026 build running a bit lackluster

[NateSaw]

Bear with me as I share my notes. This thing has the hyway 44.7mm top end, an oem wt426b (new). Custom baffled muffler cover. Fire away fellas. I could use some help here. Any and all questions welcomed! It runs, and for a seemingly narrow rpm band, with quite the gusto. I had it pig rich to the point of pudding fuel in the case, and when I picked it up, it would stall. I've been approaching "leaner is meaner" carefully. I have the low side leaned out enough that it doesn't stall when I pick it up. The high is set to 4 stroke at 14k. 9500rpm in the cut seems ideal. Running a 20" bar (17.5 usable with long dogs) and an Oregon 22lpx081g chain (. 325 .063 with a 7t sprocket). I'm in the mid Atlantic region and it's mostly hard wood out here. Anyway, it cuts. But it seems to lack torque. A loose grip is dangerous, but I have to relax and let the weight of the saw determine cut pressure. If I dog in and pry, it just bogs and slips the clutch. Carb adjustment seems to be very narrow as far as what works best. What'd I do wrong fellas? Everything?
Also, I have the ducati coil. Fwiw.

 

[NateSaw]

Exh port, and the method I used to pan out the squish band.

 

[82f100swb]

You are built around a much lower exhaust roof than my 026 is, but your numbers all look decent. I have not yet built a 44.7 jug, only the 44's. I have a little less blowdown, 24 degrees, 74 BTDC intake, 0.0165 squish, and the exhaust opens at 92 ATDC.... My band cut was done the same way. It four strokes at 16,700, and I generally run 3/8 chain on the thing. It will pull a 24 in frozen Poplar without being overly cranky about it.

 

[NateSaw]

You are built around a much lower exhaust roof than my 026 is, but your numbers all look decent. I have not yet built a 44.7 jug, only the 44's. I have a little less blowdown, 24 degrees, 74 BTDC intake, 0.0165 squish, and the exhaust opens at 92 ATDC.... My band cut was done the same way. It four strokes at 16,700, and I generally run 3/8 chain on the thing. It will pull a 24 in frozen Poplar without being overly cranky about it.

Thanks for your thoughts! After work I'll reply in depth!

 

[huskihl]

Your dogs could be part of the reason, depending on how long they are. The 026 isn’t known for having lots of torque and that would become more noticeable with those on there. The other thing that isn’t helping you is your lower transfers opened up that much.

 

[NateSaw]

Your dogs could be part of the reason, depending on how long they are. The 026 isn’t known for having lots of torque and that would become more noticeable with those on there. The other thing that isn’t helping you is your lower transfers opened up that much.

I was afraid I had possibly gone too far (With the transfers). I was thinking that allowing as much volume to funnel into the uppers, would increase velocity and perhaps aid in pushing spent charge out of the cylinder...Likely they're killing the midrange? What's the reasoning on the dogs? I'm not prying hard with the saw. Can't get that far lol. I suppose I should shoot a video so y'all can see how it's running. Also, I had a thought today whilst at work, running other saws lol... Perhaps with my compression so high, should I not consider retarding back closer to stock timing? Could the saw be making solid combustion too close to TDC do to the charge being so volatile? It pumps up to 220psi on my pressure tester(automotive), throttle closed.

 

[NateSaw]

You are built around a much lower exhaust roof than my 026 is, but your numbers all look decent. I have not yet built a 44.7 jug, only the 44's. I have a little less blowdown, 24 degrees, 74 BTDC intake, 0.0165 squish, and the exhaust opens at 92 ATDC.... My band cut was done the same way. It four strokes at 16,700, and I generally run 3/8 chain on the thing. It will pull a 24 in frozen Poplar without being overly cranky about it.

Sounds like you built a real ripper sir! When I cut the squish and decked the jug it woke up from where it was after the second tear down. However, I did also balance out the lower that was on the side that shown evidence of less fresh charge flow on the piston... I figure after another tank, and possibly ign retard, I'll tear it down again and look for new clues.

 

[NateSaw]

Your dogs could be part of the reason, depending on how long they are. The 026 isn’t known for having lots of torque and that would become more noticeable with those on there. The other thing that isn’t helping you is your lower transfers opened up that much.

