bigger carburetor for chinese chainsaw / Komatsu Zenoah clone

[Terry Syd]

I like my 58 the best, technically the 62 timberpro is a little faster in big wood but the 58 out revs it in small to medium stuff which is what I cut the most.

When an open port jug is bored, it reduces the area of the transfer ports, which drops the maximum delivery ratio lower in the powerband. I'd probably go for a 58cc jug and then try and get it breathing a bit better with the carb, filter and muffler.

For a cheap Chinese saw, these saws have some potential.

 

[Leafy]

The two port muffler has the best flow in modded. The 3 port has smaller ports which makes for less area.

 

[NSEric]

When an open port jug is bored, it reduces the area of the transfer ports, which drops the maximum delivery ratio lower in the powerband. I'd probably go for a 58cc jug and then try and get it breathing a bit better with the carb, filter and muffler.

For a cheap Chinese saw, these saws have some potential.

Your bang on the money, the transfers are quite small on the 48mm bore 62, they're quad port like the 58.
I actually hogged out the divider in the transfers to gain volume in the 62 making it a normal dual port not a quad, it gained 500 rpm in the cut doing so, I'd only do that to the 62 tho.
I tried to get more revs outa the 62 with just porting while running the stock carb, I raised the exhaust a little too much in hindsight, I should've put the big carb/intake on it and only widened the ports.

I left the divider in the 58's transfers, I only removed the bottom 1/2 inch of them for a little better flow, it screams with them set up like that. It piss revs 15000 and cuts at 12500-13000. I only raised the exhaust the thickness of the base gasket when porting it, I cant grind the top of the transfers worth a dam so I ground the top of the piston by them instead, the same amount as the exhaust was raised. The intake/intake timing is untouched.

I completely gutted the muffler and added a deflector on the top on my 62, it works better than a muffler with baffles in it and big holes in the front. Im running the old single outlet muffler off my old 45 with an extra hole in it on my 58, it has a bigger less restrictive baffle than the dual port.
What's in the muffler is more important than the outlets IMO.

 

[Stefanseiner]

Today I tried to start the saw and had some problems.
No starting ,no "cough" - nothing.

Spark plug is new and fine, also the ignition coil because I see some sparks,
compression feels good. Maybe the carburetor. I change it to a brand new but still no starting.
Maybe there is a little damage in the cylinder I hadn't seen through the outtake.

So: disassembling. Again.

for me the piston looks good

the other side too

and the piston rings

no scratches at the cylinder walls

only thing I can do is pour out some gasoline oil mixture from the bottom of the crankshaft housing (maybe 20ml), renew the cylinder head gasket and assembling the saw with the original carb

I don't understand the problem but that's it - now she is running
Maybe the gasket was leaky because the area around the cylinder is very oily

unfortunately I didn't have a tree right now for quick testing, but next week I'll look for some suitable wood

 

[Leafy]

Mine always take forever to get the first prime.

 

[NSEric]

That looks like the 52cc cylinder, the 58 should have dividers in the transfers. If your going to hop it up get the one with quad transfers, they're 20 bucks and run better.

My timberpro 62 takes 8-10 pulls after sitting to start cold with no primer on it now. The easy pull starter doesn't turn the motor over much per pull but it sure does pull easy. My joncutter 58 starts in 3-5, it has a different easy pull starter that isn't quite as easy to pull but the motor turns more per pull.

 

[Stefanseiner]

That looks like the 52cc cylinder, the 58 should have dividers in the transfers.

it is not that easy, there are several versions out
52cc
- 45mm piston / 1 port per side
- 45mm piston / dual ports per side

58cc
- 45mm / 1 port
- 45,2mm / 1 port
- 45,2mm / dual ports
- 46mm / dual ports

62cc
- 47mm / dual
- 47,5mm
- 48mm

List is not complete, just what I found out so far, and especially the 62cc are incomplete because they aren't available anywhere for some time.
Here's a good overview: garten-ersatzteile.de

 

[NSEric]

I should have worded it differently, get the 45.2mm cylinder with dual ports per side for your 58, it runs better then the cylinder with 1 port per side.
If they were cheaper the 48mm 62cc cylinder would be good to try too but they're not as common and a bunch more money than the dirt cheap 45.2mm cylinder.
They all fit and run, you could even put the 43mm 45cc cylinder on a 58 or 62 to make a longer stroke 50ishcc version if you wanted, it would be a screamer.

AFAIK the 47 and 47.5mm 62cc cylinders do not fit only the 48mm one does, you can tell by looking at the intake closely, the 47/47.5mm one has the impulse in the intake.

