Chainsaw Repair

Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => RedMax => Topic started by: Chris-PA on December 12, 2015, 06:37:07 pm

Title: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Chris-PA on December 12, 2015, 06:37:07 pm
I have a 38cc Earthquake, which is a Chinese clone of a RedMax G3800 - only they modified it to meet emissions.  It's kind of an interesting contrast given that this is the saw Zenoah started with to make the strato GZ4000, and this is the alternate non-strato approach to meeting emissions.  It had modified port timing, lower volume transfers runners and a cat (think Echo and others).  So of course I ported it and got rid of the cat muffler for a modded normal one, but I could never get the thing to rev like I wanted.  I went through maybe 4 different tear downs, cut the jug, swapped the ignition to a Ryobi system and back again, swapped the carb and back again.  That whole adventure was documented here: http://www.arboristsite.com/community/threads/what-i-learned-porting-an-earthquake.270735/

I hadn't used it in a while, but was out cutting since it was in the 60's today and decided to run the Earthquake.  And.....it was a slug.  Well maybe that's extreme, but it still just didn't want to rev and the spool up was lazy.  That's been the persistent issue with this build, and while you can convince yourself it's pretty good, if you let it sit for a while and run other better saws it's pretty apparent when you pick it up again.  So I took it down to the bench and yanked the jug.

The first obvious thing was that it's been a head slapper.  There were two spots in the casting of the combustion chamber under the spark plug boss that looked like they slumped a little, and I had tried to grind them out when I decreased the squish, but they looked to have been just kissing the piston dome - maybe just enough to polish the carbon.   So that had to be dealt with, which I did by grinding some more on those spots in the the combustion chamber, and by a little filing on the top of the piston.  I also filed off the orientation arrow which they had cast on the piston crown, as it had left a neat little dent in the edge of the squish band!  Which shows that using solder to measure squish in a couple of spots isn't necessarily good enough, especially with a domed piston.

But the main thing was the transfers.  If you look at the pictures of the transfers I showed earlier ( http://www.arboristsite.com/community/threads/what-i-learned-porting-an-earthquake.270735/#post-5157085 ), I had only ever raised the intake side outlets (and the intake side transfers are quite small on this jug).  From what I have read they should be even, or the exhaust side ones should open first.  I was pretty convinced this has been the problem.  So I took some measurements and cut some card stock, and just hacked away with a small ball end cutter until I evened them all up.  It wasn't that pretty, but not that bad either.  I left the total transfer duration at 106 (21deg blowdown).

So I slapped it back together and took it back up just before dark - and finally it has the snap I wanted!  I even took some of the extra spark advance out I had put in to try to get the rpms up.  So all the stuff I tried - compression increase, squaring up the intake, spark advance, opening the lower transfers, opening the muffler more - none of it really addressed the sluggishness problem.  Those mods may have helped it to run like it does now, but but without fixing the transfers it wasn't good enough.  Which of course I had been told. 

I'll try to get a video of it now - it's finally what I expected it should be. 
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: 3000 FPS on December 12, 2015, 09:03:51 pm
Good deal Chris.   It was a good read.   I am not a big fan of the earthquakes but I know you love to tinker with these saws and figure things out so good for you.
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Chris-PA on December 12, 2015, 09:46:02 pm
Thanks!  Really I'm a fan of Zenoah designs, and the clones are a way to get older models cheap.  Actually this saw was purchased as a parts mule for my GZ4000's for $35 delivered - but I've been playing with it ever since! 
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Cut4fun . on December 13, 2015, 12:29:37 pm
Never ran the copies. But the ported 3800 redmax was super light and nimble for 38cc.  http://chainsawrepair.createaforum.com/redmax/redmax-3800/msg444/#msg444

Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Chris-PA on December 13, 2015, 04:54:50 pm
Ran it a bit clearing brush and bucking a bit of ash.  Throttle response was nice while cutting brush.  Took this video:

https://www.youtube.com/watch?v=B-12jcD7DYc

Once it got loaded in the cut it was running around 10,500rpm.  Seemed to run pretty clean - at least I didn't stink too bad like exhaust after running it today. 
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: weimedog on December 14, 2015, 01:34:41 pm
A great read, thanks for posting. :)
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Cut4fun . on December 14, 2015, 02:22:25 pm
@Chris-PA   have you figured out why the copies weigh so much more then the redmax 3800 originals?

Sounds and looks good in the cut. Wonder if you could make the chain hungrier.  :P
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Chris-PA on December 14, 2015, 02:50:49 pm
A great read, thanks for posting. :)
Thanks!

@Chris-PA   have you figured out why the copies weigh so much more then the redmax 3800 originals?

Sounds and looks good in the cut. Wonder if you could make the chain hungrier.  :P
I don't think do weigh much if any more than the originals.  My G621 clone weighs under 12.5lb, or withing 0.1lb of the original if what I've seen is true.  I never weighed the Earthquake, but it's lighter than my GZ4000's by a little, which is about right.  The difference between how much mag is in the alloy might make a small difference, but the alloy part of the G3800 chassis is so small it would barely be noticeable. 

