Two Rides w/Wisco pistons. Scuffs?? Please See Pics, Suggestions??

[DragonSlayer1]

If you are going to run forged pistons you better know how to measure and set all the clearances up properly. You also need to understand what it takes to cold seize a motor. If you don't understand either one, you will destroy alot of cylinders and pistons and I recommend you stick will cast pistons. The pictures look to me like the clearances were a little to tight.

From my understanding. A cold seize occurs when the motor is not properly warmed up. The pistons expand faster than the cylinder walls. and Create fricton. Correct me if I'm wrong.

 

[crashnbash]

From my understanding. A cold seize occurs when the motor is not properly warmed up. The pistons expand faster than the cylinder walls. and Create fricton. Correct me if I'm wrong.

That's correct, not warmed up to a stable temp before running, or very cold coolant rushing into a motor that is running hard. A forged piston expands much faster than a cast one makeing the clearances more critical. The other thing that helps with forged pistons is when you first begin to break the motor in you run a few heat cycles on it before putting it under a load.

 

[Pownar]

That's correct, not warmed up to a stable temp before running, or very cold coolant rushing into a motor that is running hard. A forged piston expands much faster than a cast one makeing the clearances more critical. The other thing that helps with forged pistons is when you first begin to break the motor in you run a few heat cycles on it before putting it under a load.

Exactly. 100 Degrees before moving is not warmed up. With forged pistons I would let it get to it's normal running temperature(115-125), shut it off, let it heat soak for a few minutes, start it back up and ride it after a couple more minutes.

 

[skitter]

When I rebuild my motors I like to do the work myself cause I've seen what goes through dealerships they like to get it in replace and ship out the door with check in their hand. I'll usually take the cylinders to a machine shop and have them scoped to check for egg shape and dimensions. On my last set of cylinders I sent the jugs to u.s. chrome had them re-niked and cut to the pistons that were going to be installed, I made sure that my clearance was no less than .004 and no more than .006, my ring end gap was around .022 on all rings checked at top and center of cylinder squared. In the last picture it almost looks like the ring end gap may have been to close. I've got 400 miles on my motor installed the gizmo and I'm crossing my fingers that it will last. I would really like to get one of the new pros but resale sucks on these dragons and after a $1300 rebuild who can afford to buy anything!!

 

[milehighassassin]

for those saying to hone in the cylinders. You cannot really do that without re-nikasiling, correct?

 

[diamonddave]

for those saying to hone in the cylinders. You cannot really do that without re-nikasiling, correct?

Incorrect.

 

[2XM3]

Factory (cars,bmw,porsche ferrari) nik is .002 thick, so light hone only. US chrome co. nik is .006 thick in most cases allowing for honing to size. It just depends how thick the layer is. I believe they can go thicker as well but other problems (flaking) crop up..

I know on the Mercury drag 2.5 outboards we did they came back from us chrome .005-.006 thick and we final honed them with diamond hone to size taking out about .0015 to .002

 

[turbolover]

Honing

for those saying to hone in the cylinders. You cannot really do that without re-nikasiling, correct?

You can hone a nicasil cylinder to break the glaze and get a new set of rings to seat. Myself I wouldn't recommend taking more than maybe a 0.001 out of them. The nicasil lining is kinda like a chrome coating on the inside of the aluminum. It is harder than heck and wears really well but it is only a couple thousands thick. You start trying to take several thousands out of a nicasil cylinder and you'll be into the aluminum under it and its trash until you have it recoated.

 

[milehighassassin]

You can hone a nicasil cylinder to break the glaze and get a new set of rings to seat. Myself I wouldn't recommend taking more than maybe a 0.001 out of them. The nicasil lining is kinda like a chrome coating on the inside of the aluminum. It is harder than heck and wears really well but it is only a couple thousands thick. You start trying to take several thousands out of a nicasil cylinder and you'll be into the aluminum under it and its trash until you have it recoated.

Thanks. That is what I was getting at.
You certainly cannot bore it to size without a recoat/finish.

You can hone to remove glaze but that is all. The nicasil is harder than most hones.


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[DragonSlayer1]

Re-Nic

Got my cylinders back from the shop. They said it would not smooth out. Going to have to send it back to mellinium. I am done with this sled. I need a new hobbie.