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huffy

Motor overhaul conundrum - Resolved!

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huffy

I need some help boys. As part of my 2012 freshen up I'm trying to overhaul the motor. This is the first one I've ever torn down, so it's a learning experience to say the least.

Anyway, when I pulled the piston out today I found that my top compression ring is cracked. This may explain why it was smoking a bit before. The wear ridge at the top of the cylinder feels barely noticeable (the batteries in my inside micrometer are dead at the moment, so I can't get a measurement), but since I'll have to put in new rings I'd like to go ahead and get the cylinder re-bored.

Here's my problem. My engine is a model 300421 type 0120. I looked up the part no's for the .010, .020, and .030 pistons/rings on Jack's, and it's saying that they're all no longer available. The only thing that is still available is a standard piston and ring set, which of course I can't use if the cylinder's bored out.

Does anyone know of an after market source for a piston and ring set to fit a bored out cylinder? Or, would a machine shop that bore's engines out be able to sleeve it after it's bored so that I can use a new standard-sized piston/ring set? If so, any ballpark of what the latter might cost?

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DaveTenney

Chris...I had the same situation with a blown 30 cube motor last year. The best solution in my opinion is to turn it into a 32 cu. ft motor. The block has a ton of meat so it can be bored out .125 to make it work. You can get the internal parts here:

http://www.ebay.com/itm/engine-rebuild-FOR-BRIGGS-STRATTON-Cast-Iron-14-16hp-/380434359058?pt=LH_DefaultDomain_0&hash=item5893a7a312

This worked out great for me...

Dave

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1Litre

You can sleeve the block but it not common and finding a sleeve is a problem now. When you do the math it will rattle out this way.

Bore for sleeve is a alot of metal and cost is addition,cost of sleeve,cut sleeve to lenght,press in sleeve, piston assy gaskets etc... Now 32 cube solution is Bore alot of metal at additional cost,

Piston assembly gaskets etc... Much less labor and 1 less part and

much more power.

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huffy

Thanks for the info guys.

As an update, as explained by the books I read I measured the cylinder yesterday at top, middle, and bottom, both parallel to the crankshaft and perpendicular to it. By my measurements, it's over the bore and out-of-round limits as stated in the specs I have so it will need to be bored.

I'll look in the phone book and find a small engine machine shop to take it to this weekend so a pro can double check my measurements. I'm assuming the pro's measurements will be more accurate than mine, but still show that it's out of specs and needs to be bored. If so I'll order the kit that DaveTenney listed. (Thanks, Dave!).

Just out of curiosity, any ballpark on what it'll cost me for the machine shop to clean, measure, bore, hone, etc?

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DaveTenney

I ended up with about $225 in machine work on mine. Reboring was about $60; mine had to have the crank turned .020 under so that was about $75. Then of course I had a bad valve and bad guides and that took care of the rest. The core I decided to rebuild wasn't that great, so you may get off a bit cheaper.

That rebuild kit off ebay doesn't include all of the gaskets, but I was able to make the rest of them for next to nothing. There are also some shims that you may need to set the endplay on the crank and the camshaft. Turns out I didn't need any shims on my motor...You'll need a dial indicator to do this part. You'll also need a cam plug - about $3 or so.

I also had to buy a carb for my motor (new throttle body and used bottom form a member here) and threw in a Nova II module to replace the points.

Dave

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huffy

I had already ordered the Briggs gasket and seal kit before I took the motor apart, so I should be good there. Once I take it over to the machinist I guess I'll find out whether I need to order the shims and stuff too. I think the valves are okay, and that I can get away with just lapping them. But, we'll see. The pro may tell me otherwise.

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Dark

really?? seriously?? boring the block causes a lot of things to happen that most people are not really aware of like having to re-jet the carb,never being able to cheaply rebuild the engine again,and re-curving the governor settings.also under-camming can be an issue in some engines. using the same valves and lapping would be great for standard rebuild but on a overbore why not take the time to tri-cut the seats and reface the valves.I would personally mic the bore and install a set of standard rings in it after a light hone. the bore would be seasoned already and have less chance of warp-age. also ridge ream the top regardless of the ridge just to clean things up you said yourself that there wasn't much of a ridge so why overbore? a std set of rings a light hone your mowing again that afternoon.

rings are made of a lighter cast iron blend then the cylinder walls that's why they wear faster you shouldn't have to re-bore unless you have gouges,taper, or scratches deeper then .010 in the cylinder bore.

also if you do have to overbore you can look at half sizes also by matching ring sizes to all popular engines and checking the end gap of the rings before installing.

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1Litre

I like to rebuild engines so they have as much life or more than the

manufacturer produced the product. Hone up a crooked,loose bore and you will be doing the work over again sooner than you will like.

You can not bore cylinder halfway to the next size and install the next up size rings. The rings are not the only reason to bore the cylinder. The piston to wall clearance is as much of sealing function as the rings are. The piston will crack when clearance is to much.Really Seriously not a good situation.

Many manufacturers use the same cam in multiple models of engine as the displacement increases the power rating is increased.

