Weard stuttering sound

bigboi11 · Mar 4, 2005

I'm trying to figure out if i'm running to lean when after i run for a while it is making a stuttering sound when i slow down or stop. There is still a big cloud of smoke coming out when i punch it down the straight away that makes me think its not lean. The temp is at like 254 and that makes me think that it may be. So needless to say i'm confused.

CorradoPsi · Mar 4, 2005

if it is holding high revs after a high speed run. then it settles down into a nicer idle. that is a sign that your HSN is a bit too lean and your LSN is a bit too rich.

first richen your HSN about a 1/4 turn, then lean your LSN out about 1/8 of a turn to get you back in the ball park.

if your LSN is rich, it will allow fuel to puddle in the crankcase. when you punch it, you will see a large cloud of smoke as the car runs as a result, however as this "puddle reserve" runs low in the crank case, your engine will be leaning out the longer you hold it WOT. go to a BIG open parking lot to finish up your tuning. by the end of the parking lot you want the smoke trail to be just as strong as when it started. if it thins out by the end of the parking lot, you know your HSN is too lean.

Hypedonrc · Mar 4, 2005

How many gallons are thru your mill? What kind of temps does you usually run at?

CorradoPsi · Mar 4, 2005

he's still breaking in, which is why its very important to not run lean.

Hypedonrc · Mar 4, 2005

CorradoPsi said:
if it is holding high revs after a high speed run. then it settles down into a nicer idle. that is a sign that your HSN is a bit too lean and your LSN is a bit too rich.

first richen your HSN about a 1/4 turn, then lean your LSN out about 1/8 of a turn to get you back in the ball park.

if your LSN is rich, it will allow fuel to puddle in the crankcase. when you punch it, you will see a large cloud of smoke as the car runs as a result, however as this "puddle reserve" runs low in the crank case, your engine will be leaning out the longer you hold it WOT. go to a BIG open parking lot to finish up your tuning. by the end of the parking lot you want the smoke trail to be just as strong as when it started. if it thins out by the end of the parking lot, you know your HSN is too lean.

This wasn't there when I hit reply. Where do you see that he is still breaking it in? I didn't see that at all. What has been done on the break in process exactly. 254 is too hot for any part of breaking in if you ask me.

CorradoPsi · Mar 4, 2005

he's in other threads too, rolex and i have been helping get 2 guys tuned on hyper 8ports.

Hypedonrc · Mar 4, 2005

I guess I haven't been keeping up on the tuning problem threads. Just saw this one with no replies, and thought I'd give my 2 cents, but if you already know about it, you might as well help him.

Hypedonrc · Mar 4, 2005

Here is a summery of my break in procedure.

https://www.rcnitrotalk.com/forum/showpost.php?p=275157&postcount=193

bigboi11 · Mar 4, 2005

I think i'm done breaking it in I have been through 11 or 12 tanks

Hypedonrc · Mar 4, 2005

You may also compare you temp gun to others. I've seen them be off no matter if you calibrate them, or not.

Stuttering sound. I don't know? Can't even really speculate without hearing it. The only thing that comes to mind is a leaky exhaust seal, but it would probably be constant. Good luck. Maybe someone else will know. Otherwise let us know if you figure it out.

niggle · Mar 5, 2005

bigboi11 said:
I'm trying to figure out if i'm running to lean when after i run for a while it is making a stuttering sound when i slow down or stop. There is still a big cloud of smoke coming out when i punch it down the straight away that makes me think its not lean. The temp is at like 254 and that makes me think that it may be. So needless to say i'm confused.

Could be an air leak somewhere. When the carb shuts down at idle the engine will try and suck air in from other sources. Seal the carb neck and backplate with RTV sealant (Permatex Ultra-Copper or similar). Check round the front bearing for oil leaks. If oil can leak out of the front bearing then air can leak in...

Also check your glow-plug's heat range. If you have "borrowed" the plug from a smaller engine (.12 - .15) then it may be too warm and causing a misfire. Try a colder plug. A NovaRossi #6 or equivalent would be a good place to start.

mikeburgin · Mar 5, 2005

i agree with corrados version, but there is a chance of an air leak through the rear plate if its a hyper 8 port, they have been known in the past to have a problem with it, like corrado said is more likely tuning to rich down low and to lean up high,
when the tank runs dry what does the engine do, other than stop, does it rev then die at an idle or does it just die. if it revs alot then dies its to rich, and if it just stops its to lean, like corrado said, it should hold a smoke trail at full revs, if it doesn't then it is way to lean up high and is doing damage at revs, the pro guys with sponsored engines will run there engines so the smoke trail dies out at full nana, but these guys dont have to buy a new engine every time they blow it up

Weard stuttering sound

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