Farmertec MS660 big bore cylinder (issue?)

[Nathan_Anthony]

Hello!
I have noticed something that may or may not be an issue with my cylinder wich I just got from farmertec.
the issue being that there is a lip on the cylinder head wich is between 0.4-0.6mm tall(Fig 1).


If I was to sand this away I would end up with a 0.6-0.7mm gap on the exhaust port when the piston is at it's top position as I go for a squish band of about 0.5mm.
If the piston is sitting on the cylinder head right now there already is a gap of about 0.5mm, this would later be present if I was to sand the cylinder head down(Fig 2)

would this gap be an issue?
would the squish be too tight? if so, what would be best?
should I even sand it down?
I know that adjusting the squish can have a great impact on engine performance since I did that with my MS200t.
I'm most likely going to use "Aspen" for fuel but the 4 stroke type since I got a bottle of stihl oil for mixing and this saw isn't going to be used all that much.

I thank you for your help in advance

Kind regards
Nathan.

 

[cuinrearview]

That's the squish band. I'd be more worried about a ring hanging on that exhaust roof.

 

[L34]

Yes that is a very flat ex roof.

 

[cuinrearview]

Now that I look at it closer, I think the pic is upside down and he's asking about the free porting. It may run, it may not, but it'll almost definitely run worse than an OEM top end. I'm not sure how to steer people away from the inconsistent **** from China, but here's yet another example.

 

[kz1000]

just got a brake handle for a 046, looks perfect but is an inch narrower than the saw. Need to buy a Chinese brake stretcher now!

 

[computeruser]

But it cost so much less!

 

[cuinrearview]

But it cost so much less!

For an occasional user it'll be just fine... no need to spend the big OEM money.

 

[Mad Professor]

Chinesium!!!!

 

[Nathan_Anthony]

For an occasional user it'll be just fine... no need to spend the big OEM money.

exactly
the OEM cylinder kit would cost as much as the entire chinesium knockoff saw
yes, the picture of the exhaust port is upside down
if I was to leave the cylinder as is, the exhaust port should be barely closed at top dead center with 0.5mm squish
as for the port itself, is it bad if it is square like that?
would there really be a risk of piston rings getting stuck there?
what would you suggest that I do?
I got a dremel and plenty of carbide bits to fix it, if there is anything left to be saved.
frankly, this big bore cylinder is just for fun, the original one still works, in fact, is barely broke in, just wanna up the chooch factor.
any risk demaging the crankshaft if the cylinder would actually self destruct?

Kind regards
Nathan

 

[cuinrearview]

exactly
the OEM cylinder kit would cost as much as the entire chinesium knockoff saw
yes, the picture of the exhaust port is upside down
if I was to leave the cylinder as is, the exhaust port should be barely closed at top dead center with 0.5mm squish
as for the port itself, is it bad if it is square like that?
would there really be a risk of piston rings getting stuck there?
what would you suggest that I do?
I got a dremel and plenty of carbide bits to fix it, if there is anything left to be saved.
frankly, this big bore cylinder is just for fun, the original one still works, in fact, is barely broke in, just wanna up the chooch factor.
any risk demaging the crankshaft if the cylinder would actually self destruct?

Kind regards
Nathan

I suggest you trash the junk top end, put a want ad for a used OEM jug in the trading post, and buy a Meteor piston.

 

[OM617YOTA]

frankly, this big bore cylinder is just for fun, the original one still works, in fact, is barely broke in, just wanna up the chooch factor.

Am I understanding this right, you want to replace a functioning "barely broken in" OEM top end with a chinesium big bore top end?

This is not an upgrade.

 

[cuinrearview]

Am I understanding this right, you want to replace a functioning "barely broken in" OEM top end with a chinesium big bore top end?

This is not an upgrade.

"Up the chooch factor"=free porting and hung rings. Don't forget the flaking plating.

 

[Justsaws]

You do not want that gap. Your chooch factor escapes out that gap.
Put the cylinder on the saw as it is and run it, use a cylinder gasket, run through a couple tank fulls at least. This will give you a base line of performance. The fit between the AM piston and AM cylinder can be sloppier than OEM, so tightening up the squish may not be a good idea.

 

[drf255]

OK,

”Freeporting” is what the bottom of the skirt being above the exhaust floor is called. It’s not desirable, but many a strong saw has been built with it with no detriment. It’s super common on big bore 066 jugs, it has to be there unfortunately. The port is too small to allow for the floor to be raised when casting it-there won’t be enough time x area if they did. The case won’t allow a 56mm piston of standard length to drop down into it safely at BDC, so they intentionally shorten the piston skirt and voilá, Freeport City.

I’d get a few diamond balls for your dremel. A 10mm of medium grit and a 4mm fine one. Bevel the ports with the large first, then bevel the new bevel you made where it hits the plating with the smaller fine ball. Then hand sand and scotchbrite before final assembly. Just cheap insurance.

In general. Big bores under perform standard bore oem jugs for many reasons.

 

[Nathan_Anthony]

thank you very much for your reply
you cleared up a lot of things that where unclear to me
thank you for the offer about the dremel bit, but I'm from europe, so shipping would cost more than the bits themselves ;D
considering that this is a cheap cylinder I'm propably going to do some minor work with the carbide bits, they work on the plating just fine and the surface finish is acceptable

I did some test cuts last weekend after a gentle break in period, major difference compared to the old cylinder(might have something to do woth the muffler mod as well)
still running her a little rich

as for the freeporting, with the stock gasket I get a squish of 0.6mm at the edge, about 0.75mm past the step, so the port is being fully closed, I'd call it good enough.

at an other note, is it normal for bio degradable bar oil to gum up after~6 months?

 

[OM617YOTA]

Yes bio bar oil will gum up. No clue about Austria, but here in the USA, plain vegetable oil works just as well, gums up the same, and costs much less.

 

[Nathan_Anthony]

figures.
I'm just gonna use 10W40 or whatever I got handy til I get my hands on some mineral bar oil.
I don't use the long bar all that much so odds are it's conna hang on the wall for a while again.

 

[OM617YOTA]

That's what I do. Big milling bar, actual bar oil may make a difference. For my little 18" bar, I've run just about everything and not had an issue. IR thermometer says the bar and chain run similar temps.

Personal preference is veggie oil for health reasons, it just makes such a mess and gums up in the off season. What bar oil I use matters way more than two stroke oil when it comes to how much I cough and how much my sinuses burn at the end of a work day. A good chunk of that bar oil is aerosolized by the chain moving 60mph+.