What am I missing.

[lykan]

Ok here we go.

Rebuilt a mach .15 new piston sleeve. Tuned it in, got it running OK. just as I hit the power band, it over heats tuning wise. It dies, and wont start till it's nice and cool

So I take it home, over look the thing, and notice slop in the carb. So I have a down .18 XCTM waiing on a spur gear.

I take the carb off, and throw it on the mach .15


I got it to idle, and have ok take off, but still abit on the rich side. It's blubbering a bit, but looks like it is close to a decent tune., It will idle.

I turn in the HSV bit by bit, gaining power each time. (it still idles well) Then all of the sudden it dies and I notice I slowly turned the HSV all the way closed. I'm like WTF? how did it kep running ?


So now I have the screws set where I started. It starts right up, idles well, and moves ok. By all indicatins it needs to be leaned a bit. It's pouring smoke and blubbering. I turn the LSV in about a 1/16th same result. So I take the HSV in 1/4. It runs a bit better, but then dies. It's hot. Hot enough to boil fuel in the carb. Grrr

When I do get it running OK, and to where it seems tuned fine, it overheats. I just don't understand it a bit.

It seems this engine no matter what carb just wants to heat up. Even when all indications, and the wet fuel soaked ground is underneath the pipe. It still heats up. I' at a loss. Its either so blubbbery it has no power, or it has little power but heats up quickly. Quickly as in two laps around a small yard blubbering all the way.

Any ideas?
Mach .15
hot to medium plugs.
check for leaks all siliconed up.
Os 10e carb
XTM .18 carb
trininty 20% monster HP
motor saver air filter nice and clean.
18 tooth clutch bell


**edit this is in a maxx*

 

[militarymaxx]

I had problems similiar to yours where no matter how rich I set it for, it still ran hot. I too had lots of smoke, raw fuel running out of the exhaust. What I found was an air leak around the carb and around the banjo fitting. Even though I had the LSN/HSN set for rich conditions, the air leak was enough to lean it out to the point of overheating.

 

[lykan]

WTH is a banjo fitting lol.

 

[militarymaxx]

It's the little brass fitting that your fuel line connects to. If you ever take it off and look at it, it resembles a banjo. If you over
tighten that fitting, you can easily crush the two aluminum washers and an air leak will develop. Make it snug only.

 

[lykan]

You kow that might be my issue. I'm so frusterated now I can't touch the maxx tho fraid I'll hurt it. The guy at the LHS, diffferent one than the one that sucks. Says it is lacking on compression.

It still has a little pinch to me. Could that be the problem in its entirety? I just put a new piston and sleeve, I have yet to run it hard or put more tahn a quart through it.

 

[Domination]

loss of compression wont make yur temps sky rocket. But i think you may have a air leak check your bango fitting like stated above and even replace just incase seal your carb and backplate and see how tha does and also snug up your head nice and tight

 

[militarymaxx]

Ahhh, Domination made a great observation. The backplate often goes un-noticed and can be a huge source of leaks. Another source of air is you front bearing. I had an engine that ran great until it warmed up and it sucked air from the front bearing. I knew something was up when after a run I would have a puddle of fuel around my flywheel. That front bearing should be very well seated. So well seated that many folks have to bake the block in the oven to get it loose.

 

[lykan]

You know I think its possible my front bearing is leaking. I took it out again. I get it tuned where I think I can run off. Then it just slowly hesitates, then bogs down and dies.

The only way to gt it started again is to hold the throttle wide open. It will go high rpm, then cutout and die. Over and over. I think until it cools down just enough to make a lap around the yard, then make my go chase it lol.

**
Just got back from putting th old carb back on (ran a bit better)

Ok maybe this will help. After I have it warmed up. I have to old it full throttle to start it. When I do, sometimes it does it's signature

rev high, bog, rev high,bog, die at high rev.

trinity 20% nitor 12% oil is that ok to run in this engine?

 

[SkyMaxx]

The back plate issue was already mentioned, but the thing that might be overlooked here was the fact that the engine seemed to run better when you put the old carb back on. I wouldn't be surprised if the .18 carb was off by a hair on the fit. If that thing wasn't snug and sealed, it would account for what you described.

 

[lykan]

Well, I just swapped plugs. It was a longer plug so I put two washers in. It seemed to run really well. Until of course it died because it was out of fuel, hotter than hell too. (friggen murphy)

tomorrow I try with the plug I swapped in, if it is actually really a hair better. Then I go to the good LHS and get a new plug (what i wanted to do in the first place)

BTW thanks for all the help. Also another Q how much of an effect does the low speed needle have on heat if you spend no time idling. It seems it wouldnt have too much an efect.

--Mason

 

[SkyMaxx]

Very little effect, but the LSN is not just for idling. It handles the lower rpms...kind of like low gear. So if you run around at low throttle settings it can impact how the engine runs.

 

[lykan]

I think this started out with some slop in a carb, and this is why it ended up this way so fast. Not positive on the cause of the failure tho.

Note the piston chunk missing, the wrist pin gone and the scores in cylinder and piston.

 

[Domination]

looks as if the little clip for the pin on the con rod fell out