The MS150 Has Arrived

[watsonr]

Randy, I've yet to locate a new chain for it. Can you get one?

Yes, I'll grab one today..... anything else?

 

[mastermind7864]

No sir, that'll do it. I've been to Gentry's in Cookeville, and to the dealer in Jamestown, neither of them stock that chain, and said they wouldn't even order it. I'm in Stihl dealer hell here......

 

[watsonr]

No sir, that'll do it. I've been to Gentry's in Cookeville, and to the dealer in Jamestown, neither of them stock that chain, and said they wouldn't even order it. I'm in Stihl dealer hell here......

Were both in Hell... just different parts brother!

 

[mastermind7864]

If you want me to just pay you for the saw I can do that.......I didn't want it to go this way at all.

 

[watsonr]

They have one chain in stock and it's waiting for me now. I'll drop it in the mail tomorrow.

Call me in a bit so we can catch up

 

[watsonr]

They have one chain in stock and it's waiting for me now. I'll drop it in the mail tomorrow.

Call me in a bit so we can catch up

Did the chain make it?

 

[mastermind7864]

Yesterday.....

You are the man......of course you know that.

 

[watsonr]

Now lets see some pictures and stuff

 

[mastermind7864]

Deal. Not today though.......I'm at the lathe for about ten hours.

 

[Adam_P]

10 hours? What's on the menu?

Do you have any vids on youtube? When I'm older with kids who don't think I'm cool anymore I'd like to get something like a Smithy and work on small engines.

 

[mastermind7864]

Cutting 14 squish bands.

My utube channel.

http://www.youtube.com/user/mastermind7864?feature=guide

 

[Al Smith]

Which brings up a question .Do you see a big improvement by lowering the cc's of the combustion chamber as opposed to taking the compression into the stratosphere like over 200 static ?

 

[mastermind7864]

On some engines I go as high as 225psi Al. Others 185 is as high as I go. Displacement, crank strength, and performance all play a part is my "recipe" for each model.

By cutting the squish band, I gain more control over port timing numbers, and can raise compression as high as is necessary.

 

[woodworkingboy]

I can only think that a saw with 225 psi, has to have a compression release on it.

 

[mastermind7864]

This 50cc saw is blowing about 220......no need for a compression release.

The larger the bore, the more "needed" it becomes.

<iframe width="420" height="315" src="//www.youtube.com/embed/-KL-8tKliuY" frameborder="0" allowfullscreen></iframe>

 

[woodworkingboy]

225 seems like a huge amount of compression. When I was reading a lot about mods, it seemed like folks were saying that around 185psi was more or less the peak for work saws. I recall Timberwolf saying he took one up to 200 for a trial. That is really interesting that you can successfully get so high, with the heat range that is created not being a problem. Do you mind if I ask what sort of squish you are running to have the high readings?

 

[mastermind7864]

I set squish on smaller bore saws at .020 Larger saws at .025

The Dolmar 5100 comes from the factory at 190psi......heck the 410 Dollie is at 210 stock.

 

[woodworkingboy]

Ah...thanks Randy. I haven't seen stock saws like that. How are they getting such high numbers on the stock saws, tight squish to begin with? Could you advise how a saw like a Husky 242xp gets such high rpms when stock, at 15,500?

 

[Al Smith]

I've never done any chamber reductions myself .It makes sense in a way creating basically a hot spot to start the burn kind of like a prechamber diesel. It also makes sense that if you reduce the chamber size plus cut a tight piston to head deck it would raise the comp as oppossed to just a tight piston/deck by itself .

 

[mastermind7864]

Small bore, short stroke, low reciprocating weight = high rpm.....

The Dolmars in the series have small combustion chambers.

On a 372 I just go to 185psi or so. The cranks ain't real tough. The MS660 gets 205psi, after I machine the jug to get the exhaust height I want that's just how it works out. Different saws get different "recipes". I've kept really good notes, and have a spec sheet for each saw. Here's my sheet for the 390XP.

390XP

Stock:
Compression: 150psi
Squish: .014 W/O Base Gasket
Ex: 97°
Tr: 122°
In: 78°

Ported:
Compression: 205psi
Squish: .023
Ex: 99.5°
Tr: 122°
In: 81°

Notes:
Taking .040 from squish and .030 from the base netted a 205psi compression.
Ignition timing should be advanced 6-8°

I didn't really aim for a certain psi when I started building these engines, what I'm using varies depending on what I've learned about each model after doing hundreds of saws.

 

[woodworkingboy]

Great info, thanks Randy.

 

[mastermind7864]

I hate to ever sound like I know a lot about this stuff.......fact is, I'm still learning, and feel like I'm just now catching on a wee bit.

 

[woodworkingboy]

You seem to have developed guidelines that are predictably successful. That shows professionalism in a trade where there are few.

 

[gf beranek]

I went to a local saw shop yesterday and picked up a 150 and was impressed by how light it was. The shop owner said I could take it out for a spin, but since being retired I shrugged the offer off. Still the technology amazes me. It's all so cool

 

[mastermind7864]

Randy of weedeaterman.com sent me a new chain, so tomorrow I'll make a baseline video of the MS150 and start the modification process on it.