Stihl 460 mystery cylinder porting/ passages and rod knock.

[Smokehouse78]

I was out cutting last week and heard a faint random knock so decided to tear into it before something major happened. I pulled the muffler and made a clamp to squeeze a piece of rubber hose against the piston to hold it steady mid stroke so I could feel for play in the crank. It has slight play when I rock the flywheel back and forth. I pulled the top end and can't feel any vertical play in the big end bearing but I can get some tilt in the rod without much force and the bearing looks good. Wrist pin and bearing looks good also. So I'm on the fence of replacing the crank.

When cleaning the cylinder I noticed these passage ways ground in next to the transfers and peaked my curiosity to the port work done. Has anyone seen this type of work done before? I've just done mild porting myself and have not seen any work like this done on this site or anywhere else.

The history of the saw is unknown as I picked it up from a pawn shop in Montana a few years back ($225), looked super rough but ran good. It had a triple ported butchered muffler which I swapped for a stock muffler opened up and DP cover ( I need screens for cutting in California) and ditched the tattered and broken maxflow filter setup for a stock setup as a friend had those parts already from a junked saw. It does have a Steves Saw shop sticker on it out of Lolo MT so may well be his handy work.

 

[grizz55chev]

I was out cutting last week and heard a faint random knock so decided to tear into it before something major happened. I pulled the muffler and made a clamp to squeeze a piece of rubber hose against the piston to hold it steady mid stroke so I could feel for play in the crank. It has slight play when I rock the flywheel back and forth. I pulled the top end and can't feel any vertical play in the big end bearing but I can get some tilt in the rod without much force and the bearing looks good. Wrist pin and bearing looks good also. So I'm on the fence of replacing the crank.

When cleaning the cylinder I noticed these passage ways ground in next to the transfers and peaked my curiosity to the port work done. Has anyone seen this type of work done before? I've just done mild porting myself and have not seen any work like this done on this site or anywhere else.

The history of the saw is unknown as I picked it up from a pawn shop in Montana a few years back ($225), looked super rough but ran good. It had a triple ported butchered muffler which I swapped for a stock muffler opened up and DP cover ( I need screens for cutting in California) and ditched the tattered and broken maxflow filter setup for a stock setup as a friend had those parts already from a junked saw. It does have a Steves Saw shop sticker on it out of Lolo MT so may well be his handy work.

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Finger ports.

 

[pioneerguy600]

Yes, its referred to as finger ports.

 

[Smokehouse78]

Yes, its referred to as finger ports.

Thanks for the info, learn something new everyday.

 

[Sepia]

1st time I've seen finger ports on the exhaust side.

 

[pioneerguy600]

Your piston may be worn a good bit on the intake side skirt, that will cause a knocking sound, actually called piston slap. Try fitting the piston without rings up into the bore, see what thickness feeler gauge that can be inserted between the skirt and cylinder, anything more than .003 is getting quite worn.

 

[pioneerguy600]

1st time I've seen finger ports on the exhaust side.

Some do it that way to avoid the ring keeper pins from riding over the fingers. Others turn the piston around and place the fingers on the intake side.

 

[Smokehouse78]

Your piston may be worn a good bit on the intake side skirt, that will cause a knocking sound, actually called piston slap. Try fitting the piston without rings up into the bore, see what thickness feeler gauge that can be inserted between the skirt and cylinder, anything more than .003 is getting quite worn.

I will check that out this evening. Visually the piston looks good with no signs of wear as does the cylinder but looks can be deceiving so I will get some measurements.

 

[Montana Mik]

Steve's Saw Shop is still in business, still in Lolo.

 

[Smokehouse78]

I will check that out this evening. Visually the piston looks good with no signs of wear as does the cylinder but looks can be deceiving so I will get some measurements.

Piston doesn't seem worn, I couldn't squeeze in a .002 feeler gauge. I don't like throwing parts at something without seeing an obvious sign of failure, the crank bearing is probably on the cusp of excess play.

