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Old 12-02-2019, 07:39 PM
WavyThomas WavyThomas is offline
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Default Predator 212 Running Weak In Cold

I have a stock predator 212, and I took off the head recently. I was recently driving in the snow, and it felt as powerful as it was before. All of a sudden, the engine felt weak. It barely pushed my go cart at full throttle. I am new to engines and go karts. Any ideas on what happened and how I could get the power back? I also have a comet 30 series torque converter.
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Old 12-02-2019, 07:44 PM
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I'm having the same issue with two different carbs
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Old 12-02-2019, 08:09 PM
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Since you said that you were riding in the snow, I think I can rule out altitude and get right to temperature. I think that most people understand the principal that the colder an object (or gas in this case) is, the denser it is. Because of this, at low temperatures the air is denser, and therefore has more oxygen, but the jet will only allow so much fuel to enter the engine. The result is a lean condition which results in a loss of power. Try running it with the choke partially to fully closed and see if that makes a difference. And I know people don't like the fuel systems of tecumsehs, but they did at least one thing right on the OHH60. They added a block off late that is stored out of the way in the air box when not needed. But it is to be placed in a position where it blocks off air entering the engine. The plate says it is to be used below 30 degrees farienheit. That fixes the tune, preventing a lean condition.
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Old 12-02-2019, 09:24 PM
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While fixed mixture engines will run lean in the cold, they will run lean right from the get-go. It won't be a sudden power loss out of the blue.

That could be carb icing. As air is sucked through the Venturi, its pressure drops. This causes a cooling effect. The pressure drop combined with the temperature drop raises the relative humidity of the air entering the carb to the point where condensation forms. If it's below freezing out (or the resulting condition in the carb creates sub-freezing temperatures), ice will begin to accumulate in the carb throat, disrupting the airflow. This can actually happen at temperatures above freezing as well, and is one of the leading causes for emergency landings in small aircraft, as carb ice is often the last thing you think about when it's 60 out.

The result of the disrupted airflow is initially a lean condition, as the carb is unable to draw fuel properly. As the throat becomes further blocked, the engine can be starved of air, acting as a choke, and causing an over-rich condition.

This is why snowblower engines have the carb inlet under a shroud that also houses part of the muffler. It preheats the air to prevent carb icing.

Carbureted aircraft have carb heat in various forms, also usually involving air drawn from between the exhaust manifold and heat shield in the case of air cooled engines, or a heater core in liquid cooled engines.

Many air cooled carbureted snowmobiles have carb heat systems too, and many liquid cooled ones have coolant loops that run through the carbs.


Could also be your air filter clogging with snow if you're kicking a lot of it around. Also why snowblowers and most snowmobiles don't have air filters (not a lot of dust to kick up in winter either)
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Old 12-02-2019, 10:09 PM
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Quote:
Originally Posted by J.S.@SMS View Post
the principal that the colder an object (or gas in this case) is, the denser it is.
Not entirely true..
one exception is for example water, which is densest at ~4C above AND BELOW it will expand

but that brings me to a side note:

Tom, what's your oil's temperature range?
just to make sure you don't accidentally harm the engine with your oil getting too viscous.

And there's a very slight but not to be ruled out chance that your engine runs actually a tad too rich (or on too little air let's say)
A stock engine usually has a foam airfilter (soaked in oil)
if that oi gums up because of the temperatures it can block a significant portion of the intake air, making it harder for the eninge to breathe..

So if engaging the choke slightly as suggested doesn't improve
how the engine runs, but makes it even worse.
The airfilter might be the culprit (the oil it's soaked with that is)

And as anickode said.. venturi cooling is also a thing,
depends on the humidity of the air really...

In either case it helps to wrap a piece of aluminium foil
loosely around the exhaust and intake airbox (as a set)
leaving of course the actual exhaust tip open
and add a small hole sideways on the exhaust for the intake to draw air...

That way you have a makeshift air heater for the intake
and you might have solved the problem (not pretty I admit...)

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Old 12-02-2019, 10:46 PM
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sudden loss of power after cylinder head reassembly? What did you torque your head bolts to? Did you re-use the head-gasket?

