Any Chinese chainsaw and chinese parts discussion

[Czed]

Well ....... bad news on the Carburetor...

I called HL this morning (Great people BTW) they checked one of the actual carbs and they are only single jet...

So, the search continues for a suitable carb to modify and tune.

The last six china 372 carbs were not
Twin jets I've bought.
I was hoping they had changed them.

 

[Leafy]

Finally got it in wood.

 

[Czed]

Finally got it in wood.

Runs great holds it's rpm in the cut.

 

[Leafy]

So. There really isnt much meat to bore these carbs out. You cant even get the throttle to be the same as the choke. Looks like the limit for increasing flow through the zama c3s is to just put an 11/16 through the bore to make it more round. Also I seem to have had a carb where the L was fed independently of the H, I think this was the carb that came with the kit from huztl. This one would have been easier to make into a twin jet right? Damn.

I guess I'll have to wait to find a good price on a used rjw-4. I wish there was a good listing of carbs by size. There should be some good sized WJs, I want something 19mm for the venturi.

 

[Terry Syd]

The Zama has an unusual shaped venturi because it was 'flowed' on a flow bench. The built up area around the base of the main discharge nozzle prevents eddies in the flow of the air. Just because something may be a bit smaller does not indicate its' true flow characteristics.

I looked at this picture and noticed that a welch plug was placed over the transition holes instead of using a jet. I can't see where the fuel would be provided to the transition circuit. Weird design. It might be able to be converted to a 'twin jet', but I'd have to have one in my hands to follow the circuits. There are so many different carb designs that you can NEVER take anything for granted.

 

[Leafy]

All 3 of the jets after venturi are fed from the L.

I like how the c3 was "flowed" but they also put the mold parting line right in the middle of the venturi. I has another coming from Amazon, maybe I'll just take the random hump near one of the mounting holes in the venturi out with the die grinder.

Holy *s-word I just had a great idea. If I had a detailed diagram of how the dual port zamas route their flow I could make a new carb body design with proper sized venturi and throttle and print out from nylon. And just use the parts from an ebay one. I'd make it so you'd need to touch up all the critical hole diameters with small drills.

 

[Terry Syd]

Mate, if you were going to create a Zama twin jet replica, you should do it the way I think the original designer thought it out - with replaceable jets!

When you look at a Mikuni diaphragm carb they not only have replaceable jets for the idle/transition circuit, but also for the low speed flow in the auxiliary circuit AND the size of the metering orifice under the metering valve. The Mikuni also uses the same easy to dial in idle circuit of the Zama (if only Walbro had done the same)

I doubt you would find a big market for the carbs, as there are only a handful of people (like on this forum) that want to get top performance out of their engines. However, with replaceable jets and a few metering springs, a bloke could dial in his carb in an afternoon.

 

[Leafy]

Mostly for my own amusement. Its not like it takes long. Half a rainy day on the cad to design it and let it print over night is really all it costs. Any idea where I'd get nice metal jets for this?

Speaking of the carb design I posted I also noticed there doesnt seem to be a good way for them to have made the idle nozzles and path. How the heck did they make that passage without the rectangular welch plug zama used?

 

[Terry Syd]

That long channel to the idle port allows the fuel and air to set up a 'freight train' of small air bubbles along the channel using capillary action. It furnishes a more uniform mixture to the idle port.

 

[Czed]

One of the first china 372s
i built has the standard 372 oem size
Wrist pin bearing.
There's no way to tell until you tear
The saw down.
Which size they have
The newest saws i have
Are the clutch bearing size.

 

[Czed]

Update Still together no problem other than the brake would trip too easy.
Thirsty likes the fuel
Running a big bore with a 272 popup
and 28 full comp

 

[Rob Stafari]

I'd rather have a break trip too easy than not at all!

 

[huskyboy]

Only ones I have experience with are 394 am clutch covers. The problem is the springs are shorter than oem. It’s annoying having it trip in the cut. Oem spring fixed the problem.

 

[Leafy]

It looks like it's a thinner wire too and the same pitch of coils. I bet if you stretched that spring out to oem length it would have about the same spring rate as oem. Because the smaller wire lowers the rate but the less coils at the same length would increase the rate.

 

[Whitty21]

Anyone who has swapped then likely knows why they are shorter. I bet it is just laziness. Feels like I am going to lose a tooth every time you go to squeeze one in

 

[stihl_head1982]

Update Still together no problem other than the brake would trip too easy.
Thirsty likes the fuel
Running a big bore with a 272 popup
and 28 full comp
View attachment 145283

Nice looking saw. I may sometime take the punge and cross over to the dark side. I'm afraid if I buy a clone kit I may not have the
proper perspective on Hooskies. Although I must add the 395XP has pulled at me more than once.

 

[Czed]

Some of you guy's will *s-word yourselves
To know
Several of my saws don't have chain brakes lol

 

[Whitty21]

Nice looking saw. I may sometime take the punge and cross over to the dark side. I'm afraid if I buy a clone kit I may not have the
proper perspective on Hooskies. Although I must add the 395XP has pulled at me more than once.

I have a 394xp. Can confirm it puts a *s-word eating grin on my face every time. 24" bar 8 pin full comp

 

[Czed]

Nice looking saw. I may sometime take the punge and cross over to the dark side. I'm afraid if I buy a clone kit I may not have the
proper perspective on Hooskies. Although I must add the 395XP has pulled at me more than once.

I've got oem husky and johnnys can't tell the difference between them and the
Clones in performance.
I only built the one saw from huztl parts no problem.
Mine are mostly the china assembled saws.
So i can't really recommend the kit saws.
Haven't messed with them much
Several had trouble with the stihl clone kits.
@p61 western
Had a issue with the husky kit he built.
I was hoping the 365/372 was the saw they were going to build for the next
Gtg in Tennessee
But they went with dolmar for next year.
Ran mine hard
Would buy again

 

[Leafy]

Mine started leaning out again, gonna try a new fuel line. I guess and try vac testing it again. I might 3d print some urethane blockoffs for the intake and exhaust.