Porting a Chinese G621 Clone

[nenicu]

Hey Chris-Pa. I have a real G621 in work and i looking for inspiration. Have you done anything to the piston of your clone?

 

[Chris-PA]

Hey Chris-Pa. I have a real G621 in work and i looking for inspiration. Have you done anything to the piston of your clone?

No, I didn't touch the piston. For some reason I only took one shot of the piston, and none that shows the top. It was domed like most Zenoah pistons if I recall, which I think is a good thing. What is the squish clearance on the Zenoah engine?

All I did to mine was remove the base gasket, increase the intake port width and duration, and mod the muffler. I'm very happy with how it runs and have no real interest in changing it, although I do keep looking at larger carbs.


I ran this saw quite a bit the last two days and it was flawless. I'm running a 20" McCulloch bar on it that I added some oil holes to, and it's a nice set up.

 

[nenicu]

Thanks for the answer. I did not measure the squish . On the piston i rounded on both sides under the piston pin all that area as wide as the transfer port. This saw is still in pieces,butt i have a clone similar to those aussie clones [Baumr AG]. 72 cc, 50 mm piston. I did the same thing to the piston and it revs very fast. That one has ,like all clones, big squish. Same piston design as the original: domed piston top. I am looking for a bigger carb myself.

 

[Chris-PA]

Thanks for the answer. I did not measure the squish . On the piston i rounded on both sides under the piston pin all that area as wide as the transfer port. This saw is still in pieces,butt i have a clone similar to those aussie clones [Baumr AG]. 72 cc, 50 mm piston. I did the same thing to the piston and it revs very fast. That one has ,like all clones, big squish. Same piston design as the original: domed piston top. I am looking for a bigger carb myself.

I'd like to have a 72cc version but I've never seen one on eBay in the US. I'm curious how big the carb on the 72cc is - the Chinese have a habit of making increased displacement versions of the Zenoah saws but keeping the original carb.

 

[nenicu]

I just ended my quest for a bigger carb and i think a Walbro 199 should be just right : HDA 199 -16,66 venturi vs HDA 31c-15,08 venturi. The shafts have to be taken from the original carb.

 

[Chris-PA]

I just ended my quest for a bigger carb and i think a Walbro 199 should be just right : HDA 199 -16,66 venturi vs HDA 31c-15,08 venturi. The shafts have to be taken from the original carb.

Does that get the impulse through the intake block, or does it have a separate fitting on the cover? Some of the larger carbs that have the the same shafts/levers have an external fitting which is too large to fit (and there's no place to connect it anyway). I'm fairly confident I could drill the missing passages in the carb and use a cover with no fitting, but I have not been motivated to make the effort yet.

 

[nenicu]

The impulse is through the intake booth. It has the same intake setup like Husqvarna 346,353,350

 

[nenicu]

Here is my clone. On the left side the clone with new impulse port on the case. The case is bigger and you can't swap cilinders: the bolt pattern is diferent and the 72 cc jug is larger .

 

[nenicu]

Next. This clone is 72 cc and the original carb was 15.8 venturi[ hda 31 clone]. I had this new chinese carb for about 1 year: a Husky 365-372 carb and today i made the swap .I had to make another accel linkage and switch the choke , drill a hole for the acceleration rod , make an impulse port on the case. It runs,starts ok but needs more carb work.

 

[nenicu]

For Chris-Pa: for the Zenoah i am lookin' for a Walbro HDA 199 from a Husky 357-359. Has 16,6 6 venturi and same impulse setup like the Zenoah carb. Just swap the shafts and that is it. About the piston: i have seen on Ebay a Partner 65 piston whith the same shape on the transfer sides.It leaves more space for the transfer ports. Edit : the piston with the sides like mine belongs to a Partner 100[100 cc].

 

[GerrySM]

Got to page 6 of this thread and it became TL;DR, but I'd like to thank Chris for the link that brought me here and for dissecting this saw and convincing me that it would not be worth my while to buy a Chinese saw, ever. Thanks muchly.

 

[Chris-PA]

Got to page 6 of this thread and it became TL;DR, but I'd like to thank Chris for the link that brought me here and for dissecting this saw and convincing me that it would not be worth my while to buy a Chinese saw, ever. Thanks muchly.

LOL. They're surely not for everyone.

 

[ken morgan]

good write up Chris.

Living in japan I see a lot of clones floating about (cue in Weird Al's "I think I'm a clone now") and surprisingly at least 90% of the small japanese engines (.5 to 12 hp) are made in china now, including all of the big names like honda, yamaha, kawasaki, yanmar, and robin.

The difference is that the japanese have an engineer, QC specialist, and a manger working at the plants to train, oversea and supervise. Yamaha and honda go as far as to have a supervisor at every plant that feeds the main factory parts to ensure that all parts and raw materials are to spec.

