Porting a 2139t or 338xpt

[AKJonsereds]

Hi all,

I have seen lots of talk about porting the mufflers on this saw but not a lot on actual porting of the ports. Is there really no hope for these saws in the more power department?

Looking into mine again and wondering if the 45cc cylinder could be made to put out a little more. (Mine is currently 38cc). Why can’t a ported 2139t keep up with a stock 346? I already love the weight....

Ported muffler and advanced timing isn’t enough for me. Any ideas?

 

[AKJonsereds]

Alright, pulled the jug to look at the cylinder a little closer and the cylinder and piston are both pretty tired. Previous owner smashed the muffler and still ran it...

So, does anyone have an opinion on which cylinder I should go with for a replacement? Standard bore or cali bore? Going to do some educational tweaks either way... does the cali cylinder have flaws that can’t be ported out?

 

[AKJonsereds]

Going to post my findings for future reference and for anyone interested...

I have a ms200t cylinder here from a saw I gave my uncle. So, I am comparing the two off of measurements and not timing numbers. Not sure if the stihl cylinder is stock....

It appears the ms 200t was well thought out for its size. The intake track does not require the air to make sharp bends like my 2139t. The dome is tiny which gives the saw its good compression and allows for higher ports (mostly the exhaust). That gives it high rpm potential.

With the large dome and large squish on my 2139t I don’t believe it is wise to raise the exhaust. If I could just lower the cylinder some.... Luckily, the ports are no where near their max width so I will look there first.

Total area of the ports shows the 2139t has a larger exhaust vs its intake while the 200t has a slightly larger intake vs its exhaust.

Also, the area of the 200t intake appears to be larger than the 2139t and higher, which is why I think the 2139t doesn’t accelerate well.

**note the stroke on the 2139t is very slightly longer** 1.22” vs 1.1” (I think)

 

[AKJonsereds]

Does anyone still do tig weld popup pistons?

 

[Chainsaw Jim]

I'm wondering if this should be in the general chainsaw forum.
@Mastermind?

 

[ABarrick]

I've been told the 45cc cylinders didn't run any better than the 38cc ones. I have zero personal experience though. Unless they changed the intake on them, I can't see that it would run any better. That is the bottle neck on these saws. The last 2139 I rebuilt, I widened the exhaust, smoothed up the intake port at the cylinder, trimmed a little off the intake skirt, ditched the flywheel weight and used regular nylock m5 nuts to hold starter pawls on, advanced timing half a key width, muffler mod and retuned. Also plug the auto decomp if yours has it. Night and day difference from stock. Much better spool up/response and holds rpm in the cut better.

 

[AKJonsereds]

I like the sound of all that. Pretty much fits my plan. I have never heard of dropping the flyweight—-I didn’t know it was there. Thanks for the tip!

I can’t fix the long intake, but I did add some screens in the cover of mine that help. After adding the extra intake holes that bypassed the flywheel, I notice far less wood chips in the filter. It was the opposite of what I expected.

Anyone try a welded popup?

 

[Chainsaw Jim]

Anyone try a welded popup?

I doubt it was ever for this model, but there are several members here who weld and mill popup pistons.

 

[AKJonsereds]

Sweet, I think she needs more compression.
I can run a lathe but will need to find a welder.
I wonder how modified pistons (welded) hold up.

BTW, what ever happened to that 272/357 build?
Loved that saw sir. Wish my 2159 went like that...

 

[Chainsaw Jim]

I'm going to test it out soon to see if it's a worthy 5 cube entry.

 

[AKJonsereds]

Alright, got the new cylinder and piston. The intake appears to be attached using a different method. Not sure if I should trim the cylinder to fit the intake or get another intake. Leaning towards another intake as that will be easier and look better in the end. Hope the intakes fit up to the carb the same?

The intake at the cylinder appears close in size to the 38cc top end (this is the cali version (45cc)). The intake track is very restrictive. Luckily there is room to improve that.

