Porting a Chinese G621 Clone

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The Chinasaw finally got a serious workout today. Friday on a clear day with no real wind a large white oak simply fell over, taking out a tulip tree and the power lines. Yesterday I cut and moved the tulip, mostly with my ported GZ4000 McCulloch clone (which ran great) along with the Earthquake. Here's the mess:
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Today I bucked the oak. It was 34-36" at the base, and I started with the 25" Chinese bar and the loop of 75DP I bought for it. The saw ran flawlessly, without one hitch or hiccup. It had decent power for a 62cc saw pulling a buried 25" bar. Hot start was usually one pull.
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In this picture if you look across the road you can see one that rolled away - oops!. It is a fairly steep hill. The thing started rolling, hit a stone and turned right for the road.
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Eventually I touched the 75DP in the dirt and switched to the Oregon Power Match bar and a loop of full chisel. It cut a little faster for a bit but the bar oil hole clogged up like it usually does and I had to pull the bar and clean it. This is really annoying and I have to figure out if I can modify it to stop it. It's a D176 mount and for some reason it just plugs up very easily. The Chinese bar does not have this problem. Still, the saw was great, and I think maybe I'm past the endless tinkering and fixing and can actually use it as a tool. The light weight was a real help since my back is still recovering from a recent injury

Near as I can tell the roots of the oak were pretty rotten, at least on the up hill side, and it just let go. It appeared to be a big healthy tree otherwise. When I severed it from the root mass it did not settle back like they usually do, rather it moved toward the trunk. Partly because it was down hill, and partly I think because the roots were rotten.

I have a lot of work to do quartering those rounds and moving them out of there. I also had to spend a fair amount of time opening a path to get in there with the loader.
 
The saw is running great, and I believe I'm past the teething pains. It starts on about 4 pulls every time and just works. The biggest problem I have with it is the Oregon D176 mount bars just clog right up and stop oiling if I noodle, but they do that on my McCulloch too. I finaly dropped a dead hickory snag today, and did some cutting with the clone - that stuff is seriously hard and makes it feel like the chain is on backwards on all my saws. I was running a old loop of TriLink semi chisel with the guard links removed:
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Here are a couple of videos - the saw was working pretty hard, but kept on pulling. It's really a joy to use, especially given the weight.


 
Nice thread here. I enjoy seeing your efforts with various clone saws. This one seems to have some grunt actually after you got all the knick-knacks taken care of.

You might remind the nay-sayers that this saw would sit on a shelf and shine just like any other, but would cost a lot less :)
 
As documented, the "torn apart and worked on" part took an evening and part of a day doing work I enjoy (helping to stave off cabin fever) - TOTAL. And that included optional work like cleaning things up for cosmetic reasons, measuring timing, taking pictures and grinding the intake port. As stated, B&C never mattered much to me at all and I never expected much of them. I've got other bars and chains hanging in the barn that will fit, which was part of the decision to buy it. My cost will not be $275.

The saw is a faithful copy of a G621AV, which is a saw I've liked for some time. So it has all the characteristics of that saw - are you familiar with that design? What other $210 62cc saw could I get that would not need to be torn down, with as least as much time invested, plus probably new parts?

If it doesn't fail, and I doubt it will given past experience with the Earthquakes and my own mechanical judgment, then why do you think I got ripped off? Especially since I had a good understanding of exactly what I was getting?

The saw runs, and runs quite well. You are SURE it will fail, and in just a few tanks too. If it doesn't, would your opinion of it be changed?

The AM parts you bought and used were of similar source and quality to this saw. Why didn't you buy OEM?
 
I find it interesting that in Japan Zenoah still sells the G621. But they also sell a G6200.

http://www.zenoah.co.jp/int/products/chainsaws/g621/

http://www.zenoah.co.jp/int/products/chainsaws/g6200/

The only difference I see is the weight spec, which is 12.13 lbs for the G621 and 12.35 lbs for the G6200 - and I measured 12.4lbs on my clone. Also, many of these clones use some variant of "G6200" in their model number, just like this one (RD-G6200). My guess is that Zenoah makes the G6200 in China, just as they had a Japanese made GZ4000 and a Chinese made GZ400, and that these may be coming out of that same facility (maybe through the back door).
 
Don't quite agree chris-pa! The chinese clones I have seen sofar are never close to the power or weight ratings of the original!
As far as I see it the copies have a weight increase which would be quite in line with a material change from mag to only aluminum. That would also explain the one of the reasons for the price drop compared to the original.

7
 
Don't quite agree chris-pa! The chinese clones I have seen sofar are never close to the power or weight ratings of the original!
As far as I see it the copies have a weight increase which would be quite in line with a material change from mag to only aluminum. That would also explain the one of the reasons for the price drop compared to the original.

7
Well, the G6200 is heavier than the G621. And identical in weight to my clone.
 
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Final timing numbers:
E 160
I 159
T 122 (Blowdown at 19)

Exhaust port width is 54% of bore, intake is 52%. The squish is a 0.035”, which is bigger than I'd like but I'm not ready to set up a fixture for turning it – maybe another day.

It turned out the alignment problem with the air filter cover was due to the oversized holes in the cylinder (or rather the location accuracy – the oversized holes let me fix it). Once I cleaned out the antisieze from the holes I was able to rotate it so that it was centered properly. Now the carb and filter stud are properly centered, and everything fits nicely:
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The bar got the rivets peened and the tip straightened on the hydraulic press. It's still crap but might be serviceable:
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And here's the finished product:
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I did pry open the gills a bit:
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It's an under 12-½lb 62cc saw with decent timing numbers. I barely even “ported” it, as the numbers were about where I would start anyway. The 24” bar makes it fall right on it's nose.

It started and ran, but while I was tuning it it stopped running on the H. So I pulled the carb apart and sprayed it out – then it ran great. It was too late to cut with it – maybe tomorrow I can get it in some wood before we get another foot of snow. It will be humorous to see how long the bar and chain last.
I think it needs a pipe from a go ped or ktm 50
 
I think it needs a pipe from a go ped or ktm 50
Nah, just like with my ported Poulan, I use the thing and it would be in the way. Plus the porting was not set up for a pipe.

I'd open the exhaust to 62 percent of the bore.If it's not a strato you could open it even further.
I'm pretty conservative on port widths, as I don't want the ring popping into the port and causing more wear. I've read you can go 60% or even more but I generally don't go beyond 55%. I have several ported saws that run very well that way - in spite of the fact that this was a "cheap" saw, it was still more than I have ever spent on a saw and I want it to hold up as a work saw.

Hard to tell from pics. Was it a plated sleeve?
Do you mean the cylinder? It's chrome plated.
 
There's heaps of those saws here, and for the average home owner doing firewood they seem to do just fine. If run on 25:1 they seem to go for ages. They apparently hate synthetic oil, just need the "cheap" 2 stroke stuff. Here a decent quality Stihl or Husky around the 60cc range will cost you $1500 plus, so of course these things are popular, and I've seen a few which have done a LOT of work... Plus most guys only use them a few days a year.
Great write up, and enjoy yourself with it, I think you will find it will last well.
 
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