Power loss

[element10554]

Hey there I have recently done an engine swap on my go kart. I went from a 5hp Briggs to a 6.5hp Briggs (121432-0124-e1) the engine has been sitting for about 4 to 5 months with gas in it without stabilizer. I drained out the gas an put in new 93 gas. I plan on cleaning the carb out.
I went to ride the go kart and the engine didn't seem to have much power nor did it even get close to matching the speed of my 5hp I'm using a comet TC. When going down hill the go kart go up to normal speed quite easily.
So my question to you is what could rob the engine of it's power and limit it's max rpm as to not let the TC reach it's top speed. I will be cleaning the carb out soon and it has new gas. Any other suggestions would be greatly appreciated.

 

[slideways]

Well don't use 93 octane.. these motors are made to run on 87 and actually run best that way until highly modified. Check the plug and change it. Check the air filter and if its sketchy take a lap without it to eliminate it. And yes clean the carb if it has set like you said. I'm suprised it runs at all or with the choke off.

 

[Doc Sprocket]

Change out the fuel for regular octane, clean and gap the plug, make sure air filter is clean, clean and set carb to specs, and test drive. If problem continues, let us know.

 

[element10554]

Forgot to mention already had the air filter cleaned. I will take the spark plug out and wire wheel it. Any reason why 93 would be worse for the engine? Ive only ever heard good things about running the highest octane you can.

 

[element10554]

Well don't use 93 octane.. these motors are made to run on 87 and actually run best that way until highly modified. Check the plug and change it. Check the air filter and if its sketchy take a lap without it to eliminate it. And yes clean the carb if it has set like you said. I'm suprised it runs at all or with the choke off.

Believe it or not the engine starts up with 1 or 2 pulls easy. It really is a great engine that is why I am stumped that its running so crappy.

 

[Doc Sprocket]

A higher octane rating means greater resistance to detonation. This is key in high compression engines, and the additional compression and related heat can cause lower grade fuels to ignite before the spark plug fires. At the least, pre-ignition severely hurts performance. It can also cause severe engine damage in worst-case scenarios.

At any rate, there are those that believe that the higher resistance to detonation will cause a stock-timed, lower compression engine to actually make less power because of this. At the least, it's a waste of money.

 

[Russ2251]

Check compression.

 

[element10554]

A higher octane rating means greater resistance to detonation. This is key in high compression engines, and the additional compression and related heat can cause lower grade fuels to ignite before the spark plug fires. At the least, pre-ignition severely hurts performance. It can also cause severe engine damage in worst-case scenarios.

At any rate, there are those that believe that the higher resistance to detonation will cause a stock-timed, lower compression engine to actually make less power because of this. At the least, it's a waste of money.

Thanks I really appreciate the explanation. Well at least I will save a bit of money on gas for the go karts. The car still gets 93 ha.

 

[element10554]

Just and update. I cleaned out the carb today and still no change in the way the engine ran. I was told I would probably have to adjust the govenor to get the engine to speed up faster.

Also I spoke with my brother and told him about using 93 and about the detonation he said that its still better to use a higher octane gas due to the lower ethanol percentage. As some of you may know he works at a small engine repair shop and he has told me that some companies are denying warranty work if you use a low octane rating in your machine.

 

[CriticalMass]

The motor should run fine with higher octane gas. High octane with low compression will still fire on time when the spark plug fires. ethanol doesnt have anything to do with it.

Just like toystory said, high compression motors with low octane gas can pre-maturely detonate. This is sometimes heard as a "knock". My pickup takes regular, turbo golf takes premium.

It is a waste of money, regular is regular, and its all the motor requires, it will explicitly say in the manual or cap or somewhere if it takes anything more then 87 octane. The carb jet might have a small piece of gunk in it. Take it out of the carb and make sure the jet hole is clean and spiffy. Might be not enough gas.

Maybe the valves need adjusting?

 

[Doc Sprocket]

Perhaps that's an American thing. I am not aware of our ethanol content changing with the octane rating. As far as the warranty thing goes, either your ethanol content is insane, or it's a very slimy attempt to get out of warranty work.

Have you done a compression check yet?

 

[element10554]

I have not done the compression test yet I have been very busy and I am waiting for my brother to snag the compression tester. He told me that the company echo is denying coverage for anything that has more than 10% ethanol and that a recent law was passed where they are allowed to put up to 15% ethanol into the gas now.

 

[devino246]

I have not done the compression test yet I have been very busy and I am waiting for my brother to snag the compression tester. He told me that the company echo is denying coverage for anything that has more than 10% ethanol and that a recent law was passed where they are allowed to put up to 15% ethanol into the gas now.

Its been that way in NC & VA. I hate the stuff.

 

[element10554]

Yea so I am just gonna stick with the higher octane its really not that much more cost wise.
But back to the engine I disassembled the carb today took the float out and the seat or however you spell it. Sprayed every hole with carb cleaner then took it to my brother where he also sprayed it and blew it out with an air hose put in a brand new seat gave me new gaskets and everything. Ill grab the compression tester tomorrow and give an update. Hopefully its not the compression.

 

[CriticalMass]

Did you check the jet? Most carbs you have to unscrew it and really look at it. the carb i just did had a fouled jet from old bad gas.

 

[element10554]

Did you check the jet? Most carbs you have to unscrew it and really look at it. the carb i just did had a fouled jet from old bad gas.

You know I am really not sure.This was my first time ever taking apart a carb luckily I was able to put it back together the right way haha, but maybe I missed that? If the jet is on the bottom of the bowl then yes I cleaned that I ran a paper clip through it and sprayed it out with carb cleaner.

 

[Cstyle00]

http://www.harborfreight.com/engine...al-shaft-overhead-valve-gas-engine-66015.html

Good ol' Greyhound simply stats 86 octane "or better". My son's subaru manual stats 89 or better. The octane is what is flammable in the gas. The more of it you have the faster, harder, and cleaner it explodes and burns. Racing fuel starts at 103 and way on up. Now you wouldn't want to run high amounts like that in your little motor because it would hit way harder than designed but anything between 87 or 93 is fine. I run 93.

 

[element10554]

http://www.harborfreight.com/engine...al-shaft-overhead-valve-gas-engine-66015.html

Good ol' Greyhound simply stats 86 octane "or better". My son's subaru manual stats 89 or better. The octane is what is flammable in the gas. The more of it you have the faster, harder, and cleaner it explodes and burns. Racing fuel starts at 103 and way on up. Now you wouldn't want to run high amounts like that in your little motor because it would hit way harder than designed but anything between 87 or 93 is fine. I run 93.

What does your son drive? I have a subaru impreza wrx

 

[Cstyle00]

Its a little ASW 3710.....AKA Dragonfly, or Yellowjacket. My boys is red from Pep boys. They are Manco karts by American Sport Works. Wait, are we still talking about your go kart? You didn't put a 6.5hp on an Impreza did you? You might could use my go kart motor to give that car more power.

 

[Doc Sprocket]

The octane is what is flammable in the gas.

No, the gasoline is what's flammable. Please see above explanation.And this, from Wiki-

"Octane rating does not relate to the energy content of the fuel (see heating value). It is only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Where the octane number is raised by blending in ethanol, energy content per volume is reduced."