.. Instead there is just a piece of metal covering where it should be as if it should be there but... it's not it is very strange. Due to this reason I don't really know how to tune this RC car.

High Speed Needle

Where I thought the Low Speed Needle should be located..

Mid-Range Needle

Although it is running it makes a strange revving noise sometimes when I release the throttle. I am not sure if this is to do with the tuning attempt that I did to the RC car or something else. I have also recently purchased an infered temp gun that I am still yet to use.

I hope someone can help me with this problem I am having because I am really pulling my hair out about it, how can I stop the weird rev noise and make the car run properly...

 

[cbaker65]

I believe that is only a 2 needle carb ,The LSN is the brass one on the side ,I think it maybe suppose to be
set at flush with the housing ,the engine maybe running too lean with it now.
Try richening that back out a couple turns out an see if it tames the motor down some!

 

[SpontaniousCombustion]

I believe that is only a 2 needle carb ,The LSN is the brass one on the side ,I think it maybe suppose to be
set at flush with the housing ,the engine maybe running too lean with it now.
Try richening that back out a couple turns out an see if it tames the motor down some!

Okay so does this mean that this RC car doesn't have a HSN? And also am I correct about the Mid-Range Needle? One other thing I wanted to ask was could I purchase a 3 needle carb and swap them around?

Thank you.

 

[cbaker65]

Okay so does this mean that this RC car doesn't have a HSN? And also am I correct about the Mid-Range Needle? One other thing I wanted to ask was could I purchase a 3 needle carb and swap them around?

Thank you.

No ,the big brass on the side is the Lsn an the top tall one is the Hsn!
I would run the Lsn to almost flush with the housing of the carb ,an
only adjust the Hsn accordingly.

You also may have to adjust the idle screw as well to set the idle with your new tune!

I have those 2 needle carbs ,an thet are easy to tune.
Mine are an AE 28 carb ,an I ran those at Hsn 2 1/2 to 2 3/4 turn out ,an the
Lsn at about 6 to 6 1/2 turns out.

 

[SpontaniousCombustion]

No ,the big brass on the side is the Lsn an the top tall one is the Hsn!
I would run the Lsn to almost flush with the housing of the carb ,an
only adjust the Hsn accordingly.

You also may have to adjust the idle screw as well to set the idle with your new tune!

I have those 2 needle carbs ,an thet are easy to tune.
Mine are an AE 28 carb ,an I ran those at Hsn 2 1/2 to 2 3/4 turn out ,an the
Lsn at about 6 to 6 1/2 turns out.

Okay thank you very much it's finally nice to find someone who can help me with this! I will try these new settings as soon as I can! When you say you ran it for example 2 1/2 to 2 3/4 turns out is that 2 1/2 turn clockwise or anit-clockwise sorry for the stupid question I am all very new to this.

Thank you.

 

[mrbones]

Anti- clockwise. You turn it clockwise gently until it stops. That is closed. Then open it anti-clockwise the amount of turns that he said.
Then go to the the tuning guide; https://www.rcnitrotalk.com/forum/threads/nitro-tuning-tips-and-tuning-flow-chart.60832/

 

[olds97_lss]

The OS 21RG carb had the LSN adjustment like yours. You adjusted the seat of the needle vs the needle itself. Not the best way to adjust that as it also moves where the fuel/air is atomized in the carb throat, so your adjusting 2 things at the same time by moving the LSN seat around. I had a few of those engines years ago, is why I mentioned them.

The manual for your engine isn't much help as to where "factory" setting is for that either.
https://rcdocuments.com/documents/Protech SX-21.pdf

It just says that it's set at the factory and to not mess with it, but for break-in, screw the HSN in until it stops, then back it out 5 turns. This should be a rich setting.

I'd adjust the LSN seat until it's flush with the carb housing. For pretty much any LSN seat I've seen, "flush" is where they are set. Yours looks like it's screwed in a bit.

High idle off throttle is usually indicative of a lean engine. Richen the HSN a bit. Or start where the manual says, then see how it goes and adjust as necessary. I would probably set the LSN seat to be flush with the carb housing though as well.

FYI, yellow circle is the HSN, red circle is your LSN/LSN seat adjustment:

 

[SpontaniousCombustion]

The OS 21RG carb had the LSN adjustment like yours. You adjusted the seat of the needle vs the needle itself. Not the best way to adjust that as it also moves where the fuel/air is atomized in the carb throat, so your adjusting 2 things at the same time by moving the LSN seat around. I had a few of those engines years ago, is why I mentioned them.

The manual for your engine isn't much help as to where "factory" setting is for that either.
https://rcdocuments.com/documents/Protech SX-21.pdf

It just says that it's set at the factory and to not mess with it, but for break-in, screw the HSN in until it stops, then back it out 5 turns. This should be a rich setting.

I'd adjust the LSN seat until it's flush with the carb housing. For pretty much any LSN seat I've seen, "flush" is where they are set. Yours looks like it's screwed in a bit.

High idle off throttle is usually indicative of a lean engine. Richen the HSN a bit. Or start where the manual says, then see how it goes and adjust as necessary. I would probably set the LSN seat to be flush with the carb housing though as well.

FYI, yellow circle is the HSN, red circle is your LSN/LSN seat adjustment:

Thank you so much I am egar to try this and get the car working well! I have to ask where you found the information about this car I looked all over the internet for even a slither of information. I will try this new direction of fix in the morning!

Thank you

 

[Certified Mike]

Your floating revs issue may be a cracked (dry rotted) oring. I'm not familiar with your particular set up so it may not even use orings. You may also have an air leak somewhere else in the system. One thing at a time tho. Try to get your setting sorted and that reving issue may just go away. Good luck! Nice to see an older rig reserrected!

 

[olds97_lss]

Thank you so much I am egar to try this and get the car working well! I have to ask where you found the information about this car I looked all over the internet for even a slither of information. I will try this new direction of fix in the morning!

Thank you

I just googled the brand and ran across a manual that had a photo that looked similar to your engine.

 

[Certified Mike]

Watching the video, another thought occurs to me... Have you watched your throttle rods etc while the car is not running to be sure something isn't hanging up slightly, or maybe is a little loose?

 

[cbaker65]

A throttle return spring might help with that!...

 

[SpontaniousCombustion]

Hllo and thank you all for replying to this post. Unfortunatly when I came to test the Protech with the new setting the car failed to start, it also failed to prime too for some unknown reason. It was okay the last time I got it running. I have ordered myself a new car and am going to fix the Protech in spare time I am a bit fed up with it at the moment.

Thank you all for your suggestions and thoughts.

 

[Certified Mike]

Patients is part of nitro for sure. I'm sorry you're having a rough time. Of you get back to where you want to Get it running, just say so and I/we will help you out!

 

[ninnon]

Keep patient, once you get the hang of things it's a fun hobby.
Give this a read too: https://www.rcnitrotalk.com/forum/threads/nitro-rc-beginners-guide.68224/