# Briggs and Stratten engine .



## rickyjoseph701 (Oct 18, 2012)

I have a 21 hp oOHV/ic twin (model 4025A7) on a riding mower . My problem is that the engine turns over but it will try to start It has spark , getting fuel . The flywheel is spinning but it will not "kick in " to start . Any Ideas ????:wave:


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## Sir Thomas (Dec 7, 2013)

rickyjoseph701 said:


> I have a 21 hp oOHV/ic twin (model 4025A7) on a riding mower . My problem is that the engine turns over but it will try to start It has spark , getting fuel . The flywheel is spinning but it will not "kick in " to start . Any Ideas ????:wave:


Check and see if the key on the flywheel is intact. Are you feeling any puffs from the muffler when you crank it? I'm assuming this has an electric start. What condition is the sparkplug when you take it out after trying to start it. If it's soaking wet could be flooding.


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## rickyjoseph701 (Oct 18, 2012)

flywheel is intact the plugs are dry after cranking the engine . At times there appears to be a puff of smoke coming from exhaust .


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## Sir Thomas (Dec 7, 2013)

rickyjoseph701 said:


> flywheel is intact the plugs are dry after cranking the engine . At times there appears to be a puff of smoke coming from exhaust .


Do you have any carb cleaner? If you do, spray some into the carburator. If it doesn't fire try spraying some into the sparkplug hole.
Sometimes the ignition chamber gets too much fuel but a dry plug, if it is not firing indicates not enough.


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## rickyjoseph701 (Oct 18, 2012)

I sprayed carb cleaner in spark plug holes, replaced plugs and it still doesn't start or pop or nothing just cranks . Would compression have anything to do with this issue ??? and what should the compression be ?


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## Sir Thomas (Dec 7, 2013)

rickyjoseph701 said:


> I sprayed carb cleaner in spark plug holes, replaced plugs and it still doesn't start or pop or nothing just cranks . Would compression have anything to do with this issue ??? and what should the compression be ?


I have to check with a friend of mine on the compression. How old is the machine? Have you taken the flywheel off to see if there are contacts? Also is there a kill switch on it.

I wouldn't try it with the electric start but if you can turn it by hand, put your thumb on the sparkplug hole. You should feel suction. If you do, then I don't think compression is the problem.

I'm just guessing at a bunch of things to look at. I've never worked with a OHV or twin engine.

Open the valve cover and see if the clearance is correct. 

I don't think you have given the complete engine number. The format is described on this link. Then you can look for the specs.
https://www.briggsandstratton.com/~/media/Files/BriggsandStratton/NumericalDesignationSystem.pdf


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## rickyjoseph701 (Oct 18, 2012)

when I put my thumb over the plug holes , and turn by hand , there is a small suction. you mentioned something about a kill switch , where is that located ?? That is the correct model number that I gave in this thread.


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## 30yearTech (Sep 14, 2006)

How did you test for spark? 

When was the last time you ran this engine?

You may want to try priming through the carburetor to see if it will kick over and burn off the prime, I would suspect a carburetor issue if the plugs were dry after attempting to start. This engine shows to have an after fire solenoid on the carburetor, so if it's been sitting up for awhile, the solenoid valve could be stuck closed.


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## rickyjoseph701 (Oct 18, 2012)

H tested got spark with a spark tester.I tried the priming method that you suggested and it will not do anything but crank over.I removed the carb bowl and found the after fire solenoid,is there a way to test that??I was told this engine was running a couple of weeks ago.Could it somehow jumped time and is the cause of this????


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## rickyjoseph701 (Oct 18, 2012)

H tested got spark with a spark tester.I tried the priming method that you suggested and it will not do anything but crank over.I removed the carb bowl and found the after fire solenoid,is there a way to test that??I was told this engine was running a couple of weeks ago.Could it somehow jumped time and is the cause of this????


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## 30yearTech (Sep 14, 2006)

Not likely the engine jumped time, did you use a gap type spark tester or an inductive type tester? You can test the after fire solenoid, by simply plugging it in and turning the key on. When it's energized it should pull down the plunger, with the key off it should raise back up.


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## rickyjoseph701 (Oct 18, 2012)

used the gap spark tester. I also found the pigtail wiring to the anti spark resister was melted a little causing a short , Would that cause the motor to not start ???


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## 30yearTech (Sep 14, 2006)

If the after fire solenoid is not working, the engine will not run as fuel cannot flow through the nozzle. This will have no effect on starting the engine with a prime, it just will not stay running.


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## G-Mann (Dec 29, 2007)

I know you said you tested spark by I assume, a spark "gap" tester. That means the coil & other related components are good. Try a (NEW) spark plug! It is quite common for faulty spark plugs not to produce spark under compression.


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