As of right now I lack one of those digital heat meters, but I plan on picking one up soon.

So far I've been getting various opinions as to how to "measure" heat with using a drop of saliva on the cooling head and if the saliva sizzles off, its too hot. This evening, I was running my buggy with some friends in an empty parking lot and did the "saliva test" and the spit sizzled off the cooling head, is it too hot? or is this an inaccurate way to measure heat?

The person who tuned my engine used the digital temp meter and it measured at 190 degrees after several short sprints and said it was perfect. Yet even at 190 degrees the saliva still sizzles.

Also how do you know if your engine over heats? what are some of the symtoms? any long term effects?

MOST people keep there engines between 200 and 250 dergees (F) i run mine around 240... you dont seem to get the most out of your engine untill it gets up to at least 210 degrees from what i have experianced. a temp gun is one of the best things that you can get... buy one! if you run your engine too hot the engine will die prematurly.

when it melts, its too hot. u need to richen it up.

id say that high 200's is about the limit id like to run. if its really hot, a brush into the 300's isnt going to be catastrophic. but tuning for mid 200's a good pt to shoot for (as long as there is a trail of white smoke and clean running).

ive seen 350 a couple times. i shut it down and let it cool and then ran it some more after tuning it again. no problems.

Yea, there is definitely a trail of white smoke. Does that mean it is running smoothly? if there is no smoke that means its too lean right?

How does it SOUND? Tuning by temps are wrong to start with. It should run with a clean crisp 2-stroke cycle. Richen it until it 4-strokes down the straight and then lean it until it runs clean.... that's where you have the most power. Try different plugs. Run as hot plug as you can get away with without breaking them.

How hot is too hot? Seems there is no definition, or it varies from engine to engine.

I tend to rely on how my engine sound at its top and low end for tuning. Engine temperature is just one of the few things to manage the tuning. I had experienced wrong reading by a meter with dusty window that it gave a relative low reading. So, did you check the meter window before using it? If water sizzles off as soon as dropped on the heat sink, then your engine is probably at a relative high temperature but not necessary to be called over heat. Richen your engine in such a case should cause no harm.

The scence of trail of smoke depends rather on kind of fuel you use. Odonnell does smoky but Mega does less. I would rather to see if any fuel spitting at the exhaust during stand tuning.

When your engine comes to the border line, it should sound like sucking all fuel without leaving a drop. Richen your engine at this point should play safe. Once it goes beyond the border line, it should start sounding like dried throat. You have to let it cool down before doing any. The cause of over lean is premature damage.

Strange thing about my engine is when full throttle is applied, it sounds like the rpm is maxed for a few seconds, then all of a sudden its like turbo kicked in and the car REALLY flies.

I'm not all that experienced to be tuning by sound, what should my car sound like? Right now its pretty constant, no stutters or abnormal lopeing.

However, when the car is about to run out of fuel, the rpm picks up and the car moves

Sounds to me like perhaps it is your clutch slipping if the engine is screaming AND THEN the car takes off. Its hard to type out the proper sound but it should be a very high pitched and even sound. If the sound is irregular and your engine ahs a tendancy to suddenly die, your too lean. If it sounds "blubbery" then it is liekly too rich. Tune it so that you can drive a certain straightaway the fastest, then back the high speed needle of about 1/8th a turn. That should be about right.

I get really worried if i am over 270 degrees.

Top end the engine sounds very constant, last night was pretty much full throttle night.

Is it bad to go full throttle for a prolong period of time? Only time my engine died last night was when the glow plug loosened up from vibration because I didn't fully tighten it

Depends on the engine characteristic or you have the bottom end a bit richened so that your engine take sometime to clear for blasting at the top end. My previous MAX M8 behaved like this that it started grunting at at second or 2.

Differnt engine sound different. An ultimately tuned Sirio screams on top end at a very high pitch, OS sounds soft, RB roaring deeper and stronger than Novarossi. I use to keep my engine sound like draining tap water into bath tub.

What you are hearing is probably the sound it makes when it 'comes on the pipe', meaning you are reaching the optimum resonance in the tuned pipe. (This is of course if everyting is normal adn it runs good overall).
It's an awesome sound. You are going WOT down the straight (already going fast) and it suddenly kicks in to a higher gear and takes off.
If that's the case THAT'S WHAT YOU WANT TO HEAR!

If you tend to running at top end most of the time, it is better to richen the HSN for playing safe and without worry. It is to keep your engine cooled and lubricated enough at the high speed zone.

...and try not to have your engine running out of fuel, because engine is leaned out at this moment that is why the rpm picks up.

LHS recommended I move to 25% or 30% fuel. They said if I went to higher nitro mix I can run richer at cooler temps and keep the power; is this true?

Right now I am using O Donnell 20%.

Last night when I saw my spit sizzle off the heat sink I got scared. So I turned it down 1/8 turn, I'll find some time today and run it again.

Also LHS told me if my engine reaches 240 degrees just momentarily my motor will never be the same again; any truth to this?

Just make sure it runs on the rich end of the spectrum while still running with a crisp 2-stroke sound and you will have no problems going WOT all day long.

Engine has its safe optimal performance as well as fuel. Leaning out an engine with fuel of 20% nitro is able to push it to some power level of taking 25% nitro but that is not in its safe way and why it is better to go for higher nitro content fuel if you want the power.

Back to the question, how hot is hot? I haven't seen any engine specification telling what the maximum temperature should be, or any temperature range specification. On road people may race with their engine even up to 320F. So it is common practice among many of us to keep the engine temperature between 200F to 220F depends on the environment factors.

Because of the craftmanship, some engines may sustain less temperature tolerance. If you just run at 240F for a moment but not from time to time, you don't need to worry.

Sman you seem to know what your talking about. whats your experience with tuning the third needle? i would like to know how to do this thanx.

Hahahaha, I like to know that too.
I hate 3 needle carbs.


edit:
This is what I THINK I know.

The LSN and MSN should be adjusted together since they directly affect eachother.
If you look down the throat of the carb you will clearly see what's happening. The LSN goes inside the jet (MSN). When you lean the MSN then LSN will become leaner just because it sticks further inside the MSN. To keep the LSN at the same setting as before you need to richen the LSN the same amount (in distance, not turns since the thread could be diffeent)

The same applies the other way. If you want to richen the MSN you need to lean the LSN the same amount to keep the LSN constant.

Hope it helps.

Never visit your LHS again.

Thanx man that helps ill toy around with it a bit but man those three needle carbs do suck i just hate not being able to figure out things happy racing