Husky 61 big bore - is this too much slop in piston bearing?

[Drillerman]

Converting a husky 61 to a 272 and the wrist pin/piston bearing seems to have too much play. The bearing is a 12 id x 15 od x 15 long needle bearing but the new piston has 17 mm between the "shoulders." Is it me or does that seem like too much, heck if the connecting rod was to go one way and the bearing go the other, there would be over 2mm unsupported under the rod(actual bearing measured 14.6mm). Was thinking of either putting spacers either side con rod and bearing, getting a wider bearing, or maybe a different piston. Or should I just run it?

Also does anyone recognize this type of vent? I believe it is the oil tank vent, but not sure if it's broken.

 

[wood man]

OEM Husqvarna Oil Tank Vent 272 61 268 #503668403​

This is the part number for a new oil breather vent pipe. They are only about $6 so price is no problem. If you suspect it faulty, you simpy replace it.
Remember rubber goes hard and brittle over time, so will start to leak, whcih sounds like your one has.

I do these vent oil pipes when doing a full service on some saws for people as a matter of course and replace the open bearings for the crankshaft also, again just a quick easy thing for me to do while inside the crankcase.

I do crankshaft bearings to slow down the saw over years getting more and more vibration coming through to the users hands.

You might not be happy breaking crankcases to do this, and if this would be your first time, then it takes a bit of working through to get the crankcase split to replace the vent pipe.

I will put up a couple of pics of one right now I am working on. It is a 55 husky, but same technique and design of an oil pipe vent.

On the piston side, I am still trying to work out, but it sounds like far too much movement, but also they do have side to side movement, as long as no up and down movement.
Do not fit a spacer, what-ever you do, as these crankarms are machined to turn at high revs and adding spacers will cause problems to the balancing and may cause the saw to littery explode if something goes wrong.
You will understand now why they do not fit spacers, so you should not attempt this.
The needle roller bearings inside the sleeve will run side to side as is normal. it still has the needle rollers in contact with the con-rod on the crank side and the piston side.

You can take it to a machine shop, lawn-mower shop etc, and ask them to let you know if they think it is still with-in tolerance to be used like you describe.
It might cost you an hours labour for there work, but give you piece of mind.

 

[wood man]

here is an oil vent pipe on a different model, but same principal.
They have a little metal sleeve inside the pipe, brass normally or a copper compound.
This has to be a very very tight push fit into the hole. It should not be able to be almost fall into the hole without silght pressure applied to push it in, it has to be put in with a bit of force, or it will not work at sealing the hole, so will leak oil.

Not sure if this helps you any, and may make it worse for you.

 

[huskihl]

Are you certain that is the wrist pin bearing and not the clutch drum bearing? Been a while since I’ve been into a two series so I’m just hypothesizing

 

[NSEric]

I reused the 61's wrist pin bearing in the one I put a aftermarket 272 top end on. The oem bearing has more needles and looks beefier/better.

 

[Drillerman]

OEM Husqvarna Oil Tank Vent 272 61 268 #503668403​

This is the part number for a new oil breather vent pipe. They are only about $6 so price is no problem. If you suspect it faulty, you simpy replace it.
Remember rubber goes hard and brittle over time, so will start to leak, whcih sounds like your one has.

I do these vent oil pipes when doing a full service on some saws for people as a matter of course and replace the open bearings for the crankshaft also, again just a quick easy thing for me to do while inside the crankcase.

I do crankshaft bearings to slow down the saw over years getting more and more vibration coming through to the users hands.

You might not be happy breaking crankcases to do this, and if this would be your first time, then it takes a bit of working through to get the crankcase split to replace the vent pipe.

I will put up a couple of pics of one right now I am working on. It is a 55 husky, but same technique and design of an oil pipe vent.

On the piston side, I am still trying to work out, but it sounds like far too much movement, but also they do have side to side movement, as long as no up and down movement.
Do not fit a spacer, what-ever you do, as these crankarms are machined to turn at high revs and adding spacers will cause problems to the balancing and may cause the saw to littery explode if something goes wrong.
You will understand now why they do not fit spacers, so you should not attempt this.
The needle roller bearings inside the sleeve will run side to side as is normal. it still has the needle rollers in contact with the con-rod on the crank side and the piston side.

