Why does ring locating pin fall out?

what kind of pistons? spi locator pins fall out with a small amount of deto.

One of my friend's told me that I can relocate the pin's
I will be trying it shortly as I have high compression in my 670 and
recently had the pin catch the exhaust port as well. I just assumed as
I picked up my premium from another gas station then all of a
sudden I had problem's. Now I am boring and replacing sleeves and piston's.
yipee

I had 3 friends with rev 800's. 2 were 05 renegades and 1 was an 06. All 3 every year had to put new top end in. They cracked cyls and scratched them real bad. They always used Skidoo pistons. The last guy put SPI's in it and sold it. It is still running so far this year, another buddy bought it.

Needless to say, these 3 no longer own rev 800's.

Edit: all were due to the locater pins falling out and ring catching.

This happened to me it is not a Brand issue it is caused from Deto, and or exsesive heat, overheating or lean condtions, time and time again, it eventually works it out of the piston. Mine let go with no warning and it also wasn;t up to full tem yet either

Yep. Light reapeated exposure to deto and preignition.

Nice indicator you have a condition to attend too..

Gus

Make sure the exhaust port shape is symetrical. If its not it will cause the ring to rotate back and forth pushing against the locating pin.

Some SPX/SPI pistons have a soft pin. My supplier is replacing a customers top end and fixing the damaged cylinder. Not even a tank of fuel and one pin has worn off completely while the other one looks like it has 2500miles on it. Customer is paying the difference for BRP pistons again.

Mild porting and high comp. head, what fuel are you running ?

Sometimes it's just to radical , the port job may be mild but guess what it's so easy to over port...

Start with atleast 100 octane and fat jetting than go from there.

I think it's 100% detooonationnn...

X2 on SPI's pins falling out. Happens on stock engines too.

get them welded

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Why Welded Top Pin Pistons



Since the invention of the two stroke it has been plagued with the problem of the ring locator pins loosening up with time and eventually falling out of the piston. Why is this a problem? Well, when the pin falls out of the piston it get wedged between the piston and the cylinder causing the motor to seize. The purpose of the ring locator pin is to hold the ring in one location so it won’t rotate around the piston and end up with the ring gap in a transfer port or worse yet the exhaust port. If the ring finds itself in this position it expands outward and the piston breaks it off when it passes the top of the port.
This loose pin has been rubbing on the cylinder wall

Another problem with the locator pin seems to be the inability of the manufacturer to drill the hole it's pressed into to the proper depth. When the whole is drilled too deep the pin can work its way inwards leaving nothing to stop the ring from moving around the piston. The final problem with the ring locating pins is the material used to make the pin. Most pins are very soft steel. The pin should be equally hard or harder than the ring since the ring is the changeable part. In other words the ring can eventually wear out the pin.
Here is a factory top pin piston where the ring has worn clean through the soft locator pin.

Most pistons with loose locator pins have 100s of hours of run time left on them but are rendered useless because of the loose pins. Some people say, Just buy new ones. Well, despite the unbelievably high price of new pistons they still come with the same inferior pins just waiting to fall out. Nothing is indestructible but this is by far the best method to date of pinning a piston.
Welded top pin pistons address all these problems and present the perfect solution.





Here are some

other great links

I thought the SNAKE OIL sales team had left the building..LOL

The ring pins do get knocked loose from ehaust port widening that is favoring one side but ONLY in single port cylinders.
Three port exhaust cylinders do NOT have wide enough main ports to cause ring loctator pin issues.
On my old 12 port welded cat 800 triple cylinders I had not only added the exhaust sub ports but 4 other finger port, two were DIRECTLY on the ring end gap. NEVER did we EVER loosen a ring pin.!!

DETO no other reason in ANY modern MULTI port exhaust cylinder.
I have single port cylinders with exhaust port widths over 90% at the widest point that have NEVER even caught the ring let alone move or loosen the pin.

Don't get confused by the all the theory.. its deto stop that, stay off the spi piston toilet and ride ride ride.

Gus

m8magicandmystery said:

get them welded

US1 Racing Engines

.....

Click to expand...

Just curious how you weld a steel pin into an aluminum piston?

Great Thread i have been wondering for years where those marks on my head came from i thought some bearing broke in half!!!! 99 700 POO . It did melt down but from a broken recoil rope and burnt fuse in the digitron, who would thunk it would blow the water pump belt off....... oops!!

So.... back to stock head... right????

I'd like to ride with ya this season!!!

Change the squish angle and try again!!

NoSecondChances said:

Just curious how you weld a steel pin into an aluminum piston?

Click to expand...

darn if i know...i just googled loose locater pin/ piston ring and the above info site came up so i copied and pasted it for info..

ask the guy that says to do it..??

US1 Racing Engines


All work done in-house by

_____________________________________________

John Marles

Two Time National Champion Formula One Boat Racer and Engine Builder

661 250-7157

us1@sbcglobal.net