Jonsered 2150 cheap build and mod

[tolman_paul]

It may be counter intuitive, but having too much volume in the flow tract will decrease the ability of the saw to flow fuel/air.

The piston and crakcase pumps the fuel/air mixture through the ports, and increasing that volume makes it a less effective pump. At 10,000 rpm the transfer port is open for 0.002 seconds and 1/2 of that time period the piston is ascending so essentinally working against the pressurized fuel/air mix. Not alot of time to fill the cylinder with a fresh charge of fuel/air and hence having a bigger volume to pump that fuel/air won't help if the pump doesn't have enough force to move the fuel/air.

 

[modder]

It may be counter intuitive, but having too much volume in the flow tract will decrease the ability of the saw to flow fuel/air.

The piston and crakcase pumps the fuel/air mixture through the ports, and increasing that volume makes it a less effective pump. At 10,000 rpm the transfer port is open for 0.002 seconds and 1/2 of that time period the piston is ascending so essentinally working against the pressurized fuel/air mix. Not alot of time to fill the cylinder with a fresh charge of fuel/air and hence having a bigger volume to pump that fuel/air won't help if the pump doesn't have enough force to move the fuel/air.

I am fairly familiar with how a 2 stroke engine works, and lets not forget, when the piston is ascending, that is when it is sucking air and fuel into the crankcase. By shaving some off the riser, I have lowered the timing and plan on raising both sides by the same amount that I had taken off the riser, therefore increasing intake and exhaust duration. Still sounds right in my head. lol.




Posted by moody:
IMHO the OP should try the riser both ways stock. It'll be easier to find out if he's going in the right direction. The best way to try new things is to keep everything consistent to help find gains. The more variables you add the less likely you are to find solid proof of gains or losses

I don't think trying the modded riser on the saw while it is stock will prove much other than how increasing case volume impacts a saw when it is stock. Without added flow in the rest of the engine, I can't see how there would be anything but reduced performance. Now trying the two risers, modded and stock, on the ported cylinder should give a true impression on weather the modded riser helps or hinders performance.

 

[moody]

Well I am done giving you advice here. You've been given facts and ways to test things. You have a rebuttal for everything so enjoy your build. Pictures and videos will serve you better than two typed pages.

 

[modder]

Well I am done giving you advice here. You've been given facts and ways to test things. You have a rebuttal for everything so enjoy your build. Pictures and videos will serve you better than two typed pages.

Thats Ok. Don't take offence when you give what you believe to be good advice, and someone decides not to do what you suggest. I appreciate your advice and suggestions, but I'm stubborn when I get an idea in my head. Other than the riser, I'm doing very similar mods to this saw as another very respected builder on this site has done successfully, and many have commented on how well it turned out. Maybe you can take a look at the thread if you haven't already, and let me know what he did wrong. Its called ''Husky 350 Port Job''

http://www.arboristsite.com/chainsaw/140617.htm

P.S. You seam kinda moody when you reply to my posts.:msp_biggrin:

 

[Arrowhead]

I applaud your effort, keep us posted on the outcome. Opening up the transfers is a touchy deal. You can definitely see a gain by doing so, but if you open up too much... you'll loose too much velocity and loose power over stock. Then you can always do a full circle crank.

 

[moody]

I know the thread. Brad has his way of doing saws as does everyone else. I like Brad and respect him as a builder but there's plenty left on the table from that build. Not saying it's not a strong saw but there's other ways that even Brad has learned since then. Being stubborn is fine. I take offense when you ask for feedback or questions and you argue with the replies. You've done it a few times. I'm pretty familiar with this model of saw and I'm trying to help you add to what you've seen brad do. I'll go this far and then I'm done. When you finish the saw post a video.

 

[modder]

I know the thread. Brad has his way of doing saws as does everyone else. I like Brad and respect him as a builder but there's plenty left on the table from that build. Not saying it's not a strong saw but there's other ways that even Brad has learned since then. Being stubborn is fine. I take offense when you ask for feedback or questions and you argue with the replies. You've done it a few times. I'm pretty familiar with this model of saw and I'm trying to help you add to what you've seen brad do. I'll go this far and then I'm done. When you finish the saw post a video.

I just read through this thread again and I don't see where I have argued with you or rebutted. On the last page, you asked ME a question of what I expected to gain and I answered you. This same scenario happened in another thread and you said the same thing. It seams as if you just have formed an opinion of me and decided that you don't like me, or maybe you feel that since you know more than I about this subject, then I should be submissive. I don't get it. You said I should try it with the factory riser also, and I said I would, even though I didn't really plan on that unless it had very poor results. You haven't given me any advice about how to properly port this saw, which is the advice I was hoping for. You just said that it works good the way it was designed. Others that have replied have given encouragement and info. I appreciate that. If someone gives me a tip, I will tell them what I was thinking and why. How else will I know what is flawed in the way I was thinking. I believe you are taking my replies all the wrong way. I'm trying to enjoy a passion, experiment, and learn. It seams that you fault me for that...or is it that I live too far north and we have more trees...lol

To the others, thanks for your advice, tips, interest, and patience.

