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Author Topic: MS 461 "De-Limiting" the Speed Limiter  (Read 16316 times)

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Offline joe_indi

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MS 461 "De-Limiting" the Speed Limiter
« on: January 01, 2014, 06:31:38 AM »
The speed limiter on the MS461 can be a nuisance at times. >:(
#. Your old tach will not work for carb tune-ups
#. If you are used to setting your carb to any rpm above 13,500, its difficult.

In the MS461 the rpm sensing is done by the 3rd pole of the ignition module, which differentiates the 461(ignition module) from the 2 pole unit on the 460.

So, I just cut off the 3rd pole! Okay, not chopped off completely, but trimmed off enough so that this pole will not pick up any working magnetic impulses from the flywheel
And it works. 8)

I held the pole compressed with a pair of pliers that had wet cotton waste on the jaws.This prevented the iron plates from transferring heat onto the coil inside while I used a hand held cutter.
Heat transfer will sometimes cause the copper winding to snap from expansion.
 

Offline bandmiller2

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #1 on: January 01, 2014, 08:22:46 AM »
Thanks Joe, seems theirs a way around every problem they throw at us. Frank C.
A man armed with common sense is packing a big piece

Offline clww

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #2 on: January 01, 2014, 10:22:17 AM »
Another innovative tip, Joe! :) :) :)
Many Stihl Saws-16"-60"
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Offline Andyshine77

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #3 on: January 02, 2014, 12:19:20 AM »
Joe how does the saw run with the unlimited coil? I know the stock 461 coil has a pretty good advance to it, did you advance the flywheel any to compensate? You probably won't notice any difference on a work saw. 
Andre.

Offline joe_indi

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #4 on: January 02, 2014, 05:25:10 AM »
Andre,
The MS460 has what you might term as an 'unlimited coil'
I dont thing there is any difference between the basic ignition timings of a  460 and 461 .
No ,I did not advance the flywheel.I only did  the mod on the coil.
Regarding the noticeable difference on a work saw, maybe you have a point for saws running with longer bars.
But with 18 and 20" bars that speed comes up fast.
Agreed that rpm in the wood is much lower (round about 9800rpm or so) but when going through wood of small diameter, that extra rpm matters a lot.
The cut off by the limiter feels something similar to tripping a person who is running fast.
If you fit a 460 coil in a 461 you will understand much better what I am trying to explain.
If I am not mistaken, the speed limiter is there because of regulations, to ensure the user cannot tune to dangerously high rpms.

This picture will explain it better.
The MS460 had a 2 pole coil.
The MS461 has a 3 pole coil.
The 3rd pole's function is only to read magnetic impulses (via fancy electronics I think), so that when impulses cross 13500/minute.When the impulse reading is 13500/minute, the saw is running at 13500 rpm. Beyond this rpm the (say 13550) every other ignition spark is cut so that the rpm is limited to 13500.
For many users this kind of limiting acts as a leash on the potential of the saw.
 

Offline 7sleeper

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #5 on: January 02, 2014, 02:38:52 PM »
Fantastic info!

Thanks alot!

7

Offline shootingarts

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #6 on: January 02, 2014, 03:56:06 PM »
Very interesting to say the least! Wonder if the deal is similar on my Dolmar/Makita 6400?

Hu

Offline Andyshine77

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #7 on: January 02, 2014, 05:57:59 PM »
I understand, I'm quite familiar with limited coils and how they cut ignition. What I was referring to is the 461 coil advances the timing at speed for better power, and retards the timing at idle for easier starting. Limited coils are there more for durability than anything else. Saws have had rev limiting of some type since they've existed, and doesn't effect performance as long as you have the carb tuned correctly.

This video shows how the 461's coil advances timing. Like I said you likely won't notice a difference. :)

   
Andre.

Offline joe_indi

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #8 on: January 02, 2014, 10:22:49 PM »
Andre,
Thanks a ton for your post!
What I now realise is that other than removing the speed limiter, by trimming the 3rd pole I have also stopped the ignition advance! ;D
This info is great! Because the MS461 crankshaft failure here could be because of the timing advance. Not a good thing for our below average fuel.
So, I know also know that I am actually killing two birds with one stone by trimming the third pole. 8)
Once again, great useful info for me and I am really grateful! smiley_clapping
Joe

Offline joe_indi

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #9 on: January 02, 2014, 10:30:36 PM »
Very interesting to say the least! Wonder if the deal is similar on my Dolmar/Makita 6400?