You can take it to a machine shop, lawn-mower shop etc, and ask them to let you know if they think it is still with-in tolerance to be used like you describe.
It might cost you an hours labour for there work, but give you piece of mind.

Thanks for the input and the pictures, my particular model has this port/vent on the top of the case and not the side. Near the front left side underneath the muffler (as viewed while cutting). Would that be the same type of vent line...if so the line would be vertical instead of horizontal.

Now for the bearing spacer, I was thinking of machining two pieces of brass that would keep both the bearing and the conrod from sliding excessively. One on either side to keep it more centered and balanced. Also being machined on a lathe, I don't think balance will be a problem. Still might just get a wider bearing. But not a fan of the thought that the conrod could potentially be 2 mm off center.

 

[Drillerman]

Are you certain that is the wrist pin bearing and not the clutch drum bearing? Been a while since I’ve been into a two series so I’m just hypothesizing

It's the same bearing as the original 61 wrist pin bearing. Thanks for the insight though.

 

[Gord404]

bought a cheap aftermarket piston once and had the same slop side to side, put a more expensive meteor on it and fit perfectly- in otherwords your piston is probably a wrongly made piece of chineese junk made wrong and never bothered correcting the problem like so many china made stuff- people buy it and why bother improving on it

 

[Drillerman]

bought a cheap aftermarket piston once and had the same slop side to side, put a more expensive meteor on it and fit perfectly- in otherwords your piston is probably a wrongly made piece of chineese junk made wrong and never bothered correcting the problem like so many china made stuff- people buy it and why bother improving on it

You probably hit the nail on the head. This was a Proline/sawzilla piston and cylinder that claimed that it wasn't made in China. Not necessarily the cheapest kit, but not a meteor either. I also bought their "performance" series kit for a 266 im going to big bore after this one. That kit looks much nicer and the piston has way less slop in the stated area. I'm wondering if the performance series is made by hyway...it has hw on the top of the piston.

Thanks for your input

 

[Gord404]

Hyway is made taiwan not mainland china and have a good rep

 

[J D]

I had a similar experience to Gord404 (although I didn't buy the piston it came to me with the saw, a husky 350).
When assembled the saw had a very slight rattle. On investigating I found the excessive play was causing the conrod to move sideways enough to contact the counterweights! I made some shims as you are thinking of doing & while this remedied the rattle, subsequent discussions on here made me think that it probably wasn’t a good long term fix.
It's now sitting in the "naughty corner" waiting for me to work out what I'm going to do with it

 

[Drillerman]

I had a similar experience to Gord404 (although I didn't buy the piston it came to me with the saw, a husky 350).
When assembled the saw had a very slight rattle. On investigating I found the excessive play was causing the conrod to move sideways enough to contact the counterweights! I made some shims as you are thinking of doing & while this remedied the rattle, subsequent discussions on here made me think that it probably wasn’t a good long term fix.
It's now sitting in the "naughty corner" waiting for me to work out what I'm going to do with it

JD I came across a post that seemed to use this approach and it was OEM I believe.

Piston Pin Bearing and Spacer Issues -- Jonsereds 110​

Sorry I didn't share the address link...still new to using forums, not sure how to yet. But it looks like both ends of the conrod have spacers. They also talked about hardened spacer, but I don't think that is necessary. Once the conrod is centered and the saw is started, I doubt that the rod will be likely to move. Besides, limiting the actual amount of movement/slop will help it keep from "slamming" side to side.

What did you make the shims out of?
Thanks for your help.

 

[Cantdog]

JD I came across a post that seemed to use this approach and it was OEM I believe.

Piston Pin Bearing and Spacer Issues -- Jonsereds 110​

Sorry I didn't share the address link...still new to using forums, not sure how to yet. But it looks like both ends of the conrod have spacers. They also talked about hardened spacer, but I don't think that is necessary. Once the conrod is centered and the saw is started, I doubt that the rod will be likely to move. Besides, limiting the actual amount of movement/slop will help it keep from "slamming" side to side.

What did you make the shims out of?
Thanks for your help.

