120SI Porting numbers?

[huskyslinger]

So I know it is a long shot as porters like to hord their numbers! But I was given a 120SI that is in really good shape. I have put new piston in and had to make a velocity stack for it, as finding an air filter was a pain. So anyway just hoping someone will chime in and give me some numbers to work with. The thing is I have a little understanding of the numbers but still trying to figure out how guys figure out what numbers to even start with? so anyway a little help goes a long way. Thank you

 

[shorthunter]

There aren't many people who can get any more than a 10% gain with porting, I wouldn't waste your time. Tighten up the squish and open up the muffler a bit. If that isn't enough, advance your ignition

 

[jmssaws]

So I know it is a long shot as porters like to hord their numbers! But I was given a 120SI that is in really good shape. I have put new piston in and had to make a velocity stack for it, as finding an air filter was a pain. So anyway just hoping someone will chime in and give me some numbers to work with. The thing is I have a little understanding of the numbers but still trying to figure out how guys figure out what numbers to even start with? so anyway a little help goes a long way. Thank you

What's stock timing,compression,squish?

 

[Griffdog1]

120si's go very well as standard so be careful with stuffing with it too much. They respond really well to a gasket delete and just cleaning up the inlet and exhaust ports. I have three. The one in this video (hard Australian wood) is the "worst", having had a lots of aluminum transfer and a couple of nicks I could not remove. Its just running its stock (old) piston with some caber rings. Its a good comparison against a freshly built 371xp. The Husky needs to be run in and a little tuning but it gives you an idea of the excellent torque and general grunt of the Dolmar. Unbelievable underrated saws.

 

[shorthunter]

We ended up with 162° exhaust duration, 22° BD, and 154° of intake duration with .024 squish.

Finished numbers from his 2012 build thread.

 

[jmssaws]

Most any saw will run decent at 100 120 78
Obviously a tiny saw would need less exhaust duration but those are good starting points.

My brother has one I ported several years ago and I'm sure it's not far from those numbers.

I think they gain like any other saw and run well ported.

 

[blsnelling]

Many a builder here will share port timing. However, I doubt very many have ported a 120.

 

[shorthunter]

Anything over 154° of intake duration and you will see a lot of spit back. Stock intake duration is around 146°

 

[jmssaws]

Many a builder here will share port timing. However, I doubt very many have ported a 120.

We talking about the same saw?
120 dolmar?

 

[huskyslinger]

I am so pleased to see so many have responded! I hoped there were some of you gentleman that would chime in.

Jmssaws, I have been reading a lot of your post and videos. Intrigued by your builds. Blsnelling, read a lot of yours too. Imo the difference between snelling and jmssaws are one likes rpms and one likes torque. (Remember that is just my opinion). I have to say I have watched monkeys saws and love the torque! That's what I'm after, not race speeds, but that lean on brut strength! Remember TORQUE is how much you get done HP is how fast!


A little background I was an engine and fuel pump builder for a Caterpillar dealer in wa state. So a tiny lil 2stroke could have been chewed up swollen then spit back out without so much as a hickup! On the engines I've built. Got into saws after a logging accident. They were small enough to work on in my wheelchair. Was never a fan of porting till building some many stock ones. Now I've gotten into my stash of nice older saws I'd like to keep for myself(yes I can still cut my own firewood just have to set things up different).

I'm not out to start building ported saws and selling to all of you. I see no since in that as you all live in a totally different part of tge states and have plenty of builders around you. I try to get hard earned info as it is a little hardered for me to build, run, tear down, repeat. Just to much energy expelled. I work 6 hours a day but getting ready for work, getting home and taking care of all my daily needs, ends up making it about a 11 hour day. And when weekends roll around end up having to take one day and spend most in a recliner to rest up from week.

So with all that said please keep posting and a list of others I have and would like are 2X 064, 066 RL,2X 066, 660, 038, 181, 2X 394, 365/372, 372, and 385. Would like to do all this year. And for those that say just "search on here" I have spent countless hours searching and found some numbers I fell I could start with but the post get so off track I give up.

Anyway thank you, all messing with saws gives me back both getting to wrench on stuff and keeps me in the "Woods" if you know what I mean?

 

[jmssaws]

I'll grab that 120 tomorrow,best I can recall it was a good running saw.
I can't find any notes on it.

I did get a 123 a few days ago but haven't looked at it yet.
It's a good looking saw