2511 Build

[Ketchup]

I haven’t run one without the stuffer. Just looking at it, I think it would increase case volume a lot and create a bad shape to the transfer tunnel (big dead space behind the upper).

There’s definitely room to experiment there though. That transfer is very constricted and it’s a primary. I could see widening the tunnel slightly by thinning the stuffer, or removing it and pouring epoxy.

The transfers on this saw are confusing. Each one has its own entry and exit dynamics. I’ve poured a lot of water through them trying to visualize the scavenge pattern, but it’s only a crude indication of what they do in a running engine. They seem over complicated to me.

I haven’t done a 2511t in a few months. When that comes back around the first thing I will do is measure the relationship of the piston at BDC to the flange walls at the transfers. That is the major constriction point. How much of that flange you take away probably has the biggest effect on transfer efficiency.

 

[Crocky28]

I’ve been working on one today. I see what you mean in the upper transfer when the stuffers removed. I’ve decide to leave it out. After raising the uppers it smooths out a bit. I don’t think it will be a problem. I have 2 to do so I’ll do the next one with the stuffer in and see what the difference is.

They’re an odd cylinder layout. Also can’t believe how small they are. This is the first time I’ve had one apart. I’m just glad I have some tiny dental bits for inside the cylinder.


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[Crocky28]

Appreciate the info shared in this build thread. It was good reading before I tore the wee saw down.


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[Ketchup]

I’ve been working on one today. I see what you mean in the upper transfer when the stuffers removed. I’ve decide to leave it out. After raising the uppers it smooths out a bit. I don’t think it will be a problem. I have 2 to do so I’ll do the next one with the stuffer in and see what the difference is.

They’re an odd cylinder layout. Also can’t believe how small they are. This is the first time I’ve had one apart. I’m just glad I have some tiny dental bits for inside the cylinder.


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I’d love to hear your impressions on the difference.

 

[davidwyby]

Great thread, thanks.

 

[Crocky28]

Transfer stuffer removed.


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[Crocky28]

Transfer stuffer left in.


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[Ketchup]

Transfer stuffer left in.


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Nice. What’s your impression? The difference is hard to gauge but one sounded faster.

 

[Crocky28]

The one with no stuffer is approx. 2 secs faster. The difference in the cut was huge. That much that I’ve just pulled the one that had them in apart to remove it. The only other dif in the two is 0.05mm less squish. That maybe helped but half a mm isn’t much. Apart from that they’re both the same numbers, same amount off the base and same pop up.


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[Crocky28]

Need to correct myself. The one that was faster was 72 intake. The slower was 73.


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[Crocky28]

I didn’t touch the intake. It was just where it landed when I machined it.


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[Crocky28]

If you port one with a stuffer in don’t go and remove it like I did. It didn’t run right after. That void is obv not good. It’s now back in.

The other one I had ported with it out so the port shape is different and it runs fine.


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[Ketchup]

Just a little update.

I’m taking a good bit out of the piston skirt at the lowers now and eliminating all the cylinder flange cut-outs at the lower.
Before:
I’m also shaving down the insert to widen the FW primary.

I epoxy it back in so it smooths out nice.

I’ve done this on three saws now. I like it. The piston probably won’t last quite as long, but it’s got more guts in the cut and tunes easier.

 

[farminkarman]

Just a little update.
View attachment 343251
I’m taking a good bit out of the piston skirt at the lowers now and eliminating all the cylinder flange cut-outs at the lower.
Before:View attachment 343252
I’m also shaving down the insert to widen the FW primary.
View attachment 343253
I epoxy it back in so it smooths out nice.
View attachment 343254
I’ve done this on three saws now. I like it. The piston probably won’t last quite as long, but it’s got more guts in the cut and tunes easier.

Sounds like one of your builds needs to go on Joe’s dyno

 

[Ketchup]

Whelp…

I killed a set of bearings grinding a case. I botched the masking.

That motivated me to try a new way.

That’s kitchen and bath silicone. I sprayed the case and crank with WD40 first and hoped it would keep the silicone from sticking. Then I let it set.

You can see the fine aluminum grindings go everywhere. It’s always made me nervous. I’ve been really careful with tape, but eventually I screwed up. So I tried silicone this time. It’s a lot faster to apply.


It works great! There was a small schmear at the edge of one crank weight where the silicone hadn’t set all the way, but that swabbed out with a cue tip. With this technique you can probably machine cases without splitting them. Handy for hybrids and such.

 

[Crocky28]

Tried the piston mod. Def a winner. Thanks for sharing. It seems like it idles better.

If you take the transfers to 125 you can blend and reshape the FW primary so you don’t need to stick the stuffer back in.


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[Titi]

You hear anything about the 1/4 pitch sprocket availability? I also heard the 2511 is being replaced in Echo's lineup?

I found one sprocket 1/4 pitch on Amazon.com a bit pricy but considering it's one piece CNC made that explains. I can't send the link but by typing A556001710 Echo sprocket 1/4 pitch on amazon it should pop-up.

 

[mettee]

I found one sprocket 1/4 pitch on Amazon.com a bit pricy but considering it's one piece CNC made that explains. I can't send the link but by typing A556001710 Echo sprocket 1/4 pitch on amazon it should pop-up.

I tried to do a group buy on these, they would have ended up under 35 bucks shipped but no one was interested.

 

[Ketchup]

I had a pretty good stash, but it’s dwindling. I’m in for a group order if you still feel it.

I was pretty much off the internet for August and September.

 

[mettee]

Just post up in the thread and see if we can generate enough to make it happen.

https://opeforum.com/threads/2511t-8-tooth-1-4-pitch-drum-group-buy.27310/