I know this because my japanese brother in law works for a trade company and regularly travels there.

So you basically have the same item with minor changes, and looser QC on the line.

 

[Chris-PA]

good write up Chris.

Living in japan I see a lot of clones floating about (cue in Weird Al's "I think I'm a clone now") and surprisingly at least 90% of the small japanese engines (.5 to 12 hp) are made in china now, including all of the big names like honda, yamaha, kawasaki, yanmar, and robin.

The difference is that the japanese have an engineer, QC specialist, and a manger working at the plants to train, oversea and supervise. Yamaha and honda go as far as to have a supervisor at every plant that feeds the main factory parts to ensure that all parts and raw materials are to spec.

I know this because my japanese brother in law works for a trade company and regularly travels there.

So you basically have the same item with minor changes, and looser QC on the line.

If you look at this Zenoah site: http://www.zenoah.co.jp/int/products/chainsaws/ you'll see they have both a G621 and G6200, with almost identical specs but for a little different weight. "G6200" is the model number used on many of the clones, and they usually have an aluminum case rather than more magnesium, so the weight difference would make sense. Several other of the saws on that page are ones that are more commonly sold as clones than as Zenoah, such as the G5200. Also, Zenoah sold both the GZ4000 and the GZ400, which was the same basic design but the GZ400 was assembled in China. So I suspect this all stems from a production agreement Zenoah had in the days before Husqvarna bought them, and I don't know how much of that still exists.

Mine just keeps cranking along - this was all bucked with a 25" bar, with no fuss.

 

[ken morgan]

So I suspect this all stems from a production agreement Zenoah had in the days before Husqvarna bought them, and I don't know how much of that still exists.

Mine just keeps cranking along - this was all bucked with a 25" bar, with no fuss.
View attachment 521517

You are probably correct. nothing wrong if it keeps going. I currently have two saws one is a poulan pp4218 from 2012 and one is a 372xp that was rebuilt sold on fleabay. the only reason I bought the 372 is for larger logs and trees that I have been running into lately. the poulan contrary to the online reviews is a great little saw 2 years in and 14 cords of wood prior to the purchase of the 372 and it still starts on the first pull every time.

 

[GerrySM]

Got to page 6 of this thread and it became TL;DR, but I'd like to thank Chris for the link that brought me here and for dissecting this saw and convincing me that it would not be worth my while to buy a Chinese saw, ever. Thanks muchly.

Oh the irony! I ended up buying one of these Chinese things, could not resist at the price (US$66 delivered from eBay. comes with TWO chains). Don't have it yet, still in the mail.

 

[Big_Wood]

If you look at this Zenoah site: http://www.zenoah.co.jp/int/products/chainsaws/ you'll see they have both a G621 and G6200, with almost identical specs but for a little different weight. "G6200" is the model number used on many of the clones, and they usually have an aluminum case rather than more magnesium, so the weight difference would make sense. Several other of the saws on that page are ones that are more commonly sold as clones than as Zenoah, such as the G5200. Also, Zenoah sold both the GZ4000 and the GZ400, which was the same basic design but the GZ400 was assembled in China. So I suspect this all stems from a production agreement Zenoah had in the days before Husqvarna bought them, and I don't know how much of that still exists.

Mine just keeps cranking along - this was all bucked with a 25" bar, with no fuss.
View attachment 521517

how many times did you have to rering the top end to get that job done?

 

[Chris-PA]

Oh the irony! I ended up buying one of these Chinese things, could not resist at the price (US$66 delivered from eBay. comes with TWO chains). Don't have it yet, still in the mail.

View attachment 568940

LOL - looks rather nice, especially the air filter arrangement. That's based on a different Zenoah model though, the G5000 instead of the G621. I've been tempted to try one of that series, but I just haven't had the motivation. I suspect with a little conventional squish, port and muffler work it will run quite well. The carb might be a bit on the small side though.

how many times did you have to rering the top end to get that job done?

It wasn't bad at all! I got 2 or 3 rounds per ring, I buy them by the dozen and I can change them pretty fast in the woods. I find if just loosen the cylinder bolts at idle and give the throttle blurb it'll pop the jug right off. Pop on a new ring, slop a little bar oil on it and slam the jug back on, and you're back up and running in minutes!

 

[TBS]

I thought you bought them by the pound? I buy by the suitcase full, just yank the top, rubber band the cylinder back on, and I'm on to the next cut. Nice write up chris. How has this saw held up?

 

[Chris-PA]

I thought you bought them by the pound? I buy by the suitcase full, just yank the top, rubber band the cylinder back on, and I'm on to the next cut. Nice write up chris. How has this saw held up?

Saw is dead solid reliable. The only thing that doesn't work properly is the high idle throttle lock. I've never bothered to make it work because the saw starts in a couple of pulls hot or cold, goes right to a nice idle and never stalls.