Basically anything you touched may have been messed up. Start with what you disassembled.
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Old 12-03-2019, 10:53 AM
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---------- Post added at 11:52 AM ---------- Previous post was at 11:49 AM ----------

Quote:
Originally Posted by KartFab View Post
sudden loss of power after cylinder head reassembly? What did you torque your head bolts to? Did you re-use the head-gasket?

Basically anything you touched may have been messed up. Start with what you disassembled.
I have no clue what my head bolts are torqued to because I didn't use a torque wrench. I don't have a torque wrench so I just tightened the head bolts a lot. I did reuse the head gasket.

---------- Post added at 11:53 AM ---------- Previous post was at 11:52 AM ----------

Quote:
Originally Posted by itsid View Post
Not entirely true..
one exception is for example water, which is densest at ~4C above AND BELOW it will expand

but that brings me to a side note:

Tom, what's your oil's temperature range?
just to make sure you don't accidentally harm the engine with your oil getting too viscous.

The engine is using Mobil 1 full synthetic 10w-30. I'm not sure where to find the oil temperature range. On Mobil 1s website it says for cold starts, oil keeps flowing as low as -40 degrees Fahrenheit, and it can withstand high temperatures of up to 500 degrees Fahrenheit.
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Old 12-03-2019, 10:53 AM
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10W-30 Mobil 1 Synthetic is fine, that's what I run, and yes, it's fine for low temperatures.
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Old 12-03-2019, 11:52 AM
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luckily that's the easy part..
10W means good enough for -30C in the testers industrial pump.

The only problem is it still thickens up a bit
still good for the testers pump but maybe not fluid enough to climb up the pushrods
and thus lube the valves splash lube is not exactly too accurate or carefull, right

That's why Rato asks you to switch to 5W-30 if the temperatures drop below 0F
significantly (-5 or so)

And in order to keep the engine in the best possible condition for the longest possible time,
I'd say you should indeed do so if your ambient temperature drops past said -5F

You don't have to deal with that kind of freezingly cold, have you?
So I'd say you should be fine with your 10W-30

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Old 12-03-2019, 04:40 PM
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Wow lots of good info guys. Thanks.
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Old 12-03-2019, 05:36 PM
WavyThomas WavyThomas is offline
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Quote:
Originally Posted by itsid View Post

You don't have to deal with that kind of freezingly cold, have you?
So I'd say you should be fine with your 10W-30
I live in Connecticut and we have our cold moments. The coldest it gets where I live is around 20F.
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Old 12-03-2019, 09:02 PM
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My guess is a blown head gasket.
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Old 12-03-2019, 09:56 PM
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yeah, but 20F is a lot warmer than -5F, ain't it?

Still, a makeshift intake air preheater might quickly solve your problem
(hopefully)

But Grant has a very good point..
if I misread/misinterpreted your initial post and the
"I was recently driving in the snow, and it felt as powerful as it was before. All of a sudden, the engine felt weak" happened just shortly after you messed with the head,
this might not be just coincidental.
A mistorqued head bolt or a clockwise/ccw tightening could've caused the issue.
(popped the gasket cracked the cylinder head...)
And I'm afraid you might need to at least check that!

cylinder head bolts are M8x32 and are to be torqued to 30Nm (+/- 2Nm)
cylinder head cover are M6x12 to 10Nm (+/- 1Nm) [not too important just keeping dirt out and oil in]
if one is too loose... undo all
check the gasket and retighten them again;
crosswise in stages so that there is no more than 10Nm between any two bolts.

'sid
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Old 12-03-2019, 11:53 PM
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Check for a head gasket leak. You can just start the engine and spray soapy water around the gasket seal. Look for bubbles.

Readjust the valves. Since you had the head off, I assume you needed to loosen/adjust the rocker arms. Maybe something came loose.

Clean the carb. Maybe some gunk got pushed up inside the jet.

Are you sure it is the engine not making power? Are you sure that the problem is not with the torque converter delivering the power to the wheels?
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