So bought a chinese saw (holz g070)

[sliceoflife]

Hey all... been using my mac 250 here and there for limbing and breakdown of 14" and smaller stuff.

Some clutch slipping and it heats up real fast... probably needs a lot more work than I did but it runs and cuts a bit... but for milling, I went out and grabbed a chinese 105cc stihl knockoff. Its unseasonably warm this week, so I gassed it up (30:1 93 octane and 2cycle engine oil replacement). Pulled it a couple time to distribute, then gave it a real pull and it INSTANTLY siezed. Two grates from the flywheel guard blew off and the engine wouldn't budge after.

When pulled it went "pluuuf" once, would puff smoke out the muffler. But would snap back after a single turn.


So I pulled the muffler off. No scoring I can see on piston... and a jiggle of the cord (with the muffler off) immediately freed the piston.... and I see no scoring in the cylinder either. Plenty of oil/gas in there too.

Possible explanations? Malformed top of the cylinder and the piston wedges there and can't top out? Wild guess there... honestly have no clue. May just put the muffler back on and see if it was a random thing that fell out when I was taking off the muffler that I just didn't see... but curious if this behaviour sounds like anything someone has seen before.

 

[SimonHS]

Likely that the problem is in the recoil starter.

Even a Chinese saw will not seize that quickly!

Does it have a decompression valve? And did you use it?

 

[Bubster]

Coil touching the flywheel perhaps? The air gap being too tight could be a possibility. Piece of spark plug broke off and fell in the cylinder?

 

[sliceoflife]

And that's why I posted here. You were right on about the decomp valve. There's a little metal arm that actuates it underneath the cover and it was bent so that it wasn't actually doing anything. Bent it back up and it starts first pull.

 

[thompsoncustom]

good to hear, I've considered getting a 070 just to put a 090 (big bore) on it and port it incase I ever need a gaint saw for some reason.

a 137cc chainsaw would be great for milling other than maybe the weight.

 

[frogbiter]

Hey all... been using my mac 250 here and there for limbing and breakdown of 14" and smaller stuff.

Some clutch slipping and it heats up real fast... probably needs a lot more work than I did but it runs and cuts a bit... but for milling, I went out and grabbed a chinese 105cc stihl knockoff. Its unseasonably warm this week, so I gassed it up (30:1 93 octane and 2cycle engine oil replacement). Pulled it a couple time to distribute, then gave it a real pull and it INSTANTLY siezed. Two grates from the flywheel guard blew off and the engine wouldn't budge after.

When pulled it went "pluuuf" once, would puff smoke out the muffler. But would snap back after a single turn.


So I pulled the muffler off. No scoring I can see on piston... and a jiggle of the cord (with the muffler off) immediately freed the piston.... and I see no scoring in the cylinder either. Plenty of oil/gas in there too.

Possible explanations? Malformed top of the cylinder and the piston wedges there and can't top out? Wild guess there... honestly have no clue. May just put the muffler back on and see if it was a random thing that fell out when I was taking off the muffler that I just didn't see... but curious if this behaviour sounds like anything someone has seen before.

I would recommend the 365/372.

 

[fields_mj]

And that's why I posted here. You were right on about the decomp valve. There's a little metal arm that actuates it underneath the cover and it was bent so that it wasn't actually doing anything. Bent it back up and it starts first pull.

Just noticed this. If it was bent, I would HIGHLY recommend replacing the decomp valve asap. My experience has been that when something like this gets bent, it looses a LOT of its strength. If it gets bent back, it looses a lot more and is very likely to fail completely in the near future.

 

[sliceoflife]

Thanks. Holz asked me if I could buy one locally (I assume they will refund me the cost). Maybe I'll take them up on it. If anyone knows where to buy a decomp valv for this saw, please send the link.

And to clarify... There was nothing wrong with the valve. The arm that pushes the valve down was bent. It's just a little inch long piece of metal held in place above the valve and pushed on with the button on the saw housing.

Actually just got the saw out again this last Tuesday for the first time since I got it running/posted this.

Hooked it up to the mill, started it up, heaved it in place on my ladder-rails (which was laughably high because the entire tree is stacked and I'm working my way down)... and it died the second I got it into place.

Pulled it... no spark. Tried everything except pulling the plug because I didn't have a socket on me... and figured no way the plug is the problem on a new saw. So fought with it for 30+ minutes... changed gas, checked filter, checked choke (which was also broken... it wasn't actually looped around the arm so choke did nothing... fixed that too), etc... Still no spark. Figured maybe the safety switch had gone bad and was stuck in off... one last thing before I give up and research how to bypass that... go and get a socket, pull the plug... and there's a piece of carbon the size of a broken off pencil tip bridging it. Must have been in the saw when they shipped it and somehow snagged on the plug just perfect... unbelievable.

