Looper exhaust porting

[FORBESAUTO]

we need a few photos of the piston
you have cold water, is it running hot enough?

Especially with the wear being on the cold side

[FMP]

5/6 cylinders. You ran for hrs on a long trip, hot side cold side cylinder distortion from cold water? Hot side expansion loading the cylinder and pushing the piston/ring into the not expanding cold side. Unequal expansion around the sleeve on the piston? Would think opposite?
I read from a two-stroke guru that during heavy hot loading at rpm , the piston and sleeve clearance. If you could remove the piston from the sleeve you wouldn't get it back in. Clearance is actually negative, and if it weren't for the oil it would lead to the worst.
Good description here, should repost in separate thread
https://mcbperformance.com/p-25418-p...es-causes.html

[Captain75]

Two piston pics:

Cyl #4. 100psi, Idle relief gone

Cyl #6. 130psi, idle relief still closed
Same jetting.
This season water temp never went under 70 deg, (~21C)
All cyls on this bank shows identical wear.

[gfinch]

If I remember correctly. The problem Wayne Taylor and I had with the 3.3 was sticking pistons. The 3.3 had smaller exhaust runners and as they expanded they pushed on the exhaust port causing deformation of the cylinder bore. What Dave did was to reverse the water direction. Water flow goes to heads first then into the block then out, this preheated the water before it got to the block... again IF I remember correctly. It never stuck a piston again.

[BarryStrawn]

I didn't re-read the whole thread but I think this is a standard bore 3.0 and you honed it a bit oversize for the new pistons?

[Captain75]

I didn't re-read the whole thread but I think this is a standard bore 3.0 and you honed it a bit oversize for the new pistons?

Correct!

[powerabout]

like to see the piston sides.
What was the story on your cooling is it stock so it gets warm enough?

[FMP]

How was the weather when you ran? Extended running in thick fog 100% water content humidity, still looks like water? Fuel tank had no water? Piston side pic? One piston looks pretty clean

[Captain75]

How was the weather when you ran? Extended running in thick fog 100% water content humidity, still looks like water? Fuel tank had no water? Piston side pic? One piston looks pretty clean

Pic showing the #5 piston, 145psi (idle relief still stuffed)
The cyl shows wear in the same areas as all the other cyls, only slightly lesser...

[FORBESAUTO]

If I remember correctly. The problem Wayne Taylor and I had with the 3.3 was sticking pistons. The 3.3 had smaller exhaust runners and as they expanded they pushed on the exhaust port causing deformation of the cylinder bore. What Dave did was to reverse the water direction. Water flow goes to heads first then into the block then out, this preheated the water before it got to the block... again IF I remember correctly. It never stuck a piston again.

Not familiar with in and outs of the OMC, but I’m thinking this is definitely something to be looking into. From looks of it your cylinder is either running too cool, caused by this issue or too low of operating temp like power stated; or piston getting too hot ( the better cylinder has nice piston wash, first bad cylinder didn’t appear to have any indicating it needed a little more fuel. And quite possible a combination of each.

[FMP]

Standard bore if correct should clear a standard Wiseco. Pistons are sized to fit correctly. If you honed a standard your clearance should be more than ample. Did you note finished bore and piston skirt measurement, ring gap and compare.
Don't think it wasn't enough clearance but? Hate to see all the work and this.
It's all on the transfer side?
Think about this, if the tranfer side was hotter would the clearance be even less? Maybe the reverse flow, head first could help but the tranfer side would always be colder?
How does the underside look?

[BarryStrawn]

My question about honing the 3.0 standard bores for the new Wisecos is how did you measure the bores to know how round, not tapered, etc. as well as final size they ended up? How good is good enough? Obviously honing used bores will not be as good as a new overbore & hone job, at least when the work is done competently. I'm sure you know that, just speculating on causes.

[Captain75]

My question about honing the 3.0 standard bores for the new Wisecos is how did you measure the bores to know how round, not tapered, etc. as well as final size they ended up? How good is good enough? Obviously honing used bores will not be as good as a new overbore & hone job, at least when the work is done competently. I'm sure you know that, just speculating on causes.

I use a pretty simple method.
By using the rigid hone you can feel in the operating hand when the bore has shifted from oval to round.
Final size is determined by sliding the piston into the cyl upside down.(piston skirt being wider than the piston top) I use a feelet gauge to determine the play between cylinder wall and piston skirt. I have had the possibility to use a borrowed bore gauge in the past, now I have one heading my way by mail.

[FMP]

How did it look when the original pistons came out?

[baja200merk]

I don’t add extra clearance for the new wisecos u less the motor is going to turn over 7k. Wiseco builds the clearance into the piston. I added .002 to mine since it turns 7500 regularly but stock engines it’s not needed. My brother has no patience and turned his fresh wisecos 7k with about 10 mins on the motor still no issues