Briggs 3HP with piston scoring

[creia]

UPDATE: The bore ended up having only .0005-.001 wear.

With such low wear, I'd install a standard size chrome ring kit. I've had huge success with chrome ring kits. No honing needed with chrome ring kits. They bite their own way into the cylinder bore. The chrome ring kit for model 81200 is part# 297201.

The chrome ring kit has eight piston rings and they are arranged like this:

Ringland 1
- Thick Ring By Itself

Ringland 2
- Medium Thick Ring + Narrow Expander Ring*
- Thin Ring

Oh- I am WELL aware of the chrome ring sets. I used them MANY times over the years on both the Briggs 3 HP and 5 HP engines. In this particular case, with only .0005"-.001" bore wear I did not think that was enough to justify/warrant their use. I THOUGHT I could just put the original rings back in (also very minimal wear based on the ring gap I measured). I know better now...
Michael

Ringland 3
- Thin Ring
- Oil Ring + Wide Expander Ring*
- Thin Ring

*The expander ring goes on first and then the solid ring goes over the outside of the expander ring.

All ring gaps are placed 120 degrees in rotation away from each other.

I am WELL aware of the chrome rings, as I have used them MANY times over the years in both the Briggs 3HP and 5Hp engines. My reasoning for not using them this time was with such little bore wear (.0005" - .001") I did not think they would be needed or offer any benefit. I THOUGHT that I could just reinstall the original rings that also had very little wear (as determined by the ring gap). That is why I was very surprised when the engine initially smoked after putting it back together. Brian educated me otherwise....
Michael

[Merkava_4]

I am WELL aware of the chrome rings, as I have used them MANY times over the years in both the Briggs 3HP and 5Hp engines. My reasoning for not using them this time was with such little bore wear (.0005" - .001") I did not think they would be needed or offer any benefit. I THOUGHT that I could just reinstall the original rings that also had very little wear (as determined by the ring gap). That is why I was very surprised when the engine initially smoked after putting it back together. Brian educated me otherwise....
Michael

You said the engine was smoking. Same thing happened to one of my engines. I took it apart and used a new piston ring to measure the bore wear. In my case the bore was only worn .001". I think the allowable limit is .003". I didn't want to take a chance on honing the cylinder for fear of enlarging the bore any further. The chrome rings cut their own way into the bore beautifully. After the engine was assembled, it was harder to pull the rope because the compression went up so much. No more smoke and the engine runs excellent. This was the same engine that went from a 2HP to a 3HP by installing a crankshaft and connecting rod out of a 3HP engine. I also put in a Magnetron ignition upgrade kit.

[creia]

I am WELL aware of the chrome rings, as I have used them MANY times over the years in both the Briggs 3HP and 5Hp engines. My reasoning for not using them this time was with such little bore wear (.0005" - .001") I did not think they would be needed or offer any benefit. I THOUGHT that I could just reinstall the original rings that also had very little wear (as determined by the ring gap). That is why I was very surprised when the engine initially smoked after putting it back together. Brian educated me otherwise....
Michael

You said the engine was smoking. Same thing happened to one of my engines. I took it apart and used a new piston ring to measure the bore wear. In my case the bore was only worn .001". I think the allowable limit is .003". I didn't want to take a chance on honing the cylinder for fear of enlarging the bore any further. The chrome rings cut their own way into the bore beautifully. After the engine was assembled, it was harder to pull the rope because the compression went up so much. No more smoke and the engine runs excellent. This was the same engine that went from a 2HP to a 3HP by installing a crankshaft and connecting rod out of a 3HP engine. I also put in a Magnetron ignition upgrade kit.

