Wear limits

[tracerbob]

So...how can you tell when it's time. The Piston on my 67 can be pushed up through the sleeve with some moderate effort but to me, the performance is still good. I got engine used, so I do not have any reference as to the fit of a new piston/sleeve.

I can tell you one thing though. Do not wrap your hand around the sleeve and attempt to push the piston back in after it gets stuck at the top of the sleeve. As the piston comes down, it catches the little flap of skin below the base of your thumb in the exhaust port and becomes stuck again. :blink: It's like getting something else stuck in the zipper. Makes for a tense few moments and a lot of colorful language.

 

[Grimracer]

Tracerbob

Im no motor guru but i do paly one at the pond.. :blink: I kidd....

I have had and seen loose motor run fine and run badly.. The boat will be slow to launch and slow to get to speed when the parts are getting funky. Fuel draw can be compromised along with top speed.

However.. “Not a plug”.. but we are soon going to offer liner/piston fitting tools for the hobby soon and are doing final tests now.. You will be able to re fit the liner to the piston with this tool and its easy to do..

No need to buy new when the lonely thing wrong is the fit.. let www.grimrace.com help.. Now that was a very poorly approached, tacky plug… :blink:

Grim

Bottom line.. if its sill working don’t touch it.. its likely fitting quite well when it get to operation temp.

 

[RaceCraftBearings]

Robert, I ageee with Mike "If it anit broke dont fix it" I had an old worn out P/L in a Picco 67 in my Scale boat that weighs 16 lbs. and it was radared at 64 MPH at the Winter Nationals a few years back. Still ran great even though the piston went through the top of the liner. Save the money for something else.

Ron

 

[nitrotoys]

Sometimes when you think "there worn out" Thats when you get the best preformance out of them, You will notice power lose and speed lose when there worn. Right when you think you have them broken in, there already starting to wear out.

Tom

 

[tracerbob]

Thanks guys, The engine runs fine. I was always told "if you can push the piston up through the liner, it's worn out". I'll save my money and run the engine untill it starts to crap out.

 

[TimD]

Symptoms of worn out P&L's I've seen.

Motor can be hard to start without "choking" it - fuel draw under starter motor is non existant.

Starts bad sags off when the case has warmed up. Won't restart when warm.

Hard on plugs for no apparent reason.

No bottom end power and struggles to get on pipe.

 

[Rules]

Many times you can send the piston off and have it "oil grooved". I cut the grooves inverted 7, like krpnova shows in his article. I place them .025 - .050 apart down the entire piston sometimes, depending on the conditions. Do not run the grooves over the wristpin holes, stop about .100 short. The process will make the pin hard to remove, and cause hole chips. Relap the piston with oil only, not abrasives, clean with ultrasonic inverted sitting on a small piece of paper towel in the 'sonic tub for 1 - 2 minutes. John in Huntsville