Fixing scratched Briggs piston?

[Bear05]

I've been working on a Briggs 5hp flathead for a little while now, and since I've owned it I know the wall of the cylinder and sides of the piston are pretty bad scored. The engine still runs pretty good, but when you take off from a stop it smokes quite a bit. It looks like the guy I got it from ran it lean and low on oil, I'll post some pictures when I get home. I'm confident that I can fix the cylinder with a hone, but the piston's pretty rough. I looked it up and I found this video on a guy using a Scotchbrite pad and WD-40 to fix one (How to get scratches out of your pistons ! (youtube.com) ). At some point I know I want to upgrade to a predator motor, but I don't want to spend that kind of money rn. Any thoughts?

 

[Minimichael]

Oversize the rings.

 

[sparkwizard]

Will a magnet stick to the cylinder wall? If it does, you can hone the cylinder and clean up the scratches.
If not, I like Lucas oil stabilizer, follow the label instructions. Do not fill it with Lucas.

 

[Bear05]

Will a magnet stick to the cylinder wall? If it does, you can hone the cylinder and clean up the scratches.
If not, I like Lucas oil stabilizer, follow the label instructions. Do not fill it with Lucas.

I'll have to check when I get back to the house. I was wondering about the Lucas stabilizer though, does that stuff work?

 

[Bear05]

Oversize the rings.

I was wanting to do that, I saw another thread on here talking about that. I saw the guy say this (299742) was the part # I'd need, would that work or should I hone the cylinder then measure?

 

[Charles S]

I've been working on a Briggs 5hp flathead for a little while now, and since I've owned it I know the wall of the cylinder and sides of the piston are pretty bad scored. The engine still runs pretty good, but when you take off from a stop it smokes quite a bit. It looks like the guy I got it from ran it lean and low on oil, I'll post some pictures when I get home. I'm confident that I can fix the cylinder with a hone, but the piston's pretty rough. I looked it up and I found this video on a guy using a Scotchbrite pad and WD-40 to fix one (How to get scratches out of your pistons ! (youtube.com) ). At some point I know I want to upgrade to a predator motor, but I don't want to spend that kind of money rn. Any thoughts?

Personally, I wouldn't buy another Predator because I believe there are better options these days, the Ducar 212 in particular. However, if a Predator is what you want, now is the time to buy one. They're on sale, $110 for the 212, which doesn't happen often anymore.

https://oldminibikes.com/forum/index.php?threads/harbor-freight-sale.180753/

 

[sparkwizard]

I'll have to check when I get back to the house. I was wondering about the Lucas stabilizer though, does that stuff work?

I'm a retired auto repair technician. I now fix and repair mostly farm and garden equipment for old guys who don't want to spend any money.
I also have a 10 year old son who has no job, but loves to ride.
Lucas products work. If Lucas put a product in a bottle and states something on their label, it will do what they claim.
Don't expect miracles from any product, but Lucas works.
On the Lucas oil stabilizer bottle it says "keep that old engine alive". It should also say "while you look for a newer one".
Let us know about the magnet thing. If there is not a steel sleeve, they generally are not worth rebuilding.

 

[Bear05]

I'm a retired auto repair technician. I now fix and repair mostly farm and garden equipment for old guys who don't want to spend any money.
I also have a 10 year old son who has no job, but loves to ride.
Lucas products work. If Lucas put a product in a bottle and states something on their label, it will do what they claim.
Don't expect miracles from any product, but Lucas works.
On the Lucas oil stabilizer bottle it says "keep that old engine alive". It should also say "while you look for a newer one".
Let us know about the magnet thing. If there is not a steel sleeve, they generally are not worth rebuilding.

Sorry for responding so late, I checked it and it's definitely aluminum or some alloy. The only thing the magnet stuck to was the pull starter housing. I'm guessing it's a Kool-Bore then?

 

[Bear05]

Here's pictures of the bore and piston, both have been cleaned up with a scratchpad but are still far from perfect.

 

[Bear05]

Personally, I wouldn't buy another Predator because I believe there are better options these days, the Ducar 212 in particular. However, if a Predator is what you want, now is the time to buy one. They're on sale, $110 for the 212, which doesn't happen often anymore.

https://oldminibikes.com/forum/index.php?threads/harbor-freight-sale.180753/

I would be interested in trying something different, hence the reason I wanted to go old school with the Briggs. That said as far as price of parts and reliability goes I haven't found a better option aside from the Predator. Just for the heck of it I checked the website for my local Harbor Freight and they said they were out. That said, I ran by there on the way home and low and behold, there was one left under the shelf. Needless to say I have a 212 now lol.

 

[Minimichael]

That piston is history. Even if you go ahead and hone, you'll need a new piston and rings – probably oversized, depending what size you hone to. Alternatively, you could try chrome rings, which I believe are meant for giving Kool bores a second chance.

 

[creia]

Forget about that scratch pad, honing or oversize rings. Both the bore and that piston are SHOT.
Michael

 

[sparkwizard]

Keep your eyes open for a snow blower engine. They are pretty cheap and they were only used a few times a year.
Check Ebay on a regular basis. Sometimes you'll see 5 horse engines for 100 to 175 bucks with free shipping. If you find one with a carb and tank similar to your present engine, then you already have spare parts.
For now, since you are saving money, you can run it with straight 40 weight oil and maybe make it through the summer. Check your oil every time you take the bike out.

 

[Bear05]

I didn't realize that the bore was that far gone, I guess I'll let it ride with some thicker oil for now. I've seen 5 horses pop up on Marketplace for 40 to 50 bucks before so I can keep an eye out for one. Either that or I'll put it back together and sell if for a couple bucks. I've already got a billet rod and aluminum flywheel for it, but I'll probably leave those off for now. Thank you guys for the help though!

 

[Bear05]

Also one more question for y'all, how much oil does a flathead take? I've seen some people say its a quart or more, but I know in the manual it says 0.63 quarts.

 

[sparkwizard]

Less than a quart. 0.63 sounds right. Should be visible at the bottom of the threads. It shouldn't hurt that engine if you fill to closer to the top of the threads, just to be sure it doesn't burn it all out.

 

[Bear05]

I'll probably check the oil level every hour or so, when I pulled the engine apart this last time there was a fair amount of oil left on top of the piston. Thank you!

 

[EricD..]

I have a 5hp Briggs I’d sell you. I have to dig it out and look at it. If I remember right it’s a I/C. I have a grind 12 cam and high compression head for it too. If your interested I’ll look

 

[sparkwizard]

I have a "rebuildable" 5 horse with carb and tank, shroud, flywheel. Tank has holes in the top side. Easy fiberglass repair.
You can HAVE it if you pay shipping.
Collect a few, never buy parts again.
Mine is a cool bore. I/C is the one to get if you plan to run it for a long time. Steel bore and ball bearing.

 

[Bear05]

Sorry I'm replying to y'all so late, I actually sold the motor just last night. I've got a predator on it now but if I have another project pop up I'll give you guys a message.