Pressing Apart The Crank

[tdi-rick]

I'd say that it is totally possible to rebuild a chainsaw crank, even if the connecting rod and crank bearing surfaces are shot.

It might not be worth the time and effort, but then hobbies rarely are.

Trying to say that they were not designed that way so it shouldn't be done is foolish. We've all done many things that were not designed into chainsaws.



Mr. HE

Well, we just used to get kart cranks hard chromed and ground to retrieve worn surfaces, so doing the same on a chainsaw would work, if it's cost effective.

 

[Dan_IN_MN]

Well, we just used to get kart cranks hard chromed and ground to retrieve worn surfaces, so doing the same on a chainsaw would work, if it's cost effective.

Probably a good option for a saw restore where a replacement crank is non-existent. Flame spraying is a good surface rebuild too.

Dan

 

[motomedik]

I rebuild the bike cranks without the use of the jig- it costs too much to be worth purchasing, for me.
Before disassembly I check the crank for true in a lathe and while she's chucked I use the tool carriage to scribe three lines across both webs (90, 90 and 180 degrees from the pin). I also measure web width and may check that against the width between the bearings in the cases (and the spec in the manual). Then the crank is pressed apart.
The pin must be started straight (duh) but I mean REALLY straight. I was taught to check with a simple machinist's square. A pin started and pressed crooked, will always be. Then the fun part of pressing the other half. The lines I scribed earlier are my reference- with a straightedge, and a caliper, I can get them very close in the press. I'll start the web onto the pin and then play with it, may even spin it in the lathe, and keep it as perfect as I can, go slow. Get the web width in spec, and after a few choice 'whacks' with a large old brass hammer, it's good to go. I check them with the crank clamped in the 3 jaw chuck of a small lathe. The support is only on one end and therefore it's very easy to see with the dial indicator which way it's out. Beating it seems WRONG, right? A local machinist once told me of a tour he took of a major snowmobile manufacturer's facility and witnessed cranks being trued in this most brutal fashion.
One thing I've found is that small RM125 cranks are very easy to rebuild and old LT230's aren't hard but big thumpers and Euro (Rotax) ARE hard to make 'flat rate' on. Multi cylinders are not to be messed with unless you've got a jig.
I think that there's no reason a guy couldn't rework a saw crank if there was a need for it. If the need and the parts are there, then go for it and take pics so we can see, too!

 

[Kebo57]

Hi does anybody know what tonnage is required to press a 13mm dia big end journal/pin out, it’s a ms362 crankshaft
Thanks in advance

 

[Kebo57]

Hi does anybody know what tonnage is required to press a 13mm dia big end journal/pin out, it’s a ms362 crankshaft
Thanks in advance

 

[Kebo57]

Well the press in pic is a 20 ton and it just did it see pic

 

[Kebo57]

Well the press in pic is a 20 ton and it just did it see pic

The reason for this is I have a ms362 with worn clutch bearing surface, the 361 crank has the same crank halves the 362 has a bigger wrist pin & different piston so you can’t swap the crankshafts
The 362 crank is expensive and difficult to come buy so all I need now is a 361 crank can be scrap big / little ends.
Anyone on here got one

 

[sean donato]

The reason for this is I have a ms362 with worn clutch bearing surface, the 361 crank has the same crank halves the 362 has a bigger wrist pin & different piston so you can’t swap the crankshafts
The 362 crank is expensive and difficult to come buy so all I need now is a 361 crank can be scrap big / little ends.
Anyone on here got one

https://www.ebay.com/itm/1342324934...QIkJ388QTy&var=&widget_ver=artemis&media=COPY

 

[Mad Professor]

Well the press in pic is a 20 ton and it just did it see pic

You'll need a magnetic base dial indicator, a set of V-blocks, and a machinist surface plate to check if the crank is true, or the 2 halves need to be "adjusted" for run out.

