Engine temp? 230?

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Tony01

Tony01

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What's the right engine temp for a fully warmed up 4-stroke 150cc? And where do you measure it? What about oil temp?

I got these gauges in the mail... In fact the big digital one was cancelled but the china seller sent it anyway. I don't know which one is right!! The big digital one has a 6mm probe while the other has a 3.5mm I think.

I bought a gauge so that I knew when the engine was warmed up before I started riding... So how warm is warm enough?
 

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Davezilla

Davezilla

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Where are you taking the reading from? Best place to get the reading from is on the head and if you're using the spark plug mounted temp probe it'll be most accurate but might read a little cooler when moving because of the air flowing over the head with the plug up front, then read a bit hotter right after slowing down from a wot run.
230 seems on the cool side for head temp but might be about right if reading from another part of the cylinder, if you can put the probe just under the head and out of any direct air flow it should read higher and more accurately.
Oil temp should be ok as long as it stays under 200F . I got an oil temp probe on my Harley ' oil service cap and it tends to stay around 180 to 190F on hot days so I run 50 weight oil in it to ensure enough viscosity. Some people even run 60 weight in their engines since it maintains oil pressure better. If the engine doesn't use an oil pump then 50W oil might be too heavy. Oil viscosity goes down considerably above 200F so heavier oil may be needed in the summer. If the engine has an oil pump and a plug to tap into for a pressure gauge this is the best way to decide which weight oil is needed as well as if an oil cooler should be used. You should be ok by using the recommended oil in the engine as long as the oil temp stays below 200F tho so no real need for a cooler or even a pressure gauge if you can keep the temperature where it needs to be... and if the engine doesn't use an oil pump all you can really do is make sure the temp can be kept in a safe range and use the manufacturer recommended weight.
 
Tony01

Tony01

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Thanks for your reply. I just realized that both probes were not in the same place. The 230F probe was between fins on the head, in the location halfway between the spark plug and the center of the bore (flathead). The 220F probe was inserted into a hole on the edge of the head, probably not above the combustion chamber.

Putting the probe in a fill cap is a good idea. On the briggs the level is set to the line where the fill cap screws in and there are two of them; one is inaccessible right now and that's the one I will hook it up to.

My instruments panel is gonna look sweet when it's done... All illuminated for night riding too :)

So which temperature reading do you watch to know when it's ok to start driving? If the oil temp does not come up as fast as the head is it still ok, or should I wait and warm the motor till oil reaches a good temp?
 
Davezilla

Davezilla

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Depends on how you intend to ride.... if it's just a normal cruise where your not going past about half throttle then you can go by cylinder head temp but if you plan on going all out ride it like ya stole it, let the engine fully warm up as indicated by the oil temp... once the oil is up to temp you know the rest of the engine is ready for some hard riding.
The main issue of going all out on a cold engine is piston slap where it hasn't fully expanded in the bore which can accelerate wear on the piston and the bore, but there are also bearing clearances which can beat up the rod and crank journal as well as the wrist pin at the rod etc.... once an engine starts to wear this way you will start to hear the piston slap when cold and it'll go away as the engine warms up in the early stages, then as it wears more the slap eventually won't completely go away. This isn't something that happens after a few weeks of riding hard, but it'll gradually show up after several hundred miles, which can prevent an engine from lasting several thousand miles between rebuilds. It's usually the top end that wears fastest from high rpm use, but running one cold at high rpm really accelerates this wear.

The way to prevent a lot of this excessive wear is to ride at sensible rpm's most the time, but just as important, let the engine warm up before playing too hard.
 
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Uncle Bob

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As a pro mechanic I can tell you this. You want your oil temp to get to 220 at sea level minimum and run it for a good period of time. The idea is to get the condensation (water) boiled out of the engine. I have been a H.D mechanic for over 35 years and seen many many engines damaged from guys doing nothing but short rides and then parking it, the condensation builds and builds and turns the oil into sludge and at the point it is no longer lubricating bearing's, bushings or the pistons. The higher in elevation the higher the temp must get to boil the water out, the lower the elevation the lower the temp. as far as head temp I don't have a problem running engines as high as 300-320 but not any higher than that. In a H.D. engine I never run more than 3000 miles, then change oil, on these 4 stroke bicycle engines I run no more than 500 miles (no oil filter). My 142f 49 cc holds about 12 oz of oil. Thats a damn cheap oil change and will keep the motor in good shape for much longer. Oil is the life blood of any engine, more so in air cooled engines and even more so when we don't run filters. I break the engine in with castrol gtx petroleum oil then make the switch to Royal Purple synthetic.
 
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Bikeguy Joe

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I will add that max oil and max head temps will be different. Max head temps on air cooled engines tend to be higher that oil temps, but there are a lot of variables involved.
If you have a head temp somewhere around 230-250 f, you are A-OK.
 
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Uncle Bob

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Bikeguy Joe said:
I will add that max oil and max head temps will be different. Max head temps on air cooled engines tend to be higher that oil temps, but there are a lot of variables involved.
If you have a head temp somewhere around 230-250 f, you are A-OK.
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Very true! Temp reading's will be varied depending on where taken. Closer to the combustion chamber the higher. I rely greatly on the laser temp guns for accurate temps, especially when heat cycling a new engine. Heat cycling the motor prior to putting a load on it by riding the bike is critical to longevity imo. I start every new motor, let it warm up to operating temp (230-240) then let it cool down completely, I do that 4 times, then I will look at the oil and give it a sniff, if it smells burnt or I see even the slightest metal particles I change it. I know that I may sound rather anal but I have learned over the years building very expensive high horse power H.D. engines that breaking in a motor is very important to engine life and performance. Oil is cheap.
 
Tony01

Tony01

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WOW THANK YOU SO MUCH!!! Just the info I was looking for. Dang wish I'd spoken with you prior to break in. I broke in my motor using the motoman method and it seems to be fine. I let it warm up, then did alternating half throttle/deceleration, did first oil change after 1.5hrs it was synthetic and looked pretty sludgy when coming out, but getting some on a white paper it looked clean still. Right now if I don't have time I just ride it real easy 1/4 throttle until I feel the air flowing from the flywheel getting warm, and then start to open it up.

Since the two gauges I have are somewhat dissimilar in size and look, I would like to have only one on the dash and one somewhere else. If you could only have one on the dash, would it be oil or head temp? I'm leaning towards oil but I could go both ways. Would need a much bigger electronics box to fit all the gauges (I would have a large speedo, 12v tach, one or two 12v temp gauges, two toggle switches). My hour meter will be mounted out of the way under the gas tank, as it is not backlit and useless for night riding.
 
Davezilla

Davezilla

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FFV8 said:
200f is hot enough to drive off water in the oil at any altitude.

http://www.engineeringtoolbox.com/boiling-points-water-altitude-d_1344.html


Which 150cc engine is this?
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I also agree with this, as a mechanic with over 30 years experience and a Harley rider for who knows how long... my sportster never sees oil temps above 200 degrees and I ride in San Antonio Texas and the surrounding areas so it's nice and hot over here from may until at least october... and these rides are minimum of 10 miles, but usually over 50 miles between stops, and that's only due to my little 2 gallon tank...
I check my oil tank regularly and oil level daily and have never seen any signs of condensation in mine or any of my friend's bikes that I maintain. I'm not Harley certified, but I've been working on them for over 20 years, and the mechanic I just hired last month is Harley certified... I let him take my top end apart and put it back together one day when we were bored so I know he knows what he's doing as well.
I don't need a piece of paper to tell people in know how to fix their bikes nor do I call myself a pro, but I let my work and my customers do all the talking...
 
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Uncle Bob

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U

Uncle Bob

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Davezilla said:
I also agree with this, as a mechanic with over 30 years experience and a Harley rider for who knows how long... my sportster never sees oil temps above 200 degrees and I ride in San Antonio Texas and the surrounding areas so it's nice and hot over here from may until at least october... and these rides are minimum of 10 miles, but usually over 50 miles between stops, and that's only due to my little 2 gallon tank...
I check my oil tank regularly and oil level daily and have never seen any signs of condensation in mine or any of my friend's bikes that I maintain. I'm not Harley certified, but I've been working on them for over 20 years, and the mechanic I just hired last month is Harley certified... I let him take my top end apart and put it back together one day when we were bored so I know he knows what he's doing as well.
I don't need a piece of paper to tell people in know how to fix their bikes nor do I call myself a pro, but I let my work and my customers do all the talking...
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If you think the oil in your sporty never see's anything above 200 in texas, you need to find a better way to take that temp and not the oil tank fill plug type. And if you took that temp at the rocker box's and at the oil passage in the heads next to the exhaust valves you might be rather shocked. In 50 miles of riding in any weather, that oil easily hit's 280, the water is vapored off and is dumped out of the crank case via the breather's. I don't even count the years I was a shade tree mechanic. I'm not trying to be a know it all here, but this is my realm of expertise, it's the only area I will claim to be an expert in. But as I told the other guy, what you believe or practice is of no concern to me. But I am correct in what I stated, I was never looking for an argument despite the fact that there are those here that seem to want to contradict everything anyone ever says. And by the way, the optimum combustion chamber temp for any gas engine is between 930 degrees and nearly 1200 degrees with a great deal of that pulled off the engine via the oil, not just air cooling. have a good one.
 