Exhaust is very similar on the cali cylinder but appears slightly higher. Almost seems to be slightly more open on the muffler side.

Piston on the cali is slightly heavier (.2oz). The cylinder on the cali is almost a full ounce lighter. The cali cylinder is a mahle and the stock is gilardoni.

The two power defeating areas on the cali cylinder appear to be a very large combustion chamber and very tiny transfers. Transfers are like half the size of the 38cc. So, I am going for a popup on the piston thanks to help from one of the members here (thanks again) and going to attempt to open the transfers—- at least to stock like the 38cc cylinder.... wish me luck, doesn’t appear to be much room to expand the transfers on this one....


No timing numbers yet... perhaps in the future.

 

[spudzone]

The Cali cyl does indeed use a different (expensive) boot. It has a rubberized flange to bolt up to the cyl intake. Be gentle installing - the flange tears off easily. Been there... total pain to work on.
If ya get it all dialed in, They become gutsy little saws

 

[AKJonsereds]

Thanks for the tip. I have some aircraft fuel tank sealer here that I am going to coat the outside of my new boot to hopefully help prevent that.

Sent the piston off for some welding. I have started massaging the transfers, the uppers and lowers will open up like the 38cc version but not going to change the timing much. The transfer tract has been enlarged as much as I am willing to go right now... still the transfers are/feel smaller than the 38cc cylinder.

About time for the intake and exhaust. Probably spend very little time on the intake at the cylinder. The exhaust port is actually surprisingly square already.

 

[Evan King]

How's the build going, thinking of doing the same to mine

 

[AKJonsereds]

I was waiting on some back ordered parts that are now in... just need to find time to put it all back together.


I did have it together for a few tanks of gas. It had a lot of low end torque. Engine acceleration is much better. I am going to try a modified stihl 3/8 picco rim on a drum made for .325. The 6 tooth spur had excellent torque so I am hoping the 7t picco rim will pull alright. A ported 45cc saw should do alright....

 

[Nutball]

Any updates? Or is your gasoline frozen solid up there in AK?

 

[AKJonsereds]

Alright, here is another update.... finally.

Got time to throw stuff together and run several tanks through it this weekend. With the 7 tooth sprocket it cuts much better than the 6. It still has plenty of torque. I decided to file the chain more aggressively (more angle and lower depth gauges) and have found the sweet spot for the current setup.

I may mess around with different chains. .325 would have more teeth and maybe bite more then the lp? I feel like the transfers and exhaust would still benefit from being raised more. No timing numbers as most of my work was very mild and the cylinder was not lowered. Pictures were not finished product but I am not a pro so here it goes.

I doubled the size of the upper transfers (width) and reshaped the lowers with jb weld. Between the transfers and the shape of the complete air path through the saw, compact took the place of performance in the design.

Might mess with it more in the future, but not this summer. She runs great and summer up here is extremely busy...

Sorry for the delay and lack of videos. Rain isn’t great for videos....

 

[AKJonsereds]

I am behind on chains, any recommendations for more aggressive 3/8lp or .325 chisel chain? I actually gained speed by square filling the current 3/8lp

 

[davidwyby]

I am behind on chains, any recommendations for more aggressive 3/8lp or .325 chisel chain? I actually gained speed by square filling the current 3/8lp

good thread.


Oregon has their new speedcut and speedcut micro or something.

 

[AKJonsereds]

Thought that I would update this a little more. I went back in and worked over the transfers some more. I also bored out the carb, set the squish and did a better muffler mod with a pipe that protrudes out on the plastic. Not sure if I mentioned the popup piston, but got one of those done up as well. Gauge says the compression is at 230psi.

Here is the important part. Raced my t540xp this summer and it was dead even. Then I realized the 2139t chain had been in the dirt vs a new chain on the 540.

Always check your chain…..

Not even close sharp. Anyways, have a lovely evening

I should clarify, I cut a good deal of that wood with my 2149…..