# Briggs 6.5 Intek I/C - No Spark. New magneto, still no spark. Confused!!



## Desert Tripper (Jan 10, 2006)

Hi, Glad to see a good 4-cycle small-engine forum! I do pretty much all my small engine repairs so it's good to have a place to get help once in a while.

Like now! I picked up an (almost) brand new MTD chipper/shredder with a Briggs Model 121312 "Intek 6.5 I/C" at a fleamarket. Price was cheap, but the engine had thrown the rod. I thought it would be a fun project so I bought the thing. A local Briggs dealer had a rod and explained the little "trick" of using Drano to clean the old metal from the crank. I got everything clean, torqued everything to specs, patched up the hole in the side of the crankcase with a piece of soda can and a liberal application of JB Weld, put everything back together and it ran great! (How a BRAND NEW engine would throw a rod is still a mystery to me. The chipper showed no sign of use when I bought it.)  

However, about 10 hours of use later, the engine became harder to start and at times would spontaneously stop at no load (but start right up again). As luck would have it, when I just had about an hour's worth of chipping to do, it refused to start 20 minutes after I stopped it to take a break. Puzzled, I removed the spark plug and tried the usual spark tests. No spark! I removed the kill wire from the magneto coil. Still no spark. Magnets in the flywheel were in position and super strong. So, bad magneto!

Or, so I thought. After forking over $30 and change and waiting a couple weeks for a new magneto, I eagerly installed it according to directions provided in the box, using the instruction card as a gauge. Pulled the cord and... guess what? STILL no spark!  

I am now at wit's end. I thought no spark on a small engine with pointless ignition was pretty much elementary. Spark plug, plug wire, kill switch, magnet, magneto. Replacement magneto bad? Possible, but I imagine Briggs tests electrical parts before selling. Any tried and true resistance checks for a pointless magneto? I get readings to ground of 1 ohm (from kill switch terminal) and 4.6K ohms (from spark plug wire) on the new magneto. The old one measures almost the same (only difference is the kill switch measures .9 ohm instead of 1 ohm - almost negligible for anything electronic I've worked on before.)

The ONLY other thing that could potentially be a problem is that I noticed a very small amount of play in the flywheel end of the crankshaft. Not much - it only opens the magneto/flywheel gap from .010 to about .025 - and that is when the magnets are on the opposite side from the magneto armature. Could that little play make the difference between go and no go? I seem to recall the crankshaft bearings being sleeve bearings - I wonder if replacing them with roller bearings would be prudent (or possible on this model). 

I would greatly appreciate any suggestions and/or guidance!

Doug in San Bernardino, CA


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## rake60 (Oct 13, 2005)

The Briggs manual says the armature air gap should be .006 - .010
That very well could be your problem. Have you checked the magneto and PTO bearings for wear? They should be .873 for the mag end and 1.060 for the PTO end.
The reject sizes are .878 and 1.065, so if they are worn .005 or more they are shot.
Some can be replaced, but in some designs you'd have to replace the case.

Rick


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## rake60 (Oct 13, 2005)

*Wait a minute!*
You patched a hole in the in the side of the crankcase????
When an aluminum block is hit hard enough to break a hole, it often creates stress cracks in other areas that may not be easily seen. That engine block could be flexing or the bearings may be out of alignment to cause your run out, and could very well come apart on you.
*I would NOT run it!*


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## Desert Tripper (Jan 10, 2006)

Thanks for the insight, Rick. I guess a new block would be worthwhile for the peace of mind (and solve my magneto problem at the same time.) One of the online parts places sells a block for around $100 so it would still be a significant savings over $400 for a brand new engine. Just a lot of work to pretty much build the engine from scratch! So, now at least I have a direction to move towards for my winter project. Just hope the trees don't grow too fast in the meantime!! (grin)


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## bugman (Aug 12, 2004)

there was metal on the crank? guy probablly forgot the oil...... i knew a guy who would patch holes in the block with jbweld(as long as it was not a important stress point/area) said they would do great, he raced em..... briggs blocks are strong, though a new block would throw out worries, you'll have a new engine, be sure to make sure the piston isn't scared bad, nor the rings. i hope you didn't throw the old coil away......keep it as a spare.....


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## rake60 (Oct 13, 2005)

bugman
I also know a guy who decided to patch a hole in a Briggs block.
It went off like a grenade behind his 9 year old daughter on a go kart.
When I get any engine in that has broken a rod that show no obvious damage I'll 
Dy-Check them for cracks before ordering repair parts. 50% of them will have cracks that can only be seen with the Dy-Check penetrant. I maintain NOBODY should repair a damaged block. The cost of an off the shelf engine is not worth the risk of personal injury or worse.

Rick


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## William Fulghum (Jan 20, 2006)

Dear Tripper, 
Your post greatly interests me. I have had the exact experience with 6.5 HP B&S with magnito. Replaced old one with new and still no spark. Was flywheel clearance your problem? Were you ever successful in getting it running? Any help would be welcome.


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## bugman (Aug 12, 2004)

did you try it without the kill switch? and gap it correctly? i'm sure you didn't have the exact same problem, of it having thrown a rod. or did it?


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## albert (Jan 15, 2006)

hey doug try checking the key in yuor fly wheel


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## bbnissan (Nov 7, 2004)

rake60 said:


> bugman
> I also know a guy who decided to patch a hole in a Briggs block.
> It went off like a grenade behind his 9 year old daughter on a go kart.
> When I get any engine in that has broken a rod that show no obvious damage I'll
> ...


This is a very good point, but in my experience most of the engine blocks that get a hole due to a broken rod experience a rupture failure rather than a fracture failure. In other words, very rarely have I seen a hole in the block cause a crack to propogate. Also, you can stop the propogation of a crack by simply drilling a hole through the tip of the crack. This completely removes the stress raisier in the metal and will not allow the crack to propogate further.

If you want to repair a cast aluminum engine block, I recommend patching it in the same manner it's made....by casting a patch into the hole. I've done this before by first cleaning up the inside and outside of the block, then grinding away the edges of the hole to reveal fresh metal. After that you pack a sand/clay mixture into the inside of the block behind the hole, heat it up good with a torch, then pour a shot of molten aluminum into the hole until it fills up. When the aluminum cools off, you just stress relieve it by heating the patch and the area around the patch with a torch until it is good and warm then allow it to cool again and grind everything smooth.

Keep in mind that ifyou use this method, you should re-check the block for cracks using dye and recheck all the clearances and alignments to make sure the block didn't warp. Also, I wouldn't recommend repairing a block unless the hole is in a area where there are no major load bearing members.


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## rake60 (Oct 13, 2005)

I don't want to beat this to death, But..........
What is a non-stress area of an engine block? A small engine block is basically a thin wall aluminum box designed to support and contain a crankshaft that is spinning at 3600 RPM Any time there is a weak area, the load has to be carried by another area. At some point the threshold of design capacity is going to be exceeded. When they come apart it's not pretty! We're not talking about a million dollar casting here. For the cost verses possible hazards is it worth patching?


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## bbnissan (Nov 7, 2004)

rake60 said:


> I don't want to beat this to death, But..........
> What is a non-stress area of an engine block? A small engine block is basically a thin wall aluminum box designed to support and contain a crankshaft that is spinning at 3600 RPM Any time there is a weak area, the load has to be carried by another area. At some point the threshold of design capacity is going to be exceeded. When they come apart it's not pretty! We're not talking about a million dollar casting here. For the cost verses possible hazards is it worth patching?


I never said non-stress areas...you can generate a stress anywhere in the engine block just by imposing a load of any kind on it. What I said was a major load bearing member. What I mean is an area where there is a rib, pad, or bearing area built up in the casting. A non load bearing member would be the very thin areas of the casting between the ribs and bearing areas...these are the areas that only serve to hold the oil in the engine. Technically, these areas could be removed and the structural integrity of the engine block would still be intact.

I don't want to knock you here, but I've never seen an engine "grenade" before. Even on motors that were ran for long periods of time out of balance (because of a bent crankshaft) the engine never blew apart even after the oil seal finally gave out and the engine threw the rod. I've also seen high performance "tractor pulling" lawnmower engines that run up to 50hp that have come apart...the only thing that worries me on these engines is the flywheel.


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