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FFV8

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Uncle Bob said:
The higher in elevation the higher the temp must get to boil the water out, the lower the elevation the lower the temp.
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Well Bob, since you don't seem to grasp the basic relationship of water vapor pressure vs atmospheric pressure, I believe I will take the balance of your advice with a grain of salt.

Beginner01:
Since you are running the OEM cooling system, run it as hard as you like. That engine was made to stand in one place, running a constant full load. People cold start B&S engines & run them against the governor as soon as they can every day. A genset spins to 3600 as soon as it fires, and often gets loaded before the choke can be opened.

The splash lubricated Briggs design is pretty tough. Try to use oil with some Zinc (ZDDP) in it. Change it often. I did warranty repairs on B&S engines, and new engines left with 15W40 diesel oil in the crankcase.
Never had one come back, and some of them were mounted on snowblowers. 110v electric start at -20f & wide open throttle as soon as possible.

.
 
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Uncle Bob

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FFV8 said:
Well Bob, since you don't seem to grasp the basic relationship of water vapor pressure vs atmospheric pressure, I believe I will take the balance of your advice with a grain of salt.

Beginner01:
Since you are running the OEM cooling system, run it as hard as you like. That engine was made to stand in one place, running a constant full load. People cold start B&S engines & run them against the governor as soon as they can every day. A genset spins to 3600 as soon as it fires, and often gets loaded before the choke can be opened.

The splash lubricated Briggs design is pretty tough. Try to use oil with some Zinc (ZDDP) in it. Change it often. I did warranty repairs on B&S engines, and new engines left with 15W40 diesel oil in the crankcase.
Never had one come back, and some of them were mounted on snowblowers. 110v electric start at -20f & wide open throttle as soon as possible.

.
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Take what you want with what you want, as I stated I don't care. and I never gave advice,to you or anyone else, only stated what my experience has been.
 
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Tony01

Tony01

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FFV8 said:
Well Bob, since you don't seem to grasp the basic relationship of water vapor pressure vs atmospheric pressure, I believe I will take the balance of your advice with a grain of salt.

Beginner01:
Since you are running the OEM cooling system, run it as hard as you like. That engine was made to stand in one place, running a constant full load. People cold start B&S engines & run them against the governor as soon as they can every day. A genset spins to 3600 as soon as it fires, and often gets loaded before the choke can be opened.

The splash lubricated Briggs design is pretty tough. Try to use oil with some Zinc (ZDDP) in it. Change it often. I did warranty repairs on B&S engines, and new engines left with 15W40 diesel oil in the crankcase.
Never had one come back, and some of them were mounted on snowblowers. 110v electric start at -20f & wide open throttle as soon as possible.

.
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Sounds good. I will however let the engine warm up at least to a decent head temp before I run it hard. Hoping to get at least 1000hrs out of this motor as replacement shortblocks are getting rare.

And yeah the boiling temp vs pressure is one of the basic physics courses; thermodynamics. However this doesn't matter with a pressurized oil system... I'm not sure about how those work on motorcycles or any vehicles really but for our needs, the temp needs to be highest at sea level to boil the water, and the difference in altitudes that we'll see in day to day driving results in a negligible difference in temp. This is the same concept as Diesel engine ignition- rc Diesel engines don't even need a glow plug because the rapid increase in cylinder pressure is what ignites the charge.
 
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FFV8

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Beginner01:

Those I/C flatheads are some of the most durable stuff B&S ever built. I saw them come in with the cooling system packed full of debris, and overheated to the point where the head gasket failed. The complaint? "Hard to start, no power"

Run it out of oil & the rod will fail. Usually that is just a rod replacement. Over speed was the only time I ever saw holes in blocks.

Again, the biggest factor for longevity is oil. Enough of it, the right grade, and frequent oil changes.

For equipment that gets rolled & shaken while running you need to fill the sump to the top of the fill plug threads on the engines with the low mounted fill, or 1/4" ABOVE full on engines with a dipstick mounted at tank level.

All of those 93432 series engines were designed when regular motor oil had 1800 ppm (or more) of zinc. Emission controls on cars has led to the removal of zinc from motor oils. Even oils for diesels have reduced zinc levels today.

You can find oils with higher zinc levels from several specialty oil vendors (Lucas, Schaeffer, Brad Penn, etc) or use an additive. Lucas sells an additive called TB Zinc Plus that does great job. An ounce per quart brings the zinc level up.

If you doubt the need for zinc in splash oil engines, look at Jr Dragster. They tend to run as much as 6,000 ppm of zinc in their oil.

I always told customers to do 50 hour oil changes. For a guy with a truck mounted sprayer & your engine that meant an oil change every two weeks. There was some resistance to that, but the people that listened - all I ever sold them were spark plugs and air filters.

FYI, running without an air filer will destroy that engine in a few weeks...

.
 
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