Author Topic: New Cylinder and Piston for TS350 Petrol Saw  (Read 791 times)

Offline awemawson

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New Cylinder and Piston for TS350 Petrol Saw
« on: May 23, 2018, 08:33:49 AM »
I've had this Stihl TS350 petrol saw for ages - it's done good work particularly when I was rebuilding my house and barn, but it has got increasingly hard to start, with low compression.

I was given an almost identical one that I thought I could use for parts, but it's compression also was pretty dire. Nowadays clone parts are coming out of China, and I was able to buy a pattern piston, rings, gudgeon pin, cylinder barrel, and gasket for the princely sum of 32.50 including postage !

They arrived by this mornings post, so I thought I'd get on changing it before the new big CNC lathe arrives and takes all my attention.

So firstly strip out the old:
Andrew Mawson
East Sussex

Offline awemawson

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #1 on: May 23, 2018, 08:36:48 AM »
So far going quite well, I even had the correct long series Torx keys
Andrew Mawson
East Sussex

Offline awemawson

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #2 on: May 23, 2018, 08:44:47 AM »
So first thing to go back - the barrel lower gasket - fine they supplied one  :thumbup:

Ah - well no - WRONG SIZE  :bang:

I suddenly had that sinking feeling - did I order the wrong barrel and piston? But no, they are the same as the original and the supplied gasket doesn't match the supplied barrel  :bugeye:

A phone call ensued, and OK the replacement is in the post, but meanwhile the bench is covered in dismantled petrol saw. I hate leaving things in bits - hopefully play can resume shortly.
Andrew Mawson
East Sussex

Offline awemawson

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #3 on: May 23, 2018, 09:31:32 AM »
I took the opportunity of the enforced hiatus to clean up the carburettor. Only externally, though it's passages got a liberal dose of carburettor cleaner.

I won't pull it apart unless I still get starting difficulties - this isn't supposed to be a full rebuild !
Andrew Mawson
East Sussex

Offline awemawson

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #4 on: May 24, 2018, 09:59:15 AM »
New gaskets set arrived this morning by post - not bad - only ordered yesterday at 16:30  :thumbup:

So just a bit of 're-mantling' - only clever bits being gaping the rings and sloshing two stroke oil on the slidy bits before putting it all together. To gap the rings they need to be set in the bore exactly perpendicular - I do this by placing them in the bore then squaring them up with the piston. Supposed to be pre-gapped and indeed they were both 0.35 mm which is in spec

The gudgeon pin circlips supplied looked as though a 5 year old had been twisting wire, so I re-used the originals

Andrew Mawson
East Sussex

Offline awemawson

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #5 on: May 24, 2018, 10:02:42 AM »
It was pretty tricky getting the throttle and choke linkages to line up when the top cover was re-fitted but I got there in the end !
Andrew Mawson
East Sussex

Online John Rudd

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #6 on: May 24, 2018, 10:05:13 AM »
Hmmm...thought you might have had it finished, used and put away for next time, by now.... :coffee: :lol: :lol:

Ha, you were typing/posting as I wrote....

Nice job Andrew, I like this kinda job, where you identify whats needed, it duly arrives, and re-assembly begins and is completed with a successful out come......
For me, 9/10 times there's always a complication.... :doh: something else breaks, is lost or wrong part...
eccentric millionaire financed by 'er indoors
Location:  Backworth Newcastle

Skype: chippiejnr

Offline awemawson

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #7 on: May 24, 2018, 10:08:25 AM »
So what was the result?

Well the compression is now very much improved as you would expect.