I appreciate your interest in my thread, however, you are missing the point and the essence of my thread. The engine never smoked one bit BEFORE I took it apart. I did my entire detailed internal inspection, took precise bore and ring gap measurements, cleaned everything up then reassembled everything-THEN it started smoking. The compression was good, and exactly the same (90PSI) both before and after. I did not understand what could have caused it to suddenly start smoking as nothing had changed. Trust me, you do not have to "sell me" on the benefits of using chrome rings as I am already a believer...
Michael

[Merkava_4]

I appreciate your interest in my thread, however, you are missing the point and the essence of my thread. The engine never smoked one bit BEFORE I took it apart. I did my entire detailed internal inspection, took precise bore and ring gap measurements, cleaned everything up then reassembled everything-THEN it started smoking. The compression was good, and exactly the same (90PSI) both before and after. I did not understand what could have caused it to suddenly start smoking as nothing had changed. Trust me, you do not have to "sell me" on the benefits of using chrome rings as I am already a believer...
Michael

What was the reason for taking the engine apart?

[bgsengine]

I appreciate your interest in my thread, however, you are missing the point and the essence of my thread. The engine never smoked one bit BEFORE I took it apart. I did my entire detailed internal inspection, took precise bore and ring gap measurements, cleaned everything up then reassembled everything-THEN it started smoking. The compression was good, and exactly the same (90PSI) both before and after. I did not understand what could have caused it to suddenly start smoking as nothing had changed. Trust me, you do not have to "sell me" on the benefits of using chrome rings as I am already a believer...
Michael

What was the reason for taking the engine apart?

Umm, you know he does restorations of older engines, right? Since the engine came without a shroud, I would assume it was disassembled to measure bore x stroke and inspect internals to get a closer identification of model / type - One would assume it was further disassembled then since it was already mostly apart, just to clean up and do a further inspection. Used to do this from time to time when I was still doing rebuilds, and I'd keep good used "cores" handy to do my own short blocks...

Since I was a self-employed pro shop, I'd never have dreamed of trying to re-use old but good rings, although I have done quite a few "take apart and slap back together" jobs (typically some issue a customer wanted me to check and get an estimate, then wanted it put back together and they'd run it 'til it blew up... which sometimes lasted them several more years!) so I do have that experience to draw on , though never made a study of it.

[KE4AVB]

Besides when an used engine is present measurements are truly variable as you got look for overall diameter, taper, and out of round specs. With a ovaled (out of round) cylinder rings do wear lopsided so if even the least bit lopsided will cause sealing problems once reinstalled. Also flipping the rings over can cause problems too. And this don't include odd ring landings wear.

I have put old rings back cylinder bores to find end gaps are find but when I shine a light from the backside I can see areas of non contact due to odd ring wear. I always like to use a rigid hone to true up a cylinder even if means resizing and new rings.

But this just me...

[creia]

I appreciate your interest in my thread, however, you are missing the point and the essence of my thread. The engine never smoked one bit BEFORE I took it apart. I did my entire detailed internal inspection, took precise bore and ring gap measurements, cleaned everything up then reassembled everything-THEN it started smoking. The compression was good, and exactly the same (90PSI) both before and after. I did not understand what could have caused it to suddenly start smoking as nothing had changed. Trust me, you do not have to "sell me" on the benefits of using chrome rings as I am already a believer...
Michael

What was the reason for taking the engine apart?

bgsengine and KE4AVB nailed it. I take these 50+ year old old engines (some are real junkers!), rebuild/restore them back to OEM factory condition, then resell them to individuals (mostly old farts like me that are restoring bikes and go-karts for their kids or grandkids) from back in the day. I don't make much $$ doing this- if I'm lucky I make about the CA minimum wage. It's a "labor of love" that is both an enjoyable hobby for me (keeps me active) and gives me great satisfaction seeing these engines being put back into service and help someone complete their project. Soooo.... in good faith I feel that I need to completely go through the engine internals and inspect and take measurements (and correct any/all as needed) even if the engine is already running, not smoking, and has good compression. That way I can honestly represent the true condition of the engine to a buyer. Good grief, I could never come close to making a living at this- I am just a garage hack that has greatly benefited by the the knowledgeable and caring professional techs on this forum.
Michael

[Merkava_4]

Umm, you know he does restorations of older engines, right? Since the engine came without a shroud, I would assume it was disassembled to measure bore x stroke and inspect internals to get a closer identification of model / type - One would assume it was further disassembled then since it was already mostly apart, just to clean up and do a further inspection. Used to do this from time to time when I was still doing rebuilds, and I'd keep good used "cores" handy to do my own short blocks...