I feel I must weigh in on this matter finally. It matters very litle what you make the spacers out of. This is not a revolving part. It only moves a couple degrees either way. I've found over the years that many aftermarket pistons, though a good representation of the original are lax in this area. Somewhere back in the history of this site I did a report on this......try searching my posts for the info. Basically the larger/more high performance the saw the tighter this measurement is on stock saws. The whole reason this even matters is that this dimention isthe only thing that centers the rod on the crankpin.
I have to also take issue with the Scottsman that warned about the problems with changing the balance of the crank by adding or subtracting weight. Though this is very true in just about every other gas powered engine it is not that much of an issue in single cyl two stroke motors. Case in point....the Jonsereds 49Sp uses the excact same crank part number and crankcase as the 52/52E Jonsereds. Both 44 mm bores. But the 52 has a two ring piston, wider wristpin bearing with two large trust washers on either side. The 49 is single ring with a narrow wristpin bearing and no thrust washers. I forget the weights but the 52 piston/bearings/washers weigh much more than the 49 piston set. There is no difference in vibration between these saws. Does your OEM piston weigh the same as your AM 272 piston?
Optimum side play on a piston/wristpin should be between 0.008 and 0.012".

 

[Drillerman]

I feel I must weigh in on this matter finally. It matters very litle what you make the spacers out of. This is not a revolving part. It only moves a couple degrees either way. I've found over the years that many aftermarket pistons, though a good representation of the original are lax in this area. Somewhere back in the history of this site I did a report on this......try searching my posts for the info. Basically the larger/more high performance the saw the tighter this measurement is on stock saws. The whole reason this even matters is that this dimention isthe only thing that centers the rod on the crankpin.
I have to also take issue with the Scottsman that warned about the problems with changing the balance of the crank by adding or subtracting weight. Though this is very true in just about every other gas powered engine it is not that much of an issue in single cyl two stroke motors. Case in point....the Jonsereds 49Sp uses the excact same crank part number and crankcase as the 52/52E Jonsereds. Both 44 mm bores. But the 52 has a two ring piston, wider wristpin bearing with two large trust washers on either side. The 49 is single ring with a narrow wristpin bearing and no thrust washers. I forget the weights but the 52 piston/bearings/washers weigh much more than the 49 piston set. There is no difference in vibration between these saws. Does your OEM piston weigh the same as your AM 272 piston?
Optimum side play on a piston/wristpin should be between 0.008 and 0.012".

Thanks for all the information! That makes sense that that side of the conrod basically only has pivotal motion on the wrist pin but the other side has rotational motion on the crank. Feel kinda silly for not thinking of that sooner. All that being said, I think I am going to try and make some brass spacers and give it a whirl. Only reason I am choosing brass is the ease of machining/parting it to exact width.

This makes me think that JD might be able to take his saw out of the "naughty corner"

 

[Mad Professor]

I feel I must weigh in on this matter finally. It matters very litle what you make the spacers out of. This is not a revolving part. It only moves a couple degrees either way. I've found over the years that many aftermarket pistons, though a good representation of the original are lax in this area. Somewhere back in the history of this site I did a report on this......try searching my posts for the info. Basically the larger/more high performance the saw the tighter this measurement is on stock saws. The whole reason this even matters is that this dimention isthe only thing that centers the rod on the crankpin.
I have to also take issue with the Scottsman that warned about the problems with changing the balance of the crank by adding or subtracting weight. Though this is very true in just about every other gas powered engine it is not that much of an issue in single cyl two stroke motors. Case in point....the Jonsereds 49Sp uses the excact same crank part number and crankcase as the 52/52E Jonsereds. Both 44 mm bores. But the 52 has a two ring piston, wider wristpin bearing with two large trust washers on either side. The 49 is single ring with a narrow wristpin bearing and no thrust washers. I forget the weights but the 52 piston/bearings/washers weigh much more than the 49 piston set. There is no difference in vibration between these saws. Does your OEM piston weigh the same as your AM 272 piston?
Optimum side play on a piston/wristpin should be between 0.008 and 0.012".

Yes that is true. I've done 038S--->038M conversions, a long time ago. I did a lot of research and pepparatio on the first conversion. I had OEM/NOS 038M and 038S assys in hand and an Itailian Tecomec 038M.

This is what I found. About 10-12 g differences in the piston assys from the 038S and 038M, both NOS and Tecomec. The saws use the the same cranks. I had access to very good machinist tools and scales at the time. I could have weighed to 0.0001 grams but that was not needed.

