New saw compression

[Khntr85]

 

[old guy]

That don't look like a lean seize to me, but whatever.

 

[Khntr85]

I'm not sure what the cause of this was but I did put on a dual port muffler cover, pull the limiter caps and retune the saw. I don't believe I had it set to lean, but maybe I did. It would four stroke out of the cut and clean up in the cut. Max rpm I ever saw with the tach was 13600. Right now the high setting is 1 1/8 out and that's where I left it after the retune. I'm gonna reassemble and vac/ press test after and make sure no leaks. The saw never cut wood with the H screw less than 1 turn in. Fuel mix is 100LL and stihl ultra 50:1.

Well I am sorry to say, but it was lean, don't know if that was only problem, but it was lean none the less... that pic I posted it the service manual for the ms461.... the "BASIC" setting is 1 1/2 turns out....so if you only had it 1-turn out that's a problem....

I am sure some of these super knowledgeable guys on here will help you get her rebuilt....I would be using OEM parts on a NEW saw like that.....

I am not posting any of this to be a ****.... I have a ms461 I got new and i do t k ow what I would do if she broke LOL.... just trying to help ya man that's all.... please let us know what you decide to do...

Lastly, unless you have fixed it, there is no use putting it back together, as YOU WILL cause more problems...

 

[Khntr85]

is that what a dead stihl looks like? lol just kidding man. that's really ******. it would be going back to the dealer if it were mine and under warranty.

Your killing me smalls, you hate stihls don't ya lol....no offense to the OP, but come on man will any saw run leaned out this bad... this saw was ATLEAST a half turn lean..

 

[Khntr85]

That don't look like a lean seize to me, but whatever.

Me either, like I said I doubt thats the only problem, but we all know when a saw is a 1/2 turn lean, problems will arise...

 

[Deleted member 135597]

All the damage is below the first ring. Can that eliminate any causes?

 

[Khntr85]

Oh and the reason your saw was always at the same RPMs is because it has a rev-limited coil...

 

[Deleted member 135597]

Well I am sorry to say, but it was lean, don't know if that was only problem, but it was lean none the less... that pic I posted it the service manual for the ms461.... the "BASIC" setting is 1 1/2 turns out....so if you only had it 1-turn out that's a problem....

I am sure some of these super knowledgeable guys on here will help you get her rebuilt....I would be using OEM parts on a NEW saw like that.....

I am not posting any of this to be a ****.... I have a ms461 I got new and i do t k ow what I would do if she broke LOL.... just trying to help ya man that's all.... please let us know what you decide to do...

Lastly, unless you have fixed it, there is no use putting it back together, as YOU WILL cause more problems...

I ordered everything from dealer this morning. Will have it Tuesday.

 

[Khntr85]

I ordered everything from dealer this morning. Will have it Tuesday.

Good deal man.... I got the parts list and service manuals in "beg for manuals" thread, I suggest you do the same... will help you a lot to be able to reference them.....go slow, check all other parts when assembling everything

Lastly ask questions, these guys on this site are 2-stroke masters......let us know how it all goes!!!

 

[blsnelling]

If this saw were run lean, you'd see the scoring on the exhaust side, not the intake side. The intake side is cooled by the incoming charge and the exhaust sees the hottest temps from exhaust gasses. Quite honestly, I don't know what to think of this. I've never seen anything quite like it. It appears that the rest of the piston/cylinder is pristine.

I would definitely pressure/vac test this saw, just to be safe. I would also trim the limiters on the carb. Tune the H so fat that it won't run clean in the cut, then slowly lean it out until it does. That's the only way that you can tune a rev limited saw. Personally, I would put a MS460 coil on it so that there's no way to mistake the rev limited for 4-stroking.

BTW, your cylinder looks fantastic. Once you get a new piston in there, you'll have a brand new saw again for only about $50.

 

[Deleted member 135597]

Good deal man.... I got the parts list and service manuals in "beg for manuals" thread, I suggest you do the same... will help you a lot to be able to reference them.....go slow, check all other parts when assembling everything

Lastly ask questions, these guys on this site are 2-stroke masters......let us know how it all goes!!!

Yup I got that manuals. Just a little background info on me, I've been an aircraft mechanic for 25 years and have done 100s of cylinder replacements but I don't know **** about 2 strokes So I'm sure I will be asking questions. Thanks.

 

[Deleted member 135597]

If this saw were run lean, you'd see the scoring on the exhaust side, not the intake side. The intake side is cooled by the incoming charge and the exhaust sees the hottest temps from exhaust gasses. Quite honestly, I don't know what to think of this. I've never seen anything quite like it. It appears that the rest of the piston/cylinder is pristine.

I would definitely pressure/vac test this saw, just to be safe. I would also trim the limiters on the carb. Tune the H so fat that it won't run clean in the cut, then slowly lean it out until it does. That's the only way that you can tune a rev limited saw. Personally, I would put a MS460 coil on it so that there's no way to mistake the rev limited for 4-stroking.

