Husqvarna 55 base gasket delete?

[Suzuki]

Tell me about the base gasket delete on a Husqvarna 55....

Ok, instead, tell me about the relationship between the thickness of a base gasket and the cylinder compression reading.

The tale of two Husqvarna 55's
One I had since new and decided to refresh the piston and ring with a Meteor Piston and whatever ring came with it...
The second Husqvarna 55 I had bought with a scored piston and cylinder. Buffed up the cylinder with a bit of muriatic acid and sand paper.
It got the same Meteor piston and ring combo with the inexpensive gasket kits from that famous on line chainsaw parts supplier.

At any rate, both saws have around 130 PSI compression (with not enough run time on each)
How does the thickness of the base gasket affect compression on these saws, is it worth doing a delete and what would one use to seal the cylinder to the saw? Red RTV?

 

[Pioneer]

Compression difference short answer, depends on the gasket thickness. Is it worth it, maybe, it also changes the piston/port timing a bit so you have to take that into consideration. Someone who could explain it better than me can go into more detail.
I usually use motoseal on a gasket delete, has worked well for me so far. It's nice to have when you can't find a gasket for an old saw.
I just finished working on a stock Husqvarna 51 with 165 compression, so wait till the saws are broken in before you make a decision.

 

[J D]

Start by measuring squish, that will tell you how much gasket thickness you can remove (if any) & give you an idea of how much compression you could gain. Generally gains from higher compression will outweigh any port timing "losses".
RTV is not fuel rated & will deteriorate over time & eventually fail. Threebond/yamabond/hondabond, dirko, SOME of the permatex & loctite sealants are a few options

 

[Suzuki]

How much squish should there be?
I believe this is measured by placing a piece of solder on top of the piston and rotating over by hand?

I sanded the living crap out of the scored cylinder (shouldn't have done that...) but simply stuffed the new piston and ring into the cylinder that was not scored. What prep is necessary for a new ring in an old cylinder?

 

[J D]

How much squish should there be?

About 0.020"

I believe this is measured by placing a piece of solder on top of the piston and rotating over by hand?

Use ~0.050" solder & bend it so you can poke it through the plug hole to the side of the cylinder. Measure both sides a couple of times.

I sanded the living crap out of the scored cylinder (shouldn't have done that...)

Sanding is usually ok, the plating is far harder than the aluminum transfer. Some use chemicals like muratic (hydrochloric) acid or caustic soda to help break down the aluminum. That is fine too as long as appropriate care & safety measures are taken.
I usually use part of a broken ring as a scraper & then a small wheel with sand paper flaps on it in a drill/Dremel. Finally I polish up with some scotch pad on the end of the drill/Dremel

What prep is necessary for a new ring in an old cylinder?

Measure/set end gap

 

[Benwa]

Are we concerned with "more power" or just the fact that they only read 130psi? Compression is just a number If they feel good, run 'em. How many tanks of fuel have been through them since rebuild? They'll liven up pretty good around 6 tanks or so. If you don't have much run time on 'em yet, I'd wait to make your decision. That being said, If your after more, then have at 'er. I have deleted the base gasket on all of them I've owned. While I can't speak for everyone, the 51's & 55's I've done, usually land around the .030" squish range with the gasket delete. By all means measure yours, but they aren't usually dangerously tight. The gasket delete changes port timing, but only about 1°, maybe 2° on a good day in these saws. It's in the right direction anyway, lower exhaust (more torque) & a little more intake timing. Both good additions for the power/pull department. Depending on the age and wear, I usually see right around a 10psi+ increase with the .020" (or there abouts) gasket removed. Some are thicker, some thinner, you'll just have to measure. Doesn't seem like a crazy increase. However, I can tell you the added performance from a simple base gasket delete & good muffler mod, make the time spent worth every second on these saws. You won't regret it. As @J D stated, don't use RVT, you need a fuel safe gasket maker like the ones he mentioned. There is one modification to the crank case, I feel is necessary with a gasket delete on these models. It's in the beginning of the video below. Do a little research (like you're doing) and dig in! These are great "safe" saws to play with, as far as these mods go. You won't regret it.

 

[J D]

 

[Benwa]

That was a great series he did. Took the time to cover everything "the rest of us don't." I forgot about them. Way to go. Good post.

 

[5155]

I have 3 complete ones. These have a small chamber.
1 is op unmolested oem, runs great.
1 is cp 33 squish runs great.
1 is cp 22 squish and eats starters and does not run any better
than the others.

After 6 top end jobs in my time, I like 33 squish for these.
The after market tops I've tried had 60+ squish and sucked.

I'm no machinist or magician, and am sure others' mileage varies.

 

[Suzuki]

Are we concerned with "more power" or just the fact that they only read 130psi? Compression is just a number

More is better.... Ok, maybe not always but in this case...

I think I was a little disappointed with the compression number on my saw with the good cylinder being the same as the saw with the scored cylinder.
This left me with the impression that perhaps the combination of parts (base gasket and piston) I had installed wound up the lowering compression in the saw...

I'll run 6-10 tanks (each) through the saws and revisit...