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sime42

MS200T Exhaust Bolts - Thread stripped

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Good day all,

 

I'm after a bit of chainsaw repair advice. I've got a lovely little MS200T that's recently developed a wobbly exhaust. I've noticed in the past couple of years that the bolts occasionally seem to come loose, but they've always tightened up and the exhaust has held firm again for months. I recently took it in to the local dealer for a general service and repair. When I collected it they said they'd also had to put an exhaust bolt in as one had dropped out, (unbeknown to me). The first time I used it when I got it back it ran sweet as a nut for a couple hours and then the bloody exhaust came loose again, by the time I noticed and checked it was missing a bolt already. I ordered a couple of genuine stihl replacements, put the missing one back in and ran it again. This time it only lasted a couple of minutes before they both shook loose. Conclusion is that the threads are obviously stripped in the holes, (didn't feel right when I tried to tighten them so I had an idea of the problem already).

 

I'm somewhat reluctant to take it back to the dealers again as I've spent far too much money in there recently. Also I discovered that the remaining exhaust bolt in there when I got it back last time was nothing like the original stihl type. It was much coarser and looked like some kind of self tapper. So someone must have known there was a problem with the thread but it wasn't mentioned to me. Plus it seems like a crude repair attempt;- re-tapping the hole or using a helicoil would surely be better. (To be fair to the dealer place it may not have been them that put it in as I've had it repaired elsewhere in the past).

 

So my question to you knowledgeable chaps is;- how easy would it be for me to install helicoils myself? From my brief research it appears that is the best repair to this quite common problem. What exact size of helicoil do I need? If I have to drill out the holes how accurate must I be, i.e. can I use a hand-held drill?  As I don't own a drill press unfortunately.

 

Thank you. Sorry about the long-winded post again, this was my attempt at being succinct!

 

Simon

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Not an expensive repair really.

worth getting a pro mechanic or light engineering shop to do it for peace of mind

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The finished thread is M5, I usually strip off the tank and handle to do the job as it is easier to do so. I generally find the washers are missing on the exhaust bolts and the aluminium wears under the bolt and makes it come loose. A little thread lock will hold bolts in place.

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On 13/08/2018 at 21:29, sime42 said:

 

So my question to you knowledgeable chaps is;- how easy would it be for me to install helicoils myself? From my brief research it appears that is the best repair to this quite common problem. What exact size of helicoil do I need? If I have to drill out the holes how accurate must I be, i.e. can I use a hand-held drill?  As I don't own a drill press unfortunately.

 

The kit should come with a tap that you can use directly in the existing hole without the need to drill since the existing hole will be large enough already. You might need to buy a tap holder. Also, use a bit of bar oil for lubrication and make sure you stuff something in the exhaust port to stop swarf entering.

 

 

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Depending on how much wear has occurred, it can be difficult to line the tap or drill up. I bought a helicoil kit, not realising it was a Neilson set, to find that the drill was bent! so be watchful. As you've only one attempt at doing it right I'd suggest dropping into an engineering works and ask them to drill it, if it needs it. (I've done so more than once)

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Thanks for the advice you lot. Very useful as it generally is on here.
I'm going to pick up an M5 helicoil kit tomorrow. It's a Draper "Expert" one so I hope it'll be ok. I have been concerned about quality. There's loads of kits online but they mostly seem to be the same but in different colours and with different names on. Like most tools these days. It's hard to judge quality from a picture but I have my doubts based on the number of cheap crap tools around now.
Anyway I'll strip the saw down a bit as Spud suggests and then decide whether to take it somewhere to be drilled out depending on how the holes look and the state of the kit.

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Drilling the holes isn't too bad but with a decent tap cutting in alloy, there should be no need to drill it first as the stripped hole will be pretty much to size. Just get the tap going in as straight as possible when you start to cut the receiving thread.

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Get a couple of 5MM Time Serts Find them superior to Helicoils  if you are handy you can dill the fastener heads & wire lock suggest you us new M5 bolts

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