 

[modder]

Done a bit more work on the transfers and exhaust. Raised each just a bit to make up for cutting the riser down and opened them up a bit. Beveled the edges a bit to prevent hanging a ring. Went back to keeping the divider in the transfers but slimmed them down a bit and contoured the transfer covers. Matched the cover transitions with the cylinders. Here is a few pic's. Don't be too hard on me, but if anyone can tell me where I can do a bit more work, it would be appreciated. I didn't get to the intake yet but It's already quite large so I may just raise it just a bit. I'll get pic's soon of the exhaust when I do the intake.View attachment 313311View attachment 313312View attachment 313313

 

[modder]

Just got the cylinder back on and checked squish.

My squish came out at 0.43mm. Is that too tight. I am worried that it will strike the top of the cylinder at high RPM with such a tight squish. Can someone tell me if I have anything to worry about and if I should throw in a gasket to increase it a bit.

Also, I was just looking at a few bottom ends that I have for parts and all of the split cases are built similar to the way I modded my riser. The 359 and 357 looks very close. I know the 357 has stuffers but the 359 doesn't and they get great gains when modded. I wish the stuffers off my spare 357 bottom ends would fit my 350, but they look too big. Does anyone know if the 346xp have stuffers that fit.

 

[modder]

After doing some more research on squish, I decided to throw in the gasket to see what the squish came out as and I'm glad I did. Before I did that I thought I could hear the piston lightly striking the top of the cylinder and I was right. The gasket measured at .023in (I decided to change the mic. to inches as most on here use that) and after adding the gasket, my squish came out at .019 on one side and .018 on the other. Both measured above the pin on each side. I'm happy with that. I think I avoided major disaster. Hope to get it up and running tomorrow if I get the time to finish it.

 

[modder]

Its all together.

I got it all back together and compression is much higher. Don't know exact because I don't have a gauge I tested first with the original carb (zama) and didn't see any real gains, even after tuning. If anything, I lost a bit of mid torque and gained a bit at top end. I swapped out the carb for the 199 walbro and that made a real difference. Strange tuning though. Running very rich. High speed jet had to be turned all the way in, and the low speed jet became the high and low adjustment....if that makes sense. It did have a very noticeably stronger mid and high end. It is very fast on the trigger. That riser has made a difference, I think, but now I will need to swap out for the non-modified riser and piston, as I shaved them both down, reset the squish and see what the outcome is. I will be honest, I didn't get the gains that I expected, but maybe I will see better gains with the factory riser.

 

[rmh3481]

Advance the ignition 5 degrees and then see what you think.

 

[nmurph]

My squish came out at 0.43mm. Is that too tight.....

That is at the upper end of where I am comfortable setting a customer's saw. I run personal saws there (<60cc) and don't have any concerns doing so.

Does anyone know if the 346xp have stuffers that fit.

None of the saws in this family use stuffers. The 550 does, but they won't work on this saw.

After doing some more research on squish, I decided to throw in the gasket to see what the squish came out as and I'm glad I did. Before I did that I thought I could hear the piston lightly striking the top of the cylinder and I was right. The gasket measured at .023in (I decided to change the mic. to inches as most on here use that) and after adding the gasket, my squish came out at .019 on one side and .018 on the other. Both measured above the pin on each side. I'm happy with that. I think I avoided major disaster. Hope to get it up and running tomorrow if I get the time to finish it.

Either you weren't hearing the piston slapping the roof, or if you were, your initial measurements were wrong. When I get right at the edge of the envelope (less than .015-.016"), it is time to stop and double/triple check your measurements.

...Strange tuning though. Running very rich. High speed jet had to be turned all the way in, and the low speed jet became the high and low adjustment...

It sounds like you have a problem with the carb. However, it is also true that carbs feed from the L side throughout the RPM range. I have several 346's with 199's and I have never seen this issue. It could be that your saw isn't pulling enough air through it to need extra fuel from the H side.

 

[Adirondackstihl]

Well I am done giving you advice here.

Not a good business philosophy. :msp_sneaky:

 

[modder]

That is at the upper end of where I am comfortable setting a customer's saw. I run personal saws there (<60cc) and don't have any concerns doing so.



None of the saws in this family use stuffers. The 550 does, but they won't work on this saw.