 

[Leafy]

Also I belive they shorten the connecting rod as the stroke goes up. I had put a 45.2mm 58cc top end on my 52cc with no base gasket and it had pretty normal squish clearance. So they probably don't make the rod short enough so that the piston at TDC is the same exact height above the cylinder base but its not a couple millimeters higher either.

 

[Stefanseiner]

I should have worded it differently, get the 45.2mm cylinder with dual ports per side for your 58, it runs better then the cylinder with 1 port per side.

OK I will try.
Yesterday I repaired another 58cc for a friend and this saw spins up much more faster than mine, maybe this is a quad port cylinder?
Next week I will do some test cuts with my saw @ stock and then begin to modify. I ordered a quad port cylinder two weeks ago (~ 16USD @ aliexpress) so when it arrives I can test this too.

 

[nenicu]

The 58cc cylinder is built for the 34 stroke crank. Same rod that i can see with the 52 cc crank. The crank throw is difrent. I did a similar build with a 58 crank( 34 mm stroke) and normal 52 two port cylinder. I had to sand the squish band and piston to make that work. It was a good runner.

 

[nenicu]

So unless you can cut the cylinder the 52 cc jug is the best. You can adjust the squish with a diferent base gasqet and by sanding the squish band and piston. The exhaust and intatake are same size in the 52cc and 58cc cylinders.

 

[nenicu]

My next project is a china krank( 34 mm stroke) with a Redmax 5200(45 bore) cylinder. About 56 cc and long stroke. It should run with a Husky 257 if i can find a bigger intake and carb.

 

[NSEric]

So unless you can cut the cylinder the 52 cc jug is the best. You can adjust the squish with a diferent base gasqet and by sanding the squish band and piston. The exhaust and intatake are same size in the 52cc and 58cc cylinders.

The quad port 58 is better yet imo.
The 52 I had isn't even close to the 58 quad port.
The quad port 58 I have (joncutter 5800) had 175psi and .045tho squish with a base gasket, I never checked it after removing the base gasket but its pretty quick with the big carb/intake upgrade. It does not need the cylinder cut down.
I was going to sand the squish down and run a 52cc cylinder for more compression but the quad port has plenty of compression so I didn't bother.

 

[popopboat]

any updates ?

 

[Stefanseiner]

sorry but no. I squeezed in a new construction site before winter is there and working on the roof is not possible anymore, a 12 KVA photovoltaic system. After that I will continue the chainsaw project

 

[Stefanseiner]

the photovoltaics is done

and now I had some time to cut a little tree for testing

first I've done three cuts @ stock and took the time





1. power optimisation: back at the work bench for change / build in a new cylinder head with quadport instead of the original dualport





left is OEM, right is the new 45,2mm quadport.





how? The OEM dualport is a good and reliable cylinder with 3,4hp but the quadport is a little bit stronger (about 3,6hp), with better gas acceptance and higher radiation speed




it's some standard eBay-Kit for round about 12USD incl. all parts and shipping to Germany...




the following three cuts were a little slower then with the OEM, I guess because I didn't let the new engine some time to run in





next step: muffler mod





left is the original muffler with one port and catalyst, right the new 3-port muffler





it comes without catalyst and I already modded it with some 8mm extra holes and black thermo paint (delivered in silver).





all the extra-holes are invisible behind the cover. I used some washer to get a little more space between muffler and cover





calibrating the carb and some more cuts





here's a video of the two steps

conclusion (so far)

• noticeable more power
  
• better gas acceptance
  
• a little higher radiation speed, without load and with (in the wood)

the next steps are

• porting
• optimization of air intake and carb

 

[popopboat]

Hello, i also ordered same cylinder like you did, to replace my old scored, but they sent me 2 ports cylinder without additional cooling fins on the top..
What do you guys think, should i ask for a refund because i strictly searched for quad port because everyone claims that its better with quad, and also has thicker cooling fins.

 

[Leafy]

Hello, i also ordered same cylinder like you did, to replace my old scored, but they sent me 2 ports cylinder without additional cooling fins on the top..
What do you guys think, should i ask for a refund because i strictly searched for quad port because everyone claims that its better with quad, and also has thicker cooling fins.

If it doesnt match the pictures from that listing I would ask for a refund.

 

[popopboat]

They changed picture meanwhile, but luckily i bought it on aliexpress, and aliexpress saves picture from when i bought it.
I mean, its nothing wrong with the cylinder, but i paid extra just to get a quad port with thicker fins. I could have bought cylinder kit like i recieved for cheaper price.
So i think i will make a refund request and well see what happens.