 

[Smokehouse78]

Steve's Saw Shop is still in business, still in Lolo.

I was in his shop looking for parts for some project saws back in January. A week later I picked up a 362 mtronic out of a pawn shop in the zoo, it has his sticker on it. It has a muff mod and that saw is a healthy runner. Now I'm curious to know if it has the same port work. The same week I picked an 034 super in mint condition from an estate sale in Hamilton for $50. I couldn't pass up that homerun deal.

 

[cuinrearview]

1st time I've seen finger ports on the exhaust side.

I was thinking the same thing. Seems like a fuel guzzler introducing fresh charge on the exhaust side. Shows what I know though.

 

[pioneerguy600]

Piston doesn't seem worn, I couldn't squeeze in a .002 feeler gauge. I don't like throwing parts at something without seeing an obvious sign of failure, the crank bearing is probably on the cusp of excess play.

How tight is the wrist pin fit and the bearing on the rod? Side to side slop on the big end needle bearings is not a problem but vertical slop is, other than that the side bearings may be the culprit especially if the bearing cages are about to give out.

 

[blsnelling]

Even a brand new crank will have angular play in the rod. As long as you have no radial play, it's good. Also, don't mistake dwell time at TDC and BDC as bearing wear.

 

[Smokehouse78]

How tight is the wrist pin fit and the bearing on the rod? Side to side slop on the big end needle bearings is not a problem but vertical slop is, other than that the side bearings may be the culprit especially if the bearing cages are about to give out.

Wrist pin fit is snug in the piston and no apparent play in the bearing. The side bearings feel good, no side to side nor vertical play. I checked those with a dial indicator. Without the jug on I can't feel any vertical play in the crank bearings but slide the jug on and secure the piston in the bore with side pressure through the exhaust port, I can definitely feel play somewhere. I may just order up a new wrist pin and bearing since its cheap and easy to do. Process of elimination.

 

[Smokehouse78]

Even a brand new crank will have angular play in the rod. As long as you have no radial play, it's good. Also, don't mistake dwell time at TDC and BDC as bearing wear.

Much appreciated. I was checking mid stroke before and after TDC. The day I heard the noise I was running my buddies identical saw I just tuned and it his was fine. I may grab his saw to compare the amount of play to how I'm checking mine.

 

[pioneerguy600]

Wrist pin fit is snug in the piston and no apparent play in the bearing. The side bearings feel good, no side to side nor vertical play. I checked those with a dial indicator. Without the jug on I can't feel any vertical play in the crank bearings but slide the jug on and secure the piston in the bore with side pressure through the exhaust port, I can definitely feel play somewhere. I may just order up a new wrist pin and bearing since its cheap and easy to do. Process of elimination.

It really is a step by step process, you will figure it out. Once in a while I have found the main side bearings to seem good but would still be a noise from them, upon pulling the saw down one or more ball bearings could shift due to the cages being worn or missing in just one section allowing the balls to slip or bunch causing a tick tick sound when the saw was running, couldn`t detect the problem with the crank in the case. Hope this is not your problem though.

 

[mkinslow]

Could be something in the recoil or clutch also

Sent from my SM-G892A using Tapatalk

 

[Smokehouse78]

Could be something in the recoil or clutch also

Sent from my SM-G892A using Tapatalk

Already checked the recoil. Clutch drum, bearing and springs are new.

 

[Smokehouse78]

It really is a step by step process, you will figure it out. Once in a while I have found the main side bearings to seem good but would still be a noise from them, upon pulling the saw down one or more ball bearings could shift due to the cages being worn or missing in just one section allowing the balls to slip or bunch causing a tick tick sound when the saw was running, couldn`t detect the problem with the crank in the case. Hope this is not your problem though.

Anything is possible, the forces at loaded RPM can really amplify things vs checking something sitting static on a bench.