Some of the things mentioned in some of the posts will get you running but certainly will cause oil use problems.

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huffy
quote:Originally posted by Dark

I would personally mic the bore and install a set of standard rings in it after a light hone. . . . you said yourself that there wasn't much of a ridge so why overbore? a std set of rings a light hone your mowing again that afternoon.


id="quote">
id="quote">Based on the readings I got once I was finally able to measure it, and comparing them to the specs in the Haynes manual that I have, I simply don't think that lightly honing the cylinder and installing a standard set of rings is going to be an option. And yes, I did say that it didn't feel like much of a ridge. And to me, it doesn't. But, again, this is the first one that I've ever taken apart and inspected. Once I measured it, from the specs in the book it seems that it actually is a decent-sized ridge so far as engine tolerances go. Again, I can't decide exactly what I'll do until I have a machinist look at it and double check my measurements. If he finds that my measurements are off, which may very well be the case since I'm not an experienced machinist and my micrometer likely isn't as good as his, I'll just hone it and put in a new set of rings if that's an option. I'm pretty sure, though, that that's not going to be the case. That's why I asked for input about how I would find components if I do have to have it bored out. As for your comments about the valves, there again I'm not 100% sure what I'll opt/need to do yet because I haven't had the machinist at the auto parts store look at them. Based on my measurements, and what I've read in the books, I think all they need is a lapping. But, there again, this is the first set I've ever inspected. The pro may see something different and recommend additional work. I'll cross that bridge when I get there. Right now I'm just focused on the cylinder because I know that due to the broken ring I've got to do something, be it just install a new standard ring if possible or have the whole thing bored out to 32 cubic inch and get the kit Dave referenced.

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MysTiK

IMHO huffy is on track getting some hard facts, and the jury is out when the hard evidence is all presented. There are options, and some options might exist after truth is revealed, and some might no longer be available. I think preserving options is best; but I believe we will all support huffy's decision based on the facts revealed, and options presented here, or elsewhere; and his preferences.

Dark's mention of "the bore would be seasoned already and have less chance of warp-age" is a common consideration I have heard before, mainly in reference to heads being lightly sanded to delete warpage near bolt areas, then retorqued, never a problem again.

What I really love is a great discussion, exchange of ideas, experience, and broadening of horizons. This is an area that's always in the back of everyone's mind; whether the engine is stock or modified, the thoughts never vanish completely. Options are the backup plan; and it all comes down to the art of machining, whether it's the original specs, or the new. This is precision metal; tolerances are mere acceptable deviations through which precision dances with compromise. Does perfection really exist? Yes or no, it's still a lawn mower. Even pianos go out of tune. Relatively minor inputs preserve options. There's no going back with major modifications. It must needs be the right thing to do to preserve what isn't being manufactured any more. I don't see land speed records on the agenda; but, hey, whatever 'turns yer crank'.

just interested - just my humble thoughts - and just lovin all this talk.

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Dark

Dave,

Even though the carbs are simular they are differant note that a

520-630-BR Carburetor Kit Fits most 10, 11, 16 hp Horizontal Single Cylinder Engines

CARBURETOR KIT BRIGGS & STRATTON / 394989 Replaces (OEM): BRIGGS & STRATTON 394989 Fits Models: BRIGGS & STRATTON 243431, 243432, 243434, 243436, 243437, 254412, 254422, 254427, 326431, 326432, 326435, 326436 and 326437; for 10, 11 and 16 HP horizontal single cylinder engines

and this

520-072-BR Carburetor Kit Fits most 10-12hp Horizontal Single Cylinder Engines

CARBURETOR KIT BRIGGS / 391071 Replaces (OEM): BRIGGS & STRATTON 391071 Fits Models: BRIGGS & STRATTON 220400, 221400, 243400, 252500, 301400-325430; for 10 thru 12HP horizontal singlecylinder engines (early style)

As for the under-camming maybe I wasnt clear on the topic as under-camming from a 10hp to a 16hp may throw the timming settings off

timming will have to be checked in these steps...

Adjust Ignition Armature Timing

External Breaker Points Model Series

230000, 243400, 300000, 320000

NOTE: On breaker points equipped engines, before

ignition armature can be timed, flywheel must

be removed and breaker points must be

adjusted to .020(.51 mm.

1. Slide flywheel onto crankshaft taper.

2. Slip flywheel key into place.

3. Install flywheel nut finger tight.

4. Using Tool #19357 Digital Multimeter Meter,set meter to ohms (Ù) and connect one test lead to breaker point primary lead.

5. Connect second test lead to breaker point

mounting bracket.

6. Disconnect ignition armature ground wire from

ignition armature laminations and pull wire away

from laminations.

7. Disconnect ignition armature ground wire from

ignition armature laminations and pull wire away

from laminations,

8. Turn flywheel clockwise until meter shows points

are closed (low ohms reading). Turn flywheel

slowly clockwise until points open (high ohms

reading). Arrow on flywheel should be in line with

arrow on armature bracket.

