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rich_kildow

Runs great in the cold?!

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rich_kildow

I've been blowing snow with my 7116 the last 2 days and noticed that she runs amazing! Idles great for several minutes, great throttle response, doesn't bog when coming up off idle, didn't seem to foul the plug as quick, very little smoke on start up. I haven't made any changes going into winter besides a fresh batch of straight 30 weight at the end of October. I picked up leaves on a wooded acre so it isn't fresh.

What would this point to that would be causing issues when it is warm out? Worn rings that the now cold/thick oil can't get by comes to mind, which would explain most of those issues, but wouldn't they come back after the engine warms up? Most of my running issues seem to come when the plug get fouled with what looks like burned oil after about an hour, leading me back to rings.

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rfsmith1952

Could be lots of things. I know I have to tweak the carburetor come winter, and then again come summer. I've heard the colder air is drier and ignites better. When it's warmer maybe the oil could be sneaking up through the valve guide rather than the rings, or thru the breather. When the issue identifies itself, and it will, then deal with it. Till then, don't borrow trouble and enjoy the great performance!

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MysTiK

You mention plug fouling. Perhaps high/low idle mixtures on carb are set too rich. Mine was. I ended up spinning those little screws in and out until I got a combo of good response to throttle and less smoke at the same time. Pretty simple really - tune it by sight and sound and feel. Thread was called 'carb tuna' couple months ago. I was getting some smoke after idling for various periods - tweaking the carb helped methinks. It was fun - I might do it again. I did not do a carb kit; altho I could probably use one. "play it by ear".

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HubbardRA

I was going to say the same thing that Graham did. If your carb is set too rich it will foul the plug quickly. In colder weather the air is denser and requires more fuel. This basically causes the engine to run a little leaner than in warm weather.

To adjust the carb:

1. adjust the engine idle first. Turn the screw to the right till it starts to run rough, then turn the screw to the left till the engine starts to run rough, then set the screw halfway between.

2. Adjust the main jet same way as idle, except with engine at WOT. After doing the initial setting, then drop back to idle and open the throttle quickly. If there is any hesitation, open the main jet adjustment screw an additional 1/4 turn (counterclockwise looking at the head of the screw). Go from idle to WOT quickly again, if there is still hesitation, then open the screw another 1/4 turn. It should not require any more adjusting unless there is some other problem.

3. After setting the main jet, then go back and readjust the idle jet. Adjusting the main jet can affect the idle mixture also.

As Graham said, the adjustment is done by ear, but there is a methodology to follow, rather than just randomly turning the screws. I have been adjusting carbs for 50 years, but I had to sit down and figure out how to write it down for others, since it is just second nature for me to set a carb without even having to think about it. There is nothing magical about a carb. They all work basically the same way and use the same theory.

Also, unless you are having a carb problem, or significant leakage, I cannot see any reason to "rebuild" a carb. Most carb "kits" have very few parts in them, just seals and gaskets, and emulsion tube, and a needlevalve. If there is nothing wrong with these parts that are currently in the carb, then there is no reason to replace them, since the needlevalve is the only one that can wear out. If you have a worn throttle shaft, then you need a different kit, since those parts do "not" come in a carb rebuild kit.

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Talntedmrgreen

Ditto...spent years monkeying with sled carbs, as they can be super sensetive to changes in temp, humidity, altitude, etc, all because of the changing O2 in the air. In racing applications it becomes critical to dial that mixture in just right, to avoid that lean condition the guys are talking about above, which, in a high compression 2 cycle will cause detonation and burn a hole through the top of your piston in no time. Running on a 0 degree day can lean out fast when using a carb tuned to riding in 35 degrees almost immediately.

I've seen that these engines are more prone to running rich and loading up it seems. You should be able to hear the rich to lean changes through your exhaust note and how the engine responds to a load or to throttle. Good luck...glad she's running great!

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fishnwiz
quote:Originally posted by HubbardRA

I was going to say the same thing that Graham did. If your carb is set too rich it will foul the plug quickly. In colder weather the air is denser and requires more fuel. This basically causes the engine to run a little leaner than in warm weather.To adjust the carb:1. adjust the engine idle first. Turn the screw to the right till it starts to run rough, then turn the screw to the left till the engine starts to run rough, then set the screw halfway between.2. Adjust the main jet same way as idle, except with engine at WOT. After doing the initial setting, then drop back to idle and open the throttle quickly. If there is any hesitation, open the main jet adjustment screw an additional 1/4 turn (counterclockwise looking at the head of the screw). Go from idle to WOT quickly again, if there is still hesitation, then open the screw another 1/4 turn. It should not require any more adjusting unless there is some other problem.3. After setting the main jet, then go back and readjust the idle jet. Adjusting the main jet can affect the idle mixture also.As Graham said, the adjustment is done by ear, but there is a methodology to follow, rather than just randomly turning the screws. I have been adjusting carbs for 50 years, but I had to sit down and figure out how to write it down for others, since it is just second nature for me to set a carb without even having to think about it. There is nothing magical about a carb. They all work basically the same way and use the same theory. Also, unless you are having a carb problem, or significant leakage, I cannot see any reason to "rebuild" a carb. Most carb "kits" have very few parts in them, just seals and gaskets, and emulsion tube, and a needlevalve. If there is nothing wrong with these parts that are currently in the carb, then there is no reason to replace them, since the needlevalve is the only one that can wear out. If you have a worn throttle shaft, then you need a different kit, since those parts do "not" come in a carb rebuild kit.


id="quote">
id="quote">While you may not need most items in a carb kit, the bowl gasket is very important as most times when you remove the bowl, a lot of times the gasket expands or is dried out and cracked. Be sure to clean gasket surfaces very good and be sure you have a very good seal as if there is any air leak it will make the carb hard to tune.

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rich_kildow

I installed a carb kit this spring when I first got the tractor. I've fiddled with the carb settings but there always seemed to be a very fine window between running rough on either side. I'll let it go for now and give it the carb a good look between snow and grass season this spring.

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MikeES
quote:Originally posted by Talntedmrgreen

Ditto...spent years monkeying with sled carbs, as they can be super sensetive to changes in temp, humidity, altitude, etc, all because of the changing O2 in the air. In racing applications it becomes critical to dial that mixture in just right, to avoid that lean condition the guys are talking about above, which, in a high compression 2 cycle will cause detonation and burn a hole through the top of your piston in no time. Running on a 0 degree day can lean out fast when using a carb tuned to riding in 35 degrees almost immediately.


id="quote">
id="quote">I've been there, done that. Racing down a smooth fire lane road WOT for several miles at -35*F. Man do those sleds run at that temp, like being on nitrous.

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rich_kildow

Can't wait to get the sled out! It's below 0 tonight but the trails aren't open yet...hopefully this weekend. The new radius rod end should be here tomorrow and it will be ready to go.

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Kenh

The carb on the 7116 is prone to leaking at the emulsifier tube/carb body. Briggs solution is to remove the threads from an old tube then lap the sealing surface in the carb body. Then install a new tube with one of the small plastic washers that get thrown out of 99.9% of carb kits.

Briggs has a video of the procedure, but I can't post from work as I'm blocked from the video hosting site. I may be able to post a link of the video when I get home??????

Ken

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