# 6.5 BS Won't start when hot



## cooper4x4 (Aug 17, 2008)

I have a craftsman mower with a Briggs and Stratton 6.5 hp motor (model #917-388950). It will not start once it get hot. It will start on one pull when cold but if I stop it to empty the bag, it is impossible to restart it without waiting a few hours. I have replaced the spark plug gapped to .030, replaced the coil and spark plug wire and replaced the air filter. the carbuerator bowl looked clean. any suggestions on how to fix this problem? Thanks.


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## 30yearTech (Sep 14, 2006)

Check for ignition spark when it's hot. If you have no spark then you may need a new CDI. You should also check the engine control cable and make sure it's disengaging the kill switch.


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## cooper4x4 (Aug 17, 2008)

what is a CDI?


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## dawgpile (Apr 28, 2008)

I suspect you may have a problem with the autochoke sytem on this engine. Pretty sure it's a B&S Quantum engine and you should make sure it's all there(sometimes the return spring comes off). I'm not exactly sure what the temperature compensation mechanism is with this setup as my newest B&S repair manual is at home and I'm not!

Problems with hot restart on engines with this style carb are often related to the autochoke. IOW, the engine is still fully choked when hot and is a you-know-what to start. I'll see about checking in my manual tonight when I get home.

BTW, you can go to the B&S site for a better parts list than the sears site. The B&S # is model 123K02, type 0541.

Let us know if you find out anything else!


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## dawgpile (Apr 28, 2008)

I looked at my manual at home and unfortunately it's not new enough to cover the autochoke system of this type, so I have no 'pearls of B&S wisdom' to share from it. However, I suggest you download the IPL from B&S and look at page 4, on the right side, half way down the page. Item 1386 is the airvane, 1387 is the spring I was referring to(make sure it's there and connected!), and finally item 291 is the thermostat. This is what controls the choke position based on engine temp and what I suspect is your problem. I'd consider replacing this to start with. It's around $15-$20. (this assumes of course you verified that you still have spark when it's hot!)

BTW, when 30YT mentioned CDI, that stands for Capacitive Discharge Ignition. That's a fancy acronym for the ignition 'module'.

Let us know how you make out!


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## cooper4x4 (Aug 17, 2008)

I will check our the return spring and thermostat. 

What would cause it not to have spark when it is hot? the whole ignition system has been replaced.


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## dawgpile (Apr 28, 2008)

While not very frequent, you can have a defective 'new' part such as the ignition module you replaced. Not likely, but it's always good to be sure by checking for spark when you try and restart hot! A 'gap type' ignition tester is an invaluable and inexpensive tool to have in your bag of tricks for small engine repair. This way you can be sure, and be able to eliminate ignition as the source of the problem. Cheap insurance!

Keep us posted!


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## 30yearTech (Sep 14, 2006)

cooper4x4 said:


> I will check our the return spring and thermostat.
> 
> What would cause it not to have spark when it is hot? the whole ignition system has been replaced.


If you are in fact loosing spark, be sure to isolate the ignition module from the kill switch by disconnecting the kill switch lead wire when you test for spark, and using a spark tester such as dawgpile suggests.

There is always the possibility that a no spark issue can be caused by a problem with the kill switch, kill switch lead wire, or the engine control cable.


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