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pds00

7013 Briggs 30 cu in rebuild

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pds00
I'm going to sell my 7013 this spring. I checked the compression and thought that it was low (80 psi)so i'd just rebuild it. I've gotten the motor half apart and just found out that piston kits are Not available. 299716, 717, 718 are the part numbers for .10 .20 .30 over. What i'm looking for is any info on where someone has a stock pile of these and wants to sell one. I'm also looking into possibly boring it out to a 32 cu in making it a 16 hp. Not sure how all the pieces will line up but the crank is the only part with a different # between the two. I'm looking for some advice on where to go.

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JimDk
Brian, Was your engine smoking and low on power? 80# is not that bad for these old engines. There is a decompression bump on the cam which makes it hard to do a compression test. If your rod and piston is decent, you probably could get by with new rings. I recently bought a set of standard rings for my 12hp. from Sandy Lake Implement, one of the site sponsers. As to boring out to 32CI, I would be interested to know the results if you do that. I did a little checking with a small engine machinist. He thought it could be done if the block had enough meat. I think the only difference in the cranks is the position of the balance gear. The 30CI has the gear on the PTO end and the 32CI is on the flywheel end.

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dynodave
The problem of piston availabiliity somewhat discussed here: http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=115581 I had a shop in NE Ohio say he could get me a +10 piston for $120+shipping...sorry not me If pistons are not available from Briggs OR aftermarket either then I may get some made, +20 +40 +60 +80 etc.... Rings are listed at Hastings. But I have not tried to order some +10 or bigger.... I do believe you could bore the 30 3-7/16" out +125 to a std 32cid 326431 3-9/16". I found std +10 and +20 and now have one of each for the 32cid.

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pds00
There wqs a grove in the bore so I'm assuming a ring is broke. It was hard to start and the only way it would run is with the main jet needle 3 .25 turns out. I knew something was wrong so that's why I took it apart. The bore is past its limit so rings will not work. I'm leaning to boring it out cause I can't find the 10 over. I'll repost with the results. Thanks for all the info.

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HubbardRA
If you bore to the 16 Hp bore and install a 16 Hp piston, the engine will not be balanced anymore. The reason that the cranks carry different numbers is most likely because the one in a 12 Hp has the counterweight ground down to match the lighter 12 Hp piston. With the heavier 16 Hp piston you will either need a 16 Hp crank with the heavier counterweight or you will have to weld on additional weight to 12 Hp crank to make up the difference.

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powerking_one
Rod, Actually the 30 C.I engine and 32 C.I. engines carry the same PN crankshafts; I have done the parts lookups for the variations thereof of these engines. The biggest differences are the main bearing pilot milled area on the PTO end for whether they have the front/PTO counter balancer or not. They all use the same connecting rod PN's too. Case in point for example; the 14HP rated 320431 series uses the same piston assy as the 325431 and 32643x 16HP engines. Therefore, the net weight of pistons whether 12/13 HP versions or the 14,15,16 HP versions should be the same. Tom (PK)

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sovereign72
The pistons will weigh alittle different but the difference in the engine balance will be minor. Piston weights really start to matter more when there are two or more pistons in the engine. If you want everything to be perfect the easiest thing to do is lighten the larger piston by removing metal in non critical areas until the two pistons match weight. If it were me I would just assemble it anyway and not worry about it. the 10hp isnt even balanced and they run well.

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HubbardRA
The 10 Hp engine is definitely balanced. I am talking about balancing the counterweight throw on the crank to the piston. The synchrobalance weights that are used on the larger engines are designed to remove harmonic imbalances, not the first order balance of the engine. You can run one without the synchrobalance weights and it will not cause an engine problem only driver discomfort, but if you have an imbalance between the piston and crank this will eventually fatigue the crankshaft and cause failure.