BTW, your cylinder looks fantastic. Once you get a new piston in there, you'll have a brand new saw again for only about $50.

I ordered the adapter plate for vac/press test when I ordered the piston. I have a mighty vac tester at work but it only does vacuum. You think it's necessary to test pressure to on a new saw? I guess I could hook up a regulator and use shop air and then check the bleed down

 

[Deleted member 135597]

If this saw were run lean, you'd see the scoring on the exhaust side, not the intake side. The intake side is cooled by the incoming charge and the exhaust sees the hottest temps from exhaust gasses. Quite honestly, I don't know what to think of this. I've never seen anything quite like it. It appears that the rest of the piston/cylinder is pristine.

I would definitely pressure/vac test this saw, just to be safe. I would also trim the limiters on the carb. Tune the H so fat that it won't run clean in the cut, then slowly lean it out until it does. That's the only way that you can tune a rev limited saw. Personally, I would put a MS460 coil on it so that there's no way to mistake the rev limited for 4-stroking.

BTW, your cylinder looks fantastic. Once you get a new piston in there, you'll have a brand new saw again for only about $50.

Yeah the exhaust side of piston and cylinder are pristine.

 

[Deleted member 135597]

Exhaust side of piston

 

[blsnelling]

If this saw were run lean, you'd see the scoring on the exhaust side, not the intake side. The intake side is cooled by the incoming charge and the exhaust sees the hottest temps from exhaust gasses. Quite honestly, I don't know what to think of this. I've never seen anything quite like it. It appears that the rest of the piston/cylinder is pristine.

I would definitely pressure/vac test this saw, just to be safe. I would also trim the limiters on the carb. Tune the H so fat that it won't run clean in the cut, then slowly lean it out until it does. That's the only way that you can tune a rev limited saw. Personally, I would put a MS460 coil on it so that there's no way to mistake the rev limited for 4-stroking.

BTW, your cylinder looks fantastic. Once you get a new piston in there, you'll have a brand new saw again for only about $50.

I would also check piston to cylinder clearance.

 

[Deleted member 135597]

I would also check piston to cylinder clearance.

Ok I will mic both

 

[blsnelling]

Ok I will mic both

For these purposes, a feeler gauge would also work. You might want to check that with the original piston, since you can do that now. You could also do your vac and pressure test now as well, even though it's best after final assembly. You could at least verify the crank seals, etc.

 

[Deleted member 135597]

I assume there's a table of limits in the shop manual? I didn't get a chance to go through it all

 

[Karla]

Ok - On being a mechanic for 25 years, but Its still a shame you need to go through this experience, and I think there was definitely something wrong with the saw, not your problem and could have been repaired by a "Good" Dealer under warranty. Anyhow I did have a chainsaw which I just recently worked on, and the piston looked almost identical but a little less damage. (see attached picture) or search "Another new chainsaw project", and you can read the blog. I did look at the spark plug photo, which also looks a little Hokie, like something was definitely going on there. The spark plug picture was a little fuzzy so difficult to Zoom in, but the plug looked extremely hot on one side and cold on the other, which is strange and definitely means something. I am wondering If maybe at some point you had a stuck de-compression valve ? I would definitely pull the decompression valve and check it, test it, and Inspect it, I have seen a number of these fail, and that could be an indication on the spark plug ? Really not sure. I hope this info helps, also very difficult to do the forensic diagnostics, but please thoroughly inspect all the crankcase parts and look for any debris, of course, it could have blown out thru the exhaust and its no longer there, Again just my two cents. Oh the chainsaw which I just rebuilt and got running again, did have a stuck de-compression valve too, and stuck open two out of every three starts, I am ordering a replacement.

ver

 

[Khntr85]

If this saw were run lean, you'd see the scoring on the exhaust side, not the intake side. The intake side is cooled by the incoming charge and the exhaust sees the hottest temps from exhaust gasses. Quite honestly, I don't know what to think of this. I've never seen anything quite like it. It appears that the rest of the piston/cylinder is pristine.

I would definitely pressure/vac test this saw, just to be safe. I would also trim the limiters on the carb. Tune the H so fat that it won't run clean in the cut, then slowly lean it out until it does. That's the only way that you can tune a rev limited saw. Personally, I would put a MS460 coil on it so that there's no way to mistake the rev limited for 4-stroking.

BTW, your cylinder looks fantastic. Once you get a new piston in there, you'll have a brand new saw again for only about $50.

Do you think something could have gotten hot, and/or broke loose to cause this scoring on the intake side...... I know the saw is "virgin" but could something have came off of big end to cause this.... surely with the brand spanking new air filter something wouldn't have got threw....

To the OP, how long did the saw run with the 1-turn out setting, before you knew something was wrong....

This is very interesting!!!