Hu
I dont think its a similar set up on the Dolmar/Makita. The earlier coils and the present coils (like Huskies) have the same location, without any change.Plus they are 2 pole types.
I am not an electronic expert, but what I think happens is that when impulses(rpm) cross a set limit, a thyristor or scr shorts out the current thus controlling the rpm.This is what happens in some Stihl brushcutter and cut-off saw coils.
Like I said I am no expert in electronics, this is just a personal theory

Joe

Offline Andyshine77

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #10 on: January 02, 2014, 11:18:22 PM »
You don't need three poles to make the coils limited or have timing advance. The Dolmars, and newer husky coils are limited, and some have advance as well. Husky's normally had more advance than the Stihl anyway, but as you can see that's changing with new Stihl models. The newer stihl also have quad transfer, this improves power and efficiency. Case stuffers don't hurt either.
smiley_beertoast

Andre. 
Andre.

Offline splitpost

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #11 on: January 03, 2014, 02:17:52 AM »
do the 461 flywheels have the extra poles ?

Offline joe_indi

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #12 on: January 03, 2014, 12:26:40 PM »
do the 461 flywheels have the extra poles ?

No. They are the same two pole flywheels as those that come on the 460.
Both saws use the same flywheel.

Offline splitpost

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #13 on: January 03, 2014, 04:46:20 PM »
cool,i was just thinking that if it had the extra pole it maybe swapped for an earlier version ,to overcome the limiter ,seems like the coil mod or complete coil swap is the way to go smiley_thumbsup

Offline joe_indi

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #14 on: January 05, 2014, 11:29:58 PM »
cool,i was just thinking that if it had the extra pole it maybe swapped for an earlier version ,to overcome the limiter ,seems like the coil mod or complete coil swap is the way to go smiley_thumbsup
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Offline sharkey

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #15 on: January 06, 2014, 07:43:47 PM »
Good job Joe, thanks for the heads up on the third pole.

Offline 4x4American

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #16 on: August 08, 2014, 09:09:30 PM »
So from what I'm seeing here, the best thing to do is remove that third pole?  Is there anything else besides that?  The limited coil I think made me believe it was four stroking when really it wasn't.
Boy, back in my day..

Offline celliott

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #17 on: August 08, 2014, 11:50:31 PM »
So from what I'm seeing here, the best thing to do is remove that third pole?  Is there anything else besides that?  The limited coil I think made me believe it was four stroking when really it wasn't.

A rev limited coil can sound like it's "4 stroking" under no load, free revs, thus making tuning difficult. Best way to properly tune the high speed on a saw with a rev limited coil, IMO, is to do it in the cut- tune so the saw cleans up the 4 stroke sound under load, but when you let up it's 4 stroking  :)
This doesn't mean fiddling with the screwdriver in one hand while trying to run the saw with the other! Start pig rich and make small adjustments to the H jet between your test cuts.

Sorry, can't speak to what is "best" to do with the coil on the 461, never seen one...
Chris Elliott

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Offline 4x4American

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #18 on: August 09, 2014, 01:01:58 PM »
Thanks.  I opened up the muff hole a bit today on the ol girl. Now just trying to tune her in. Hard for me to figure out whether its strokin or bouncing off rev limiter.

If I have her WOT in the wood, and then pull out to listen, it'll rev up fast and I'm not sure if that's rev limiter or strokin.  Is it better to be more 13/16 or 5/8 throttle than WOT?

Also, is there carb limiters on the 461?  If there is, looks like it might be a pita to fix em.

Thanks yawl!
Boy, back in my day..

Offline CTYank

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Re: MS 461 "De-Limiting" the Speed Limiter
« Reply #19 on: August 09, 2014, 02:32:26 PM »
If you're using a tach for H adjustment, you're really into wishful thinking. Before mfgs encouraged laziness with that kludge, they said "adjust H for max speed under load.".

Exactly what Auto-tune does, for example. Going much beyond the power peak is just flogging a mule.

I've seen a few competent techs do the tach-tuning thing and get the mixture way rich. (They insisted on their righteousness all the while.) Easily remedied, though. Excessive richness can do long-term damage. Just think of little black diamonds being grown in the chamber, then shed.

Takes a few minutes longer, and is messier, to do it right. IMHO, well worth it.

It's helpful to look at plug color after some full-load running.
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