I only used OEM bearings and forgot to check side play on the top side between pistons.

Piston Assy Mass (g)	Piston dia. Skirt (in.)	Piston dia. Top (in.)	Cyl bore dia. (in.)	Cyl clearance (in.)	Piston pin. Dia. (in.)	Piston pin Bore (in)	Piston pin Clearance (in.)
O38S
94.48	1.967	1.962 (0.005 taper)	1.969	0.002	0.4725	0.4735	0.001
038M OEM
106.67	2.045	2.039 (0.006 taper)	2.047	0.002	0.4725	0.4735	0.001
038M Tecomec
104.27	2.046	2.041 (0.005 taper)	2.0485	0.0025	0.4725	0.4735	0.001

 

[Drillerman]

Yes that is true. I've done 038S--->038M conversions, a long time ago. I did a lot of research and pepparatio on the first conversion. I had OEM/NOS 038M and 038S assys in hand and an Itailian Tecomec 038M.

This is what I found. About 10-12 g differences in the piston assys from the 038S and 038M, both NOS and Tecomec. The saws use the the same cranks. I had access to very good machinist tools and scales at the time. I could have weighed to 0.0001 grams but that was not needed.

I only used OEM bearings and forgot to check side play on the top side between pistons.

Piston Assy Mass (g)	Piston dia. Skirt (in.)	Piston dia. Top (in.)	Cyl bore dia. (in.)	Cyl clearance (in.)	Piston pin. Dia. (in.)	Piston pin Bore (in)	Piston pin Clearance (in.)
O38S
94.48	1.967	1.962 (0.005 taper)	1.969	0.002	0.4725	0.4735	0.001
038M OEM
106.67	2.045	2.039 (0.006 taper)	2.047	0.002	0.4725	0.4735	0.001
038M Tecomec
104.27	2.046	2.041 (0.005 taper)	2.0485	0.0025	0.4725	0.4735	0.001

I currently don't have that accurate of a scale to check the weight difference. Would be interested to know though.

Changing the subject to the other question. Has anyone changed the vertical style oil vent that I described earlier?

Thanks for your time professor!

 

[J D]

What did you make the shims out of?

I made them out of some spacing washers I had that were conveniently close to the perfect size (I had to enlarge the center hole by about 0.015"). They were fairly hard but definitely weren't hardened steel. At the time I was unable to find much information regarding choice of material for the spacers so I went with what I had that worked. I didn't want to use anything "soft" as the spacers were only around 0.050" thick & I was concerned they might wallow out & disintegrate. I was also reluctant to use anything hardened in case it damaged the piston pin.

This makes me think that JD might be able to take his saw out of the "naughty corner"

I may indeed... it will only make it as far as the "to do" pile though as from memory it also needed the carb going over

 

[Drillerman]

I made them out of some spacing washers I had that were conveniently close to the perfect size (I had to enlarge the center hole by about 0.015"). They were fairly hard but definitely weren't hardened steel. At the time I was unable to find much information regarding choice of material for the spacers so I went with what I had that worked. I didn't want to use anything "soft" as the spacers were only around 0.050" thick & I was concerned they might wallow out & disintegrate. I was also reluctant to use anything hardened in case it damaged the piston pin.


I may indeed... it will only make it as far as the "to do" pile though as from memory it also needed the carb going over

My "to do" pile encompasses my entire shop...

Thanks JD

 

[J D]

My "to do" pile encompasses my entire shop...

Thanks JD

You're not alone

 

[wood man]

I have to also take issue with the Scottsman that warned about the problems with changing the balance of the crank by adding or subtracting weight. Though this is very true in just about every other gas powered engine it is not that much of an issue in single cyl two stroke motors. Case in point..

Myself also after re-reading what I wrote. Just over-thinking the problem this end and thinking too much on vehicle engines.
Also thinking back, I too am sure I remember people using spacers before to take up the slack as you mention to get them out of a jam as the slapping against the side of the arm was physically noticable when running it heavy and scored badly with grooves when taken apart..
I also forget people are machinists and know about balancing, and I never allowed for this, as in you know what and how to make them to fit and be perfect.
At least you now have better information from others you need to help you in all this.