Chainsaw and 2 stroke maintence

[Kram]

Thats the decompression port hole

 

[dobbslc]

That explains it! You don't get them on racing bikes

 

[JOEPRO]

Thats the decompression port hole

Ahah that explains it.

I'll let myself out then

 

[Kram]

To be honest tho it would make much more sense to me on roof of cylinder because I dont see it on the side and always forget to press it, and then the piston rings wouldnt go over it.

 

[Colin Barron]

Ref chain cleaning.... have you tried Kerosene? I find it superior to diesel (& lots of pricey cleaners).
I use it to clean my MTB chains (which are used in appalling forest grit, mud sawdust, water etc etc).

(I use Chainsaw chain oil as lube in preference to all the expensive chain lubes as well on my MTB chains - as I did on my motorcycle chains. IME nothing works better).

I tried vegetable oil in the chain lube reservoir but the result was bits sticking to the chain and sprockets. I discussed this at the stihl supplier and he opened a bottle of chainsaw lube and demonstrated how the oil put between his finger and thumb formed a link between them as he moved them apart. When i have tried this oil bits do not stick to the chain.

 

[DAPPH]

What are all the fine score marks on the cylinder wall ? It loos like someone has used a rotary wire brush on them My addled brain/ memory says they should be nice and smooth, indeed polished shiny

 

[Kram]

So could one of the more experienced here answer these:

1) use the needle bearing or source a branded one, or reuse the current one?
2) any adjustment to the roof of cylinder, the lumps visible in second pic.

It also appears to come with crankcase gasket and crank seals, but afaik theres no need to touch those for this task?

 

[DAPPH]

You'll curse yourself if you don't do the crank case seals whilst it's stripped down , I would always put new bearings in everything if I was doing an honest overhaul & putting my name to it .

 

[Migmac]

I use the needle bearings that Husky/ Stihl supply, same with crank shaft oil seals

 

[dobbslc]

So could one of the more experienced here answer these:

1) use the needle bearing or source a branded one, or reuse the current one?
2) any adjustment to the roof of cylinder, the lumps visible in second pic.

It also appears to come with crankcase gasket and crank seals, but afaik theres no need to touch those for this task?

I'm pretty sure I put good branded bearings in my Stihl saw when I rebuilt it and as for those lumps on the combustion chamber roof I'd carefully grind them down because as you said they might become hot spots and cause pre ignition.

 

[Kram]

I will have a go at this today, first thing to strip the old cyl off and compare the two.

I'll use threadlock to reassemble but any idea what torque for the M5 cylinder bolts?

 

[dobbslc]

No idea of the torque setting but I must nip them up with a T bar .

 

[pedrobedro]

To be honest tho it would make much more sense to me on roof of cylinder because I dont see it on the side and always forget to press it, and then the piston rings wouldnt go over it.

It's a single ring piston and the hole is in the squish band, I doubt the ring goes that high.

 

[Kram]

I have started on this, well stripping the old cyl off, I would value any input as I am new to 2 strokes. Also note having just fixed a tank issue she has had a lot of starting attempts recently and not done any real work or warmed up for couple weeks - may explain the carbon?

Nice to see well oiled for a 50:1 mix.

The light vertical scoring can not be felt by fingernail and I believe was there from new. Glazing/burning in the last pic?

Roof of cyl has some tiny marks, a sign of debris getting in, or running lean?

Thanks for reading.

 

[dobbslc]

The pock mark's in the cylinder head look like pre ignition OR very poor casting, looks worse in the squish band.
Did it have a base gasket and is the ignition adjustable?

 

[JOEPRO]

RE carbon buildup- what oil do you use?

I use Stihl HP Ultra which is supposed to help with reducing carbon deposits but I've never had one apart after running on it for a significant time to confirm myself.

What is The Role of Engine Oil in a STIHL 2 Stroke Engine? | STIHL Blog

Engine oils have a critical role to play in the workings of a 2-stroke engine and without good quality oil, your engine may not last and won’t perform at its best.

blog.stihl.co.uk

 

[Kram]

Hmm thought it might be. Dont think its from the casting.

I dont believe its easily adjustable on most chainsaws.. flywheel key..?

Base gasket is on there.

 

[Kram]

RE carbon buildup- what oil do you use?

I use Stihl HP Ultra which is supposed to help with reducing carbon deposits but I've never had one apart after running on it for a significant time to confirm myself.

What is The Role of Engine Oil in a STIHL 2 Stroke Engine? | STIHL Blog

Engine oils have a critical role to play in the workings of a 2-stroke engine and without good quality oil, your engine may not last and won’t perform at its best.

blog.stihl.co.uk

View attachment 460678

Likely due to short runs, I imagine it would have cleaned and burnt off a lot of it with a bit of use. Perhaps my mix was a bit rich on oil.

I refused to buy ultra as they do t have any closeup pics of the bottle and appear to have a spec misprint on all the sites selling it as Jaso-FB in which case its poo!

My oil is all Jaso-FD which is highest standard and should be way more than adequate.

I have Stihl HP super and Castrol POWER1 2T Motorcycle Oil, seems to smell a little nicer but probably not the same as the legandary Castrol stuff.

https://www.amazon.co.uk/dp/B0C813TSXN

 

[dobbslc]

Perhaps my mix was a bit rich on oil.

If you run it at 50:1 and I think that's what they recommend then it's not rich on oil.
I run my gear at 40:1 and that is a bit on the smokey side but everything works fine and has for years.
If you go way over the top with oil it weakens the fuel mix and you can get pre ignition.

 

[JOEPRO]

Likely due to short runs, I imagine it would have cleaned and burnt off a lot of it with a bit of use. Perhaps my mix was a bit rich on oil.

I refused to buy ultra as they do t have any closeup pics of the bottle and appear to have a spec misprint on all the sites selling it as Jaso-FB in which case its poo!

My oil is all Jaso-FD which is highest standard and should be way more than adequate.

I have Stihl HP super and Castrol POWER1 2T Motorcycle Oil, seems to smell a little nicer but probably not the same as the legandary Castrol stuff.

https://www.amazon.co.uk/dp/B0C813TSXN

I like the HP Ultra over their red oils as it smokes less. I also prefer to use the 100ml one shot bottles which makes the measuring accurate. I fill a 5L petrol can each time with Super UL which has very little or since the pump doesn't say anything it may well have zero ethanol locally. (Legally they are required to display the ethanol % and they do that for all other grades of fuel)