Inferno MP 7.5 sports problems!!!

[tayler]

Inferno MP 7.5 sports rtr problems!!!

Hello everybody , I have the mp 7.5 sports rtr and I have had a lot of problems tuning it.First of all I broke the conrod –piston after only 15 tanks of fuel.(The first 8-9 tanks were for break-in).I used Meccafuel 10% nitro and MacCoy MC-55 glow plug.The needle settings during break-in were 3-3,5 turns from close position for the high (H) needle and 4,5 for the middle (M) .After each tank of fuel during break in I was leaning it out 1/8 of a turn and till the day it broke down I was running the high at 2,5 turns and middle at 4,5 at my first half tank of fuel.The low needle (L) was as it came from the factory!I don`t know what went wrong and I can say that I haven`t run it very hard or push it to it`s limits!!Anyway I have already order the new set cylinder-piston and conrod but I would be greatful if anybody with the same buggy/engine could inform about the carb settings (high low and middle needle) during break in period , for normal run and factory settings as the only thing that manual mentions is about the high needle for normal run should be 2 or 2,5 turns , so I can double check them when the time comes because I want to believe that the engine failure was because of wrong carb settings.Any other advice/tip will be appreciated!!Thanks!

 

[RatzoRC]

The mid setting should not be touched! It states that in the directions.
Did you run the engine without the airfilter? If yes, dirt might have entered the engine.
If you had the filter on, did, did you oil the filter?
A temp gun is a handy tool to have when breaking in an engine.
A good temp for break in on a .21 size block is around 190-200 degrees.
Optimum running temp is about 225.

 

[robriguez]

I'm not sure where you guys are getting your info but as far as I know the 7.5 SPORTS come witht he GX-21 engine. ( I own one ) The stock carb does not have an MSN at all. There are only 2 needles. The large copper looking one at the bottom of the carb (LSN) and the smaller one in the tube (HSN). If I keep the LSN flush with the body of the carb and the HSN at 2.25 turns out I can run all day at 250 degrees. I have a little over 2 galons run through mine with no problems. I did have to replace the Orings in the HSN housing because dirt got in there but other than that its run fine for me.

What you have listed as the LSN is nothing more than a screw that holds the arm on the carb valve. I've taken mine apart to clean it a few times already.

 

[tayler]

I'm not sure where you guys are getting your info but as far as I know the 7.5 SPORTS come witht he GX-21 engine. ( I own one ) The stock carb does not have an MSN at all. There are only 2 needles. The large copper looking one at the bottom of the carb (LSN) and the smaller one in the tube (HSN). If I keep the LSN flush with the body of the carb and the HSN at 2.25 turns out I can run all day at 250 degrees. I have a little over 2 galons run through mine with no problems. I did have to replace the Orings in the HSN housing because dirt got in there but other than that its run fine for me.

What you have listed as the LSN is nothing more than a screw that holds the arm on the carb valve. I've taken mine apart to clean it a few times already.

How many tanks did you run during break in and with what needle adjustments??I don`t know what to say but when the conrod broke the HSN was at 2.5 turns out and the LSN at 4.5 and 1/8 from fully close!I was in the middle of my first tank for the day, i don`t really remember the engine temperature but i remember that i put a drope of water in the top of the cylinder head and it dissapeared in about 2 sec.That shows that it was overheating but why???Could you check how many turns from fully closed your LSN is so i can tune it??Any other advice will be very helpful now that i will have to break it in again!!Thanks!!

 

[robriguez]

I broke it in at 3.5 turns out on the HSN and 1/4 turn out from flush on the LSN. I let it idle for a full tank. Second tank I leaned HSN a tiny bit and would run it in figure 8 pattern for 1-2 min at 1/4-1/2 throttle then shut her down let it cool. I did this through the 3rd tank. By the time i was on my fourth I was leaning both needles and never more than 2 seconds of WOT with a full 2 min of idle/ 1/4 throttle cool down in between. Did this for another tank then started tuning for performance. The best I could get mine was just a ahair under 2.5 out on HSN and 1/4 turn IN from flush on LSN but my temps were floating around 280-290

 

[dgrobe2112]

I'm not sure where you guys are getting your info but as far as I know the 7.5 SPORTS come witht he GX-21 engine. ( I own one ) The stock carb does not have an MSN at all. There are only 2 needles. The large copper looking one at the bottom of the carb (LSN) and the smaller one in the tube (HSN). If I keep the LSN flush with the body of the carb and the HSN at 2.25 turns out I can run all day at 250 degrees. I have a little over 2 galons run through mine with no problems. I did have to replace the Orings in the HSN housing because dirt got in there but other than that its run fine for me.

What you have listed as the LSN is nothing more than a screw that holds the arm on the carb valve. I've taken mine apart to clean it a few times already.

Rob, a screw to hold on the arm?? if it is a flat head screw.. and can turn in and out.. then that is not a screw to hold the arm on the carb valve.. i will have to check tomorrow at the hobby shop.. but if in fact.. this is a 3 needle carb.. do not mess with the MID needle.. and if factory setting on the HSN was 3 1/2 turns out.. after break in.. you should be at around 3 turns out.. .. or more.. also.. breakin is the hardest time on the motor.. have to be careful. Also.. 10% nitro.. wow.. thats low.. i think they are designed for 25% if I'm not mistaken..

 

[robriguez]

I'm going to use newb speak here for a min as I am not exactly sure of the terminology:

The slidey thingy in the carb (throttle?) has a large protrusion at the very end (arm?) that is attached to the movy thingy (throttle linkage?).

That arm is attached to the Throttle by means of a screw with no o-ring. Once you remove the boot you can see that it is only used to attach the arm to the throttle. It did not seem to be a needle adjustment screw. While I could be wrong i dont beleive I am.

BTW it is the GX-21 engine I am speaking of. As far as I know it is the stock engine that comes with the 7.5 Sports RTR.

 

[dgrobe2112]

Rob, you are correct.. here is a pic of the motor i think.. from that side.. http://www.kyosho.com/cars/kyod01a.jpg

now.. then.. in the picture above.. he has a mid range.. and i think its been mentioned.. that is the low end needle.. not the mid range..