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Joined: Mar 2008
Posts: 87
Trainee
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I would just like to thank the people that have helped me out with this problem, notably grumpy :-)
I got the mower going and it is running as well as it used to, still a bit of variation in the RPM, maybe some issue with the magic bit that regulates the RPM???? dunno, but it goes well..
my next drama is the starter.. I will post a new thread.
Thanks again Nathan
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Joined: Jan 2009
Posts: 6,926 Likes: 10
Pushrod Honda preferrer
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When you get to it, that engine speed variability needs to be fixed. The most common cause is lean mixture. The mixture is adjusted by the screw sticking vertically down from the center of the bottom of the float bowl.
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Joined: Mar 2008
Posts: 87
Trainee
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Now I'm back from the little starter motor side track.... listening to the engine when I had it going then, as the revs slow down the sound changes, the explosions sound more "pop" than "bang".. a little difficult to put in to words.. I could try doing a sound recording on my phone and upload that.. considering I was mucking around with the carby a fair bit I should probably make sure it is tuned correctly and the mixture is OK.. Awaiting my next tip from the gurus 
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Joined: Jan 2009
Posts: 6,926 Likes: 10
Pushrod Honda preferrer
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Get the engine running at medium speed or higher. Get someone to sit on the seat, or put a weight on it, or temporarily bypass the seat microswitch. Stand in a safe place where you can see the carburetor's throttle butterfly linkage (from the governor), while simultaneously rotating the high speed mixture screw sticking downward from the middle of the float bowl. See if the governor is hunting - that is, the butterfly linkage is tending to shift around, fairly regularly. This indicates lean mixture. If it is hunting, turn the mixture screw so as to unscrew it about a quarter of a turn (as if you were loosening the screw). You can probably do this with your fingers. If the engine speeds up a bit, and/or the hunting decreases, you are making progress.
You can also check your adjustment against the B&S recommended starting point for tuning, which for your carburetor is 1.5 turns from fully screwed-in. If you unscrew it too far you will notice the engine slows down a bit and the exhaust starts to smell. The best position will be more or less mid-way between too rich (engine slows down) and too lean (engine slows down), but I have found it best to watch the butterfly movement and try to find the leanest setting where it is completely steady. If it is moving, it's lean.
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Joined: Mar 2008
Posts: 87
Trainee
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that seemed to help, running a bit more smoothly..
Now I need to work out how to get to the bearing on the cutting disc. not easy to turn by hand so I suspect the bearing is a little lacking of grease or even worse..
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Joined: Jan 2009
Posts: 6,926 Likes: 10
Pushrod Honda preferrer
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Now that you have the high speed jet adjusted, you should adjust the low speed jet. That is the screw with a spring underneath its head, that sticks out the top of the carburetor's body a bit to the left of the middle. You just set the speed control for minimum, and adjust the idle jet by finding the lean limit (it slows down and runs a bit erratically) and finding the rich limit (it slows down, sounds sluggish, and gets erratic in a different way). Then you set it halfway between the two limits.
You need information from the manual to deal with the cutting disk. They tend to have a sort of disk brake to keep them from spinning when they are declutched, so from what you have said there may be nothing wrong with it.
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