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Constant revving and reluctance to turn off

Started by Coreytroy, March 26, 2014, 02:18:53 AM

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JohnG28

Chris, I had never thought of "Works" toilet cleaner for that.   We used to have some fun with that stuff and aluminum foil as kids, sure it would do the trick in this situation too.
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

Coreytroy

I bought some 100% Hydrochloric Acid for cleaning bricks etc
I diluted it to around 20% before using a cotton bud, but it did not clean up much.

I will try a little maybe 100% tomorrow instead of diluting it.

I am looking at replacing all Annular Buffers, though I have not checked them yet.
For a few dollars, they may be split or worn anyhow.

JohnG28

Maybe try diluting it a little less, maybe 50/50 first. I haven't had to clean one up yet myself, but I'd just want to take it slow and easy. As was said before, you don't want the acid to get into any of the ports and you have a good bit to clean up by the exhaust port. If you have any buffers that look or feel bad/worn/loose etc might as well do them now. Like you said, for a few bucks a piece it's worth it not to have to take the saw all apart to do later.
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

Al_Smith

Aha I as right 8) .Well that aside it looks like the cylinder will clean up .That crude is just transfered aluminum .

The safest way is with 3M Scotch-Brite pads and kerosine .You don't want to run a hone down through it .Muratic acid or oven cleaner could gas you .

I've saved pistons that looked worse than that but due to your lack of experiance I'd suggest a new piston and rings .After market like a Meteor will be under 40 dollars US funds .OEM Stihl probabley twice that .

Coreytroy

I bought a non-OEM Piston & Ring set c/w gudgeon pin & clips for AU$20.07 delivered, and a non-OEM air filter for AU$25.00 delivered.

Hopefully I can have a better look/attempt at cleaning up the cylinder this afternoon when home from work.
I am still waiting on other parts for now.
Being the cylinder gasket(OEM), manifold & annular buffer rubbers(non-OEM) to arrive, before the re-assembly process will be able to occur.
The manifold and buffers were < 1/2 the price of OEM (non-OEM Manifold - AU$29.00) [OEM - AU$66.00], so thought even if I get a couple of years out of them before they deteriorated, I'd be still ahead buying a 2nd set.
The gasket was only AU$5.75 OEM anyhow.

Coreytroy

Gave the cylinder a clean but have established that just under the exhaust port the cylinder wall has lost the coating slightly.
Ordered a non-OEM cylinder instead of trying salvage this one.

schmeg

Good choice replacing the jug. Once the Nikasil coating starts to go, the cylinder is junk. You can send the jug away and get it re-Plated if you want it as a spare. I once was riding snowmobiles with a friend that had a Polaris 800 do the same thing. When into an uncontrollable run-on. Surprisingly the piston wasn't melted. Unfortunately this is becoming more of an issue with the use of ethanol enhanced fuel when lean conditions are encountered. Alcohol has a lower flash point making it easier for this to occur with no spark at the plug needed.
2023 MS400
2014 562XP
2007 357XP (stolen)
2004 346XP
1997 350
1992 55

Al_Smith

Generally speaking if the plating is nicked above or below the ring travel the cylinder can be saved .

For what it's worth to have a cylinder replated would exceed what a replacement cylinder would cost .In other words it's not cost effective .

Coreytroy

Progress report.
Newly fitted items:

  • cylinder incl. gasket
  • Piston incl. needle bearing
  • Annular buffer
Fuelled up and started saw.

My question.
Now it has new cylinder and piston, should is run it richer for the first few tanks, say 40:1 instead of 50?
What running in precautions should I take?
Not run it fully open for 1st tank?
Don't run it at same revs for long times?

schmeg

50:1 will be fine. Give it some extra fuel on the high side won't hurt. Just not too much. What I do on the first tank is a good warm up at idle, then just normal bucking. By bucking, you will allow for some brief cool downs followed by applying pressure on the rings which is what you need for the rings to seat. Some people will say just run the saw. I agree, with some caveats, don't let the saw get too hot by letting it idle too long. The big deal is making sure any air leaks are fixed, and your using good clean fuel mixed properly.
2023 MS400
2014 562XP
2007 357XP (stolen)
2004 346XP
1997 350
1992 55

Coreytroy

Took the MS380 out for a timber run this afternoon, new hurricane bar and chain(keep the Carlton for later).
Like a hot knife through butter.

Only issue apart from all the mosquitoes hanging around was, the MS380 did not like to idle that well.
I suspect due to an increase in compression, I may have to adjust up the idle slightly till the piston sets in more.
Happy with the rebuild though, sense of accomplishment for a non-mechanic 😉

Appreciate all the advice from you guys on this forum. 👍👍👍

sablatnic

Don't hope that the idling problems are caused by forgetting the pulse line. I have done that, it took some thinking to find it!

Coreytroy


sablatnic

The thin rubber tube from the cylinder or crankcase to the back of the carburettor.
It gives the pump pulse from the crankcase to the fuel pump in the carburettor.

Al_Smith

Most likely the low speed jet isn't set up right .Compression  shouldn't have anything to do with how it idles .Fact being my souped up 038 mag is probabley pushing close to 180-200 PSI static and it idles fine .

Coreytroy

Quote from: sablatnic on April 19, 2014, 07:18:12 AM
The thin rubber tube from the cylinder or crankcase to the back of the carburettor.
It gives the pump pulse from the crankcase to the fuel pump in the carburettor.
Ok, thanks.

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