Echo 490 to ported 4910…to cs-5484

[thedude74]

That popping noise sounds like detonation.... I could be wrong. Awesome project though! I've been following along.

 

[Dolkitafreak]

The chain is awful and I may take the secondaries up to meet the primaries. That was a nasty chunk of knotty petrified Honeylocust. Some weird popping noises in the cut. Almost like too much ignition advance. May e I’ll put a light on it.

@Dolkitafreak, have you run into problems getting the RWJ butterfly to open all the way? I really have to mash the trigger on this HD 12. Feels like the linkage is flexing.

I don’t think I’ll ever be satisfied, but it’s a strong saw now.

I’ve never used an RWJ on one and using an air horn I’ve never used a larger carb. Might make a custom linkage that’s stiffer.

Still missing something I feel-also their timing is interesting. They pull timing fast at higher rpm but you may wanna see what you’re pulling in the cut.

 

[drf256]

Great job on this build. I’m digging it.

 

[Ketchup]

Sounds way too fat to me...

I leaned it out about 1/4 turn after the video, but it didn’t seem to change much. More cut time needed.

That popping noise sounds like detonation.... I could be wrong. Awesome project though! I've been following along.

That’s a scary thought. I’ll take a look through the plug hole. I’ve only had one saw detonate. That one wouldn’t shut off.

I’ve never used an RWJ on one and using an air horn I’ve never used a larger carb. Might make a custom linkage that’s stiffer.

Still missing something I feel-also their timing is interesting. They pull timing fast at higher rpm but you may wanna see what you’re pulling in the cut.

Gotcha. What WJ are you running? Custom linkage or maybe reinforce this one. Maybe even weaken the shaft spring. Seems like it’s only opening about 85%.

I haven’t read the timing on this thing but it has seemed weird since the beginning. The magnet is in an odd spot. Looks too far advanced though I know it doesn’t indicate the spark timing. I’m running the limited coil as well, I haven’t noticed the limiter thus far.

Getting sick of all the details but must plow on…

 

[Dolkitafreak]

I leaned it out about 1/4 turn after the video, but it didn’t seem to change much. More cut time needed.


That’s a scary thought. I’ll take a look through the plug hole. I’ve only had one saw detonate. That one wouldn’t shut off.

Gotcha. What WJ are you running? Custom linkage or maybe reinforce this one. Maybe even weaken the shaft spring. Seems like it’s only opening about 85%.

I haven’t read the timing on this thing but it has seemed weird since the beginning. The magnet is in an odd spot. Looks too far advanced though I know it doesn’t indicate the spark timing. I’m running the limited coil as well, I haven’t noticed the limiter thus far.

Getting sick of all the details but must plow on…

I used a clone WJ for gas and a tillotson HS for nitro. Custom linkage for HS, stock on WJ and worked well.

I’m not sure what rpm they’re even limited at. 13.5 or so iirc.

Keep going! You can do it lol

 

[Red97]

Limiter will be right around 13k. Popping is odd seems like it is right after some longer cuts it pops worse.

What kind of rpm is it turning on your tac?

Seems a couple of the pieces are not playing nice.

 

[thedude74]

My ported echo 490 did the same thing (popping) when set too lean. Sounded like detonation....but perhaps it's unburnt fuel igniting in the muffler caused by the limited coil not providing %100 ignition??? Set at 12,800 the popping went away....and it makes WAY MORE power.

Edit. Is it possible the limited coil is retarding the ignition so far it's firing with the exhaust port open?

Maybe yours isn't running as rich as you think and your hearing the effects of the limited coil and not four stroking?

 

[Ketchup]

My ported echo 490 did the same thing (popping) when set too lean. Sounded like detonation....but perhaps it's unburnt fuel igniting in the muffler caused by the limited coil not providing %100 ignition??? Set at 12,800 the popping went away....and it makes WAY MORE power.

Edit. Is it possible the limited coil is retarding the ignition so far it's firing with the exhaust port open?

Maybe yours isn't running as rich as you think and your hearing the effects of the limited coil and not four stroking?

I don’t think I’m hitting the limiter because it revs fine out of the cut. Too lean is possible and easy to check. I will. I’ve had other saws that seemed rich but were actually lean. 2511 does that.

It is also possible the coil is bad. This saw was a freebie, history unknown.

 

[Ketchup]

Could this be the popping? I had to cut the magnets a bit to make it fit.

 

[Ketchup]

Actually, I also ground a bit off the spark plug. About 3mm.

 

[Woodpecker]

This has been a really enjoyable thread. Thanks for posting man!

 

[Red97]

Could this be the popping? I had to cut the magnets a bit to make it fit.View attachment 370882

I wouldn't think so. Is the key in the stock position?

Maybe set it pig rich 12k or so and slowly lean out? Just sounds way off.

But you are giving me too many ideas

 

[thedude74]

I don’t think I’m hitting the limiter because it revs fine out of the cut. Too lean is possible and easy to check. I will. I’ve had other saws that seemed rich but were actually lean. 2511 does that.

It is also possible the coil is bad. This saw was a freebie, history unknown.

That's pretty much what mine did too right after porting. Revved fine, cut small wood fine(4-6")....Then buried the bar in some big birch and it starting making a popping sound....lacked torque...
Turned the high almost a full turn out to get it below the rev limiter. Popping went away, saw ran way stronger....its still not a %100 dialed in yet either.
My ignition timing is stock(no advance)...
I beleive both @Red97 and Doc @drf256 found the stock timing to be fairly aggressive and further advancing it showed no gains.
That said your custom build with the higher rpm potential may benefit from some timing advance??

Looking forward to your build testing/progress.

 

[thedude74]

Maybe set it pig rich 12k or so and slowly lean out? Just sounds way off.

This ⬆⬆⬆

 

[Woodpecker]

But you are giving me too many ideas

I have a donor 501… You know for the cause n stuff

 

[Ketchup]

Welp. Not a tuning thing. Went both ways with it for over an hour. Pops happily along at the strongest tune.

 

[thedude74]

Welp. Not a tuning thing. Went both ways with it for over an hour. Pops happily along at the strongest tune.

I'm assuming by tuning you mean adjusting the High screw? Really odd it's still popping. Have you tried retarding the timing some? Hopefully someone with first hand experience on this phenomenon will chime in.

 

[Ketchup]

I'm assuming by tuning you mean adjusting the High screw? Really odd it's still popping. Have you tried regarding the timing some? Hopefully someone with first hand experience on this phenomenon will chime in.

That’s right. I tuned the H 3/4 of a turn in tiny increments. Both ways. 3 times. I cut quite a lot of firewood in the process.

I haven’t tried dialing the timing back yet but I think that’s the next step. It sounds too advanced.

 

[huskihl]

That’s right. I tuned the H 3/4 of a turn in tiny increments. Both ways. 3 times. I cut quite a lot of firewood in the process.

I haven’t tried dialing the timing back yet but I think that’s the next step. It sounds too advanced.

The 4910 and 501 coils are pretty well maxed out where they are. But maybe it’s something to do with having the larger cylinder set on top of there. Usually advancing the timing just forces you to tune a little bit higher to get rid of it. But if you’re saying it’s not changing, it makes me think it’s something with the larger cylinder

 

[drf256]

Did you pull a compression reading by any chance?