I did MX bike cranks many years ago

 

[Kebo57]

Yeah that one way I’ll align the two halves in my Hardinge HLVH lathe one side in collet other side with revolving centre in leaver arm tail stock with DTI, I did a few year in the Royal Ordnance calibration centre so it won’t be much of a problem

 

[Kebo57]

Well the 361 crank separation was a lot more difficult than I thought
I’d done a 291 just pushed the big end pin straight through the 361 is a total different construction
I’ll add two pics here 1st is the 291 2nd is the 361 the 361 big end is turned in to one side of the crank this makes it a lot more involved
I had to make a pot with a 2mm shoulder that would go between the con rod & the crank half with 0.010” clearance so as not to damage the cage
The next pic is the set up in the 10 ton press with the crank separated
I separated the old 362 & the new 361 crankshafts then swapped the con rod over
Next is a video of the alignment
Cheapest 362 crank in uk is £256.20 the new 361 was £46 from Garden Hire Spares Warrington it’s good company.

 

[Hulpio]

The pin material and German words to use in search.
https://www.ebay.de/itm/39430329070...oY1HhdbNziQj9IbI2PmeF7rQ==|tkp:Bk9SR-yL1YbiYg

 

[Kebo57]

Well the 361 crank separation was a lot more difficult than I thought
I’d done a 291 just pushed the big end pin straight through the 361 is a total different construction
I’ll add two pics here 1st is the 291 2nd is the 361 the 361 big end is turned in to one side of the crank this makes it a lot more involved
I had to make a pot with a 2mm shoulder that would go between the con rod & the crank half with 0.010” clearance so as not to damage the cage
The next pic is the set up in the 10 ton press with the crank separated
I separated the old 362 & the new 361 crankshafts then swapped the con rod over
Next is a video of the alignment
Cheapest 362 crank in uk is £256.20 the new 361 was £46 from Garden Hire Spares Warrington it’s good company.

Well a months has pasted and only got two thumbs up but no comments so that confirmation that I’m not in the inner circle on here I all ready new this as it’s happened before thing is I’m my own inner circle there won’t be many people on her that has a t slotting tool to produce the pot in the pic

 

[Hulpio]

Well a months has pasted and only got two thumbs up but no comments so that confirmation that I’m not in the inner circle on here I all ready new this as it’s happened before thing is I’m my own inner circle there won’t be many people on her that has a t slotting tool to produce the pot in the pic

Hmm. I personally found your post and pics very usefull. If crankpins, bearings and conrods would be easily available it would have perhaps raised more discussion. Crankpins are let us say between 12 and 15 mm in most of chainsaws and at least I have not been able to find supplier. It may or may not be necessary to replace pin and connecting rod if they show no visible wear. That is the procedure on motorbikes though. If this incredible lazyness gives me some slack I will weld a press kind of thing but instead of using hydraulics I will use M24 bolt. It should give me 20T if torqued 55kgm.
It is a problem that often it is enough for me to know how things can be done. It is not necessary to really do it.
Occasionally I do test my thoughts in practice and thank God I mostly find them right.

 

[pioneerguy600]

Well a months has pasted and only got two thumbs up but no comments so that confirmation that I’m not in the inner circle on here I all ready new this as it’s happened before thing is I’m my own inner circle there won’t be many people on her that has a t slotting tool to produce the pot in the pic

You are working in an area where very few on here have ever been involved in, pressing cranks apart is not something usually done on chainsaws as replacement cranks are not that expensive, don`t require specialized equipment and not everyone has the experience or expertise to carry this off, nothing to do with being on the inner circle.

 

[sean donato]

Well a months has pasted and only got two thumbs up but no comments so that confirmation that I’m not in the inner circle on here I all ready new this as it’s happened before thing is I’m my own inner circle there won’t be many people on her that has a t slotting tool to produce the pot in the pic

Honestly, we gave opinions, and different options. you decided that way forward and went with it. Didn't know kudos were needed.