Running in a new OEM top end?

[bullittman281]

No De-comp valve. The new top end doesn't have it. Saw runs and idles great. I can't see it needing seals. The saw is supper low time. I ran the stuffing out of the old top end. I cleaned the melted cylinder and piston up and gave it the beans while I waited on new parts. I would think that would have cleaned it out....... I've cleaned and oiled the air filter. It should not be letting anything in. Who knows???? Its odd. Every new piston I've done has little gremlins like this. Maybe its what little two strokes do...... As long as it looks kinda ok and there is no reason for panic, I'll run it. As it is the saw is a screamer.

Edit:
Fuel is 91 Premium no alcohol and orange bottle Stihl oil. It spent the day at work getting some time on it. Not a believer in Stihl oil but that's what we burn. I had it tuned fairly rich for the first tank and subsequently leaned it out. I think its around 13K no load on the tach now. Still obviously 4 stroking. I didn't want to give it too much too long just yet.

Bullittman

 

[cookies]

Do you wash out your muffler? that looks like sucked in trash marks. mine get a new air filter, fuel filter the carb gone through and the muffler washed out really well. Often the muffler has carbon slag built up that can get sucked in through the exhaust port.

 

[SteveSr]

Good evening.
Here are a few pics of the cylinder and piston after a couple of tanks of gas. Not sure what the marks are and the scratches. Have a look and see. The couple of top ends I've done do this. Not sure why. Cold saw has over 160 PSI compression. Hot is over 140. Gauge only goes to 160. This is at 6500 Ft. so the numbers will be lower than those at sea level. Saw cuts well. The intake scratch can be felt with a sharp pick. No evidence of the same damage on the piston. Foreign object damage?? The rest of the marks are just marks. They can't be felt. I'm nor sure if this is a cleanliness thing. Not sure how to get things any cleaner than with hot soap and water. Squish was ~.025" with no base gasket. Squish was measured by crushing lead solder. Ring end gap was ~ .011". All of the parts are new OEM Husqvarna 346XP. Let me know if anybody has any thoughts. For now Its back together and I'm gonna run it. Thanks!


Bullittman

BTW, How well did you clean the crankcase / cylinder before removing it? One of your photos shows some dust/dirt in the area which may end up in the crankcase.

 

[BrettS]

Certainly some grit getting in from somewhere that it shouldn't.

 

[bullittman281]

The muffler may be the culprit. I did wash it out but I've always given them the least attention. Never gave them much thought. Everything got a good bath in the solvent and hot water. The saw was completely disassembled, short of splitting the cases. They got washed out really well and blown dry while still warm. Everything was clean going together the first time. This evening I blew it off really well before pulling the cylinder but that was it. There may have been a bit of dust around but it was still pretty clean. The cylinder got a good hot water bath and 2T oil for pre-lube when it went back together. I used yamabond for the cylinder as there is no base gasket. That stuff sticks like mad. Never had a problem with it.

Bullittman

 

[Fatherwheels]

The muffler may be the culprit. I did wash it out but I've always given them the least attention. Never gave them much thought. Everything got a good bath in the solvent and hot water. The saw was completely disassembled, short of splitting the cases. They got washed out really well and blown dry while still warm. Everything was clean going together the first time. This evening I blew it off really well before pulling the cylinder but that was it. There may have been a bit of dust around but it was still pretty clean. The cylinder got a good hot water bath and 2T oil for pre-lube when it went back together. I used yamabond for the cylinder as there is no base gasket. That stuff sticks like mad. Never had a problem with it.

Bullittman

Definately particles of some kind getting in there. I blow out muffler with air
and steep it in a bucket of bleech overnight, then use a tooth brush or small wire brush to scrub the inside of the muffler again using raw bleach, then use air line to blow all out, mind your eyes and make sure not to blow dust into the case or on to parts going in the saw, or into your eyes. Then I steep muffler in gas / petrol
overnight, use a small brush to again wash around the inside of the muffler using gas, then dry and blow out, then wash muffler in hot water and dish soap a few times and dry on a hot plate or in the sun. Then do a visual inspection to ensure there is no dirt filings or anything else in there, give muffler a few whacks with a flat piece of wood to dislodge any possible trapped material, shake it and listen to ensure there is nothing rattling around in there, it seems like a lot of work, but it only takes a particle of the correct hardness and dimension to get sucked in the exhaust port, or air filter side and you will end up with what you have.

I have also seen people assemble engines with dust falling and even blowing in the breeze from their sleeves or jacket or coat or shirt right onto the nicely oiled shell bearings they were holding in their other hand, only saying, these people I have seen do this would argue all day long that nothing like this happened, that it was my imagination, maybe an eye test and pair of glasses would help them, but then again, if you have to tell someone there is dust on their cloths blowing onto their work, will glasses help them.
I have had many a dispute about people opening up filthy engines, instead of cleaning them first, that is one way to guarantee crap will fall in and lay unseen on the big end bearing, where it will destroy all in front of it.
Keep the crap out, then was wash wash and clean out the case regardless.

 

[cookies]

mufflers that separate I wash with stainless steel scrubbers and dawn until i hit paint or metal, can styles you can not open either get cut open and scrubbed then welded shut or they get a serious porting and then soaked in diesel and scraped with long picks until all trash is gone since porting or drilling holes always leaves steel particles in the muffler even if rinsed and the carbon/oil etc holds it until it gets sucked back into the engine when its running really hard and hot and the trash breaks loose.

