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briggs crank


l.mitchell's Avatar
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07-28-05, 07:46 PM   #1  
briggs crank

i have an 8hp briggs model 190702 3by1 crank that sits on a rear engine snapper mower. the rod broke. i took block to repair shop to see if it was worth putting back together. rings were said to be good as well as cylinder and piston. crank was microned? and said to be within range. i put back together and it smoked out the neighborhood. i took it apart and found scored cylinder and piston which repair shop thought was caused by bad rings which i was told were good earlier. they now said it was unrepairable. so i spent the last several weeks looking for a good briggs 8 hp. i finally found one locally of all things. it was 190702 but with a short 7/8 step down crank. the old timer i bought it from saidput my old 3by1 crank in it, so i did. the newer 1988 engine good with no noise before i put my crank in it. with my 3by1 crank in it it sounds like a rod knocking. i put in according to specs. i called the old timer and he says the rod may need filing. i dont want to run this good engine with a rod knock and end up where i started. can anyone recall past similar experiences and possible remedies? thank you.

 
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cheese's Avatar
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07-28-05, 10:55 PM   #2  
I'd take it back apart and check the rod clearance. The rod in the engine was seated to the old crank journal. Now, you have a different crank in it and it has to wear to fit that journal. Chances are, the rod is just worn out, and I would replace it.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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07-29-05, 10:59 PM   #3  
the old timer filed down the rod. it seemed to help but didnot cause knocking to stop. i then took the new rod and put into engine. i wont know till tomorrow if this stops the knock. i can say the new rod is much tighter and there seems to be less play meaning when you turn the crankthe piston almost immediately turns whereas with the old rod the piston would not turn immediately and would jump about 1/8in. before it would turn. after he filed rod cap piston had about 1/16 in. play. the new rod cap would not even fit on old rod. the new rod cap was skinnier. old timer thinks briggs may have made 2 types of rods for 8hp or this replacement rod was made undersized to account for crank wear. the 3by1 crank i put in this engine does look a little smaller around the place where the rod bolts onto than the original crank which did not knock a 2in. 7/8 stepdown. the filing did diminish the knock almost non existent at high speed but noticeable at lower speed. any way i didnt want to take a chance with this good engine so i put the new rod in. i mowed last year with a 3.5 hp briggs with a rod knock and it made it to sept before breaking. when i took the engine apart the block was ruined. that is why i am going through extraordinary lengths to make sure i dont ruin this engine. any comments would be greatly appreciated.

 
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08-01-05, 12:43 AM   #4  
You're doing the right thing here. Filing the rod is not an acceptable repair. (which is why I reccomended replacing it).

The rod is not oversized unless you ordered an oversized rod. If you did, then it wouldn't fit the crank journal unless it was ground. Sounds like you just got a new rod, one that fits like it should. Let us know how it turns out!


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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08-01-05, 01:09 PM   #5  
after installing new rod, i noticed minor engine noise on occassion at low speed. i called the old timer and asked him to listen to the engine over the phone. he said he thought it would be ok. i mowed with it 9 times covering half hour to 1 hour about 6-7 hrs. total at half throttle. there is no noise under load but occasionally there is a little noise at low idle that seems to improve each time it has been run. there is an occasional puff of gray smoke from the exhaust and it uses a little oil but the oil is still relatively clean for 7 hrs. use in dusty conditons. when the old rod broke aluminum stuck to the crank. i sanded off aluminum but had left some on when i had it microned. he microned it saying it was .001 to .002 to the good. he said get the rest of that aluminum off of there. he told me to buy emery cloth and and use it like a shoe shine. ibought extra fine emery cloth and took all the aluminum off but stopped when the crank was shiny like new. the new rod is from the old engine that went bad (scored). i had just bought that rod new and it did not make any noise when attached to this crankshaft when in the old engine block.

 
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