.010 oversize piston???

StarTech said:
Well another DIYer just throwing parts at a problem before knowing what the actual cause is.

You must have the correct tools. For cylinder resizing if needed it is a ridge hone, a 1/2" high torque drill, and a good pair of calipers. Just ordering a piston before knowing how bad a cylinder worn can be expensive as might require a larger size or have a cylinder that is worn beyond any available oversize piston and rings.

Plus these old L head engines tends to smoke when the exhaust valve guide is worn out. Intake guides seldom fails. Many users assumes the worst like a blown head gasket or rings. Again you must have the correct reaming tools and drivers to install a replacement valve guide if you can even get a replacement guide. Several about ten years ago were going NLA and I had resort to making my own guides out of brass tubes. Also there is more than one style of replacement guides that were once available for these engines depending the model and type numbers. One was even a cast bushing valve guide.

The lesson here is; unless, you know exactly what you are doing and the right tools you are just wasting your money throwing parts at it and hoping you have guessed right.

I got a customer that just tried to repair his mower after he insisted on an electric fuel. The cheap Chinese pump failed. During his attempt to find the problem he nicked the wire going to pump even I installed bullet connector that simply needed to be separated for testing the pump. Now it is in the shop and he said smoke was going out the debris screen. I did order a stator and voltage regulator without checking as he might have fried both coils. But being a shop I can always sale it later to someone else.

Kinda pissed me off he did this releasing of the magic smoke. Now I got figure exactly what he shorted out and how. I think without actually testing he grounded the stator and regulator because smoked the engine turning on the ignition switch.

As the old saying goes "A fool and his money are soon parted." can ring true at times. What worst is Brian just voided his repair warranty. It may have cost only the additional parts now labor is back in the mix.
Click to expand...
All day, every day, then they take it to us and have us give an answer they don't like and dont wanna pay. You know the suicide rate of mechanics ( based on auto repair) has massively jumped since COVID? This is probably why across all forms of repair.
 
I was reading last night about the aluminum used in the coolbore engines. It is a special Aluminum-Silica alloy. After the cylinder is bored at the factory it is sent thru a special process that etches the aluminum bore to eat the aluminum and leave the silica on the surface of the cylinder. The aluminum piston is actually sliding on the slica and not the aluminum itself. When one of these engines is bored, that layer is gone and the piston rides on both aluminum and silica. Although the engine will have the additional life from boring it, it will never have the life expectancy of the original bore. In fact it will be more prone to wear, galling, and seizing if it gets too hot. For most people, it is uneconomical to rebuild these engines. The 120000 series engine I am presently rebuilding will cost about $160 in parts. If it was bored to an oversize piston, that might add another $125 in labor and $100 in parts. A brand new Briggs and Stratton engine like the one I am rebuilding is $340 - $360. A HF Predator engine that is similar is between $200 and $300 depending if you catch it on sale.

If you are in California, you can only buy small replacement engines not sold yet that were manufactured prior to January 1, 2024, or engines specifically designed for Farm, Ranch, or Construction. There are no other exemptions. So - if someone lives in California, and they are considering buying a small engine that is being sold off as existing stock, better get it because when those are gone there will be no others unless the laws change here.
 
Last edited:
Heck, in California they have managed to ban everything to a point no one will be left with anything. I will not go off on a political tangent, but I think most people can relate to history beginning to repeat itself once again.
 
sgkent said:
I was reading last night about the aluminum used in the coolbore engines. It is a special Aluminum-Silica alloy. After the cylinder is bored at the factory it is sent thru a special process that etches the aluminum bore to eat the aluminum and leave the silica on the surface of the cylinder. The aluminum piston is actually sliding on the slica and not the aluminum itself. When one of these engines is bored, that layer is gone and the piston rides on both aluminum and silica. Although the engine will have the additional life from boring it, it will never have the life expectancy of the original bore. In fact it will be more prone to wear, galling, and seizing if it gets too hot. For most people, it is uneconomical to rebuild these engines. The 120000 series engine I am presently rebuilding will cost about $160 in parts. If it was bored to an oversize piston, that might add another $125 in labor and $100 in parts. A brand new Briggs and Stratton engine like the one I am rebuilding is $340 - $360. A HF Predator engine that is similar is between $200 and $300 depending if you catch it on sale.

If you are in California, you can only buy small replacement engines not sold yet that were manufactured prior to January 1, 2024, or engines specifically designed for Farm, Ranch, or Construction. There are no other exemptions. So - if someone lives in California, and they are considering buying a small engine that is being sold off as existing stock, better get it because when those are gone there will be no others unless the laws change here.
Click to expand...
A 1985 3HP very well could have been cast-sleeved or an all-aluminum "koolbore" block but 100% on what you say as far as the koolbores go, their trash engines in my opinion and parts are not interchangeable, and this entire thread would be alot of bad info as myself and others assumed it was a cast bore based on the answeres and responses. Model numbers and serial numbers help, not just 1985 3hp. The 5hp horizontal shaft koolbore that everyone seems to love so much is a koolbore, and I have no idea why people liked them so much. Box store specials of the day I suppose. If his 3hp is an IC engine, it's most certainly a cast sleeve, but again, model numbers help, and I sure hope his parts were bought using those numbers.
 
You must log in or register to reply here.
Back
Top