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Discussion Starter · #1 ·
Hello all. I need a way of adjusting the mixture on a mikuni carb. As mine is running vary rich.... I don't think there is a tuning screw on these so I can only think of changing the jet a size or two smaller. Is there jets available? Or is there another option. ...

Thank you in advance
 

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carb adjustment

Hi,
Carbs usually don't just start running rich, especially ones that don't have any mixture adjustments.

The gasoline we are being sold today has varying amounts of alcohol in it.
This alcohol absorbs moisture from the air while sitting in your tank/ carb, causing water deposits and damage. Rust can form inside your steel tank and then it flakes off and goes into your carb. The rubber hoses also get attacked
by the alcohol and they swell shut on the inside restricting fuel flow. All these will make your carb run lean, not rich.
I've run into all these problems in the last two years or so.

First of all, check your ignition system. A smart mechanic told me a long time ago; "90 percent of Carb problems are really ignition problems".
Make sure you have a good spark.
If your mixture is not firing, your exhaust will look rich, your engine will sound like it's rich, but it's because of incomplete combustion.

If you still think you have a carb problem, install a known good one and try it. Save yourself a lot of frustration.
I bought a brand new replacement carb on Amazon for $18. These work very nicely and fit with just a few modifications.
Perform a search for; "Honda GCV160 replacement carb". I bought mine from "ZY Parts Service 4 You." Mine is not a Honda, I believe it's a Chinese copy, but it works so nice. It does have a mixture adjustment screw for the idle, but not high speed. That is done by a screw in main jet.

The center to center mounting studs were about 1/8 inch different, I filed one hole into a slot and got it to fit. That's really about all you have to do to try it. If it runs better and you want to use it, you will need to cut a little bit of the plastic air cleaner and possibly drill one of the governor linkage connections out slightly.

My 2-stroke ran a little lean at full speed and had a little lean surge "Hunt"; the RPMs would go up and down about 500 RPM.
These carbs are set up to run on a 4-stroke and run lean. When we add the oil to gasoline for our 2-strokes, I believe it causes them to run leaner yet.
I drilled out the main jet, several times to get it right.
It started out with a #72 sized jet, I drilled it out with a #71, then a #70 and finally a #69, until the lean surge was completely gone.

I'm so happy I got one of these carbs, I actually bought another for a spare, I know with todays gas, these carbs will not last forever.
I've talked to a local lawnmower shop owner and he has noticed a lot more fuel system problems recently. He suggested only mixing small amounts of fuel at a time, no more than you need for a month or so.
I have also installed a fuel shut of valve at the bottom of my tank and close it when I'm finished mowing the lawn. I let the mower run to use up all the gas in it's bowl so there's no gas sitting there until next week.
Good Luck to you,
Need any help, please feel free to e-mail me;
[email protected]

Mike
 

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Discussion Starter · #3 ·
Thanks Mike for the help. I found my problem it was clogged air bleed hole to the pickup tube. This toro is new to me so still working out the bugs. I personally don't use gas with alcohol. .. and now not even pump gas without alcohol. I am using Av. Gas in everything thing now as it don't go bad and runs much cleaner and better.

Now I have to adjust the govener as it's turning a little hi on rpms.
 

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Av gas?
You go to the airport with a gas can?

I tried white gas once, Coleman fuel, but still had problems I hadn't fixed up til then.

Mike
 

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Discussion Starter · #5 ·
Yes most small airports have self serve pumps and is only a few cents more than E0 and is cleaner and does not need any additives to store and will last at least two years.

Camp fuel won't work as it has a octane around 60... Av gas 100ll octane is around 96... go to 100ll.com and you can find it near you. You may need permission at some airports to access the pumps. Try some and let me know what you think
 
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