Chainsaw problems

[Connagh]

Can anyone help me or do I need to take it to proper machinery repairs or can I buy the parts to replace

exhaust on my ms391 keeps falling off looks like the threads have gone in the head. 

the bolt which you connect the sprocket cover to has managed to also damage all the threads inside and on the screw. Ms211 do I need to change the whole chainsaw frame

[spudulike]

Your MS391 needs the threads helicoiling. It is a relatively simple job if you have reasonable engineering acumen. You basically dril the existing hole, tap it and then insert a stainless new thread that looks a bit like a spring. This is dependent on the amount of land around the existing hole.

 

Your MS211....you can remove the damaged bar stud and fit a new one. Typically you can lock two bar nuts together on the damaged stud to remove it. A rattle gun helps or you can sometimes use plumbers grips to grip and turn it. 

Thread-lock the new stud in place.

[Connagh]

On 28/01/2023 at 18:27, spudulike said:

Your MS391 needs the threads helicoiling. It is a relatively simple job if you have reasonable engineering acumen. You basically dril the existing hole, tap it and then insert a stainless new thread that looks a bit like a spring. This is dependent on the amount of land around the existing hole.

 

Your MS211....you can remove the damaged bar stud and fit a new one. Typically you can lock two bar nuts together on the damaged stud to remove it. A rattle gun helps or you can sometimes use plumbers grips to grip and turn it. 

Thread-lock the new stud in place.

I’ve tried this on both ms211 worked but the threads were damaged in the plastic. So had to super glue the screw in to keep it from turning and being able to tighten the nut. Friend helicoiled the 391 but still it continues to shake the screws lose. Has suggested loctite but if that’s doesn’t work to buy the spare parts for the ms391 isn’t worth it will cost £200 plus. 

[pleasant]

On the ms211 are you referring to the bar stud that you are having issues with? If so, stihl produce an oversized thread repair stud, which simply cuts its own thread over the smaller one that has stripped.....providing you haven't boogered up what was left of it already trying to repair it with loctite etc

 

Part number is easily on the 'net' just order it online or through your dealer. Stihl produce these bar repair studs for all plastic saws in their range.

 

Here you go-

 stihl part number 1123 664 2405

 

Just take your bolts out, DONT DRILL out the holes as the above p/n are oversize and self tapping and are made to screw straight into the knackered holes. 5 minute job to fix with the above bolts.

Edited February 1, 2023 by pleasant

[Dan Maynard]

On the 391 I'm not sure you'll have much luck with Loctite as the temperature is too high, the glue is basically plastic.

 

Could try different bolts so the surface hopefully sticks, maybe black oxide or even stainless as they seem to take root when you don't want them to. Also thought maybe exhaust assembly paste would handle the heat but be removable.

 

Otherwise if the option is scrapping the saw then glue the screws in with plenty of high temperature JB weld, probably never get them out but how often do you really need to take the exhaust off a saw anyway?

[Macpherson]

4 hours ago, Dan Maynard said:

On the 391 I'm not sure you'll have much luck with Loctite as the temperature is too high, the glue is basically plastic.

 

 

 

Hi, I've never had any problems using Loctite on exhaust studs, although as you say the temp range  says up to 150C for the one I'd try first for this which would be medium strength Loctite 243 blue or high strength 2700 green, and although as said high heat degrades Loctite and a common way to undo a Loctite bond would be with a Oxyacetylene torch but this is far hotter than any engine would get and for instance would give you a good chance of removing the stud without pulling out the Helicoil with it, if that was ever something that was needed... I recon it's a easy and cheap first option with really nothing lost if it were to come loose again.

 

And to the OP, nearly always when a helicoil is fitted [ properly ] the feel of the bolt / stud in the repaired hole is slightly sloppier than an original cut thread.. this is normal.

Loctite goes off/ hardens anaerobically with the lack of air in the gaps it fills so if trying this, get the refitted stud vertical so nothing can run out before it sets... a wee bit of gentle heat from a blowtorch will speed this process up to no time at all.

Should it ever fail again you still have the option of using another other repair medium.

 

Just to add.. at this stage it would be a good idea to fit new studs just to be sure, as the last thing you'd want is for one to shear off flush with the face at the last thread.. which is exactly where it will shear if the stud is damaged from too many ins and oots or stretched from many attempts to tighten it.

 

Cheers to you both and good luck with the repair. 👍 

I used both of these [ or their older equivalents ]  on a daily basis most of my working life.

 

Thread Lock 243 10ml Loctite Blue Bolt Stud Nut Screw Fast Fix Glue Compound NEW

WWW.EBAY.CO.UK

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Locktite 243 Thread Lock 10ml Blue. Net Content: 10ml per bottle. This Blue 243 Thread Locker is designed for the locking and sealing of threaded fasteners which require normal...

 

Loctite 2700 OEM Specified High Strength Thread Lock & Sealant- Stud/ Nutlock

WWW.EBAY.CO.UK

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Henkel Loctite 2700 High Strength Threadlock. Fast Acting Thread Lock & Sealant. Up to thread size M20. High Strength- Designed for permanent locking. OEM Specified.

 

[Dan Maynard]

Fair play, if you've tried it and it's worked then why not. Think anything is worth a shot before scrapping the cylinder.