Oh, and thanks for your response huskihl! Also, the articulating dogs are 2.5". I clean up alot of downed , dead trees with thick rot in the cambium. Hard wood inside. But yes, these dogs are far out of proportion. I'd been waiting for the wcs 3 point, but they sell out so fast. What dogs are you happiest running? And what type of wood in?

 

[dmb2613]

I have said this before the 44.7 want run with the 44 and it being a china jug and piston does not help any

 

[huskihl]

I was afraid I had possibly gone too far (With the transfers). I was thinking that allowing as much volume to funnel into the uppers, would increase velocity and perhaps aid in pushing spent charge out of the cylinder...Likely they're killing the midrange? What's the reasoning on the dogs? I'm not prying hard with the saw. Can't get that far lol. I suppose I should shoot a video so y'all can see how it's running. Also, I had a thought today whilst at work, running other saws lol... Perhaps with my compression so high, should I not consider retarding back closer to stock timing? Could the saw be making solid combustion too close to TDC do to the charge being so volatile? It pumps up to 220psi on my pressure tester(automotive), throttle closed.

Some builds benefit from it, but they are usually extreme high rpm builds with much larger carburetors than what comes on an 026. I’m not saying that it’s ruined or anything, just that given the size of the lower window compared to the size of the upper window, and the size of the piston going up and down, that it probably took you backwards a little bit by lowering the case compression that much. It’s OK to round and smooth things out for flow, but you usually want to do it by removing as little material as possible.

Going to longer dogs changes the fulcrum point and with a lightweight powerhead, you lose some of the control. They tend to throw the chain and bar into the log rather than allowing it to ease in like with shorter dogs.
An easy test is to pull the saw back an inch so that the dogs aren’t touching and see if it still does it

 

[NateSaw]

I have said this before the 44.7 want run with the 44 and it being a china jug and piston does not help any

Taiwan lol. And it's basically an ms260 w/44.7mm. Are the 260's weaker than the 026? I haven't run one yet.

 

[NateSaw]

Some builds benefit from it, but they are usually extreme high rpm builds with much larger carburetors than what comes on an 026. I’m not saying that it’s ruined or anything, just that given the size of the lower window compared to the size of the upper window, and the size of the piston going up and down, that it probably took you backwards a little bit by lowering the case compression that much. It’s OK to round and smooth things out for flow, but you usually want to do it by removing as little material as possible.

Going to longer dogs changes the fulcrum point and with a lightweight powerhead, you lose some of the control. They tend to throw the chain and bar into the log rather than allowing it to ease in like with shorter dogs.
An easy test is to pull the saw back an inch so that the dogs aren’t touching and see if it still does it

Ruined? Nah. I already prepared myself for the likelihood of having to drop another hundo on another topend. I'm a noob Kevin. I expected to break some eggs for the sake of learning! I love what you're telling about upper to lower relationship. When I get a 90* grinder attachment... The first thing I thought looked like an idea, without changing blow down (provided I shouldn't have less) was to widen the uppers on the intake side. Also, now that you mention it, it does cruise through the wood smoother when not dogged. Perhaps I should shorten the articulating dog in the center? I copied what wcs does with that one on plane with the curf of the chain. Sure does pivot nice, when it doesn't snag and bog... Thanks again for your knowledge Kevin!

 

[NateSaw]

You are built around a much lower exhaust roof than my 026 is, but your numbers all look decent. I have not yet built a 44.7 jug, only the 44's. I have a little less blowdown, 24 degrees, 74 BTDC intake, 0.0165 squish, and the exhaust opens at 92 ATDC.... My band cut was done the same way. It four strokes at 16,700, and I generally run 3/8 chain on the thing. It will pull a 24 in frozen Poplar without being overly cranky about it.

So I assume you raised your uppers as well... To have less blow down with a higher exh roof. Is that where the rpms come from? I'm still trying to wrap my mind around these relationships. Seems to me, later exh timing, gets more out of the power stroke... And longer blow down incourages more spent gasses exit cylinder before fresh charge enters. However, I know I'm missing something critical with pressures both top and bottom end. At the end of the day my timing numbers are what they are because I've been chicken poo to raise or lower any ports. All I know is that I don't know enough to charge in. Plus, I need a 90* grinder.

