# Briggs and straton motor



## shaneallen (Jun 11, 2012)

_*I have what i believe is a 14.5hp (briggs and straton motor*_) _*and when i turn the key to start all it does is continuously crank over with no starting and if i do that long enough it will backfire so dam loud that it sounds like a 45 was just fired next to my ear...i know the timing is correct because i timed it by linning up the two marks and then after putting it back together i adjusted the valves (although i think i might have to do it again dont think i quite got it right)........is there any chance that the govenor could have gotten screwed up or maybe something with the carburator....i am hopping that it is something quick easy and simple that i missed i really like the gears and trans on this mower...please help!!!!!!!!!!*_


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## MrChooks (Apr 19, 2008)

Sounds like a timing / ignition timing issue to me. If you are sure that the cam shaft / valve timing is correct - look to see if the flywheel key is good and that the flywheel is exactly where it should be. 

In the end if an engine has fuel, spark and correct timing - IT MUST START - The loud back fire would indicate you are getting fuel - so I would look for a spark or timing issue


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## shaneallen (Jun 11, 2012)

i found out that i keep breaking the damn flywheel key...why??????????i dont understand why that keeps happening


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## MrChooks (Apr 19, 2008)

shaneallen:
Your question is timely as I have just been thru a big problem with a sheared flywheel key - see thread "Tecumseh HM80 Flywheel Key Sheared" and the text of how to successfully replace flywheel key below.

My guess is you haven't got a good fit between the flywheel & crankshaft - pay particular attention to items 4 , 5 & 6 below. A really good mating fit and absolute cleanliness of the shaft taper and flywheel taper are critical.

If you have a good fit and the key is snug in its keyway - the flywheel will not move and you will stop shearing flywheel woodruff keys - see how you go with it




Re: Tecumseh HM80 Flywheel Key Sheared 

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OK - BG, K2S, Wrench & SABL - As I mentioned in my earlier post & in case these steps might help others - Here is a distillation of all the very welcome tips and advice I received from you all of what I did once I got the flywheel free.


1 Recover the broken piece of woodruff key from the flywheel and set aside
2 Using a pin punch with slightly smaller diameter than the key thickness – tap out the remaining sheared off piece of woodruff key from crankshaft. Don’t use a screwdriver or cold chisel as it is very important that the woodruff keyways are clear, burr free and undamaged
3 Fit the 2 broken pieces of key back together the correct way round and stick them down on to a piece of sticky tape – this allows you to take the broken key and flywheel to the mower shop to get an exact replacement key – (They are so cheap I bought 2 – so I would have a spare)
4 The woodruff key is a slight interference fit in the crankshaft and a sliding fit in the flywheel keyway, so the keyways need to be perfectly clear and clean before installing a new key – Using a small, sharp flat needle file – carefully dress any burs and broken key remnants from edges of the crankshaft keyway and make sure that the new key will slide nicely along the flywheel keyway.
5. As the crankshaft / flywheel woodruff key is positive and accurate locating devise and NOT a power transmission devise – it is critical that the taper fit between the crankshaft and flywheel is as near perfect as possible. 
So, this is probably the most important step in the process. Using #1 cut / coarse lapping compound, lap the taper of the flywheel and crankshaft together until they are clean and without any ridges whatsoever. If there are a few minor gouge marks from the damaged key moving on the taper that’s not a concern – it’s the ridges that must be completely removed to ensure a tight taper fit.
6. Thoroughly wash all the remnant grinding compound from the tapers on crank and inside the flywheel with diesel or kerosene and use an old toothbrush to scrub away all remaining grinding compound until it is spotlessly clean & dry.
7. A very fine film of grease or “Neversieze” applied to the new woodruff key makes it easier to install and remove if it needs replacing again at some point in the future. The important point is that no grease or Neverseize finds its way onto the taper fit – as you need a tight interference fit between the male and female tapers and any lubricant on the tapers can allow the shaft to slip and the key will shear all over again.
8. Using a small hammer – tap the new key carefully into position in its keyway ensuring that it is all the way home and centered in its half moon cut keyway.
9. If the new woodruff key is properly home in its place on the crnkshaft – the flywheel will slide easily back onto the crankshaft and slide virtually all the way home without any force. Once in place, pull the flywheel home using its retaining nut and just nip up to tight then remove the retaining nut again and inspect the final position of the flywheel to ensure that it has engaged the crankshaft taper over its full length.
10. Once satisfied the flywheel is fully home, reinstall the retaining nut, lock washers etc and torque up tight and it’s all done- now you just have to put all the cowls, linkages and fuel lines back and job’s finished.


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## Basementgeek (Feb 7, 2005)

Are you torqueing the flywheel down? What is the model number off the engine?

BG


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