Part Seven: Carburation

[Mastermind]

How does one go about changing a jet in one of these HD carbs?

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I just drill the main jet.

 

[srcarr52]

Intake duration and carb size have an inverse relationship. If I plan on using a very large carb on a saw I'll leave the timing short and it helps with the starting and idling problems.

I often swap carbs on older saws to a larger carb but there is the added benefit of going to a nozzle style instead of the old orifice. 2100's, 181's, 288's often get a WJ-39 or 71 from a 394.

 

[Mastermind]

The WJ 39 is getting harder to find too.

 

[RI Chevy]

I just drill the main jet.

What size bit for a carb to fit on a ported 460?
I will need a magnifying glass for this one. Lol

Looking for something around .74mm or so. Just a bit bigger than the .7 stock oem size.

 

[srcarr52]

The WJ 39 is getting harder to find too.

I've used the WJ-70 EPA carb too. They seem to have a little crisper throttle response but I hate the limiter cap screws once you remove the caps.

 

[Chainsaw Jim]

How does one go about changing a jet in one of these HD carbs?

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The ones that you can easily change are slotted for a flathead and have sizes stamped one them.

 

[Dub11]

Feel better Randy.

I've got tendonitis in my right arm for 2 months now. I used to think guys were just being wimps when they complained about it. I can assure you now that they were not.

Age and healing don't go together. It really sucks.

Dude that chit is real! Now the 21 year old kid at my work crying about not sleeping enough after having a baby thats a whimp

 

[mdavlee]

HD11A still available new here:
http://www.ebay.com/itm/New-OEM-Sti...tor-Walbro-HD-11-1128-120-0620-/322471805778?

I am such a parts hoe.

is this too much carb for a four cube?
View attachment 69532
Dave

Just right Dave

 

[RI Chevy]

The ones that you can easily change are slotted for a flathead and have sizes stamped one them.

Ok. Thanks Jim.

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[Terry Syd]

The Mikuni manual for their diaphragm carbs cleared up a few questions for me.

 

[MustangMike]

Re: 044/440 & 046/460 ... Anyone do any testing to determine how much better a HD11 works than say a HD16?

Or how the HD50 compares to both of them?

 

[MattG]

Listening in on this one.

 

[Deets066]

This seems to be about the right ratio.....

 

[T.Roller]

View attachment 73710

This seems to be about the right ratio.....

372?

 

[Deets066]

372?

365

 

[T.Roller]

365

That'll be nasty!

 

[Magic_Man]

Let's go back to the very basics. When does one know he needs to drill or change a jet ? Or make a metering spring change ?

 

[MustangMike]

W/O an air flow meter, it is trial an error.

Reflecting back on my car hot rodding days, bolting a Holley carb on your car often made a very noticeable difference, and the main reason was richer fuel jets.

With the saws, I think it will be mostly trial & error, maybe with some testing.

 

[Magic_Man]

W/O an air flow meter, it is trial an error.

Reflecting back on my car hot rodding days, bolting a Holley carb on your car often made a very noticeable difference, and the main reason was richer fuel jets.

With the saws, I think it will be mostly trial & error, maybe with some testing.

But what's the tell tale sign ? If a saw tunes and cuts within a reasonable adjustment on the high side, what are you looking for that says hey, I need a bigger jet.

 

[MustangMike]

More power in the cut. Often (not always) a little more fuel in the A/F mix will do that.

Piss revving the the saw is at higher RPMs and the venture will draw more fuel. At lower RPMs (in the cut), a larger jet may provide a more desirable A/F ratio as the larger jet will flow more fuel.

Each saw will have an ideal A/F ratio for max power, and making it richer or leaner from there will result in a decline in performance.