hpi savage x with tm728 motor problems

[swexelman]

Hey I'm new to the forum, I just picked up two savage x's, I've been out of the hobby for 6 years or so and forgot some stuff. One of them has a tm728 motor, I messed with the carb screws and it will not stay running once the glow plug starter is removed, I've searched high and low on google for the carb setting but I am confused about which screw is what, I found the main needle is 4 and the idle is 6 but there is also another screw on the opposite side where the throttle linkage, how many turns is that one supposed to be? The idle screw is the small black screw coming off at an angle on the carb right? The main is the biggest screw with the brass housing right?

 

[srusinek]

There's usually 3 screws on a nitro engine. High speed, Low speed and idle. The high speed is the screw that is above where the fuel line attaches to the engine. The low speed is where the linkage goes on the engine and the screw is inside that arm so to speak. The idle screw usually is in the middle of the carb under where the air filter goes onto the engine. The other screw you're referring to is called the mid speed mixture screw and is on the side of the carb opposite the low speed needle. Most manufactures do not recommend adjusting this screw. For a visual look at the stickys posted on the nitro section of the forum and youtube will have plenty of videos explaining what I explained in the above.

 

[swexelman]

Awesome thanks for the quick response, I'm worried about the mid speed screw because i did move it, is there a estimate of turns it should be at? Also I talked to a shop and he said it could be the rear or front bearing, or slop in the rod that is causing it die when the glow plug ingiter is removed? Does that sound right?

 

[Snook Man]

I dont think the 728 has a mid speed needle...
If it does you would see 4 adjustment screws 1 HSN (large brass fitting with the fuel line going into it), 1 LSN (on the end of the slide valve), 1 Mid speed (usually flush with the housing if present and opposite side of the lsn) and the idle screw (the angled screw going through the carb housing into the slide valve notch).

The idle screw should be set so you have a 1.0 to 0.5mm gap at the slide valve inside the carb throat when at idle and it should close no further when you apply the brake.

 

[swexelman]

yea I think it is a low speed needle, so I have the high speed out 4 turns as recommended, what is the low speed supposed to be at normally? also I am running 20% cool power heli nitro which I didnt want to use but it was all the shop near me had and him and another shop said it should work (they didnt sound confident). I also found out today that the previous owner ran 30% nitro in both the trucks, so is the nitro I'm running maybe the problem? should I run 30% and which brand? thanks guys

 

[srusinek]

Chances are you're either too rich or the glow plug is fried. I would not run the heli fuel because it's not designed for surface engines. I would get some surface fuel and go from there. Trying to tune with the wrong fuel will get you no where because you'll have to re tune once you get the right fuel.

 

[Phatsavage]

You need a new glow plug there sir

 

[swexelman]

Can someone tell me a few compatible glow plugs for the tm728? My local shops are clueless and all I can find on google is it takes a 1055-6 plug,