# Popping/rough at high rpm



## chaben1121

I have a Craftsman lt1000 that i bought off of someone recently. I used it once with no problem. Next time I went to use it, it was running horribly rough when I throttled up and with a significant loss in power. The battery on it isnt good, so I charge it a bit when i start it up, i havnt had a chance to get a new one yet. But it starts up fine, runs excellent at low RPMs, very smooth, but when i make it about half way up the throttle, it sounds almost like the choke is on, but its not. If i take the air filter and cleaner out it is a very very loud popping sound that comes out. 

From similar situations that I have read about online, Im guessing it could be carburetor related? Ive been running gas and oil with sea foam in it through the engine with no luck. I also took the carb off and apart to clean it but it didnt help. And actually, it was pretty clean as far as i could tell. Although it was my first time taking apart a carburetor. I was going to order a rebuild kit for the carb and see if that helps as its a 2004 model mower i believe it could use it. When i took it apart the bowl was filled with gas and the float and parts seemed to all be moving fine. Could faulty gaskets and seals cause this problem? 

I am new to small engine repair and havnt done much with cars and trucks either. Im sure there is somthing im missing that could help me diagnose the problem better. What else should i be checking for? 

I have also drained the old nasty oil out and put fresh in, have not got around to changing the oil filter, spark plug, or fuel filter. The air cleaner seems in decent shape.


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## jhngardner367

Welcome to the forum!
What engine does it have,and what model / spec # on the engine? 
Have you checked the spark? Connect a spark tester between the plug and the wire,then start it,and watch the spark as you increase the speed. Isit still blue/steady,or does it turn orange/yellow,and get jumpy?
If it stays blue, it's good. If not,you could have a weak coil(armature).
If it's good,drain the fuel,and use fresh gas,with no additives(seafoam),and see if it clears up. If it doesn't,get some carb spray,and spray short bursts near the carb base,and at the manifold ,where it mounts to the engine. Any change in speed/sound,indicates a leak(lean).


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## chaben1121

Briggs&Stratton Model 21H777 Type 0202-e1


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## Bill Kapaun

chaben1121 said:


> Briggs&Stratton Model 21H777 Type 0202-e1


I'll assume you missed a digit and it's a 31H777-0202-E1

Your tractor has only a 3 AMP charging system. It would take 10-12 hours of high speed running to fully charge a totally discharged battery.
IF you have a charger, give it a FULL charge.
Chances are it's bad, but give it a try.

For your "popping" sound.
You might want to check the valve adjustment.
IF that's good, make sure the flywheel key is intact. IF sheared, it affects ignition timing.


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## chaben1121

Any tips on how/where to check valve adjustment? perhaps a how-to


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## Bill Kapaun

chaben1121 said:


> Any tips on how/where to check valve adjustment? perhaps a how-to


A simple web search will yield oodles of valve adjustment procedures.
Intake .003-.005"
Exhaust .005-.007"


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## chaben1121

Well i went to check the valves and noticed this

http://youtu.be/9g-rTa6_04M


What is my problem? The rod shakes. is this repairable?


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## Bill Kapaun

That is the rocker arm.
You may have a serious problem, maybe not.
Adjust the valves.
After that is done, rotate the engine and see if both valves move an equal amount. They should.
IF not, you may have a flat cam lobe.
Also look for a bent push rod.

I suggest you go to the Briggs website and download the IPL for your specific engine.
That will allow you to use proper terminology and avoid possible confusion.


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## chaben1121

So I am about at my mechanical limit. :dazed: 

The top valve with the burn under it is messed up somehow. Looking at the valves inside the spring, one of them looks good, like a little piston, and the other looks like the base of the little piston has come up about 3/4th the length of the spring and so when it compresses, the top of the spring/valve is coming in contact with the base of this little piston and is only able to open a tiny bit. The rods seem fine... unfortunately. 


Is this repairable? Im going to take it into a small engine shop I think. However any insight would be great.

sorry for lack of proper terminology.


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## Bill Kapaun

Typical repair will be a new head.
Some mechanics will have a repair method that might work.


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## chaben1121

Might work? Like I also 'might' have to get a new engine?


Also, I appreciate all of your help on this. This is the most involving mechanical task I've undertaken so far and learned a lot thanks to your answers.


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## Bill Kapaun

*Typical repair will be a new head.*


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## chaben1121

Someone offered me a head but the engine it came from is a lower HP. He told me that most heads for a Briggs and Stratton between 14 and 20 HP would fit my 18hp engine. Is this true?


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## Bill Kapaun

Well, since you took my advice and downloaded the IPL for your engine, download the IPL for the donor engine and see if they use the same part#.

Since said engines between 14 & 20 HP may be-
Singles or twins
Flathead or OHV
........


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