Engine Temp??

Hi Everyone - Just completed my 1st bike this past weekend, trying to take all the tips I have harvested from this site, so needless to say the install took about 3x as long following all tips such as silicone on the inside of the engine covers etc. Ok on to my post..

Has anyone used a thermometer of sorts on their engine? I want to know what is going on in my engine before it even gets to grenade or runs under-tuned.

What engine temps are acceptable for these motors after say 15 min of running?

I have a Nitro 2-stroke RC car and tuning that thing is all about engine temp since it is the only constant compared to altitude, air density, air temp etc.. when it is hot outside you richen it up and measure the engine temp using a small RC non-contact infrared thermometer (any RC store or Radio shack sells them). On that motor if it goes over 220 it is hot and will grenade at 270 degrees. I run it around 180 -210 degrees, but this is not a 18000 rpm RC motor. My other two-stroke is a small jet boat with 2x 800cc Rotax 2-strokes in it and I always watch the temp on that. BTW here is the rule of thumb for RC cars if you dont have a temp guage:"For owners that do not have access to a temperature probe, a drop of water on the cooling head (around the glow plug area) should slowly sizzle for approximately 6 to 8 seconds around 200 to 210 degrees. If the water sizzles for only a few seconds, then it is likely that it is over 220 degrees, and needs to cool down"

As many have recommended I started with between a 16:1 - 20:1 gas/oil mixture and idled it for 15min with a fan on it then turn off for 30min (did it 3x) to break in/ temper the chrome cylinder barrel and then one road test. It was running between 170 - 190 degrees just at idle with a fan on it.

I think engine temp is one of the most important gauges of how your engine is performing so I want to benchmark this thing. Any input or ideas on a engine thermometer? Looks like we have a couple options for a tachometer already so I can geek out on that.

Thanks,
Bdubya

bdubya,
Welcome to the forum.
Not many of us check, or for that matter seem too concerned with engine temps. It is essentially run-what-cha-got. It might be interesting however because there is always questions about paint, exhaust gaskets, and such that involves temperature. Maybe someone will take a look at a running engine with infrared some day and determine just what temps we're dealing with. By the way, There are more and more bike owners from Colorado showing up here. We need to think about getting together before the snow starts.
Tom

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I tune my HT to run at around 180C, 175 is about perfect.

This is measured next to the sparkplug at full throttle and load when its around 25C ambient.

I don't know who suggested that break in proceedure, but it's a very bad one.

You need to vary the throttle amount and engine rpm for break in.

When tuned properly, these engines run the same temp as any air cooled two stroke.

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Thanks for the feedback. I see 175C that is 347F Wowsa hot or was that a typo?

The break in recommendation was the tip of the day coming from the site moderator. In turn he got that from off-road.com ATV site who got it from Duncan Racings tech sheet. Maybe some Spooky advice?

Here is my temp using an RC infrared gun after 15min ride at around 70F ambient temp
140 - 160F Exhaust surface temp at exhaust port
180 -210F Base of cylinder head
180F Top of cylinder head next to spark plug

I will post some more observations over time.
Bdubya

I never worry about engine temps. On really hot days just keep the bike moving so there's air blowing through the fins.

Also... I was heavily into nitro R/C car racing... NovaRossi actually recomends 260 degrees as a running temp for their engines! (this doesn't apply to bike engines tho...)

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I checked mine with my infa-red gun today.. for the most part everything is about 200* F.. it's about 185* on the head, and 160* at the intake base... but everything else is right at 195-200*.. the muffler registered 110*

I measured my engine & exhaust with an infrared thermometer some time ago and as I recall, the engine was less than 200 deg F. The exhaust pipe between the engine and muffler ran about 125 deg F, but the muffler exceeded the 400 deg F limit of my thermometer (I assumed at the time that it was because the catalytic converter was burning off unburned fuel).

I don't know if you folks are aware of it, but the emissivity changes according to the surface being read. A chrome surface (for instance) emits less inferred than a flat black surface. That's why a wood burning stove is usually flat black, and a pizza oven has a stainless steel door. Hence a chrome exhaust pipe will usually read lower with an inferred thermometer. A painted surface will probably read more accurately than a shiny surface.

Yuk,
RC car engine break in which is bad advice for an rc engine (idling an engine for break in is stupid) is similarly silly for a larger 2 stroke engine.

Please freshen up on the theory of an RC ABC/ABN engine. the piston is ringless and compresison is obtained by a tapered cylinder that provides compression/pinch. The engine must be heated up sufficiently under load or you will wear away the pinch and decrease engine longevity. Idling an ABC/ABN engine actuallly is the worst thing you can do to an RC engine. Its a proven fact that ABN/ABC engines last longer when they are run at 1/2 to full throttle continuously. I've got 30+ years in RC hobby and can attest to this fact.