Couple of Husqvarna 55 questions

[Ronie]

The main question I have is how much can be taken off the base before you start getting into the impulse and mess it up? I was also was wondering what the threaded hole on top of the cylinder is for.

 

[ayoungtexan]

Not sure on the first question. The threaded hole is for the decomp valve

 

[Ronie]

Not sure on the first question. The threaded hole is for the decomp valve

That's not for the decomp valve, the decomp is on the side. It' looks like it's threaded for a 5mm screw.

Thanks for trying

 

[Dub11]

The main question I have is how much can be taken off the base before you start getting into the impulse and mess it up? I was also was wondering what the threaded hole on top of the cylinder is for.

View attachment 255943

Whole on top is for a little rubber buffer iirc.

 

[Ronie]

I thought it might be for a stand off for the cover or maybe a cover hold down . I looked at the IPL but it doesn't show anything for the hole, thanks for clearing that up.

 

[Dub11]

I thought it might be for a stand off for the cover or maybe a cover hold down . I looked at the IPL but it doesn't show anything for the hole, thanks for clearing that up.

I'm only guessing and I didn't see a part listed either.

 

[JohnnyBlade]

The main question I have is how much can be taken off the base before you start getting into the impulse and mess it up? I was also was wondering what the threaded hole on top of the cylinder is for.

View attachment 255943

Its for the spark plug Ronie

 

[kneedeepinsaws]

Its for the spark plug Ronie

Old school micro plugs they used way back.


If i had to guess maybe a rubber isolator for the top cover.

 

[cus_deluxe]

id bet that its just sort of an artifact of the molds they used. the jonsered/partner/poulan versions of basically the same cylinder used a metal stud in there to secure the top cover.

 

[Ronie]

id bet that its just sort of an artifact of the molds they used. the jonsered/partner/poulan versions of basically the same cylinder used a metal stud in there to secure the top cover.

I was just looking at a Jonsered 455 and it has a cover hold down in the same spot as that hole.

 

[Ronie]

I see they have a different cylinder. I was looking at 590's and that pic was in there.

 

[cus_deluxe]

yep, the 590 bolts onto a 51/55, and uses that stud.

 

[cus_deluxe]

same as closed port 55 cylinder im pretty sure

 

[Ronie]

I just saw that, looks like the 590 has the same hole.

 

[Ronie]

I think I've looked at just about every 55 thread on both sites and haven't found how much I can take off the base. @GoBigBlue1984 , would you happen to remember how much you can take off the base before needing one of them spacers you made?

 

[GoBigBlue1984]

Take as much as you want, I’ll send you a spacer if you need. I think I’ve got a couple left anyhow.



.020 thick

 

[Ronie]

Thanks @GoBigBlue1984 . When I cut the base I'll take a few pics of the impulse hole at different depths in case someone in the future has the same question.

 

[Ronie]

I took some pics while cutting the base but they pretty much look the same until I got to .040, you can see by the flange that it's just starting to break through into the impulse hole. The last pic is at .060 off the base, that's as far as I'm going to go.

 

[Savage Saws]

I've taken .0748" off on a Partner 500. Base is thin but not terrible. With the exhaust at 104° it was at 260psi. I didn't leave it there, had to reshape the chamber.

 

[Ronie]

Better pic of the impulse hole