Redline and overheating (CG/CD/HT engine)

ImpulseRocket89

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I am feeling much better about my temps. I've barely hit 300's...
That's not a bad thing at all. When I say I try not to exceed 400 that is my stopping point where I will either ease off or shut down. Thankfully my Phantom has been doing ok so far just cruising along. I have come close pulling a long hill on a hot day though but I also have my fueling intentionally on the rich side to help combat the heat.

As far as tachometers go you would be using an inductance style of tach where a wire is wrapped around the spark plug lead and the unit itself is usually battery operated. They use common button style batteries in most instances.

I am currently using this unit for tach and temp https://www.amazon.com/Runleader-Te...ps,119&sr=8-22-spons&smid=A3H26M0OO8MHA9&th=1

It's worked well for me so far but some people have complained about some quality/reliability issues. The thermocouple for the head temp is designed to go under the spark plug but that proved a bit tricky with the way the phantom is designed so I have been running it under one of the head nuts with a fender washer to hold it down better. It's going to read a bit cooler there but it still functions well enough to give me an idea of how hot the motor is running. My infared thermometer shows about a 10-15 degree difference between the two locations so I adjust accordingly (390 is actually 400ish).
 

noah9988

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The phantom comes with an almost 2mm squish gap, right? I wonder if they did that on purpose to keep the heat down?
 

ImpulseRocket89

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The phantom comes with an almost 2mm squish gap, right? I wonder if they did that on purpose to keep the heat down?
Mine was 1.77mm. Possibly. Or for a few other reasons. I removed 1 base gasket and the Meteor piston is .14mm taller in crown height than the stock one so my squish gap is just a hair under 1mm with the head torqued down. LA Hover is running no base gaskets with an aftermarket MS460 piston. Plenty of others out there with way tighter than stock squish gaps. None of us are having an issue.
 

noah9988

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Also, either I have been extremely lucky, or people underestimate how tough these engines are. All the failures I have had with my engine was the result of me being stupid and ruining the cylinder and piston (scoring). I have a stock bottom end and it has seen some abuse. I believe I have 17-18 hours on it, and they have all been hard hours. A lot of wide open at 8000 rpm, and recently 9000. I don't recommend doing that of course, and I'm sure it has accelerated the wear on all the components. I'm not afraid to push it though, seeing how it's held up.
 

noah9988

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Mine was 1.77mm. Possibly. Or for a few other reasons. I removed 1 base gasket and the Meteor piston is .14mm taller in crown height than the stock one so my squish gap is just a hair under 1mm with the head torqued down. LA Hover is running no base gaskets with an aftermarket MS460 piston. Plenty of others out there with way tighter than stock squish gaps. None of us are having an issue.
But a larger squish should lower temps, right? That's why I was wondering if they're large from the factory to keep them running cooler.
 

ImpulseRocket89

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But a larger squish should lower temps, right? That's why I was wondering if they're large from the factory to keep them running cooler.
As I stated in my first reply it's not always so straight forward. A squish band with a tighter squish gap causes dynamic shifts in how the flame front and intake charge behave that alter the temperature of different parts of an engine. The tighter squish band can lead to higher compression that can increase head tempuratures but will also reduce piston temperatures. It has to do with the intake charge that gets trapped between the squish band of the head and the piston and how it behaves. The short version is that the intake charge trapped in the larger squish gap has less energy in it and causes it to be cooler than the charge that ends up in the combustion chamber and this in turn causes a temperature differential in the two regions. That causes the flame front to spread more slowly and creates a slower burn that transfers more heat to the piston and thus reduces efficiency.

Plus if I have to choose where I want more heat to go I will choose a higher head temp over a higher piston temp since the head is designed to shed heat and is exposed to the air that cools it directly. Pistons only shed heat by evaporative cooling from the fuel and by passing the heat through the rings which are the only thing in actual contact with the cylinder. Neither of which cool as efficiently since the cooling effect is small and brief in comparison.
 

Kehkou

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It has to do with the intake charge that gets trapped between the squish band of the head and the piston and how it behaves. The short version is that the intake charge trapped in the larger squish gap has less energy in it and causes it to be cooler than the charge that ends up in the combustion chamber and this in turn causes a temperature differential in the two regions. That causes the flame front to spread more slowly and creates a slower burn that transfers more heat to the piston and thus reduces efficiency
This effect is greatly enhanced by the alcohol content of the fuel, but said additive also does...bad things.
Ears and feel can deceive you; a tachometer and temp gauge will let you know exactly what your engine is doing.
Yes, but it is even better to correlate all three. Like I said, depending on how much four-stroke there is, which the tach cannot detect but can be very easily heard or felt, I can let off a mm or so, suppress the four-stroking, and get more, smooth, acceleration, as verified by all three (feel the G, hear the engine pitch climb and smooth out, and see the tach speed increase).
Any recommended tach?
I use this one; It's the same brand and style as the one Sidewinder Jerry recommended but comes with a temp sensor and handlebar bracket.
Runleader Digital Tach Hour Meter with Mounting Bracket, Engine Temperature Gauge,
How does one attach to one of these engines?
Not sure what you mean exactly. Physically, you screw in the bracket and zip-tie the resulting assembly to the bars. Electrically, the RPM sensor is a wire that you wrap around the spark wire about 6 1/2 rotations for a stock CDI, and the head temp sensor is a ring that fits on the spark plug.
 

Sidewinder Jerry

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This effect is greatly enhanced by the alcohol content of the fuel, but said additive also does...bad things.

Yes, but it is even better to correlate all three. Like I said, depending on how much four-stroke there is, which the tach cannot detect but can be very easily heard or felt, I can let off a mm or so, suppress the four-stroking, and get more, smooth, acceleration, as verified by all three (feel the G, hear the engine pitch climb and smooth out, and see the tach speed increase).

I use this one; It's the same brand and style as the one Sidewinder Jerry recommended but comes with a temp sensor and handlebar bracket.
Runleader Digital Tach Hour Meter with Mounting Bracket, Engine Temperature Gauge,

Not sure what you mean exactly. Physically, you screw in the bracket and zip-tie the resulting assembly to the bars. Electrically, the RPM sensor is a wire that you wrap around the spark wire about 6 1/2 rotations for a stock CDI, and the head temp sensor is a ring that fits on the spark plug.
Wouldn't the rpm drop on the tach while it was 4 stroking?????
 

Kehkou

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Wouldn't the rpm drop on the tach while it was 4 stroking?????
No, the tach picks up the electricity in the spark plug wire. The spark plug is still firing, it just doesn't go boom.
Theoretically, four-stroking can slow the engine down if it is severe enough or slow the rate of acceleration at best. In practice, your gonna know about it before the tach reports a nominal drop in RPM. Yes, the plug is still firing, but the drop in power could manifest as slower RPM (again, theoretically).
 
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