5 HP Cool Bore Chrome Piston

J

jaredbird

New member
I'm rebuilding an old roto tiller with my son. I'm doing it more as a project to teach him to work on engines than anything. Once I got it torn apart, I realized it had an all aluminum Cool Bore Cylinder. It's a 5 HP L-Head Briggs and Stratton Engine. I have not bored the engine yet, but it will need it as the cylinder is scored pretty bad. Does anyone know where I can find a chrome plated Cool Bore Piston? I could take .010, .020, or .030. This engine does have the dual shafts, so I think that makes finding a replacement block harder, but I could be wrong on that. Any help appreciated. Thanks.
 
Welcome to the forum Jared.
All of the Briggs O/S piston/ring assemblies for your engine are still available. You will see some listings on eBay.
Here are your Briggs part numbers:
.010" = 298905
.020" = 298906
.030" = 298907
Michael
*** Edit: Another option would be to find a good used block that does not need reboring (that could be a bit of a challenge). Your roto tiller with the dual shafts uses the same BLOCK as the single shaft engines. Only the side cover and the cam with the extended driveshaft are different, which you could remove from your engine and swap them over to the replacement block.
Sidebar comment: My son started helping me with engine rebuilds/restorations when he was just 13 (He is now 32). During his junior year in high school he got a job interning at Terry Nash's "Hyper Racing" performance kart shop in Upland, CA. He really learned a lot (and really enjoyed) working alongside Terry and his assistant Dwight - both master engine builders.
 
Last edited:
I can look in my plethora of new old stock flatty parts I have gathered throughout the years if you would like. Does the block itself need bored or would a good honing work?
 
So is this the chromed piston that I need: https://ebay.io/m/z4WYJq if I bore the cylinder .020 over?

I think the block needs bored. I don't have a set of micrometers myself to measure everything, but the bore looks pretty rough.

Thanks for the information on the block being the same. I didn't realize that. That might open some options for me.

My son is only 9, but he at least enjoyed the tear down of this engine. Hopefully he enjoys putting it back together as much once we get this all sorted out.
 
jaredbird said:
I'm rebuilding an old roto tiller with my son. I'm doing it more as a project to teach him to work on engines than anything. Once I got it torn apart, I realized it had an all aluminum Cool Bore Cylinder. It's a 5 HP L-Head Briggs and Stratton Engine. I have not bored the engine yet, but it will need it as the cylinder is scored pretty bad. Does anyone know where I can find a chrome plated Cool Bore Piston? I could take .010, .020, or .030. This engine does have the dual shafts, so I think that makes finding a replacement block harder, but I could be wrong on that. Any help appreciated. Thanks.
Click to expand...
We "may" have a chromed piston for your build in stock. Sarah would know best. That old inventory is buried in the shop. We can also do the align boring and finish honing if you need.
Give us a call during normal business hours.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
www.youtube.com
38 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
How are you going to bore it? You realize that .003" is allot of honing. For .020" you need a milling machine. If you just want to teach, then give it a hone job to smooth it a little and put the old parts back in. It'll run and he'll learn just as much.
 
Feeler gauge is a easy , teach . Torque wrench use . lapping the valves . setting end checking ring gap. You might get lucky and find a .005 over piston.
 
As racers we tend to take as little as possible off the bore for longevity of the block. What is your intention with the finished product? Are you going to basically let the local engine shop bore to whatever they want or do you have a specific size you are aiming for? I can look in my parts bins and may have some hidden goodies I forgot about, but know the size of bore you intend to cut the cylinder to. And I would hand that local engine shop the piston you intend to use. So they can cut it to what you want than shooting in the dark.
 
I'm planning on putting the engine back in the roto tiller and continuing to use it as a roto tiller. I use it for about 30 minutes a year to till a small garden. It's made it many years on this original engine, so I don't think I'll ever be rebuilding it again after this. So I'm not too concerned as to whether I get a .010, .020, or .030 over piston. I'm just waiting to get the piston so I can send it with the block to get it machined.
 
jaredbird said:
So is this the chromed piston that I need: https://ebay.io/m/z4WYJq if I bore the cylinder .020 over?

I think the block needs bored. I don't have a set of micrometers myself to measure everything, but the bore looks pretty rough.

Thanks for the information on the block being the same. I didn't realize that. That might open some options for me.

My son is only 9, but he at least enjoyed the tear down of this engine. Hopefully he enjoys putting it back together as much once we get this all sorted out.
Click to expand...
By what method are you determining that the cylinder needs to be bored .020" O/S? You really cannot tell just by looking. You have repeatedly stated how bad the bore scoring is. Along with scoring, the bore could be significantly worn, tapered, and/or or out-of- round out of specs. My point is, combining that with the scoring, .020" may not be enough. If you are going to the time, trouble, and $$, why not do it right? You need to have a professional accurately measure your bore and advise you on what bore O/S (and hence what O/S piston/ring assembly you need to purchase). Your "local engine shop" should be able to advise you in this regard...
Michael
 
Only 30 minutes a year? For all the downtime that engine has, a cylinder hone might suffice but it would behoove you to do the proper maintenance to help prevent the scoring. Assuming the air filter is doing its job, the most probable cause of scoring is carbon buildup. Briggs prescribed carbon scraping as a maintenance procedure. I forget the interval (maybe every 100 hours), but you simply remove the cylinder head and mechanically remove the carbon buildup on the head, valves and piston top. Carbon buildup and excess carbon flaking off into the cylinder is a prime cause of cylinder scoring.

My advice is to purchase a worn out engine that you can both enjoy for kart or minibike use.
 
You must log in or register to reply here.
Back
Top