 

[bullittman281]

I've got a new OEM top end on order for a MS360 rebuild. Its back ordered so I'll see if it even ever comes. Everything will get built on a clean blanket and a supper wash/scrub job. I'll see if that produces better results. Hopefully the top end comes sometime this year. Been waiting on saws for work for Close to 6 months I think. Long time. I'll see what happens.

Bullittman

 

[SteveSr]

I've got a new OEM top end on order for a MS360 rebuild. Its back ordered so I'll see if it even ever comes. Everything will get built on a clean blanket and a supper wash/scrub job. I'll see if that produces better results. Hopefully the top end comes sometime this year. Been waiting on saws for work for Close to 6 months I think. Long time. I'll see what happens.

Bullittman

Based on your previous photos I think that at least some of your issues stem from NOT cleaning the cylinder/crankcase before pulling the top end. This would be a GREAT way to get contamination into the engine. I am always amazed by the photos posted here of folks doing exactly this. Sometimes you are lucky and sometimes NOT!

Everything that I have rebuilt gets a kerosene bath BEFORE it gets pulled apart. If there is any doubt the bottom end gets double or triple flushed with fresh mix. After the bottom end is clean it gets covered with rags/plastic to keep any airborne dust out.

 

[Fatherwheels]

I've got a new OEM top end on order for a MS360 rebuild. Its back ordered so I'll see if it even ever comes. Everything will get built on a clean blanket and a supper wash/scrub job. I'll see if that produces better results. Hopefully the top end comes sometime this year. Been waiting on saws for work for Close to 6 months I think. Long time. I'll see what happens.

Bullittman

Im looking for a few parts to sort my saw, and what used to be a simple
click find and order is fast becoming a nightmare, even when you do find
something, it takes forever.

 

[Fatherwheels]

Im looking for a few parts to sort my saw, and what used to be a simple
click find and order is fast becoming a nightmare, even when you do find
something, it takes forever.

Forgot to add, remember windy drafty places, dust gets brought in and
distrubuted everywhere, its unreal at times, difficult to notice, I used to
do a lot of mig welding, and drafts are something I constantly fought,
even inside with doors far away, its amazing how the draft gets to your
welding area, I had the fumes of the welder to help find them, if they were
not going straight up past my shield I knew they were around me somewhere,
its not always obvious until your shielding gas takes a hit, too late then.

 

[CJ1]

Warm it up to operating temperature and then run it like you stole it.

Best info available! And don't overheat it. Proper warm up and cooldown will help any engine live a long life. CJ

 

[CJ1]

That is what we are told to do with 4 cycle engines with shell type bearings.
Two cycles have roller and ball bearings which require no break in. The only break in that takes place in a two cycle is seating of the rings to the cylinder wall. This needs to happen ASAP and only happens with high loads. Babying your motor under the guise of break in is counter productive.
When I raced snowmobiles the engine builder I used broke them in by making a series of full load dyno runs. By the end the exhaust pipes would be smoking hot! His motors always performed too.

Even with shell type bearings, if everything is correct [clearances] there is no break in as you know. As far as the babying and being bad for break in, google Yamaha SHO " making oil" and anyone can see the results of a easy break in!! The only thing in a engine that needs a break in period is the rings and the old style cam and lifters and that is basically obsolete now. The piston skirts are either coated or a non issue!! I am helping a friend break in 4 BBC engines in the next couple of months [one happens to be mine] and I am sure none will be broke in at idle! Bring them up to temp, check fluids, timing, valve lash then let em eat!! Just like you said. CJ

 

[ChillyB]

Humble new guy question. Do you use any kind of abrasives for cleaning up your cylinders or pistons? Scotch-Brite, for example? That stuff is from the devil and should be banned in any engine assembly area (and is banned in some engine assembly outfits with whom I am familiar). Scotch-Brite is particularly bad because the abrasive bits are very lightly adhered to the nylon mesh with a crunch candy coating. Rub a new Scotch-Brite pad over a white piece of paper. What comes off is a mix of abrasives and the crunchy candy coating that sort of holds it in place. Scotch-Brite doesn't get "dull", what happens is the abrasives (still sharp) fall off. The abrasives might embed in aluminum and become impossible to wash away, too.

 

[SteveSr]

Humble new guy question. Do you use any kind of abrasives for cleaning up your cylinders or pistons? Scotch-Brite, for example? That stuff is from the devil and should be banned in any engine assembly area (and is banned in some engine assembly outfits with whom I am familiar). Scotch-Brite is particularly bad because the abrasive bits are very lightly adhered to the nylon mesh with a crunch candy coating. Rub a new Scotch-Brite pad over a white piece of paper. What comes off is a mix of abrasives and the crunchy candy coating that sort of holds it in place. Scotch-Brite doesn't get "dull", what happens is the abrasives (still sharp) fall off. The abrasives might embed in aluminum and become impossible to wash away, too.

Nothing wrong with Scotch-brite... As long as it is used and handled properly. This includes meticulous cleaning of the cylinder afterwards.

I use red Scotch-brite as a final step after removing transfer from a cylinder... followed by a bath with hot water and dish soap.

 

[Patrick1903]

I've got a new OEM top end on order for a MS360 rebuild. Its back ordered so I'll see if it even ever comes. Everything will get built on a clean blanket and a supper wash/scrub job. I'll see if that produces better results. Hopefully the top end comes sometime this year. Been waiting on saws for work for Close to 6 months I think. Long time. I'll see what happens.

Bullittman

Did you ever get your new top end?