Briggs 5 hp no go

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  #1  
Old 06-28-07, 01:46 AM
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Briggs 5 hp no go

Hi, I have a B&S 5hp - mod. 130902, type 062501, code 79102406 on a "Rover Mower" brand chipper mod 95213.
Have been asked to try and get it started by an old bloke that says that it run out of petrol and now will not start.
Have adjusted the points and magneto gaps (20 thou and match book as air gap on magneto) and have GOOD blue spark. It will not fire - even with fuel sprayed directly into the carby - it actually backfires through the carby, a lovely flame. The flywheel key (so I'm finding out from the owner) has been changed - the straight aluminium key in it at the moment has a '6' or possibly a '9' stamped into it. Is this the right key, or did they sometimes have a "stepped" key that would alter the timing? Am I on the right track? It has a carby that is mounted on the tank and all the diaphragms and pickups seem fine (sucking and blowing)and all the manifold seals etc. are good. It seems like timing to me.....thanks (an excellent forum by the way)
 
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Old 06-28-07, 02:22 AM
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Here in the States a standard Briggs flywheel key has no numbering system, it merely has the Briggs diamond logo stamped into it. I've seen aftermarket keys like such but are intended for racing kart engines to alter the timing. If this is a stock Briggs engine and he has installed an offset key I'd say you need to go with a stock, standard key, Briggs part number 222698S. Also, it is important to be sure the flywheel nut (starter clutch) is torqued properly to 55 foot pounds (or your metric equivalent) so that you don't chance a sheared key. Was the key indeed straight and not offset? If you did not torque the flywheel nut you may now have a sheared key and this would explain the apparent timing issue. If you have a straight key and you reinspect it and it is not sheared and you still have the trouble you have then I'd be concerned with a possible valve issue affecting the compression and would recommend checking the valve clearances. The intake valve should have .006" (.1524mm) and the exhaust valve will be .010" (.2540mm). If either are off, I'd say the intake valve is off, with no clearance, since you have blowby through the carburetor. By the way, the .020" and the matchbook cover for settings on the points and coil, respectively, are good.
 
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Old 06-28-07, 10:18 PM
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Sounds to me like the intake valve is stuck open.
 
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Old 06-28-07, 11:30 PM
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Briggs 5 hp No go

Thanks Cheese and Puey61 - I will check both these scenarios you have mentioned in daylight over here - (Adelaide, South Australia) - I haven't looked as yet, but don't recall seeing an obvious valve adjustment. Where would the adjustment be made?
The original flywheel key was apparently "twisted" (appeared to him distorted) - the words the owner used.
I really appreciate the feedback, you blokes are great. - Thanks.
 
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Old 06-29-07, 02:37 AM
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With a "twisted" flywheel key, you will have an ignition timing issue and could explain your trouble. And, again, be sure to torque the flywheel nut properly if you remove the flywheel in order to replace the key. I don't know what style muffler you may have but it may be in the way of the valve cover/crankcase breather. Just to the right of the muffler mount point you will see a rectangular shaped cover (about half the size of a credit card) that has a tube running from it to the carburetor through the flywheel shroud. This is the breather assembly and must be removed to check the valve clearances. You can only CHECK the clearances here, if you need to make any adjustments to the clearances you must remove the cylinder head and remove each valve in order to grind the valve stem to increase your clearance. If you determine you have an issue with the clearances and therefore must remove the cylinder head the valve cover gasket is part number 27549S and the head gasket is part number 272157S and the head torque will be 160 inch pounds. Good luck and keep us updated on your progress.
 
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Old 06-30-07, 01:32 AM
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Yep, that distorted key could be the "key" to your troubles .
 
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