The chain was Tri-Link lo pro semi chisel.  I had touched a rock with it cutting brush earlier, so it had just been filed and the depth gauges set.  That was a 16" bar on a 38cc saw cutting a pretty hard piece of ash - I feel like that was all it's got and a more aggressive chain would just bog it. 
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Cut4fun on December 14, 2015, 03:18:40 pm
A great read, thanks for posting. :)
Thanks!

@Chris-PA   have you figured out why the copies weigh so much more then the redmax 3800 originals?

Sounds and looks good in the cut. Wonder if you could make the chain hungrier.  :P
I don't think do weigh much if any more than the originals.  My G621 clone weighs under 12.5lb, or withing 0.1lb of the original if what I've seen is true.  I never weighed the Earthquake, but it's lighter than my GZ4000's by a little, which is about right.  The difference between how much mag is in the alloy might make a small difference, but the alloy part of the G3800 chassis is so small it would barely be noticeable. 

The chain was Tri-Link lo pro semi chisel.  I had touched a rock with it cutting brush earlier, so it had just been filed and the depth gauges set.  That was a 16" bar on a 38cc saw cutting a pretty hard piece of ash - I feel like that was all it's got and a more aggressive chain would just bog it. 

Thats what I was wondering how it would do with a PS PS3 chain on it.  You got any to try?
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Cut4fun on December 14, 2015, 03:27:10 pm
Just trying to save some paper weights listed.  Paper weight listed for 5000 is  accurate as I owned one.

G3800AVS 9.1lbs

GZ400 9.7

GZ4500 9.6

GZ4000 9.5

G5000AVS 11.2
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Chris-PA on December 14, 2015, 05:31:56 pm
One of these days I'll have to take the Earthquake into work and weigh it.  However, you might have pointed to the source of the weight discrepancy:  the 38 and 41cc Quakes are based on the G3800.  The 45cc models are based on the G5000 - they're going to be significantly heavier.  They didn't appeal to me.   
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Cut4fun . on December 14, 2015, 07:46:27 pm
One of these days I'll have to take the Earthquake into work and weigh it.  However, you might have ointed to the source of the weight discrepancy:  the 38 and 41cc Quakes are based on the G3800.  The 45cc models are based on the G5000 - they're going to be significantly heavier.  They didn't appeal to me.   

That was something I was wondering too. Was the 38cc copies on the heavier cases. But when you said about the same earlier I figured not.
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: sharkey on December 16, 2015, 03:32:56 pm
Nice Job Chris, that engine is holding its revs real well now.  Maybe look around for a rim drive and swap on .325 chain?
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Chris-PA on December 16, 2015, 07:50:27 pm
Nice Job Chris, that engine is holding its revs real well now.  Maybe look around for a rim drive and swap on .325 chain?
Thanks, it's a nice little saw now and I can run it without being bugged that it won't rev. 

I'm actually a fan of 3/8 lo pro, and I have not seen any rim drive sprockets for these little Zenoah-based designs.  The GZ4500s have 0.325" chain, but you need both the drive sprocket and the different oil pump worm gear.  Anyway, it would need narrow kerf, and I already have a bunch of lo pro bars. 

I was trying to decide which saw I've taken apart more times, this one of the 42cc Cratsman/Poulan I've been experimenting with.  I had to put six helicoils in the Poulan case as several of them finally stripped out, and only one in this.  I'm hoping to leave both of them together and just use them now!
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: 3000 FPS on December 16, 2015, 08:57:23 pm
I had to put six helicoils in the Poulan case as several of them finally stripped out, and only one in this.  I'm hoping to leave both of them together and just use them now!

That is funny.
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Chris-PA on December 20, 2015, 08:55:37 pm
In spite of being sick most of last week I did get out and use the Earthquake a bit more this weekend, and the little bugger runs!  I have no doubts about it now.  It's a great light weight saw and balances well with a 16" bar.  It's also very nice for clearing brush. 

Thinking about other chain options, this saw would be perfect for some 0.043" 90S chain.  Still, I have several of those Tiger-branded bars I had on it in the video and I like the larger nose sprocket, so I'm not going to change it. 

I pulled the plug to check it out and I wish I could get a good shot of the piston fit.  The domed piston matches the squish band pretty tightly, leaving a compact combustion chamber.  I doubt the strange casting cracks matter much. 

(http://chainsawrepair.createaforum.com/index.php?action=dlattach;topic=5469.0;attach=16234;image)
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Cut4fun . on December 20, 2015, 09:17:54 pm
Wonder how it would pull these chain build off chains we have.  Going use a stock 39cc echo 3900 for first run.
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Chris-PA on December 20, 2015, 09:43:13 pm
I'm sure it would haul with a 12" bar!  I considered getting a 12' bar for it but I have one on my mildly modded 32cc McCulloch, and I like a little longer bar for clearing brush. 

I think it would spank a 39cc Echo at this point!   ;)
Title: Re: Finally Have My Ported Earthquake G3800 Clone Running Right!
Post by: Cut4fun . on December 20, 2015, 09:53:57 pm
I would hope so. ;)  Looks good in the wood.