 

[huskihl]

Ruined? Nah. I already prepared myself for the likelihood of having to drop another hundo on another topend. I'm a noob Kevin. I expected to break some eggs for the sake of learning! I love what you're telling about upper to lower relationship. When I get a 90* grinder attachment... The first thing I thought looked like an idea, without changing blow down (provided I shouldn't have less) was to widen the uppers on the intake side. Also, now that you mention it, it does cruise through the wood smoother when not dogged. Perhaps I should shorten the articulating dog in the center? I copied what wcs does with that one on plane with the curf of the chain. Sure does pivot nice, when it doesn't snag and bog... Thanks again for your knowledge Kevin!

It’s usually the bottom point on the dogs. By the time the middle one comes into play the bar is more loaded up and it’s not as bad

 

[NateSaw]

It’s usually the bottom point on the dogs. By the time the middle one comes into play the bar is more loaded up and it’s not as bad

Well, I made them. It won't hurt my feelings to shorten them. But first I may see what, if anything else I can do to widen the power band a bit. The last time I put it together, I had made more than one change, and it woke up from where it had been. I have my suspicions that setting the squish to match the piston, and decking the jug may have been it. But, I had also evened the lowers, lightly flowed the intake, and removed a portion of the baffle in the muffler cover. Never mind the fact that all the timing numbers should have changed slightly, as the jug is lower. I know better than to make more than one change at a time. Haste makes waste.

 

[NateSaw]

I genuinely appreciate all of your experience! It has to be somewhat frustrating watching someone who doesn't know, try to know. I'm reading A. Graham Bell's 2 stroke tuning. I'm soon to start chapter 3, porting!

 

[NateSaw]

Anyone know if the ducati coil for this saw is limited?

 

[82f100swb]

I don't believe there are any limited coils on this chassis.
My lower transfers aren't quite as big as yours, but I can see that causing an issue on a 44.7. You have to remember that an 026 is a big bore, and a stroker on this chassis. 44mm stuff is finicky about case volume, and doesn't like any case mods at all. Idle quality and low end power suffers.
I have not built a 44.7, but everything I have ever read says ported a 44 will always outrun a 44.7.

My upper transfers are completely untouched on this particular saw, they were where I wanted them, and I built the saw a few months after a fire where we lost damn near everything, so I didn't have a 90 degree grinder at the time.




Yes, the lower ring is missing, the supporting area for the gap got in the way of my intake port.

This was a super simple build, and it just plain runs.






Hardwood, softwood, short bar, long bar, it doesn't care, just don't open up the muffler, then it falls on its face.
This is a stock carb WT194 build.

 

[NateSaw]

I don't believe there are any limited coils on this chassis.
My lower transfers aren't quite as big as yours, but I can see that causing an issue on a 44.7. You have to remember that an 026 is a big bore, and a stroker on this chassis. 44mm stuff is finicky about case volume, and doesn't like any case mods at all. Idle quality and low end power suffers.
I have not built a 44.7, but everything I have ever read says ported a 44 will always outrun a 44.7.

My upper transfers are completely untouched on this particular saw, they were where I wanted them, and I built the saw a few months after a fire where we lost damn near anything, so I didn't have a 90 degree grinder at the time.

View attachment 369578

View attachment 369577
Yes, the lower ring is missing, the supporting area for the gap got in the way of my intake port.

This was a super simple build, and it just plain runs.






Hardwood, softwood, short bar, long bar, it doesn't care, just don't open up the muffler, then it falls on its face.
This is a stock carb WT194 build.

Ahhh the single ring... I've read there are benefits to deleting the lower. My moped runs a single ring and it screams! So it seems you spent some time widening the intake then? I've done minimal there on this saw. Last night I deleted the baffle I had welded in the muffler cover I made, and leaned it out some. I think I was being too cautious with mixer. It was pig rich. Now, it's 4 stroking at 15,100rpms. I'll get it in some wood soon and take a video. The idle has never been an issue. It's stays where I set it... Also, @huskihl was spot on with the dogs being too long, especially the lower... I'm going to re profile them too. Thanks for your input! I'm dying to know where you went with your intake!

 

[NateSaw]