Heat Issues

[Prasinos]

I don't hear much about this being an issue for people, but my engine seems to have far more power when it is cool compared to when it has warmed up.

Especially after making a hard top speed run or going up a long hill I notice that my engine has very little torque, I'd say almost half. If I coast down a long hill with the bike out of gear, my power returns once I open it up again.

I would think that the problem is that the engine gets too hot so the air inside expands and makes the engine run rich. However, going to a smaller jet lowers my performance all around.

So I may decide to build some sort of cowling to get more air past the engine but what are some other ways to keep my engine running cooler?

 

[Bikeguy Joe]

Running richer will help to run cooler.
What gas to oil mix are you using?
You should be able to run your engine pretty hard without a power loss.

 

[Prasinos]

around 30:1 using amsoil interceptor. Running richer will help to run cooler but if it runs cooler it doesn't get rid of heat as efficiently, right? I would think that if your engine is made to run hotter (leaner) then it will cool faster.

When it has the bigger jet in it the power loss is more noticeable. With the smaller jet there is less power loss when it is running hot but there is also less power all around.

 

[Prasinos]

Btw would water injection into the carb help with cooling?

 

[Venice Motor Bikes]

I think Joe is on the right track... Try going a little heavier on the oil mix & see if that helps.

 

[diceman2004]

Prasinos , that theory may hold true for making ice cubes out of hot water , but if you wanna melt your motor by all means , the hotter the better .

Its always better to run too rich ( cooler ) than too lean ( hot ) , You want your motor to stay as cool as possible , and the cooler your motor is the higher your compression will be . If the air going into your motor gets expanded by the motor heat , then you get less expansion in the chamber after detonation also , resulting in less power

on my motorcycle , as opposed to hot humid days , on cold crisp days my bike feels like it has 10 extra hp , because the air going into the motor is cold

go with Joe and Venice on this one

 

[Prasinos]

I realize that it is better to run to rich rather than too lean, but if I am having a problem with over heating running leaner would allow the engine to put off more heat energy and would make the equilibrium temperature more constant.

First of all its not like i plan on burning hole in my piston, I check my spark plug often and even with the leaner jet it is still brown.

Second, the main issue is that my engine goes through a broad range of temperatures. The problem arises when the engine gets hot and starts running too rich, once it gets to this point it cant produce enough power to get a sufficient amount of air past the engine, so it just keeps heating up.

The bigger jet puts out more power when the engine is heating up, but once it is at temperature the power is less than the leaner jet running at temperature.

you cant deny there are diminishing returns with this, otherwise. If you want your motor to stay as cool as possible why would you ever go leaner?

let me know if anyone has any info on the water injection, also, I know increasing compression increases heat, but would removing my head gasket help with power anyway?

 

[Venice Motor Bikes]

Running the engine lean will cause the engine to run hotter!! Thats just the way it works..

 

[Prasinos]

i never denied this fact venice boy i was just saying that running the engine lean also makes it run most efficiently at a higher temperature.

 

[Venice Motor Bikes]

Just try adding more oil to the gas & tell us if that solves the problem... OK?
It's a real easy thing to try first.

 

[Prasinos]

Normally when we say lean and rich we are talking about the fuel to air mixture.

It seems that your talking about oil to gas, in which case i used to run 20:1 and since then i ran 25:1, at this point im running 30:1 in an attempt to keep the carbon deposits off of my engine. Like I said earlier I haven't noticed much of a performance change until i move past 40:1.

I think the biggest issue is that im a 220 lb guy using a 36 tooth sprocket.

I'm definitely a tinkerer boys and believe me i have tried everything, spark plugs, jet sizes from #72 to #53, oil mix ratios from 40:1 to 16:1, different oils, different additives, 3 different carburetors and 2 different engines. This has always been an issue in weather above 50 degrees.

The problem was minimized the most when I had put a Tomos head on my 50cc engine, the cooling fins went out 4 inches on each side for some serious surface area.

Anyways i now have a 67cc engine with a NGK B6HS plug, performance wire, sbp expansion chamber, 36 tooth rear sprocket, and a dellorto 12mm carb.

So im looking for new ideas boys, Ive been on these forums for a while and i understand you have to do this default questioning first but Ive tried all the obvious solutions.

Are there any unique solutions that people have heard of, Ive heard water injected into the intake can cool the cylinder...

 

[Outrunner]

around 30:1 using amsoil interceptor. Running richer will help to run cooler but if it runs cooler it doesn't get rid of heat as efficiently, right? I would think that if your engine is made to run hotter (leaner) then it will cool faster.

When it has the bigger jet in it the power loss is more noticeable. With the smaller jet there is less power loss when it is running hot but there is also less power all around.

Definitely, running leaner will always make an engine run hotter for sure.
I suggest mixing your Amsoil to 50:1 and not worry about lubrication. It
sounds like you may be sucking some air through your manifold somewhere between the carb and cylinder. That will cause a lean and hot burn in the combustion chamber too. Check for air leaks at the gasket junction of the manifold. In fact, I'd take it off and flat file the flange to make sure it isn't warped. You might also have a retarded ignition timing issue also, but I doubt
that. Does this happen after a WOT event or mid throttle, or after 4-5 minutes
of normal driving? Where are your needle clips set at?

 

[FlyJSH]

Water injection is used to prevent detonation.

Water injection (engines) - Wikipedia, the free encyclopedia
http://www.enginehistory.org/Convention/2005/Presentations/LawPete/ADI.pdf
Water Injection - A technical description

Unless you are turbo charging your MB, using 60 octane gas, or running way too lean, water injection is not the answer.

In piston engine airplanes, mixture is used to control cylinder head temps at high power settings. Going from 14:1 to around 12:1 drops CHT by 150 degrees in some engines.

 

[linnix13]

i run 20:1 in mine, never let me down,

 

[xlite]

I think Joe is on the right track... Try going a little heavier on the oil mix & see if that helps.

Note that more oil causes engine to run LEAN not rich and HOTTER not cooler.

 

[Venice Motor Bikes]

True; but friction is also a cause of engine heat.

 

[Prasinos]

it happens after long hills and wot for like a full min. My carb is a dellorto with a #63 jet. I honestly don't think there is any problem with the setup.

I was just wondering if anyone had any NEW ideas for cooling these engines.

 

[Outrunner]

it happens after long hills and wot for like a full min. My carb is a dellorto with a #63 jet. I honestly don't think there is any problem with the setup.

I was just wondering if anyone had any NEW ideas for cooling these engines.

Move to Alaska! Has anyone mentioned that yet?

 

[Prasinos]

first helpfull comment yet, outrunner

 

[xlite]

True; but friction is also a cause of engine heat.

Not much compared to the cooling effect of vaporized gasoline. I didn't believe it myself until one day tried this with an IR thermometer pointed at Rotax engine.