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LT1000 Problems

7322 Views 22 Replies 3 Participants Last post by  Five Points
Hello,

I have an LT1000 with 17.5 B&S model 31C707-0230E1. I've been having problems with the engine. To keep it brief as of now, it starts up fine with choke and runs good with choke. At idle speed it continues to run fine. As I increase throttle speed it gets rough, surges, misses and is inconsistent.

To date I've confirmed; fresh fuel, gas cap vent is good, new fuel filter, air filter, spark plug, fresh oil. I took carb apart cleaned thoroughly (more than once), replaced float needle and new gaskets. Ran Sea Foam thru carb. Added Sea Foam to fuel. Adjusted valves to specs. Adjusted throttle linkage per the manual. Took float bowl solenoid out and confirmed it operates when the key is turned. Any other suggestions?

It seems like its not getting enough fuel every 2 seconds but don't see how the carb isn't clean. Only has idle adjust screw and mixture needle with limiter cap. Manual says the mixture needle can't be removed without breaking it. I suspect it could be a problem sense it doesn't seem to effect engine when adjusting it within the range allowed by the limiter cap. I sprayed carb cleaner in the hole while turning the needle hoping to clean it. Also, I replaced the fuel filter with the same kind that was on it. The package says for engines with fuel pumps (which mine doesnt have) although it originally ran fine with the old one.

The throttle/air vane moves sporadically as the engine does. Possibly governor issue? Any suggestions would be greatly appreciated, I'm out of ideas. Thanks in advance.
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Hello and welcome, Just to verify, did you completely take the carb apart and soak it in a carb cleaner like gunk or berrymans and throughly blast every hole and orifice clear with compressed air?
Also some of those non-adjustable mixture needles do come out. You have to pop the cap out and there is a regular screw head on the needle. You can remove it, there not adjusted just torqued in there to some inch pound rating. There could be junk in there.
Also there is an aluminum welch plug you need to pull out on the side of the carb to expose the mixing chamber. There could be junk in there as well. The replacement welch plugs come in a rebuild kit however the plastic cap for the mixture screw may not. Also did you check the play in the throttle shaft? They are brass (usually) and could wear and suck air creating another vacuum leak.
Maybe this might get you going.
Dirt and debris cause wear on the throttle shaft. There is usually a seal, felt or foam to keep it out but they disappear after time from oil, gas or someone blasting the carb off with water or air. The wear would look very subtle but would be enough to allow a vacuum leak and yes it would wobble back and forth.
I will do the welch plug when rebuilding to eliminate any problems later. All you need is a little varnish or gunk inside of the chamber to plug a hole and you'll be chasing problems later
The mixture needle has a manufactures torque (carb specific)when you tighten it so it does not loosen up with vibrations. You can over torque it too smashing the seat. Some needles have small hole or ports in the sides near the end that can plug up too.
Reference the throttle/choke shaft, there may not be resistance but it should be nice and smooth with a good fit without back and forth play.
Just so I'm not thinking about a different carb could you give me the model, type, name of the carb.
If its a walbro than yes it does have spring, I was thinking of a different series, but they do come out and I would inspect the tip for any grooves or nicks. The throttle shaft also has a replacable bushing, so I would inspect both the bushing and shaft for wear.

Reinstalling the idle mixture needle, you would turn it in untill it just seats and back off 1 1/4 to 1 1/2 turns.

Here is a blow up of your NIKKI
Font Material property Parallel Schematic Rectangle

Yours is on the right, if you look at part1091 you can see the two seperated. It may or may not come in a rebuild kit.
You can also replace the throttle shaft seal. I would inspect the shaft for wear though just in case.
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BTW You may or may not break the cap while removing it. You can order it seperatly if it does not come in the kit.
Your welcome, let me know how it goes and if we can help with any other issue, feel free to ask.
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This is what I'm finding,

Item 131A
699501 BRIGGS AND STRATTON ENGINE PART 699501

This is the throttle shaft kit that you can get for 24.90

Item 141B
792777 BRIGGS AND STRATTON ENGINE PART 792777

This is the choke shaft kit that you can get for 11.30

These are for the Nikki Carb that you can get from M&D mower.

Yes, I like the Walbro carbs better. I dislike disposable.

The price for a new carb is between 80-95 bucks
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Are the throttle shafts on the Nikkis steel or brass? I usually end up with the Walbros and they are a piece of cake.
Have you checked for vacuum leaks at the manifold? Your plastic manifold has an o-ring at the part that bolts to the head. Have you changed or checked that one? Does it chase like that when under load like when you are mowing or does it settle out?
You can spray carb cleaner, wd40, ether around the base of carb and intake areas and listen for a change in RPMs if it does change you can narrow down the area. You could even have a crack in the intake from being over torqued or hit.

BE CAREFUL spraying flammable liquids around the running engine! If you use carb cleaner be sure not to get any on the painted surfaces as it will mess up your paint.
If you are referring to wear on the side of the push rod/s were they make contact with the guides than yes, especially if they are *aluminum. If they are solid steel and the wear is minimal it would be up to you.

*They are known to fail in that area and bend or break.

Simple wear on the side of the push rod should not cause the engine to run bad, if the wear was on the ends not allowing you to properly adjust your valves than yes, the rest you know ;)
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