Author Topic: Stihl 461 piston  (Read 35 times)

0 Members and 0 Guests are viewing this topic.

Offline Cut4fun

  • Administrator
  • Nitro Hotsaw
  • *******
  • Posts: 4334
  • Karma: 189
  • OHIO REDNECK
Stihl 461 piston
« on: June 26, 2021, 08:59:53 am »
Just got to save these pics and explanation on new saws pistons.  Have seen it before and wondered why.

Question was - 461R New out of box and never been started or fueled yet outside of the factory. Why?

Answer - Trevor Saville
All of these pistons are washed with Tin from the manufacturer (Mahle, KS, Stihl BR/DL, Gilardoni) to help with break-in/cold seizures. The bright area at the bottom is not slop it indicates the max clearance Spec'd for the part. The edge of the skirt is being shined up from all the loose Tin coming off the piston plus the iron from the rings. It also indicates there's a draft angle for piston crown growth. The human eye will pick up on something like that even though its clearnce is .0005 and perfectly fine. As you get past about the 5th tank. Pull the cylinder again you'll see the pattern grow and change as it breaks into the cylinder and washes all the tin off. Run it.
Where you want to worry is when you pull the cylinder on one with dirty ingestion and it's peened the skirt edge plus has gouges that can be felt by touch. That .005 will start the downward spiral of slop and eventually 🔥.

More added - Trevor Saville
 I found the right person to ask years back. Remember when Baileys sold the Wiseco pistons they would grow in the cylinder and cold sieze? Too tight on clearance and no coating to help break-in.They were like little marshmellows if you didn't properly warm them. There has to be cold clearance or you would have to preheat the cylinder with a torch to get it free enough to pull over. An engineer at Mahle told me the F1 motors are preheated hours in advance of a race to even be able to start them as the pistons are clearanced so tight below operation temperature they are literally stuck in the cylinder bore.

REDNECK Saw Repair

Share on Facebook Share on Twitter


 

Related Topics

  Subject / Started by Replies Last post
2 Replies
419 Views
Last post August 04, 2011, 08:04:28 pm
by Old Iron Logging
0 Replies
233 Views
Last post May 24, 2012, 08:20:22 pm
by MP5N
15 Replies
457 Views
Last post December 17, 2012, 12:02:09 pm
by Remington
1 Replies
44 Views
Last post March 11, 2014, 04:13:31 pm
by Cut4fun .
4 Replies
133 Views
Last post October 10, 2014, 09:07:16 am
by aclarke
Stihl 046 Piston

Started by farmboy « 1 2 » Stihl

13 Replies
307 Views
Last post January 13, 2015, 09:13:30 pm
by jacob j.
49 Replies
758 Views
Last post September 09, 2015, 07:46:42 pm
by Cut4fun .
3 Replies
190 Views
Last post March 01, 2015, 09:28:18 pm
by SquareFile
0 Replies
58 Views
Last post March 04, 2015, 08:35:50 am
by jmester
0 Replies
102 Views
Last post January 16, 2018, 11:11:53 am
by Cut4fun .