9. If arrows do not line up, remove flywheel without

moving crankshaft. Loosen screws holding armature

bracket until bracket can be moved with a

slight drag. Slip flywheel back on crankshaft

without moving crankshaft. Insert flywheel key.

Install flywheel key and nut finger tight. Move

armature bracket assembly until arrows line up, Remove flywheel and tighten armature

bracket screws.

In response to 1Liter yes you can bore half sizes anything under .007 can use standard ring half sizes would include .015 .025 and .035

granted you will not find the rings in any Briggs book but remember your starting with a 3-7/16 bore so Chevy,Ford, Honda Mitsubishi and others all have rings in their engines that can be "Fitted" just check the end gaps and the thicknesses of the rings and pistons can be knurled or crossed over to fit the tolerances that are needed a piston is just a slug of aluminum going up and down at top speed 3600 rpm.

http://www.indiamart.com/chromeflex/piston-rings.html#piston-rings-for-briggs-straton

one more comment ... if you don't know the machinist talk about options the reason would be to remember that there are some that just wanna bore anything because it is money in their coffer a good machinist will give you options before they do the work.

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huffy

I appreciate the tips Dark. But I have reason to expect that the place I'm taking it to is going to treat me fair.

I won't get a chance to take it over there until sometime next week, but I'll let you guys know how it goes.

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powerking_one

Chris,

Once your machine shop "guy" confirms whether or not the cylinder is out of spec, I'd either just re-ring it or bore to the 32 C.I. standard diameter. As others have done/stated; there's plenty of meat in the block to accomodate boring it to 3.5625". Granted this would be a full 1/8" of boring, and they'd probably surcharge you a hefty amount due to the extra time and iterations involved with the boring bar operation. Unfortunately, the .020" undersize rod (PN 390306) is no longer available from B&S; only in after market offerings hence quality thereof is unknown. As far as the valves, inspect and determine if they need (or can be) refaced (both are still available PN's from Briggs; 394435, 394436). Valve seats and guides are typically not an issue on these C.I. singles.

Definately resuscitate and save the old girl (IMHO; LOL).

Tom (PK)

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huffy

Thanks PK-1

I took the block to the machinist a few minutes ago. He confirmed my measurements. He's charging me $48 to bore it out, clean it, and prime it. I think that's very fair.

He said the crankshaft journal's fine and within tolerances. He also said the valves are fine and just need to be lapped.

I ordered the 32 CI kit that Dave Tenney showed me. It should be here Thursday or Friday. The machinist wants me to drop it off so that he can confirm that it complies with the Briggs 3.5615 specs before he actually bores the cylinder, so it'll probably be next week sometime before I get everything back and am ready to start re-assembling it.

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1Litre

Good price for bore on a single. I charge 40 up to .030" and 10 more for each .060" . Dark , I responded to prevent a failure that could

put the rod threw the block. Your post did not cover the piston

just rings and not .007" wear or less. That was my concern. There are options. I felt some of them are not worth discussion as they

are expensive. As you stated you can custom build bore/ piston combinations from other engines but that can be costly and many

measurements must be taken into consideration before you order. If you want ring selection for custom builds try Hastings for vintage

engines like the types discussed on this site. They have many more

to choose from in the widths that are in the older engines.

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powerking_one

Chris,

That price of $48.00 is almost too good to be true. To overbore it .125" and finish hone it, I would have expected around $100. I hope this guy is "good" and knows what he's doing for your sake. I don't see much profit for the shop at that price.

Tom (PK)

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huffy
quote:Originally posted by powerking_one

Chris,That price of $48.00 is almost too good to be true. To overbore it .125" and finish hone it, I would have expected around $100. I hope this guy is "good" and knows what he's doing for your sake. I don't see much profit for the shop at that price. Tom (PK)


id="quote">
id="quote">PK:No worries. This machine shop is good. I'm just getting a bit of a discount because I've represented some of their auto parts stores in the past.

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1Litre

OK Change of subject. Powerking ,Have you seen the 60"mower deck from the early eighties for Powerking tractor? It looks like a Simplicity deck with brackets to attach to the Powerking tractor.

Do you know who manufactured the deck?

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huffy

Sorry, 1Litre, but I'm changing the subject back.

I just got a call from the machinist and the block's done and ready to be picked up!!!!

Unfortunately, it'll be tomorrow afternoon before I can retrieve it. Then comes the real hurdle in this resto project - whether I can actually manage to get the motor back together again.

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huffy

Well, I've got the engine back together now. Only question left is whether it'll run. Hopefully I'll be able to get it wired up and test fire it tomorrow. Everybody keep their fingers crossed . . .

2012_0320Landlord0007.JPG

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2012_0320Landlord0007.JPG.17c3f5515189e694d4c8659deeca127b.JPG

2012_0320Landlord0009.JPG.4fa11f6136fedf5094cfdcdf8a10ff15.JPG

2012_0320Landlord0002.JPG.d92130fc06af819774f645f59c79e4f6.JPG

2012_0320Landlord0028.JPG.f0d72305b68ddc1d9062c4b97a0b3364.JPG

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