Fake MS361 - Too hard to pull cord??

[davefr]

I saw this fake MS361 at a flea market and the seller agreed to sell it for $20. I thought it might be a fun project. It looks brand new and it shows no signs it ever ran. My theory is the original owner gave up when he couldn't start it.

It's really hard to pull the cord. I could barely get a compression test done. (110 PSI)

So I pull the cylinder and piston off and the crankcase turns over just fine. I insert the piston w/rings into the cylinder and it seems a little more snug then I'm used to. Ring gap is .005".

I could not visually see any piston, cylinder or ring defects or issues.

I'll try a new $30 aftermarket cylinder kit for the heck of it. I can't think of much else to do. Is there anything else I should look for? I'm only doing this as a spare time killing winter project.

TIA

 

[motorhead99999]

Very strange for only 110 psi. Is your pressure gauge right?

 

[davefr]

Very strange for only 110 psi. Is your pressure gauge right?

Yes, it's always been accurate. I don't think I've been able to give it a good enough spin to get an accurate pressure test. Plus it's a cold engine that's never been run before. I'll start with a new cylinder kit. I think the rings are overly expanded and putting too much pressure on the cylinder walls. Don't know if that's a common issue with these aftermarket saws.

 

[woodbuckin]

pull the plug, still hard to pull?

take side cover off and turn over by rotating the flywheel?

could it be the starter assembly binding?

 

[TomW]

Check and rings close. I had an aftermarket piston that the ring grooves were too shallow and held the rings outside the piston OD. Also, on the 361 clone that I built, the crankshaft scrubbed the piston skirt when the piston was in the bottom position. A slight filing on the piston skirt fixed that.

 

[Freudianfloyd]

Could the crank have been installed off center and binding when the cylinder is back on?

 

[noodlewalker]

Yes, it's always been accurate. I don't think I've been able to give it a good enough spin to get an accurate pressure test. Plus it's a cold engine that's never been run before. I'll start with a new cylinder kit. I think the rings are overly expanded and putting too much pressure on the cylinder walls. Don't know if that's a common issue with these aftermarket saws.

I had one where the wrist pin was too big for the holes on the Piston. Caused similar symptoms. Better to just get another p/c IMO.

 

[William Balaska]

Rings might be upside down.

 

[quantico]

William.. you mean the wrong ring in each groove ?? Because i never knew each ring could have a top and bottom. Please let me know. Always trying to learn more.

 

[Tape]

I thought all Stihl's were hard on the cranking because of good compression. I know my 250 feels kind of hard for the first two pulls then it starts.

 

[Justsaws]

Check the clutch for being bound up against everything on that side of the saw. The clutch washers are to soft, replace with a OEM washer/spacer.

The starter pulley/spring area can be messed up as well. If the pulley is damaged or bound up the saw is very difficult to pull over.

I would have bought that saw at a fleamarket for that price.

 

[drf255]

That’s an AM saw as you know. Therefore it could be just about anything.

Rings upside down? No disrespect meant, but that’s impossible to do because of the locating pins.

Cylinder could easily be out of round or unsquare at base. I’ve had to roundfile an AM 036 jug I was testing out for a manufacturer because of that, and it was on an oem case.

If the crank was off center, it would be hard to turn over with the jug off.

Honestly, it could be just about anything. Inspect the slug. See if it’s rubbed in any odd spots to indicate an off center situation.

If your compression tester doesn’t have a shrader valve at the tip, it will be off on compression.

 

[jltrent]

As much practice as those Chinese have had copying our products you would think they could get it better than that. Pull the cylinder only and test everything leaving the piston on. You will find the problem that way. I would try another cheapo piston if that is the problem. Sometimes boredom is a good thing when dealing with some of these winter projects.

 

[davefr]

Thanks for all the suggestions. One of the first things I did was remove the plug and held the starter handle and the saw would not lower itself to the ground very quickly. Then I removed the cylinder/piston and I could easily spin the flywheel with my finger. Everything looks fine from connecting rod on down and I just don't see how it could be bottom end related. I installed the piston with jug off and it does not hit the case but there sure isn't much clearance. I did not see any evidence of the skirt grazing the case. But if it did, wouldn't it lock up totally vs. be hard to pull?

The rings seem to fit the piston OK but when installed in the cylinder, moving the piston up and down manually seems pretty tight.

My theory is just bad fitment of piston/rings/cylinder. I'll throw a $30 Hutzl cylinder kit on it and see if that fixes it. I just don't see what else it could be.

I bought this $20 saw for entertainment/challenge. It's sure a pleasure working on a brand new CLEAN saw for a change. I'm actually fairly impressed. The overall quality comes closer to a real MS361 then I thought.

 

[a. palmer jr.]

William.. you mean the wrong ring in each groove ?? Because i never knew each ring could have a top and bottom. Please let me know. Always trying to learn more.

I think he means turning the ring upside down in the groove with the locating pin holding it apart. By the way: most of us would be thrilled to get any kind of 361 for that price, nice catch!

 

[arto_wa]

As much practice as those Chinese have had copying our products you would think they could get it better than that....zip...................................

They actually have for sure, but as most of us have seen they can still also produce low quality stuff, so it's buyer be-aware!

I just finished assembling MS660 clone and am pretty impressed how good the parts look. Nothing missing all 100% there and no defects that I could see, but time will tell.

 

[arto_wa]

..................................................
The rings seem to fit the piston OK but when installed in the cylinder, moving the piston up and down manually seems pretty tight..................................................

My observation just for comparison:

The piston to cylinder fit (I.E. piston without the rings) in my MS660 kit was such that the dry piston without the rings would slide back and forth inside the cylinder just by gravity.

I did not measure the clearance, but the engine runs good and has plenty of power for cutting.

 

[davefr]

Guys, this saw really has me stumped.

I just installed a new Hutzl top end kit and I have the same exact problems. The saw turns over easy and feels smooth with compression released or no spark plug inserted. Trying to turn it over w/compression is extremely hard. I might get one revolution with a very hard yank. (Squish is .0375). It must be bottom end related but I don't see anything obvious.

Just curious what problems in the bottom end would cause this extremely hard to pull w/compression problem?? I would think problems in the bottom end would also make it hard to pull even w/o compression but it's not the case.

This saw has never run so it must be some kind of defect. (not surprised!!)

 

[a. palmer jr.]

The flywheel rubbing on something?

 

[kevin j]

put put some bluing on the piston and try it again and see if the rod journal may not be parallel to the crank axis and it may be pushing the rod at an angle pushing the piston to the left or right side and rubbing hard on the wall. Have you assembled it without rings and had the same thing?