It starts much more easily

BUT it won't tick over and needs choke all the time  :bang:

I've set and tweaked the low running and high speed jets but I suspect carburettor diaphragm problems

So it looks like a carb re-build after all. Carb kit ordered - in fact I've ordered two as I may as well do the other saw while I'm at it - the kits are only 3.90 ! 
Andrew Mawson
East Sussex

Offline appletree

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #8 on: May 24, 2018, 11:19:47 AM »
Another thing to watch out for ,is the in tank fuel pick up its like a clunck fuel pick up as used in model aircraft. The tube is a specially moulded affair which is made of a very flexible neoprene/silicone type rubber over time and allow air to seep in.
Did you fit a new carb gasket/s these have port holes which connect the crankcase to the pumper carburettor. Lastly are the carb spindles badly worn, they often are on disc cutters because of the "grinding compound"


Phil

Offline hermetic

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #9 on: May 24, 2018, 01:09:17 PM »
looks like virtually the same engine as on my venerable Stihl chainsaw, completely agree with you on the circlips, those bends are far too tight, and you can imagine the mess if one of those broke off!

Offline awemawson

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #10 on: May 24, 2018, 03:41:03 PM »
Yes I have an ancient Stihl 023 chainsaw that I replaced the barrel and piston on a few years back - pretty well identical
Andrew Mawson
East Sussex

Offline appletree

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #11 on: May 24, 2018, 04:01:51 PM »
I have an old a Ts350 and 2 of the chains saws on which it is based the 08s. Keep threatening to covert 1 of the saws into a TS350 I have loads of dead TS350 front ends covers left over from our hire fleet.
There are lots of safer (chain brakes) saws available, lighter too.

Phil 

Offline PekkaNF

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #12 on: May 24, 2018, 04:43:01 PM »
Good work.

Doesn' that engine need high quality oil bigger than normal %? Here if you rent the saw (100/day) they give you the labeled canister of gasoline to go with it. Rental comppany inform to use only that, because it seizes really quickly with normal two stroke oil/gasoline.

Had to rebuild some carbs long time ago....some diagraph/gasoline combos seem to work better than others. Remember changing the fuel line and the clunker in the tank.

Pekka
« Last Edit: May 26, 2018, 04:17:32 PM by PekkaNF »

Offline Bob-tech

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #13 on: May 26, 2018, 01:28:55 AM »
After clening the carb and installing new membranes I would start with the basic adjustment for this carb (H = 1
L = 1 turn from closed).

Are the crankshaft seals still airtight? Leaks might show more now that your piston is new.

Offline awemawson

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #14 on: May 26, 2018, 01:34:43 AM »
Any tips for checking the crankshaft seals Bob?
Andrew Mawson
East Sussex

Offline Bob-tech

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #15 on: May 26, 2018, 03:07:10 PM »
The seals are very important for a predictable and stable tick-over. When they leak air you never get a constant carburation in tick-over and it will be impossible to adjust the carb. The seals are just ordinary Simmerrings. There is an impulse connection between crankcase and carburator. This might be a hose or a fixed connection with gaskets. This could also be the problem.

You can test the hose and the seals by spraying it with brake cleaner while the saw/cutter runs. It this changes the idle speed the seals are shot. An indicator towards shot seals is also when the saw changes idle speed when turning it to the side. The seals can be changed without splitting the crankcase, but you have to remove the clutch and the flywheel. There are left hand threads around. An impact wrench is useful to loosen screws without locking the piston.

Offline awemawson

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Re: New Cylinder and Piston for TS350 Petrol Saw
« Reply #16 on: June 01, 2018, 06:44:02 AM »
Carburettor gasket and diaphragm kit arrived yesterday, so I pulled it all apart again, and rebuilt the carb. Turns out that a previous person had assembled it in the wrong order, the gasket for the pump diaphragm being on the wrong side. Also the tiny 'o' rings on the low and high speed jet needles were missing - these seal the thread of the needle to the carb body. Fortunately I had suitable O rings, but had to make their backing washers by turning down standard 4 mm ones as the o/d was too large.

No pictures but here is an excellent video that I followed:



Then having made a flywheel puller (M25 by 1.5 mm pitch for future reference) I set too and replaced the crank case seals

She now starts and runs, but I can't set the idle speed low enough - I suspect that the throttle butterfly mounting shaft may be a bit worn though it feels not too bad. The one for the choke is  quite worn, but I can't see how that can affect anything when the choke is fully open anyway  :scratch:

Somewhere along the way the Stop switch has ceased to work - I may rob one off the other saw.

Andrew Mawson
East Sussex