617 N/A Piston needed ASAP!

[ROLLGUY]

I am in need of a 617 N/A piston for the engine I have been working on for the past few months OM617 N/A main bearing problem- I'm baffled (last post). I put a piston in, but the vibration is such that it is not acceptable. It seems that the piston I put in is a little different, and has a different weight than the other four. I won't make this mistake again, and will weigh the piston that I put in, and compare it to the old one. I hope the replacement piston is a little heavier, or the same weight. Lighter would not be good. Photo attached of the correct piston top. If you have one, please PM me with a price with shipping. Thanks, Rich

[Stretch]

Oh wow I can almost feel the stress from here!

Thread #3!

From the original =>

Originally Posted by Stretch

You need to specify (in your ad) the required piston size and the weight if that is important to you!

######

I have some questions

1) How heavy is the new piston - how heavy is the old - what's the difference in weight?

The book says max 10g on a "worn" engine - max 5g for new (Chap 03-316)

2) When you fitted the new piston did you replace the rings with new?

3) Did you hone the cylinder walls before fitting?

4) Have you done a compression test - if so did you piss about tipping oil down the cylinder bores?

[mach4]

Several on eBay....

[leathermang]

Do you know the Group....
and the version of that group..
is it for the number one hole .... or 2-5 ... which are different sizes....

[ROLLGUY]

Originally Posted by leathermang

Do you know the Group....
and the version of that group..
is it for the number one hole .... or 2-5 ... which are different sizes....

I do know it is #2, and the piston I put in was from #2 of the parts engine. I also know the head of the piston is different. That is why I posted a photo. I think the head being different is the reason it is a different weight than the original. Also, I used the rod and piston together, and should have just used the replacement piston and the original rod. I plan to use the original rod and hopefully get a piston that is the same in design and weight. I do know that there are at least three different designs. I will get a photo of the other design soon, it is quite different around the pin and skirt bottom.

[ROLLGUY]

Here is a better photo

[capflya]

I'll see what I can locate... I have a couple sources locally that might have one.

[ROLLGUY]

Originally Posted by capflya

I'll see what I can locate... I have a couple sources locally that might have one.

Thanks, and please let me know...Rich

[leathermang]

Don't yall need to be sharing weights ?

[ROLLGUY]

Originally Posted by leathermang

Don't yall need to be sharing weights ?

As soon as I get the bad piston weighed, I will have a weight. It won't do any good to know the weight if all anyone has is one with the wrong top design. It will be a different weight for sure, if not the same top. Been there, done that.

[ROLLGUY]

Okay, I got the rod off and the bare piston weighs 1lb, 8.6 oz on my postal scale.

[Mölyapina]

Can you just lighten pistons to match? I'm sure there is a reason you can't, but just curious.

[ROLLGUY]

Originally Posted by Jooseppi Luna

Can you just lighten pistons to match? I'm sure there is a reason you can't, but just curious.

If I had a piston with the correct top, and it was heavier than the bad piston, then yes I would lighten it to 1lb 8.6 ounces.

[ROLLGUY]

I got the piston out and weighed it. It weighs 1lb 8.7 oz. Just .1 oz more than the original one. I have yet to weigh the rod, so that may determine how much more or less the entire assembly is. If it is real close, I can only assume the vibration was from lack of compression in that cylinder from using the old rings....Rich

[Stretch]

So that's a difference of 3 grams?

Well within the FSM specifications