Either you weren't hearing the piston slapping the roof, or if you were, your initial measurements were wrong. When I get right at the edge of the envelope (less than .015-.016"), it is time to stop and double/triple check your measurements.



I do believe it was slapping as the gasket measured .023 and after installing the gasket it was under .020.
I could have a carb problem and can try my Zama from the 357xp that I know works good but I could also be running into the problem that Moody warned me of from removing the dividers in the riser. I'll try the Zama to see if its carb problems first. I just don't want Moody to be right after him giving me crap for not listening to him. lol I don't mean any disrespect to Moody and wish him and I could find a way to communicate without misunderstanding because I'm sure I could learn from him.

 

[tolman_paul]

I am fairly familiar with how a 2 stroke engine works, and lets not forget, when the piston is ascending, that is when it is sucking air and fuel into the crankcase. By shaving some off the riser, I have lowered the timing and plan on raising both sides by the same amount that I had taken off the riser, therefore increasing intake and exhaust duration. Still sounds right in my head. lol.




Posted by moody:
IMHO the OP should try the riser both ways stock. It'll be easier to find out if he's going in the right direction. The best way to try new things is to keep everything consistent to help find gains. The more variables you add the less likely you are to find solid proof of gains or losses

I don't think trying the modded riser on the saw while it is stock will prove much other than how increasing case volume impacts a saw when it is stock. Without added flow in the rest of the engine, I can't see how there would be anything but reduced performance. Now trying the two risers, modded and stock, on the ported cylinder should give a true impression on weather the modded riser helps or hinders performance.

My comment was in regards to increasing the volume of the ports. With the port volume increased, the ability of the ascending piston to draw in a fresh charge of air and fuel is dimished as the pressure differential between atmoshperic outside the saw and inside the saw is reduced.

When it comes to "improving" the ability of a two stroke engine to flow air, you have to realize that everything is a tradeoff and compromise. Going too far in one direction can bite you in an unintended location.

 

[modder]

Advance the ignition 5 degrees and then see what you think.

I can give it a try and see what happens. It is a very quick mod and nothing to loose that can't be changed back.

My comment was in regards to increasing the volume of the ports. With the port volume increased, the ability of the ascending piston to draw in a fresh charge of air and fuel is dimished as the pressure differential between atmoshperic outside the saw and inside the saw is reduced.

When it comes to "improving" the ability of a two stroke engine to flow air, you have to realize that everything is a tradeoff and compromise. Going too far in one direction can bite you in an unintended location.

I'm becoming a believer . I would have always wondered if I had never tried it myself.

I have another idea after I try the other 357 (zama) carb. I thought I would weld in a piece of aluminum where I took out the dividers. Not like it was originally, but on a 45 deg. angle from the edge that touches the bottom of the cylinder to the edge that is above the bearing. This will (or I feel it should) give a better flow as it will cover that 90 deg. angle where I took out the dividers, and reduce the case volume at the same time, thus increasing velocity. I know that I have to be careful of warping from the heat, so it will be a slow process and I'm sure some will say its a waist of time, but I love playing with new ideas.

Thanks again for everyone's help, tips, and ideas. It helps a lot in the learning process. Keep them coming.

 

[modder]

Swapped out carbs for another walbro 199 off one of my other saws and rich problem solved. I then switched out to the zama off a 357xp and it worked perfect. Adjusted as it should and runs like a monster. Advanced timing and its even better. I'm sure it doesn't run like a pro ported saw but I'm very happy. Compression came out at 192psi after 8 pulls. I only have a 16'' bar and full chisel chain but when cutting a 20'' piece of dry rock maple, it pulled great and even handled some good pressure without bogging. It would only bog when I dig in the spikes and pulled hard. Pulls way better that it ever did stock, but I'm sure Moodys saws pull as well or better with a stock carb...or at least they look like they do in the videos. I didnt try the stock riser on it yet but it will be interesting to see if there are any gains there.

 

[ChainFinn]

And i thought my old 2150 with 346xpOE , with gentle porting, abandoned base gasket and an gutted muffler was something.


Keep on posting how it all goes, i am interested.

 

[modder]

And i thought my old 2150 with 346xpOE , with gentle porting, abandoned base gasket and an gutted muffler was something.


Keep on posting how it all goes, i am interested.

I'm not sure mine would run with yours but my goal is to surpass a 346xpne. I know that bar is pretty high for a amature like me, but why not try. I still have a lot I want to do and some adventurist ideas rolling around. As long as there is some interest, I'll keep updating and wouldn't mind hearing more from those who know what they are doing. I have some more parts are on the way. Also got a box of mystery pistons to try to match up a domed piston for it. Wish me luck.