Wipe it off and saw starts right up and takes off my first (~4ftx20" elm) slab like it's cutting through warm butter. It's now getting dark so I called it a day.


All told, three pretty minor problems/easy fixes... and it seems to be a good saw otherwise. For the savings I'm willing to put up with those problems... Now lifespan/durability is the question. If the saw lasts me as long as a Stihl would now; it's a steal; despite these problems. But that's a big 'if', I'm guessing.

 

[fields_mj]

Thanks. Holz asked me if I could buy one locally (I assume they will refund me the cost). Maybe I'll take them up on it. If anyone knows where to buy a decomp valv for this saw, please send the link.

And to clarify... There was nothing wrong with the valve. The arm that pushes the valve down was bent. It's just a little inch long piece of metal held in place above the valve and pushed on with the button on the saw housing.

Actually just got the saw out again this last Tuesday for the first time since I got it running/posted this.

Hooked it up to the mill, started it up, heaved it in place on my ladder-rails (which was laughably high because the entire tree is stacked and I'm working my way down)... and it died the second I got it into place.

Pulled it... no spark. Tried everything except pulling the plug because I didn't have a socket on me... and figured no way the plug is the problem on a new saw. So fought with it for 30+ minutes... changed gas, checked filter, checked choke (which was also broken... it wasn't actually looped around the arm so choke did nothing... fixed that too), etc... Still no spark. Figured maybe the safety switch had gone bad and was stuck in off... one last thing before I give up and research how to bypass that... go and get a socket, pull the plug... and there's a piece of carbon the size of a broken off pencil tip bridging it. Must have been in the saw when they shipped it and somehow snagged on the plug just perfect... unbelievable.

Wipe it off and saw starts right up and takes off my first (~4ftx20" elm) slab like it's cutting through warm butter. It's now getting dark so I called it a day.


All told, three pretty minor problems/easy fixes... and it seems to be a good saw otherwise. For the savings I'm willing to put up with those problems... Now lifespan/durability is the question. If the saw lasts me as long as a Stihl would now; it's a steal; despite these problems. But that's a big 'if', I'm guessing.

I'm not familiar with that part. If it's part of the decomp valve, I'd just go to a Husqvarna or Stihl dealership and purchase one. If it's not part of the valve, and its not obvious which brand/model of saw that part was copied from, then I'd probably try to reach out to Hyway and see if they can give you some direction.

 

[pioneerguy600]

I'm not familiar with that part. If it's part of the decomp valve, I'd just go to a Husqvarna or Stihl dealership and purchase one. If it's not part of the valve, and its not obvious which brand/model of saw that part was copied from, then I'd probably try to reach out to Hyway and see if they can give you some direction.

It is a copy of a Stihl 070 and both the 070 and 090 use a transfer bar type of mechanism to operate the decomp valve which is full time closed until the bar pushes down on the valve stem and opens the decomp. The metal in these copies is not always the same metal used in a real Stihl saw so it might be softer and easier to bend. It likely could be replaced with a real OEM part.

 

[sliceoflife]

Thank you, yes.

Google says the part is called the "Decompression arm" or "Decompression spring". Seen here from an eBay sellers listing.

 

[sliceoflife]

Two more uses.. Still trying to get the High adjust tuned in to where the saw doesn't sound like it's about to blow up whenever I punch it when milling... I'm about 3 turns out and I think I'm close but maybe still a little lean. I'm having to hold the trigger half in because I can't lock it at full throttle; it sounds too angry at full throttle and Im worried it'll blow up. Got a Tachometer ordered to try and get some peace of mind.


Also... So the Decomp valve stops working for 5-15 minutes with the saw hot (stopping it between slabs for instance). It works if the shutoff is turned off... Pulls like normal (but obviously doesn't start) but as soon as I turn the shutoff back to Run, the decomp no longer works and I damn near break my hand trying to pull the saw over because as soon as the cylinder tops out (half a revolution of the flywheel) it Snaps the pull cord back. Let it cool off for 5-15 minutes and it works again.

Too tight a fit in the cylinder when it's hot I'm guessing... and the shutoff/kill switch being turned to OFF somehow fixes that why? Anyone have any theories?

