Echo 490 to ported 4910…to cs-5484

[Ketchup]

 

[Ketchup]

Flew the crane with the Hybrid today. It did 24” crane picks like a 70cc saw. I’m sold. My buddies ported 346 just wasn’t as good.

 

[drf256]

Flew the crane with the Hybrid today. It did 24” crane picks like a 70cc saw. I’m sold. My buddies ported 346 just wasn’t as good.
View attachment 381771
View attachment 381770

That’s great. Your plan worked. Always satisfying. Thanks for documenting.

 

[Ketchup]

Back to the ported 4910.
I still haven’t fully sorted the carb setup on this one. The C3M knockoff performs well now that the bypass is plugged, but the carb goes lean when I point the bar in the sky. It just doesn’t hold idle right. Even when the AM stuff works, it kind of doesn’t.
So I got this HD58 carb thinking it would be the same as a HD12, but with a smaller main nozzle. That’s more or less true, but it’s too rich, just like the HD12. It tunes pretty good at 1/8 turn out on the High, which I don’t really feel is far enough out. So I popped it open to see what the circuits look like.
My guess is the bypass for the high is that brass marked 64 and the pickup for the H needle is the hole beside the main nozzle.

Looking for advise. Should I plug the 64? (Drill smaller?)

Alternatively, a friend suggested lowering the metering lever.

@huskihl , @Dolkitafreak , or anyone else. This carb cost $40 and was kinda hard to get, so I’m being a little cautious.

 

[cus_deluxe]

if ur idle is wacky id pop that welch plug out and see whats up. if ur unhappy with the hi screw being only 1/8 turn out then you could plug the 64 jet and do the same as you did on the other carb. lowering the lever will address the sypmtom
but not the cause, id view that as a last resort. but thats just me.

 

[huskihl]

Back to the ported 4910.
I still haven’t fully sorted the carb setup on this one. The C3M knockoff performs well now that the bypass is plugged, but the carb goes lean when I point the bar in the sky. It just doesn’t hold idle right. Even when the AM stuff works, it kind of doesn’t.
So I got this HD58 carb thinking it would be the same as a HD12, but with a smaller main nozzle. That’s more or less true, but it’s too rich, just like the HD12. It tunes pretty good at 1/8 turn out on the High, which I don’t really feel is far enough out. So I popped it open to see what the circuits look like. View attachment 381979
My guess is the bypass for the high is that brass marked 64 and the pickup for the H needle is the hole beside the main nozzle.

Looking for advise. Should I plug the 64? (Drill smaller?)

Alternatively, a friend suggested lowering the metering lever.

@huskihl , @Dolkitafreak , or anyone else. This carb cost $40 and was kinda hard to get, so I’m being a little cautious.

You could pack it full of epoxy and then drill it out. Or you could leave it if you don’t think you’re going to need to lean it out much more. Nothing wrong with 1/8 or 1/4 turn out on the needle. It’s still getting fuel, it’s just getting it through that brass jet rather than through your needle.

 

[drf256]

You vac test that saw? When you point the bar to the sky? How’s the fuel line?

 

[Dolkitafreak]

if ur idle is wacky id pop that welch plug out and see whats up. if ur unhappy with the hi screw being only 1/8 turn out then you could plug the 64 jet and do the same as you did on the other carb. lowering the lever will address the sypmtom
but not the cause, id view that as a last resort. but thats just me.

This^.

I don’t like correcting things the wrong way, leave lever correct and reduce area somewhere else imo. 1/8 turn is fine like Kev said unless it bugs you.

 

[Ketchup]

You vac test that saw? When you point the bar to the sky? How’s the fuel line?

Yep. Pressure and vac. Engine, fuel lines, the works. Went away as soon as I swapped carbs. Put it back on, same symptoms.

This^.

I don’t like correcting things the wrong way, leave lever correct and reduce area somewhere else imo. 1/8 turn is fine like Kev said unless it bugs you.

I was reluctant to bend the lever as well. The 1/8th of a turn is still a kinda rich at 5500’, but it cleans up in the cut. Up at my house (9400) its a frog hair off closed and still fat. I wanted a tune for both elevations.

So I pressed a piece of Solder into the 64 jet on this HD58 and tried it plugged. The tune was much better for idle and WOT (7/8L, 1H), but there was an annoying bog that wouldn’t tune away. I don’t think that 64 Jet is part of the H circuit. I think it’s a step-up before the main nozzle really pulls fuel. So I drilled it to 0.35mm. The bog was smaller, but still irritated me (tune shifted to 5/8L, 3/4H). Back apart again, drilled to 0.45mm. There is still a small bog, but my tune is 1/2L, 1/2H. I think I’ll leave it there. Should be plenty of room to adjust as it breaks in and it screams up at my house.

 

[Ketchup]

Well, I had a little problem. My original intake horn cracked at the bolt. Here you can see the crack and how much I shaved away vs a stock one.

 

[Ketchup]

There’s some grinding work to make that horn fit up with the big carb. The bore of the horn is 20mm, the choke butterfly on the HD58 is 21mm, so you have to thin the horn a good bit for the choke to open and close.

Belt sander hackery!


I added some washers to the carb bolts hoping to distribute force on the thinned flange. I think the real key is not to over tighten.

 

[Ketchup]

Since I had the carb off, I decided to drill the step jet a tiny bit bigger. It was 0.045mm. I bumped it to 0.52mm.

I also noticed the screw heads on the metering side of the carb were touching the case in the carb box.



Fixed

 

[Ketchup]

Looking through the intake port, I also noticed that the cylinder flanges don’t match the transfer feeds in the case. If I pull the jug I will definitely remove a significant amount of flange on the exhaust side.

 

[Ketchup]

Bumping the carb jet up to 0.052 got rid of the rest of the mid throttle bog, but it also brought the H tune to 3/8 out. I can live with that. Unfortunately, now the throttle response isn’t very snappy. I may be able to adjust the L and Idle to get a more instant rev or it may just have to be a little slow to take off. I’m deep in the weeds on this one, but I keep finding little gains that add up.

 

[Ketchup]

In regards to all the fines that made it into the hybrid, I think my modified air horn was to blame. If you look close here you can see a lot of fines stuck in the 1184 I used to seal it to the carb. This time I think that was from the mount cracking, but originally I don’t think I got the face that mounts to the carb even enough.

Although I think it cleared the first time, it’s important to grind some space between the air filter mount nut and the bigger carb. The screw that holds the filter and cover on also needs to be shortened so it doesn’t touch the carb and not over tightened. The filter mount and base mounts can really torque and deform the air horn.

All that said, I think the mesh filter was never the problem and probably help’s slightly with performance. Here’s a link of where to get one.

Genuine Shindaiwa AIR FILTER-LOWER Part # A226001580 | eBay

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