The famous D jug...

[Payson Oberly]

I'm seeing a lot about this "d jug" in the 460s/046s. I'm wondering what's so different about the cylinder, and what kind I've got... If anyone's got pictures that would be awesome. (A D next to an H jug, if I'm correct) but explaination would do fine too. TIA!

 

[drf255]

Show us a pic of yours.

D jugs are both desirable/undesirable because they have tighter/smaller chambers and a larger squish band. So without machine work, you’ll get more psi with a D jug.

After machine work, a D jug may be less desirable because you’ll have too much compression.

The real reason D jugs are desirable is better port shape and geometry than comparable Hemi head 460 jugs.

 

[JonCraig]

https://www.arboristsite.com/community/threads/046-rebuild-complete-pic-heavy.312534/#post-6328973

https://www.arboristsite.com/community/threads/which-046-did-i-just-buy.310907/

 

[CR888]

I'd either post a pic of your jug so folks can tell you what you got or use the search function. It works.

 

[Payson Oberly]

Thanks to the helpful folks, I'll be able to tell once disassembled. I did some searching around but didn't quite find what I was looking for

I'd either post a pic of your jug so folks can tell you what you got or use the search function. It works.

 

[Overkill338]

D jug




Hemi

 

[Cantdog]

As an off shoot the Jonsered 630 Super II has the "D" shape combustion chamber too. I had one that made 225 lbs of comp with no work just a gasket delete which got the squish down 0.024" or so. I ported that saw and was/is a real smart 61cc saw......it sweet spot is tuned to 14,400 rpm......sold it 5-6 years ago but the guy brings it back for tune ups and/or repairs.....had the cyl off looking things over a couple weeks ago......almost wished I hadn't sold it.......

 

[JonCraig]

This is all just info I picked up from @blsnelling and @Jacob J. and others, but as I understand it, the early D-jugs are good performers because of the good port timing moreso than the combustion chamber shape. The “good ones” are from the first year or two of the 046, before EPA regs forced Stihl to increase blowdown. Therefore, just because it’s a D doesn’t mean it’s a “good one”; the port timing (specifically shorter blowdown, if I’m not mistaken) is how to truly tell.

And while I’ve never ported one, I believe I’ve heard folks smarter than me say that they either don’t notice a difference or just plain prefer the hemi if they’re going to grind the ports into good timing anyway and/or machine the base and squish band anyway.

 

[blsnelling]

Yup. It's only 1st production year cylinders that are so desirable.

 

[lead farmer]

I like size D jugs...[emoji41]

Sent from my SM-G930V using Tapatalk

 

[cgraham1]

I like double D jugs.

 

[Chainsaw Jim]

I hide D jugs under my motorboat.

 

[Overkill338]

I like double D jugs.

Then take my ex wife lol

 

[CsClimbr]

Yup. It's only 1st production year cylinders that are so desirable.

Any way to tell if a cylinder were a 1st year production without the saw serial #’s? For example, just the jug itself and no other parts..

 

[cgraham1]

I had a ported hybrid 440 with a D chamber 046 jug. It ran good, but my ported 7900 was faster.

 

[Overkill338]

I had a ported hybrid 440 with a D chamber 046 jug. It ran good, but my ported 7900 was faster.

If the 7900/7910 is so good, why did Dolmar sell out and why dont you see their saws on professional job sites?

 

[Overkill338]

I had a ported hybrid 440 with a D chamber 046 jug. It ran good, but my ported 7900 was faster.

PS: I'm kidding by the way. I want a Dolly of some sort. I'm waiting on the 462 for 70cc. So I'm thinking of seeing what Dolkita has in the 60cc Pro class.

 

[JonCraig]

Any way to tell if a cylinder were a 1st year production without the saw serial #’s? For example, just the jug itself and no other parts..

The 100% accurate way to tell is to put the jug on a degree wheel and look at the timing numbers. And don’t ask me to interpret them—I’m not that smart. ;-)

 

[homemade]

If the 7900/7910 is so good, why did Dolmar sell out and why dont you see their saws on professional job sites?

Marketing and dealership network. Just because you have a better product doesn’t mean squat if the competition can convince you that there saw is better.