 

[Maintenance supervisor]

Two more uses.. Still trying to get the High adjust tuned in to where the saw doesn't sound like it's about to blow up whenever I punch it when milling... I'm about 3 turns out and I think I'm close but maybe still a little lean. I'm having to hold the trigger half in because I can't lock it at full throttle; it sounds too angry at full throttle and Im worried it'll blow up. Got a Tachometer ordered to try and get some peace of mind.


Also... So the Decomp valve stops working for 5-15 minutes with the saw hot (stopping it between slabs for instance). It works if the shutoff is turned off... Pulls like normal (but obviously doesn't start) but as soon as I turn the shutoff back to Run, the decomp no longer works and I damn near break my hand trying to pull the saw over because as soon as the cylinder tops out (half a revolution of the flywheel) it Snaps the pull cord back. Let it cool off for 5-15 minutes and it works again.

Too tight a fit in the cylinder when it's hot I'm guessing... and the shutoff/kill switch being turned to OFF somehow fixes that why? Anyone have any theories?

Its ignited the spark plug which then ripps the handle from your hand. One your not pulling the rope fast enough or with enuff Authority, you gotta roll the piston just past TDC and pull the handle like a winning lottery ticket is gonna pop out od the starter.
Or the flywheel key is sheared / missing, causing the timing to be off.

 

[sliceoflife]

Makes sense. Maybe its me needing the 5-15 minutes cooloff to get the deadarm effect off so I can pull properly. I'll confirm next time I use.

 

[Ted Jenkins]

I bought several Stihl decomp valves as I remember from the UK. I was happy to find brand new. As soon as I got them was thinking I will double my money. Then I remember how hard they were to find and said it would not hurt to just keep them. I have two 070, 075 and 076 which uses the same valve. From experience I put some lock tite on the valve and made a key to tighten them as I do not want them to come loose. I fabricated a control arm but don't do it as it is too much work. Take your Dremel tool and make both groves a little wider. Take some machine washers about 3/16'' and cut a slot in them. twist the washers wide enough to go over the stem and settle in the grove. Take a pencil torch and braze the open slot so that the washer can not come off. Find a suitable spring to wind under the washer so that there is plenty of tension keeping the valve shut. Now your decomp system is bullet proof. After all this I never use the decomp valve in several years. At my age no body else needs a decomp valve either but it is handy when your engine is flooded and you are just too tired to be safe. I bought an extra carburetor and some kits which made a world of difference. What makes the saws stand out is the chain. I cut several cords of Oak not needing to sharpen chain. The thing is just plain reliable. Thanks

 

[J D]

I'm having to hold the trigger half in because I can't lock it at full throttle; it sounds too angry at full throttle and Im worried it'll blow up.

You are just as likely (if not more) to blow it up at half throttle... a chainsaw carb is only tuned at WOT & idle, anything in-between & it's in the transitional state. Running any saw at part throttle for an extended period of time (like milling) is a never a good idea.
Do some research & if you're not confident get someone that knows what they're doing to tune it so you know its good.
@Vintage Engine Repairs did a good YouTube tutorial a while back, steves small engine saloon has one too & Madsens has a good write up on their site.
Ideally run a bit more oil & tune on the rich side for milling too

 

[Vintage Engine Repairs]

it

You are just as likely (if not more) to blow it up at half throttle... a chainsaw carb is only tuned at WOT & idle, anything in-between & it's in the transitional state. Running any saw at part throttle for an extended period of time (like milling) is a never a good idea.
Do some research & if you're not confident get someone that knows what they're doing to tune it so you know its good.
@Vintage Engine Repairs did a good YouTube tutorial a while back, steves small engine saloon has one too & Madsens has a good write up on their site.
Ideally run a bit more oil & tune on the rich side for milling too

I did a new one recently lol

 

[sliceoflife]

Thank you, I appreciate it. Watched tons of video's on this task, but none really gave nice definitive rules like this that should make it a lot more easy as someone who doesn't have the ear for trusting what I do using the methods most videos suggest. Once my Tach gets here, I'll retune and get back to work.

 

[sliceoflife]

So the tachometer got here and I've done the adjustment like in the video, I have to set the idle for 1440 anything higher than that and the chain spins at idle, and even with the high adjustment completely counterclockwise and loose at Full Throttle my Revs are 7,800.

Saw is only rated for 7500 max rpm right? Any way to bring the revs down or should it be ok at 7800?

Holzfforma says saw is 9000 rpm @ max power... but stihl say 7000 w/ 7500 max. Who do I believe?

 

[Maintenance supervisor]

Something is mechanically wrong, you should be able to bog the crap out of that saw with the high jet.