365 no base gasket compression question

[82F100SWB]

Working on a friend of mine's 365 SP, he figures it is getting weak, and compared to mine it is, but mine has been base gasket delete for long enough that I don't remember what stock was like, my saw is also very low time, maybe 15 tanks since new in 09.
Was right at 28 degrees yesterday morning, his was 5 pulls to fire to 3 on mine. Once running it idles good, and pulls rpm ok no load, and it cuts OK, but it is nowhere close to mine, I don't have a tach so I swapped my unlimited coil onto it to tune it, and it definitely doesn't come close to holding rpm as well when I lean on it as my saw does.
I ran it and my saw, as well as my newly acquired R21T Partner back to back with the same 18" bar and chain, and even the Partner pulls it better.
Cylinder and piston look good, piston to wall clearance is good, currently trying to find my home set of feeler guages to check ring end gap, moving sucks...
Compression is where I am a bit fuzzy, I think my gauge might be a bit suspect, we are at 1200 feet elevation, after 20 min of cool down, my saw blew 165, his 135. I think that both of them are low, hence my suspicion of the guage being off.
Outside of measuring ring end gap, I think his saw is actually pretty healthy. Even if my guage is a bit wonky, is a 30 psi gain about right for a no base gasket build?
I would just delete the gasket and try it, but I am out of Yamabond until Tuesday, so I have too much time to think about this and wonder if my guage has gone crazy... LOL

 

[old guy]

165 is about rite for yours, 135 is a bit low for his, I'll bet his ring gap is about .020

 

[DeckSetter]

What's his cylinder and piston look like?

 

[82F100SWB]

Everything looks to be in pretty good shape, the piston skirt shows some wear, but nothing abnormal.
The one dark line on the cyl you can see does not catch a nail. That end gap looks wider in a picture than it does to the naked eye. I'm going to pick up a new set of feeler guages in the morning...

.

 

[Dave27483]

http://www.arboristsite.com/community/threads/dads-nice-365-special.302912/
I just did up my dads 365 special
Muffler mod base gasket delete and it increased power by about 10 15% is my guess
So yes I would say it's worth it

 

[weimedog]

Nothing here is out of the realm of reason. His saw having more time and possibly on the wrong side of manufacturing tolerances. Think right after checking compression I would check squish and while the cylinder is off, ring gap. Usually a base gasket delete or decking the cylinder .020 gains 15-18 lbs. on my gauge. My gauge also reads low so seeing 135 wouldn't scare me either. Especially seeing the condition of those internals. Sometime on an older saw scuffing up the bore with 220 grit wet/dry and a new ring or even a aftermarket "caber" brand can yield a little more compression. But seeing how clean your piston is suggests your ring seal is quite good so not a lot of ground to till there for that saw. Also for whatever reason that mod wakes those OE 365's up more than other saws....I think it has a little to do with the slight change in port timing in addition to the compression gain suggesting a few other tweaks could yield more power.. His saw would be a great candidate to measure squish & then chuck that cylinder on a lathe to get it at .018" regardless of your choice of gasket materials.

 

[82F100SWB]

I really wanted a reason to do a Huztl big bore top end on this saw, but there is nothing wrong in that cylinder.
I am leaning towards decking the cylinder on this one, he does lots of firewood, so I would rather have a gasket in it for longevity's sake.
Ring seal does look to be very good, I would have just leaked it down, but, that's yet another tool on my want list for the home shop, I honestly don't remember the last time I did a compression test on a 2 stroke at work(snowmobile and marine stuff.)
I have some Hutzl mufflers on order, and I am going to touch up a few things with the flat file. Debating getting out the pencil grinder, but I don't want to affect reliability or longevity too much. Definitely going to step him up to an 8 pin sprocket as well, he only runs an 18 on it.

 

[old guy]

I tried an 8 pin on a 372 once and thought it was pretty good until one day I had a short chain and had to go back to the 7, then I saw how much better the 7 was.

 

[82F100SWB]

I ran the 7 and 8 back to back on my saw in the same wood he is cutting yesterday, the 8 was definitely a significant performance improvement, I don't lean on the saw unless I have to, and I would much rather have a bumper than spikes. But, that probably comes from having grown up on the east coast in the bush with my old man, and the first saw I ever ran in the woods being a very hot 42 special, he beat letting the saw do the work into my head with a 9 pound hammer.
I am going to give my buddy both sprockets to swap out as he pleases.

 

[82F100SWB]

Just to follow up, base gasket delete ended up putting his saw within 2 psi of mine. Let him try them both out, and he wanted the 8 tooth.

 

[blsnelling]

No way does an 8-pin rim belong on a 65cc saw.

 

[82F100SWB]

Husky says an 18" bar doesn't either. Both work just fine for me. The majority of what is used for firewood around here is paper birch, and s/p/f, about the hardest we have here is black ash. None of which are very hard on the old Janka scale. If I was dealing with harder wood I would be running the 7.

 

[weimedog]

No way does an 8-pin rim belong on a 65cc saw.

How about a 70cc saw?

 

[blsnelling]

IMHO, no. Put a stop watch to it and you'll see. Not only that, but it's easier to stall and requires much more finesse.

 

[weimedog]

IMHO, no. Put a stop watch to it and you'll see. Not only that, but it's easier to stall and requires much more finesse.

Yes I agree. For me the 70cc is sort of that fuzzy line. Tweaked saws in that class seem to do well with the 8 pin sprocket in under 20 inch wood in my test areas, mostly hard maple and ash. But even with them, a dull chain or longer bar/ larger wood 7 is still best. This actually would make a nice thread, especially if you were leading the discussion. So much discussion on "bling" and very little on chain. To me it seems to be as much about sprocket diameter...considering a 9 pin .325 (if I can find one!) and that new Oregon .325 chain and sugi 18-20 in bar on a tweaked 576 for evaluation. Any thoughts on that as a concept?

 

[cus_deluxe]

I put an pin on my stock 272 with a 20" bar, and immediately took it back off. Just too grabby, cutting firewood and stuff i like a little more forgiveness, but to each their own.

 

[cus_deluxe]

Though if i cut softwoods mostly then an 8 pin would probably be something i would mess with.

 

[82F100SWB]

If it stops raining this afternoon before it turns back to snow I'll get out the camera and run them back to back. It might be slower but it feels like what I am used to.
I think alot of this has as much to do with what you are used to as it does the wood you are dealing with.
I grew up in the bush in Cape Breton, in the 8 foot pulpwood business, by the time I was big enough to run a saw myself dad had been at it for 40 years. My dad's saws that were always tuned to the very limit(if the hood wasn't melted over the muffler, it wasn't his saw), chains were never dull, and always turning as fast as possible as probably 60% of your time was spent limbing. He even ran an 8 pin .325 with a 15" bar on his 242.
The chain got touched up every second tank when he stopped for coffee, no matter what.
That is hardly big wood or firewood production, but it's what I'm used to and I'm sure greatly effects how I run a saw.

 

[82F100SWB]

The weather finally cooperated.

The 8 pin is a hair faster, but more importantly it keeps me off the rev limiter.