Low Compression on Cylinder #2

[FWDan]

That sound like a good deal! Is it oversize pistons?
Maybe find a machine shop and have them look at it to determine what oversize you should be ordering.
Maybe have them chamfer the ports at the same time, I know I would do it when in there!
And like Jerry said, try and figure out why it clipped the rings. Chances are when you reassemble it you also fix any leaking gasket it had beforehand.
It could also be due to carbon build up and you just got unlucky.

I'm not sure all will require oversize pistons, until they are measured and cleaned up. Trying to find a machine shop in my area that can do it. Not having much luck so far. Regarding cause, what about water in fuel? I had that problem early this summer. Engine stopped while motoring across the lake. Ended up being water in the tank.

 

[las]

I'm not sure all will require oversize pistons, until they are measured and cleaned up. Trying to find a machine shop in my area that can do it. Not having much luck so far. Regarding cause, what about water in fuel? I had that problem early this summer. Engine stopped while motoring across the lake. Ended up being water in the tank.

In my experience water doesn't do any damage to cylinder or piston when running. But carbon build up could seize the ring, making it catch the port opening. A piece of carbon could fall of and lodge itself under the ring or the port.
It could even be something else being sucked in.
Could even be that the water helped loosen the carbon! Lot's of possibilities for failures.
Many times these catastrophic ring failures could be avoided with a chamfering of the ports, in my experience and especially if the ports are wide without much ring support.

Edit: with a bore you will need oversize piston!

 

[jerryjerry05]

Can't find anyone to do the bore job?
Call the local marine sales/service and ask the service manager who they use??

 

[FWDan]

I called around last week looking for a place to do the machine work and only found one, so far. They want $75 a hole to bore, $30 to machine hone and $10 to hand hone. Thanks Jerry, I'll be calling sales/service places this week to see who they use.

Until measured, I don't know if 1, 2 or all 3 holes will require oversized bore and oversized pistons. I didn't have time to pull the powerhead this weekend. Once I do though, I plan to take the block to a machine shop along with the bore size limits to see what they say. My Seloc book says for my 1995, 70hp Force motor the standard bore is 3.3750 with a service limit of 3.3762, max taper 0.002 and max cylinder distortion 0.0005. Since I don't have a real service manual, does anyone know if the full up service manual numbers agree? Does anything outside these numbers require an oversize bore?

 

[las]

When you get it bored it will require oversize pistons! and worn cylinders out of spec will require a bore.
I would recommend you get all barrels measured and then take it from there.
If they are out of spec, have them bored at the same time.
But do change the rings on all cylinders and get a hone on the ones you don't bore if that's the route you go.
But ask the shop what they recommend, always a good idea. They should be the experts after all.
And like I mentioned earlier I would chamfer the ports for better longevity, but others might disagree. It's your choice.

 

[jerryjerry05]

Have the shop tell you if it needs a bore or a hone.
The middle piston(if I read right) was the bad hole and needs the bore job.
You don't need to do all 3 holes unless they're damaged.
There are lots of 3 and 4 cyl Forces running around with 1 over sized piston.
On the Eastern Shore of Va. is a 125 I rebuilt 2010 only needed 1 piston.
That said any more than .020 over and then I look into boring the others.
Any more than .020 and you need to look into re-jetting the carbs high speed jets.
I said figure out why it went bad(said nothing about clipping a ring) if the motor EVER backfired or even coughed it could blow a gasket in a couple different places?? The port cover being the first place I'd look. Especially the cover with the fuel pump.
The gaskets are thin and put in with no sealer and blow out easily and sets the motor up for sucking air and running hot on that cyl. causing the rings to fail.

 

[FWDan]

Have the shop tell you if it needs a bore or a hone.
The middle piston(if I read right) was the bad hole and needs the bore job.
You don't need to do all 3 holes unless they're damaged.
There are lots of 3 and 4 cyl Forces running around with 1 over sized piston.
On the Eastern Shore of Va. is a 125 I rebuilt 2010 only needed 1 piston.
That said any more than .020 over and then I look into boring the others.
Any more than .020 and you need to look into re-jetting the carbs high speed jets.
I said figure out why it went bad(said nothing about clipping a ring) if the motor EVER backfired or even coughed it could blow a gasket in a couple different places?? The port cover being the first place I'd look. Especially the cover with the fuel pump.
The gaskets are thin and put in with no sealer and blow out easily and sets the motor up for sucking air and running hot on that cyl. causing the rings to fail.

Good points Jerry.

The only shop I've found so far said I need to bring the size limits in with the motor. Where can I get those?

Regarding failure cause, I can inspect the port gaskets and look for leaks. When I go back down with all new gaskets, what's the best sealer to use?

 

[Nordin]

The limit for the 3-4 cylinder Chrysler/Force is 0.04 in OD.
Pistons are available in 0,01, 0,02, 0,03 and 0,04 in OD.
If I do not remember wrong OEM pistons are not available in all those four OD sizes.
Aftermarket have all four, I believe.

 

[jerryjerry05]

The shop manual has the bore size.
The shop should be able to tell if the scoring can be cleaned up by a .020 or .010 bore.
Then you buy the oversized piston.
This is my opinion: I wouldn't spend $ on that motor. It's one of the worst Force ever made. My opinion.

 

[FWDan]

Yes, the shop can tell me if .010, .020, .030 or .040 will clean it up the damage, but they said I should provide the size to bore it to, so it will fit the oversize piston. I don't have the piston yet and I don't think they want to be responsible for the piston not fitting right. Seloc says the standard bore is 3.3750. Therefore, .010 oversize would be 3.3850 and .020 over would be 3.3950 and so on. Right? If they hit those numbers within +/- .0005, will the oversize pistons fit properly?

 

[jerryjerry05]

If they say .010 will work? then but a .010 piston and they can do the work.
Where are you buying pistons?
Every one I've ever done has needed a .020 over piston, even when the scoring didn't seem that bad??
Wiseco pistons is a bit more expensive(most cases) and easier to work with.
Your piston could be one of two styles? one is the older style that used pressure to keep the wrist pin in place the other uses a retainer(snap ring style)
Wiseco uses the snap ring and they are much easier to use.
The down side is you have to buy their rings and wrist pin.

 

[FWDan]

My pistons have the retainer rings. The wrist pins don't slide out freely, but they do move pretty easy with a light tap using a punch. I've been looking at the Wiseco pistons, but have not decided on forged or cast. Any suggestions on best place to buy them?

 

[jerryjerry05]

Right from Wiseco.
The Wiseco rings won't fit the regular pistons.