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Simplicity Rider....

Ken S.'s Avatar
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09-18-01, 04:52 PM   #1  
Ken S.
My Simplicity (10HP Briggs&Stratton) riding mower will not cold start on choke but rather toward the lower end of the throttle range. The engine starts by chugging slowly until it picks up RPM and then appears to run fine. During normal cutting conditions the engine sometimes surges. Any suggestions on how to correct these two problems?

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Frosty's Avatar
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09-18-01, 06:52 PM   #2  
Hi Ken S.,

Did the mower always need the use of the choke to start cold? Is your air filter clean? Does is only occur on hot days?(air density does play a role in the need for the use of a choke)

We're most likely talking about an Air Restriction on startup.

My advice is to FIRST clean and re-oil your Air Filter, or replace if you have a paper filter. This should fix your not needing the choke during a cold start.

(SECOND, try this only if the first did not work...)
Although unlikely, your problem may also be too much fuel and not enough air during a cold start with the choke on. This is essentially drowning the engine. Therefore you're having to crack the throttle allowing more air to mix with the fuel to get it to combust. Because as I'm sure you know, fire needs oxygen(air) to burn. The only cause i can think of, aside from a clogged air filter, is that maybe your mixture adjusting screw was perhaps bumped(loosened), which would explain the need for more oxygen at startup. If it was loosed, your getting to much gas with the choke on. You can try adjusting the mixture screw if you want(i.e.-tightening it), BUT YOU STATED THAT THE ENGINE DOES START AND THEN DOES RUN FINE. Therefore, I wouldn't try this option if all the more starting is requiring you to do is crack the throttle.

As for the surges during normally operation, I would make sure governor linkages are all intact and working properly.

Good luck and hope this helps.

Wow, i better call my publisher and find out about this book i just wrote.

Fisher's Avatar
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09-19-01, 09:03 AM   #3  
Sounds like an older engine with points. But leaky
valves can give you similar symptoms. Post your
engine's model numbers so we know what you have,
and check the spark with a new plug. If it is
bright white/blue, the points are probably OK.

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09-19-01, 03:50 PM   #4  
Hello Ken S

A surging engine or one that starts as you discribed, often has a lean fuel mixture. This may be do to a fuel restriction within the carbs low speed fuel system.

The engine is actually attempt to start with only the high speed fuel flow. In this type of situation, the engine will gather low speed slowly but will run at high speed.

Low compression with also cause the same cold starting conditions you discribed. Once warmed up, the internal parts expand slightly and help raise the compression slightly.

Post more specific engine information using the reply button and the forum will then be better able to assist you.


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09-19-01, 04:40 PM   #5  
Before you get too involved, check to make sure the carburetor is actually choking all the way. It sounds like the throttle cable may have slipped out of adjustment and is not fully engaging the choke. Look into the throat of the carburetor when the choke is on and see if the choke plate is completely closed. Good luck!

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09-19-01, 04:41 PM   #6  
also, as for the surging, there is a screw at the bottom of the carburetor, under the bowl. Loosen it about 1/2 turn and see if that stops the surge.

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