357 carb on 346xp

[sunfish]

I figured best to start a new thread, the quote from Brad below is from Wigg's filter thread. umpkin2:

No mods are required at all. All you need is the following:

Carb - 505 20 30-01 - $59 on eBay. Make sure you get a C3-EL42.
Intake Elbow - 503 92 46-01 - $4.23
Filter retaining spring - 503 96 27-01 - $5.21
Filter - 537 01 09-02 Yellow / 537 01 09-03 Felt - $13.33
Carb bolts x 2 - 725 53 41-55 - $2.28

Brad, I just today put a new 357 carb on my old OE 346 and everything fit, except I had to trim a little plastic off the housing around the H/L screws. I used all the 346 parts. The intake elbow, was very close to same dia as the new carb, just under 3/4".

I'm guessing the 357 intake elbow and filter will flow more? And longer screws for the 357 elbow?

Just curious why the new parts, if the 346 parts work?

I ordered the 357 parts this morning and will use them on my new 346.

Thanks for the info.

 

[spike60]

There is a new flange that goes with the Zama carb, 503928502.

Or just trim it like you did. :msp_smile:

 

[Stumpys Customs]

Does it run any better:msp_w00t:

 

[sunfish]

There is a new flange that goes with the Zama carb, 503928502.

Or just trim it like you did. :msp_smile:

Thanks, Spike!

Does it run any better:msp_w00t:

Not sure, maybe. First impression is not much difference.

Only made a couple cuts. But I need to adjust it and make more cuts.

Only 45cc here, might need 50cc for this big carb.

It's gotta help. :msp_smile:

 

[albert]

My thought is unless you have some very radical porting and muffler outlet size the bigger carb may be a step backwards in performance. Usually throttle response and transition from low to mid range suffers. There may be replacable jets you can play with.

 

[sunfish]

My thought is unless you have some very radical porting and muffler outlet size the bigger carb may be a step backwards in performance. Usually throttle response and transition from low to mid range suffers. There may be replacable jets you can play with.

I should mentioned, I ported this one, my first. Nice gains too! Might need to open the muff more.

This 357 carb will likely go on the new 50cc 346 after porting. Just wanted to see if it made a diff on the old 45cc 346?

 

[sunfish]

My thought is unless you have some very radical porting and muffler outlet size the bigger carb may be a step backwards in performance. Usually throttle response and transition from low to mid range suffers. There may be replacable jets you can play with.

You could be right. Throttle response is great, spools up very quick and overall runs great. Feels like it lost a little torque? But like said, I need to run it more.

Thanks for the input.

 

[Terry Syd]

It may not be that it has lost any torque, but simply shifted the torque peak higher in the rpm range. The point of maximum delivery to the crankcase now occurs at a higher rpm. Below that max delivery rate is when you start to get backflow out of the carb, so it feels like you lost some 'low end torque'. The solution to keeping that previous torque peak is to use less intake duration so the peak still occurs at the old rpm. The bigger carb will still allow the engine to rev better at the higher speeds.

If you run into problems with the transition, you can modify the throttle valve. Put a small divet on the side of the valve on the side OPPOSITE the idle mixture hole. That will lean out the idle - then open up the low speed needle to get the mixture right. Of course, the idle speed is now too high, so you turn down the idle screw. - When you open the throttle, the valve will move across the low speed circuit holes and pull in extra fuel because you have opened up the low speed needle.

You may have have to adjust the pop-off pressure on the needle to pick up some more fuel down lower in the rpm range. You can check that by testing both the horsepower peak and the torque peak. Tune the carb to give you the best high speed cutting, then put a load on the saw and pull it down to peak torque. Check and see if opening up the high speed needle a bit at peak torque will increase the torque. If it does, then you can decrease the pop-off pressure to change the fuel curve to give you more fuel at the lower air velocities. After changing the pop-off, you will have to go back and re-set both the high and low speed needles. Test and repeat...

 

[sunfish]

Thanks Terry!

I need to learn about tweakin these carbs and your info is a great start.

 

[WoodChuck'r]

A four barrel carb from a 440 hemi would probably fuel the saw better.

 

[tlandrum]

tillitson hl360 double stacked,ohhhh yeeeaaaaahhhhhh

 

[sunfish]

Don't have enough saw here for them giant carbs.

But maybe if I get the grinder back out. :msp_biggrin:

 

[logging22]

Good on ya for trying the new stuff Don. Keep it up brother.

 

[sunfish]

Adjusted H/L a bit, running at 14400 rpm. Maybe a bit of gain over the stock carb, but not $58 worth.

I'll open up the muff more tomorrow and give it another go. My MM was modest.

I feel the 357 carb would be better on a ported 50cc NE. If anyone is thinking of this mod for a stock saw, I don't think it'll do much for ya.

Eventually this saw will get a 50cc top end.

 

[Stumpys Customs]

Adjusted H/L a bit, running at 14400 rpm. Maybe a bit of gain over the stock carb, but not $58 worth.

I'll open up the muff more tomorrow and give it another go. My MM was modest.

I feel the 357 carb would be better on a ported 50cc NE. If anyone is thinking of this mod for a stock saw, I don't think it'll do much for ya.

Eventually this saw will get a 50cc top end.

14,400?? yer bein awfull consevative, those things are factory rated fer 15,500. Lean her out & let her rip.

 

[sunfish]

14,400?? yer bein awfull consevative, those things are factory rated fer 15,500. Lean her out & let her rip.

No Stump, I believe it's 14700 for the OE and 14200 for the NE. I'll lean it out to 15000 and see how it eats tomorrow.

 

[Stumpys Customs]

No Stump, I believe it's 14700 for the OE and 14200 for the NE. I'll lean it out to 15000 and see how it eats tomorrow.

I was just goin off of the copy of a Husqvarna 1998 tech specs bullitin. Max rpm freeload is 15,500.:msp_confused:

 

[sunfish]

I was just goin off of the copy of a Husqvarna 1998 tech specs bullitin. Max rpm freeload is 15,500.:msp_confused:

Must have been an early target max rpm?

My 2001 owner's manual says 14700. And I've heard the NE 346 is a bit lower.

Be fun to see what 15000, or 15500 does. Just as long as it 4 strokes a bit. :msp_biggrin:

 

[albert]

The OE's were 15,500 when they first came out. They lowered it shortly afterward. !5,500 was ok for short burst light limbing, but lacked torque for heavier cuts. Correctly ported with the larger carb, I would think you should be over 15,000 no load.

 

[sunfish]

The OE's were 15,500 when they first came out. They lowered it shortly afterward. !5,500 was ok for short burst light limbing, but lacked torque for heavier cuts. Correctly ported with the larger carb, I would think you should be over 15,000 no load.

Well, that explains Stumpy's numbers.

Correctly ported is key here. This is the first saw I ported. :msp_biggrin:

I've been scarred to lean it out more, but will do it tomorrow.