Chainsaw Repair
Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Stihl => Topic started by: Cut4fun . on August 01, 2012, 02:22:20 pm
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Just want you guys to be aware that some aftermarket 036 kits are not flat across top of base where bolt heads are.
This is a post and pic from a guy trying to rebuild a 036 with AFM 036 cylinder kit that came from Northwood saw. $89 for P+C.
Yes it is the wrong bolts in pic, they are just being used to show the unevenness across top of base.
(((What I was trying to show is that the surfaces that the bolt heads bear against weren't machined,
and are far from being parallel to the machined flange that mates to the crankcase .
The Torx bolts would sit in there the same way.
It's as-cast & the flange faces have about a 7 or 8 degree draft angle to them.
Even if I could torque those bolts to spec without snapping heads, they won't last long once I start cutting.)))
He is going to mill the bases flat he said and Northwood offered another cylinder kit or $25 credit on one he has.
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I've pondered this for a few hours and came up with the conclusion it might not be a bad idea for those so inclined to face off the flanges .
Case in point of several OEM Mahle cylinders I 've done there has been a slight difference in the flange thickness in retrospect to the machined face that meets the crankcase .
It might sound anal but a better thickness and fit on an enhanced compression engine would be benificial .
If you could get a tilt on the axis of the bolt and cant the head out of alignment it could theoretically pull the threads on one side .Highly unlikely but possible .
I don't think you could get a miss fit nor tilt the flange of the bolt that much no more torque than it gets but everything counts an enhanced performance engine .
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Great site here - I have been lurking for a week or so.
Thanks for posting that, Cut4fun2.
That's my cylinder and fat fingers in the photo.
Will provide more details if anyone is interested.
I asked Northwood to check their inventory, as I have to believe they will be losing some customers if they sell many units like that one.
I work with design of bolted flanges in my day job and I have to tell you that assembling what you see in the photo is a sure way to gaurantee that you'll be tearing it down again - probably soner than later.
-Jim
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I'm with you on that because part of my job deals with threaded fasteners in the automotive industry .
It might sound odd but until certain measures were taken to assure integretity of these fasteners most warrentee issues were directly connected to failures of same .
When you deal with aluminum alloys of which a chainsaw or modern auto engine because of the nature of the material you have to be somewhat anal in regards to the tightening .Cast iron for example is much more forgiving .
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its not just the AM 036 jug either,seen that on the 044bb kit and 066 jug too