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sovereign72
I am aware of that, the counter weights of the crank offset the weight and force applied by the piston and rod in motion. It seemed the main point of contention came down to piston weight and my point is it doesnt matter. When a person bores a block and installs a .20 over piston they dont go back and rebalance the crank or lighten the new piston except in 7000rpm plus racing engines. I would be willing to bet nobody has even bothered to note the weight difference between the stock briggs pistons available versus the aftermarket ones of the same size, furthermore in all the years I built racing engines (12 to be exact I used alot of different pistons of different sizes and vastly differnent weights, im talking hundreds of grams of weight difference between an old Speeed Pro eyebrow flattop and a JE or Mahle piston all attached to the same SBC crank with the stock balance. If I remember right my machinist recomended that in multi piston engines the weight difference between any two pistons in the rotating assembly needed to be +or- 10 grams to maintain factory balance and we maintianed + or - 3 grams on the racing engines I did all the. however on a single cylinder engine with the same crank the and same rod the piston weight does not ammount to a hill of beans, especially only running up to 3500rpm. The weak link on these cast iron motors is not the crank, it is the aluminum connecting rod. If one these cranks fails before the aluminum connecting rod or the piston I will eat my hat.

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mroman59
Are you sure it's not worth repowering? Do you have attachments that you use that will be expensive to get with a new tractor? Below is a link to one place that will have engine ready to drop in. They give warranty and support for installation. http://www.smallenginewarehouse.com/RepowerItems.asp?Brand=Simplicity&Model=7013 Yes, I know ... the cost of the engine alone may make you think about putting that money towards a new tractor.

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pds00
i installed a 32 cu crank, connecting rod with my piston and everything seemed to move like it should. i was concerned with the piston height at tdc and piston geometry. i'm not using the crank but wanted to make sure there wasn't a difference. i'm going to do a little more measuring but i think i'm gonna go with the the 32 cu in piston. whats the worst that can happen?

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jasper
Well I am glad you ask ("Whats the worst that can happen"). You could cause a major harmonic in the second order causing the crank to fracture or the flywheel to crack, maybe even fly apart, but it is not like your foot and ankle are sitting right next to the flywheel!....Wait a minute I think they are! Lol All joking aside, Sovereign72 is probably right. The weight will probably not be significant but to be on the safe side I think I would weigh the rings, rod, wrist pin and piston to see what the difference was then remove the appropriate amount of weight from the piston. If you decide to go this route be anal about the measuring, to light is just as bad as to heavy! I took a quick look at the block and would think there is enough meat to bore it .125 without a problem but only time will tell!

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HubbardRA
The 12 Hp engine "can" be bored out to use a 16 Hp piston. I have a friend who did it for a pulling tractor. I am not sure what he did about balancing on the B/S, or how well it held up. Shortly afterward he got into Pro Stock class where he used Kohler 16 Hp engines. He bored them about .190 when modifying them. As I said, these were for pulling and were not run for long periods of time at a constant speed. He told me that at the .190 bore about 75% of the engines would survive without blowing the side of the cylinder out. Some people bored them to 4.00, which is .250, at that bore only about 25% would survive.

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Chris727
Don't file anything off the piston. The balance is not thrown off. The 13 and 16 use the same balance gears and crankshaft. I do however think the cylinder heads are differnt between the two. I would put a 16hp head on it.

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dynodave
302431 head is 80cc, this head actually has more fin surface area than the 16hp headOO 326431 head is 80cc The 326431: std aftermarket piston is 439.1 gm +10 rotary piston is 443.5 gm +20 oem B&S is 428.1 gm pin is 77.8 gm

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pds00
I'm sure by now that everyone who read or posted to this has forgotten about my rebuild project. I didn't. I finally got it back together and running this week. There aren't any problems with any of the internal parts such as the crank, heads, timing or anything that was in question to a few. Boring it out .125 doesn't seem to be an issue however I have only 4.5 hrs on it so far. This is just an fyi for those that run into this problem in the future.

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