357/359 piston to conecting rod cleareance

[Eric Modell]

I am putting a new mahle 357 piston and cylinder on my 359 saw.

The new piston does not slide on the connecting rod. The old rod is about 0.050" to large. I am filing out the piston to fit. My question is how much clearance do I need.


Thanks

Eric

 

[troutfisher]

I would measure the old piston.

 

[Eric Modell]

The old piston has about 0.005" clearance.

 

[troutfisher]

Sounds good to me, that .0025 on each side of a roller bearing. I've never run into this before, the piston always just slid on.

 

[romeo]

You just need more clearance, thats all. There is no "centering" thrust quality on the top side of the rod. I have seen pistons with nearly .250 clearance and some with only .020.

 

[Eric Modell]

Thanks romeo that's what I needed to know. I did not want to screw up my new $300 p&C

 

[SawTroll]

Thanks romeo that's what I needed to know. I did not want to screw up my new $300 p&C

Romeo knows his stuff - I would trust him.....

 

[Cliff R]

I would follow his advice as well. There is no maximum clearance. Just for good measure I would make sure the minimum clearance should be a few thousanths more than the crankshaft endplay plus the rod side play on the crank pin. It can be a lot more (probably wouldn't hurt anything if it was less), but I would make sure it has at least enough clearance that the rod can float in the between the insides of the piston without any potential for side loading either end of the connecting rod...FWIW.....Cliff

 

[troutfisher]

few thousanths more than the crankshaft endplay plus the rod side play on the crank pin.

That is a very good point........I think there should be a bit more clearance at the wrist pin than at the crank. The side clearance at the big end of the rod should limit travel.

 

[Lakeside53]

I don't agree with the last two posts at all.

Most I see have a lot more horizontal travel at the big end than the wrist pin. This allows for any assembly offsets. Stihl's have a small piston clearance - you need to be sure the wrist pin bearing stays captured (and on) the rod end... and not travel out to one side. Are Husky's different? Not on the few that I have seen. A big clearance (one of my many bitc#es about some aftermarket crap) is that it allows the bearing to slide to the point the rod end is no longer fully supported.


As for rod side play.... as they wear it can be a lot - it "tilts" side to side way way more than it "moves horizontally". And.. the 359 crank is supported by deep groove radial bearings - effectively eliminating "end play" (but not slight assembly offset).

 

[troutfisher]

So you're saying that the piston clearance needs to be tight enuff so that the bearing stays fully inside the rod. That makes some sense. Maybe measure the length of the cage, and the length of the roller, and split the difference for side clearance?

 

[Lakeside53]

It needs to be wide enough to allow for thermal expansion of the piston and rod and is some cases, lube.

Most bearing cages are exactly the same width as the rod.

Using a file to open the piston boss is going to be "inexact at best". I'd by trying for the 0.005 you measured but err slightly on the larger side incase you are not square. Actually, I'd use a mill and just set it exactly!;

 

[fredmc]

357 359 crank

I thought that they had different cranks as well as different p/c. Look at the IPL could i be wrong...

 

[AZLOGGER]

I am putting a new mahle 357 piston and cylinder on my 359 saw.

The new piston does not slide on the connecting rod. The old rod is about 0.050" to large. I am filing out the piston to fit. My question is how much clearance do I need.

Thanks Eric

Eric:
This information is for Eric and any others that plan on exchanging the 359 cylinder to a 357 cylinder. Husqvarna changed the width of the small end of the con-rod on the 357 from 13mm to 15mm beginning with ser.#02-0700001. The 359 con-rod was always 15mm, so if you are converting a 359 to 357 you will need the following parts to eliminate any fitment problems.

In order to further improve reliability, and improve the compatibility of other components with model
359, the width of the connecting rod has been increased from 13 mm to 15 mm.
NOTE! These parts are not fully interchangeable with those on earlier models. Please see below.
New part no. Description Excl. part no. Remark
537 21 92-01 Crankshaft assy. 503 93 31-71 *
537 21 95-02 Cylinder assy. 503 91 98-71 *
537 21 96-02 Piston assy. 503 92 04-71 *
503 25 56-01 Gudgeon pin bearing 15 mm 501 86 18-01 13 mm *

*still available as spare part for earlier versions of saw

Introduced from serial number: 357 020700001

Hope this clears up any confusion with the problems like Eric encountered!

 

[Lakeside53]

I thought that they had different cranks as well as different p/c. Look at the IPL could i be wrong...

They added "bells" to reduce the crankcase volume on the 357. They can be popped off, and subject to the info just given by AZlogger... they are the same.

 

[HiOctane]

You can only buy the "large con rod" piston under # 537219602.

 

[AZLOGGER]

You can only buy the "large con rod" piston under # 537219602.

?


15mm=537 21 96-02 Piston assy. 13mm=503 92 04-71 Still available part#

 

[Eric Modell]

Thanks for all the help. I have been filing the piston by hand, but can not remove enough material on the side to keep it square. I will take it to work and have it fixed on a mill. I will have to hang my head low and beg. I work on the production side, and the maintenance people walk on water and will not let me use the equipment.

I had two dead huskys and all the local dealers told me to throw them away.
I do not understand why chainsaws can not be affordably repaired.

With your help my 285CD runs as good as new , only 27 years old. (did not cost any money)



Thanks

Eric

 

[romeo]

Good discussion, I just ran into to this last night. Just put the piston on the mill and cut it to the dimensions of the old one. No PROB!!


FYI though, I have some saws that have huge clearance and no probs

 

[Lakeside53]

What did we do before we got mills? :greenchainsaw: