Lets talk about Jugs! Stihl 044/MS440

Arborist Forum

Help Support Arborist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

WoodChip333

Jesse
Joined
Sep 25, 2019
Messages
32
Reaction score
25
Location
Ontario
The jugs I want to talk about are... 044 KS vs Meteor vs MS440

I have a new project on the go. I am trying to replicate port timing, window shapes, squish band shapes and compression numbers from one jug to another. I have a ripper of a 10mm KS 044 and I want to try my best to replicate its performance in a Meteor jug and a MS440 jug. Shortly I will upload all the port timing numbers and other data goodies plotted on to a degree wheel sheet plus a few pics of the JUGS! I plan on documenting the whole experiment/project on this thread and hopefully you guys can chime in and give me your thoughts and experience.

Cheers!
 
I'd prefer precise measurements of the port heights relative to the base or squish, include a base to squish measurement also. A frottage/rubbing (look up the art meaning) of the port layout with precise measurements of the port sizes and relative locations from each other would be great too, because, for example, you would want to make sure the transfer ports are the same distance from the exhaust port and the same front and back heights as your best running cylinder.

And before messing with the other 2 cylinders, if you haven't already, run them to be sure they are not any better than the KS. By the numbers, I'd say the meteor doesn't have a chance. Looks like the KS has a pretty wide intake, but those less wide of transfer ports may be hard to copy over to the really wide looking ones on the Meteor.

Also consider the combustion chamber shape. Maybe the narrower squish, large D shape, and the large radius transition helps things?
 
Those 044 #’s are very close to my ported 044 slant fin. I’m at 101 ex
74 in
123 trans
.034” squish without gasket
So your intake is 8 degrees less or more duration than mine? Duration is easier to understand rather that ATDC and ABDC etc
 
So your intake is 8 degrees less or more duration than mine? Duration is easier to understand rather that ATDC and ABDC etc
Intake duration is 148. For intake it’s always double if your zeroed correctly. If it opens at 74 btdc it closes at 74 atdc. Same with exhaust. It it opens at 102 atdc it closes 102 btdc. Good way to check zero.
For exhaust double your open timing and subtract it from 360. That gives you the duration
I may add a little to the intake but for a work saw I’m pretty happy with the results
 
Intake duration is 148. For intake it’s always double if your zeroed correctly. If it opens at 74 btdc it closes at 74 atdc. Same with exhaust. It it opens at 102 atdc it closes 102 btdc. Good way to check zero.
For exhaust double your open timing and subtract it from 360. That gives you the duration
I may add a little to the intake but for a work saw I’m pretty happy with the results
Yeah I agree 100% with that on those degree wheel sheets I did the open and close degree which were all the same before and after tdc or bdc. I also degree wheeled and calculated the duration and they all were on par. So do you find you get more torque with longer intake duration? I left all the port times stock just did some flow improving because this 044 slant puts my ms 440 to bed and I didn’t want to ruin the factory hotrod numbers.
 
Yeah I agree 100% with that on those degree wheel sheets I did the open and close degree which were all the same before and after tdc or bdc. I also degree wheeled and calculated the duration and they all were on par. So do you find you get more torque with longer intake duration? I left all the port times stock just did some flow improving because this 044 slant puts my ms 440 to bed and I didn’t want to ruin the factory hotrod numbers.
Btw I don’t like to go higher than about 10000 or so rpms. I like the bottom end stump grinding grunt. I cut all hardwood here in southwestern Ontario.
 
Douglas fir and larch are about the hardest woods I cut. I’m still learning so I port a little then assemble. If it’s not amazing I go a little more. Tiny bits at a time. So far my best saw is 156 duration both intake and exhaust. But I’ve been pretty conservative with the 044 as it has good numbers to start. First thing I learned when hyping up any motor was to upgrade exhaust first. Dosent matter how much fuel and air you can stuff in it if it can’t get it out. So I focused on exhaust and fine tuned intake till it seamed to not make a difference. Might be able to go further than my numbers but don’t think it will yield much gains with out reducing squish
 
From what I’ve seen you reach a point where more intake timing dosent result in more anything. Maybe if you can reduce squish it could. But I don’t have a lathe that could handle that
Yeah that’s what I was thinking. Exhaust runs the show for the easy gains. I am going to take 0.010” off the bottom of the cylinder bringing my squish to 0.024” with a base gasket. I don’t want to go the sealant route. Then I will have to redo the timing numbers and I’ll get back to you.
 
Check your timing on the Meteor again.
If it’s right, the transfers are 7 degrees higher. (Meteor blowdown 13 degrees, KS 20 degrees. Very few saws do well with less than 15).

I would go more aggressive on tightening your squish. 0.018-.0.020 is ideal. It will help get the transfers lower. Then when you raise the exhaust, the meteor blowdown will be more similar to the KS (though still smaller). Your intake will end up a few degrees lower than the KS, but it shouldn’t be a big deal.
 
Freshly ported and fully rebuilt 044 slant fin. 4th tank of fuel. Still running her fat (12800 max) averaging 9800 buried in the cut. Frozen red fir, 28” bar with brand new un touched stihl chain, full comp yellow box. Still waiting on some parts so I stole a few from my other 044.
Ex 101
Transfer 120
In 78

Learned a lot on this saw. Will be re porting few others with what I’ve learned.

 
Okay spent some time getting my lathe setup and a mandrel made. I cut the base of the meteor jug 0.013” making the squish a perfect 0.020”. All my numbers moved by 1 degree after a quick degree wheel spin.

Ex 101
In 70
Tr 114

Where should I go from here... only way I could make the blow down any more is delete the 0.020” base gasket, cut the base 0.020” more and raise all the ports to make the good numbers. Is this smart?
 

Attachments

  • 57F58BAE-C045-4511-8AD7-354646F963AC.jpeg
    57F58BAE-C045-4511-8AD7-354646F963AC.jpeg
    1.9 MB · Views: 9
  • 7DC57DB7-E396-449F-A471-0A46FC73CFD5.jpeg
    7DC57DB7-E396-449F-A471-0A46FC73CFD5.jpeg
    2.3 MB · Views: 11
So, the exhaust and transfers went up 1deg and the intake down 1deg by cutting the base, lowering the cylinder? Am I missing something? Are you cutting a popup piston?
 
I’d increase that intake to 75 and clean up exhaust and run it. You may be happy with the short blow down. If so slowly increase your intake to 77-78 and just run it. Or you could take .020” from the squish band and off the base and gain a hair more blow down then address the intake and exhaust.
 
So, the exhaust and transfers went up 1deg and the intake down 1deg by cutting the base, lowering the cylinder? Am I missing something? Are you cutting a popup piston?
No popup I cut the base lowering all the ports but the blowdown is what I’m concerned about
 
You need to lower the jug more to get your transfer opening in the 118-124 range. That means you have to cut the squish band as well. It can be done with a boring bar on the lathe or manually with a cutting mandrel. The manual method is slower but you’re less likely to cut too much. Once you get the squish set grind the roof of the exhaust port back up to 105-101 range. In general a wider exhaust will need less blowdown to accomplish the same port time area so if you widen the exhaust you could probably get by with 16 degrees blowdown. Mimic the factory arch of the exhaust roof and make sure you bevel any edge you grind on. You can widen the exhaust up to 70% of bore diameter, but only if the piston skirt is wide enough. I usually don’t widen more than 60%. Measure the skirt width and leave 0.025” on either side.

Watch these videos if you’re not sure how do something.

https://youtube.com/playlist?list=PL1Tu41TyyY_74E0awOsWCN0cMDq8AeCIb
 

Latest posts

Back
Top