HDA-199 Mod Questions

[ZukiRyder400]

I have a question for some of the more experienced guys. On a 357/359, do you guys even mod the carb. If so what ado you guys recommend?

 

[Ketchup]

Yep. Replace the blue diaphragm with tan, drill a small hole in the plate on the impulse side of the carb.

 

[ZukiRyder400]

Yep. Replace the blue diaphragm with tan, drill a small hole in the plate on the impulse side of the carb.

I actually updated the carb when I rebuilt my 2159. I was wondering what some other guys drill the jets out to inside the carb

 

[ZukiRyder400]

Sorry I wasn’t clearer in my 1st post. But thanks for the tip anyways

 

[huskyboy]

I wouldn’t drill the jets unless the saw needed it. How far out on the H/L are you?

 

[Duane(Pa)]

I’m with Mason. I’ve never felt like I didn’t have enough adjustment.

 

[ZukiRyder400]

I wouldn’t drill the jets unless the saw needed it. How far out on the H/L are you?

1 1/2 for the high, 1 1/8 on the low side.

 

[huskyboy]

1 1/2 for the high, 1 1/8 on the low side.

That’s pretty good man, I wouldn’t worry about it if it were me. You want some fudge room for temp and elevation change. If you bored out the carb/cleaned up venturi it would probably need to be drilled.

 

[ZukiRyder400]

That’s pretty good man, I wouldn’t worry about it if it were me. You want some fudge room for temp and elevation change. If you bored out the carb/cleaned up venturi it would probably need to be drilled.

Ahh. I see. Thanks for the halp. I am still thinking about modding either a Zama C3M 365 carb or a Walbro HD-30 to make it fit a 357/359. They are basically the same body but the Zama and the Walbro have a slightly larger venturi and the throttle rod is mounted differently than a 199. Still not 100% set on this idea though. The big question is, is the juice worth the squeeze? Maybe, Maybe not, who knows...

 

[ZukiRyder400]

I will get side by side pics when I get home.

 

[huskihl]

It kinda depends on where the screw stops adding fuel. Some quit at 1.5 turns. The rwj adds fuel until the screw gets sloppy at 4 turns. Just be careful drilling because it’s easy to go too far to where you can’t lean them out enough.

I’ve found that in “most” circumstances, feeling the need to drill jets is a bandaid to fix a different issue like weak impulse, plugged jets, or stiff diaphragms.
The faster flowing air of a ported or muff modded saw usually pulls more fuel through the main nozzle. Sometimes they need to be leaned out afterwards rather than richened

 

[ZukiRyder400]

It kinda depends on where the screw stops adding fuel. Some quit at 1.5 turns. The rwj adds fuel until the screw gets sloppy at 4 turns. Just be careful drilling because it’s easy to go too far to where you can’t lean them out enough.

I’ve found that in “most” circumstances, feeling the need to drill jets is a bandaid to fix a different issue like weak impulse, plugged jets, or stiff diaphragms.
The faster flowing air of a ported or muff modded saw usually pulls more fuel through the main nozzle. Sometimes they need to be leaned out afterwards rather than richened

Thanks Kevin. I MIGHT drill the main.. idk yet. Gonna run it first then ill make a decision

 

[Ketchup]

357 or 359 jug?

 

[ZukiRyder400]

357 or 359 jug?

Tree fiddy nine

 

[drf256]

It kinda depends on where the screw stops adding fuel. Some quit at 1.5 turns. The rwj adds fuel until the screw gets sloppy at 4 turns. Just be careful drilling because it’s easy to go too far to where you can’t lean them out enough.

I’ve found that in “most” circumstances, feeling the need to drill jets is a bandaid to fix a different issue like weak impulse, plugged jets, or stiff diaphragms.
The faster flowing air of a ported or muff modded saw usually pulls more fuel through the main nozzle. Sometimes they need to be leaned out afterwards rather than richened

I’ve had the same experience Kev. Adding an HD carb to an 026 needed the main drilled from 68 to around an 80 for proper stoichiometric ratio and adjustment ability. The same carb ran fine on an 044 with the 68 jet. Bigger ain’t always better. Jet size is counterintuitive in some ways.

Less airflow = Less negative Venturi pressure to pull fuel from the nozzle.

 

[ZukiRyder400]

HDA right, HD-30 left

 

[drf256]

262XP’s run like a raped ape ported with the 198/199 bore. I don’t think it’s worth your time or trouble to swap in the other.

But then again, it’s better to try and fail than to never try.

 

[ZukiRyder400]

262XP’s run like a raped ape ported with the 198/199 bore. I don’t think it’s worth your time or trouble to swap in the other.

But then again, it’s better to try and fail than to never try.

Good point Doc. It would be a grand pain in the arse to try and make the HD-12/HD-30 even be somewhat doable.

 

[huskyboy]

Good point Doc. It would be a grand pain in the arse to try and make the HD-12/HD-30 even be somewhat doable.

You’d have to drill it for internal impulse (it is external) and somehow swap/modify the shafts. Would be a lot of work.

 

[ZukiRyder400]

You’d have to drill it for internal impulse (it is external) and somehow swap/modify the shafts. Would be a lot of work.

Yeah, too much work for what might be a little gain