Stihl MS271 Puzzler

[waffenschmidt]

I have an MS271 with maybe 20 hours on it over 4 years. Last time I used it, after running fine for about 20 minutes, it bogged down and then stopped halfway through an easy cut. I was able to restart it and finish the cut, but it stopped halfway through the next cut. It hasn’t run since.

It had some 3-year old gas/oil mix in it (with stabilizer, but still old) so I figured I had gummed something up and I did this:

• Dumped the old gas and refilled with pre-mixed.
• Pulled the spark arrestor and verified it was clean.
• Blew the dust off the intake filter with compressed air.
• Replaced the spark plug and verified that I had spark.
• Cleaned the gas pickup/filter with carb cleaner (including soaking overnight).
• Took apart the carb but found nothing gummy or anything that looked fishy.
• Replaced the carb with a new one.
• Checked the impulse line (through the intake boot) and verified that it’s clear.
• Hooked a clear plastic syringe up to the gas line carb connection, pulled out a couple ounces of fuel and saw no bubbles. Was able to push about half of it back into the tank and then needed to open the fuel cap to relieve pressure, so it seems there are no leaks in the line and the relief valve on the tank works.

It’s just dead when I try to start it. It must not be getting fuel, but I can’t figure out why. A couple times after putting it back together to test, it fired for a few cycles that was it.

Any thoughts about what to try next? I don’t have a compression tester or any way to verify that the crankcase is sealed.

I don't have much experience with small engines, although I pretty much understand how stuff works. Still, I could very well be missing something that would stick out to someone with experience.

Sorry for posting this as my first post, but I found you guys when looking for ideas and people here obviously know what they’re talking about.

 

[atpchas]

Have you removed the muffler to see the condition of the piston? If there is no scoring and the rings are not stuck, compression is likely OK.
Have you tried to start it by dribbling some mix into the carb throat? If it fires but then dies, it points to the carb. If no fire, then consider spark or compression.

 

[waffenschmidt]

Thanks atpchas. I haven't tried dripping gas into the carb, but I will. I suspect it will fire and die, but I should verify. I'll also pull the muffler assuming I don't have to pull the engine out to do so.

 

[atpchas]

Thanks atpchas. I haven't tried dripping gas into the carb, but I will. I suspect it will fire and die, but I should verify. I'll also pull the muffler assuming I don't have to pull the engine out to do so.

Check your Inbox for a link to a shop manual for your saw. Should answer your questions about muffler removal (and lots of other stuff).

 

[waffenschmidt]

Thanks!

 

[waffenschmidt]

OK, I couldn't get it to fire by dripping fuel into the carb.

I pulled the muffler and the top 3/4 inch or so of the piston is scored, at least at the outlet to the muffler. It's wet from fuel, and the fuel bubbles when the piston seals off the exhaust opening and continues up.

So is it toast? And if so, can I get parts to fix it?

 

[waffenschmidt]

So I did a little more reading and a little more searching. Assuming I need to replace the piston and cylinder, this seems to be a good deal:

https://www.stovek.com/product/stih...ampaign=product&utm_medium=cpc&utm_term=78886

Any advice? If I go ahead and replace the top end, is there anything else I need to do at the same time? Are there any special tools I need? I have all the normal wrenches, sockets, screwdrivers, punches, etc. but do I need anything else?

TIA

 

[HarleyT]

You need a long Torx T27 tool to get to the screws, after prying out the metal plugs.

 

[HarleyT]

Here is a handy video I made, one of these days I'll load the part 2.
I think that the teardown was under 8 minutes total.

 

[HarleyT]

I mean I filmed a friend of mine........

 

[HarleyT]

Here is what you will be getting down to.

 

[waffenschmidt]

Thanks. I'll give the video a look.

I have long enough Torx bits to get the muffler off. Do I need one of those thingies to compress the rings while I slide the piston into the cylinder?

 

[waffenschmidt]

Does that $75 top end look like what I need? Seems like it should be, but I don't know much about small engines.

 

[atpchas]

Thanks. I'll give the video a look.

I have long enough Torx bits to get the muffler off. Do I need one of those thingies to compress the rings while I slide the piston into the cylinder?

No ring compressor needed. See page 40 in the shop manual.

 

[waffenschmidt]

OK, thanks all. I ordered the cylinder/piston and I think I should be able to do the rebuild. I'll post how things turn out.

Any other advice is appreciated.

 

[cookies]

That stovek website looks like a scammer web page

 

[waffenschmidt]

I didn't get that feeling, but in retrospect it does look a bit hinky. I guess I'll find out. I paid with PayPal, so hopefully they'll help if I end up with a problem.

Thanks

 

[cookies]

honda generators for 76 bucks, 100 foot rolls of chain for 75 bucks and the site is only a few weeks old..that kit you ordered should be over double that price.

 

[waffenschmidt]

honda generators for 76 bucks, 100 foot rolls of chain for 75 bucks and the site is only a few weeks old..that kit you ordered should be over double that price.

Yeah, I usually can sense when something doesn't look right, but this one got past me. Thanks, I'll see if I can get PayPal to cancel.

 

[waffenschmidt]

OK, after that brief diversion, I ordered the whole top end from Fisher on eBay, who I'm pretty sure is legit. It's a pull from a new saw. I have my saw torn down, and am waiting for the top end. A few questions, if someone would be so kind as to help me out:

• I ordered the Yamalube sealant, so I'm set there. How do I get the old sealant off the bottom of the clamshell?
• Can I use a bit of 3-in-1 oil or some motor oil to add a bit of oil to the sensitive bits before I put the engine together? Or should I buy a can of 2-cycle oil? (I've decided to use pre-mix going forward, although I choke on the cost, because I really don't use the saw very much.)
• Do I need the oil seal installation sleeves called for in the service manual? Assuming I can get away without them, is there anything special I need to do to make sure the seals are seated properly?
• Anything else I should know about before I put this thing back together?

Thanks for all your help!