Since I was a self-employed pro shop, I'd never have dreamed of trying to re-use old but good rings, although I have done quite a few "take apart and slap back together" jobs (typically some issue a customer wanted me to check and get an estimate, then wanted it put back together and they'd run it 'til it blew up... which sometimes lasted them several more years!) so I do have that experience to draw on , though never made a study of it.

No I didn't know he restored engines for re-sale.

The one thing I don't understand about regular ring kits is they don't come with expander rings. Expander rings go underneath the solid rings and push them out against the cylinder bore. The chrome ring kit comes with two expander rings and six solid rings. I can't say enough about that chrome ring kit. It seals against the cylinder bore fantastic.

[bgsengine]

The one thing I don't understand about regular ring kits is they don't come with expander rings. Expander rings go underneath the solid rings and push them out against the cylinder bore. The chrome ring kit comes with two expander rings and six solid rings. I can't say enough about that chrome ring kit. It seals against the cylinder bore fantastic.

Yeah - Regular ring kits are a cast iron-like material , extremely brittle and can't get too thin on them so they can't make the rings thin enough to utilize an expander.
- They wear in to a perfect bore very well and seat themselves, but they don't have as much "give" to form themselves to a worn cylinder (even though within specs) so they'll take much longer to seat in - even a new regular ring set would have had trouble with a worn bore.

However chrome rings are more of a steel / chrome molybdenum composition, they are a bit more flexible, superior wear resistance, and able to be manufactured much thinner, so expanders (and oil scraper ring rails) can more precisely form a ring to a slightly odd-shaped bore - The Chrome is far harder than cast iron but more flexible, so are ideal for re-ring sets.

However, due to the hardness, they used to warn against using chrome ring sets in aluminum kool-bore engines due to the risk that the rings could too quickly cut in to the aluminum.(Rapid wear, and potential for problems with piston slap, rings moving out of square and digging into the aluminum) However once Kool-Bore became an obsolete production item (last produced in 2011), they (chrome ring sets) pretty much no longer carried that warning. Used with caution in a well-within-spec Kool-Bore engine though, they work just fine... I'd only hesitate at using chrome rings in Kool-Bore when the bore is closer to reject tolerances than in spec, especially out of roundness and taper specs.

[Merkava_4]

Yeah - Regular ring kits are a cast iron-like material , extremely brittle and can't get too thin on them so they can't make the rings thin enough to utilize an expander.
- They wear in to a perfect bore very well and seat themselves, but they don't have as much "give" to form themselves to a worn cylinder (even though within specs) so they'll take much longer to seat in - even a new regular ring set would have had trouble with a worn bore.

However chrome rings are more of a steel / chrome molybdenum composition, they are a bit more flexible, superior wear resistance, and able to be manufactured much thinner, so expanders (and oil scraper ring rails) can more precisely form a ring to a slightly odd-shaped bore - The Chrome is far harder than cast iron but more flexible, so are ideal for re-ring sets.

However, due to the hardness, they used to warn against using chrome ring sets in aluminum kool-bore engines due to the risk that the rings could too quickly cut in to the aluminum.(Rapid wear, and potential for problems with piston slap, rings moving out of square and digging into the aluminum) However once Kool-Bore became an obsolete production item (last produced in 2011), they (chrome ring sets) pretty much no longer carried that warning. Used with caution in a well-within-spec Kool-Bore engine though, they work just fine... I'd only hesitate at using chrome rings in Kool-Bore when the bore is closer to reject tolerances than in spec, especially out of roundness and taper specs.

I can't remember if my engine was a kool-bore or not. It's a very old Model 60100 series. Horizontal shaft 2HP. Date code was 1968 I think. It was originally painted white and put on a King-O-Lawn edger. It now sits on a McLane edger. Fantastic engine. Runs real good and has a 3HP crankshaft assembly with Magnetron ignition kit.

The Vac-U-Jet carburetor is my favorite. Super easy to dial in mixture at full throttle by just using my ears. Thanks for the info bgsengine.