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Engine runs at half-3/4 throttle when warm.


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#1 GilsonRider OFFLINE  

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Posted November 06, 2016 - 09:24 PM

Briggs 16HP Twin, model 402707, type 0010 on a Wards G33470A. Seems to start and run out fine. When cold, I choke it to start, starts right up. Then starts all day without choking. When cold, it idles right down. However, after running a few minutes, I can't get the idle down from the mid point. The throttle goes all the way down, it just doesn't idle down to where it was when cold. 

 

From looking at the manual I downloaded yesterday from here, it looks like 1000 -1300 RPM is where the idle gets set? (don't recall if 1000 or 1300 was the setting for this engine off hand). Is this the normal idle speed, or is this just what the preset is supposed to do? 

 

I don't have a tach to use anymore. Any suggestions on a tach would be helpful. Also I need to know where to hook it up. 

 

Kraig



#2 MiCarl ONLINE  

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Posted November 06, 2016 - 09:38 PM

If a motorcycle engine were doing that I'd assume it's running lean.  Most likely from an intake air leak.


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#3 ol' stonebreaker OFFLINE  

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Posted November 06, 2016 - 10:27 PM

  I agree it has an intake leak or it's running rich when cold and after it warms up it makes the engine seeit as a leaner mixture. My HF phototach I've had for several yrs has served me well and is accurate when checked against an electric motor shaft.

                                                     Mike


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#4 boyscout862 ONLINE  

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Posted November 06, 2016 - 10:40 PM

It does sound like a vacuum leak. Check the bolts for carb to maifold and manifold to block. The B & S manual has a "Trouble Shooting" guide which can help diagnose the problem. Good Luck, Rick
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#5 EricFromPa ONLINE  

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Posted November 07, 2016 - 12:40 AM

Does that a 2 piece intake manifold like my old MW 16 hydro? Mine was leaking,had to split it apart and clean it up and seal it up.I used Honda Bond HT on mine.The gray stuff.I had some leftover from when I did the rear main,oil pan gasket and rocker tube O-ring replacement on our 94 Honda accord.I like the stuff.It sets up harder than permatex gasket maker and seems to last alot longer.

 

 

Did the same thing with the Briggs opposed twin in my Cub Cadet 582 when I tore it apart a couple weeks ago to rebuild the carb,fuel pump and replace the Breather assembly gaskets a couple weeks ago.It also has a 2 piece intake manifold.

 

3.163 hours on a briggs opposed twin and it actually runs really good.Slight bit of blow-by till it warms up but it doesn't smoke and has good power.

I'm getting another engine for it here in a couple days but it's going to get cleaned up and put on the shelf till it Needs it.


Edited by EricFromPa, November 07, 2016 - 12:40 AM.

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#6 GilsonRider OFFLINE  

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Posted November 07, 2016 - 05:35 PM

Does that a 2 piece intake manifold like my old MW 16 hydro? Mine was leaking,had to split it apart and clean it up and seal it up.I used Honda Bond HT on mine.The gray stuff.I had some leftover from when I did the rear main,oil pan gasket and rocker tube O-ring replacement on our 94 Honda accord.I like the stuff.It sets up harder than permatex gasket maker and seems to last alot longer.

 

 

Did the same thing with the Briggs opposed twin in my Cub Cadet 582 when I tore it apart a couple weeks ago to rebuild the carb,fuel pump and replace the Breather assembly gaskets a couple weeks ago.It also has a 2 piece intake manifold.

 

3.163 hours on a briggs opposed twin and it actually runs really good.Slight bit of blow-by till it warms up but it doesn't smoke and has good power.

I'm getting another engine for it here in a couple days but it's going to get cleaned up and put on the shelf till it Needs it.

I don't know if it's a 2 piece. I'll dig in to it tomorrow. I was leaning toward a vac leak too. I'll spray some carb cleaner around the gaskets when running to see if the speed changes. 






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