HT bicycle engine Ideal running engine temperature?

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Technocyclist

Technocyclist

Motorized Bicycle Senior Technologist
Jul 7, 2008
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Ok... my aluminum head gasket melted into the cylinder... the engine still starts, runs for a few minutes and just dies... upon inspection, it was discovered about this issue... so did my engine run too hot? too lean? what should be the ideal running temperature of an HT engine? and what are the ways to know this temperature without using a thermometer? like a drop of water should not boil on the head, or if it does how long before it fully evaporates?

any comments are highly appreciated... Thanks...
 
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stv1jzgte

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Feb 11, 2009
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Re: HT Ideal running engine temperature?

Yes water will boil in the motor but ive never checked the opperating temp. At a guess between 100-150 degreese c possibly more!
The only way i could think you would melt a gasket is if you had the wrong heat range plug.
Im pretty brutal to my bike and it gets hot here, never had that happen.

Got a pic??
 
Pablo

Pablo

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Re: HT Ideal running engine temperature?

Anyone have an infrared gun?

Or heat melt crayons?

But if your HG melted, you are running to hot. My guess is that you are running too lean on your air fuel mix.
 
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Gareth

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Re: HT Ideal running engine temperature?

If your cylinder and head surfaces are not flat you run the risk of blowing a head gasket. Once the head seal is lost oxygen will enter creating a leaner condition causing that section of gasket to melt. Eventually the leak will become so great that compression is lost sufficiently to the point that the engine will no longer run, if seizure does not occur first.

This can be aggravated by the natural tendency of 2 strokes to lean out upon long wide open runs, and the natural tendency to run a little engine wide open.
 
Norman

Norman

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Jan 16, 2008
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Re: HT Ideal running engine temperature?

I've done some reading with infrared heat gun these may not be the best reading but here is what I've seen.
at idle speed they run about 200 to 250 f.
The limit should be 450f this is just a good guess as I've read that an air cooled vw engine this is the higher limit for them. I've seen higher temps on my racing kart up to 500f(read off the cylinder temp probe under the spark plug) which is not supposed to be good for them and the 450f is what I've read is supposed to be the higher limit. I didn't know I'd reached that temp until back in the pits when I read the history off the tack/head temp gauge.
Under riding conditions they run around 350f best guess as it to hard to shoot it with the temp gun. I'll ride it stop, then shoot it right by the spark plug base. This gun has a laser pointer that shows where you are pointed when reading. It's probably not real accurate.
I installed the head temp and rpm gauge on the bike it had so much RF from the ignition the gauge didn't work properly. Plus I didn't try to correct it a quick try it would not read right and I didn't want to change all the set points in the gauge from the kart.
I was lazy.
 
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professor

professor

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Re: HT Ideal running engine temperature?

If you do use an infra red reader, the part you shoot needs to be flat black or the results will be off some.
 
Technocyclist

Technocyclist

Motorized Bicycle Senior Technologist
Jul 7, 2008
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Melted Aluminum Head Gasket into barrel... my head hurts... :(

stv1jzgte said:
Got a pic??
Click to expand...
Here's some pics. Did'nt had the time to dismantle and take pics till now...

As you can see the inner edges of the Aluminum gasket melted, which scratched the sidewalls of the barrel, and made some small holes on the piston head... :(

I think using a head gasket sealer is better than this Aluminum gasket...
 

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S

stv1jzgte

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Feb 11, 2009
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Re: HT Ideal running engine temperature?

Techno i think thats happened because the gasket can sometimes protrude into the cylinder and is exposed to combustion temps. Either shoddy manufacturing or from being squished alot if its old.
 
Venice Motor Bikes

Venice Motor Bikes

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Mar 20, 2008
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Re: HT Ideal running engine temperature?

Yeah... Just install a new gasket & recheck your mixture! Make sure the plug tip looks like a nice light brown color! ( & use the right # plug!) ;)
 
bairdco

bairdco

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Aug 18, 2009
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Re: HT Ideal running engine temperature?

i'd check the surfaces of the head and the jug, make sure they're flat. if not, tape a piece of 400 grit wet or dry sandpaper to a glass table and wet sand them, in a circular motion till they're flat and mate up perfectly.

this is assuming the jug is save-able. if it's scratched and gouge, time to recycle it.

from the "burn pattern" on the head and jug, it looks like one or the other was warped, and the hot gasses escaping melted it.
 
thatsdax

thatsdax

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Re: HT Ideal running engine temperature?

Hi.. Ideal Running Temp measured at cylinder head is 375-385 degrees F. 410F is too high and will burn the motor up. Exhaust temp 1175 to 1185 is ideal. Measure 3.5 inches from Ring of exhaust port. Measure Exhaust Temp first, follow up by Cylinder head measurement. These are optimum parameters taken from Rotax 2 stroke motors using synthetic 2 stroke oil. Since our 2 stroke Bicycle Assist motors have such low compression, my Guess is that they run with less heat than the ideals I have posted. Enjoy the ride...
 
Goat Herder

Goat Herder

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Apr 28, 2008
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Re: Melted Aluminum Head Gasket into barrel...

Technocyclist said:
Here's some pics. Did'nt had the time to dismantle and take pics till now...

As you can see the inner edges of the Aluminum gasket melted, which scratched the sidewalls of the barrel, and made some small holes on the piston head... :(

I think using a head gasket sealer is better than this Aluminum gasket...
Click to expand...
Excess RTV squishing into the cylinder walls will turn into hard scratchy carbon. Suspect that's what I see here?
 
A

aliston

New Member
Jun 24, 2009
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Re: HT Ideal running engine temperature?

It seems to me that my head gasket is leaking. Is there are certain torque the nuts should be tightened to?
 
F

Fabian

Member
Sep 9, 2009
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Re: HT Ideal running engine temperature?

Been there, done that, although not quite as far as a melted head gasket.

Next time, swap out the original main jet and run a genuine Dellorto No 84 main jet.

You'll never see a melted head gasket ever again.

Fabian
 
James912

James912

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Apr 12, 2011
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Re: HT Ideal running engine temperature?

My engine seems to run rather hot. Everything is stock. Except the 44 tooth sprocket. moved the c-clip 1 notch down from the middle stock position and its still seems to overheat after running at idle for 15 minutes. The head gasket looks fine to me beside it has gas on it. I cleaned the top of the piston, and the walls to make sure theres no debris creating extra friction. I'm going to tighten the head bolts again and see if that doesn't make the engine run a bit cooler. If not, then I'll check the plug and if it still looks lean, ill move the c-clip to the very bottom notch and hope that makes it run at the right temperature.
 
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rohmell

rohmell

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Jun 2, 2010
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Re: HT Ideal running engine temperature?

James912 said:
still seems to overheat after running at idle for 15 minutes.
Click to expand...
Idling this type of engine for long periods is not recommended, since it has no fan blowing air over the cylinder and head like a lawnmower or weedwacker engine has.

It is designed to be cooled from the airflow breeze past it while riding it.
 
James912

James912

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Re: HT Ideal running engine temperature?

I fixed my bike. The reason it would stop working after 15 minutes is the gas cap does not have a top vent, there are only air holes on the bottom of it, below the rubber seal. I drilled a hole in the top and she keeps running. Just get a waterbottle cap and hot glue it over the hole and drill a hole in the side of that if u want to ride in the rain.
 
Goat Herder

Goat Herder

Gutter Rider
Apr 28, 2008
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Re: HT Ideal running engine temperature?

Technically all you need in the gas cap hole wise is roughly about the same size as the carb jet. Then you matched the flow. Air will go through the gas cap, gas will go through the jet.
 
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