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MS461 carb adjustment: RPM too high on full throtle

Maxi5566

Maxi5566

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I’m trying to adjust the carburetor on my MS461 and I have 2 problems:

1- I cannot lower the RPM on full throttle below 13800.
2- when the saw is idling (2800-2900rpm), the chain run a little bit (it moves a inch every 1-2 seconds). Is that normal?
Thanks
 
DND 9000

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There are limiter caps on the screws (H and L). You are maybe on the rich stop point with the cap and it has to be removed maybe. Best would be to go to your dealer and let him tune it.

The idle is a little to high. Turn it down with the LA screw. Specification is 2500 rpm. It can also help if you clean your clutch drum inside.
 
lambs

lambs

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Make sure the chain is properly tensioned to begin with.

Also, it could well be you are at the limiter on the H adjustment screw. But I wouldn't worry too much about it turning 13,800.

On some saws I have pulled the H limiter cap, rotated it 1/4 turn clockwise, and then put it back on. Then the H adjustment screw can be backed out another quarter turn. That's probably all the additional adjustment you need if everything else is ok.
 
Wood Doctor

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On some saws I have pulled the H limiter cap, rotated it 1/4 turn clockwise, and then put it back on. Then the H adjustment screw can be backed out another quarter turn. That's probably all the additional adjustment you need if everything else is ok.
Agreed. I did this on an 046 Mag seven years ago that I bought as a non-runner. That was about all that it needed to make it run perfectly:
Stihl046 Magnum Restored.JPG
I later added a dual-port muffler. Still a heckuva saw.
 
trains

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If its too high on the H, and you have limiters on the carb, get a 2mm allen key, put it in the H thru the limiters hole, engage the H needle, and give yourself a few extra clicks anti clockwise to drop your rpm to 13500 or what your wanting.
make sure the key is seated well in the H needle before you turn it, there are small nylon teeth on the limiter that engage with the steel needle, using allen key will move it past them.

Providing you have gone thru the carb, put a kit thru it, and made sure you dont have a blocked fuel filter or air leak etc, and all other usual disclaimers apply.

edited to add.
As already mentioned, clean your clutch drum, if its ok, and the bearing is clean and has grease, your clutch springs might be a bit weak, cluch engagement should be around the 3600 rpm, so chain creep may be from a dirty clutch drum, or bearing, or weak clutch springs, the springs are only a few dollars each, so easy cheap fix.

also, if the idle is a bit high, use the L to richen it up to 2500 rpm, if it loads up when idling for 30-40 seconds, then lean it a bit back up to current rpm, and then use the LA to drop your idle to 2500.
 
Maxi5566

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Thanks guys. I was able to tune the LA and L screws (it idles @ 2500 rpm and the chain doesnt move at all).

I will order a limiter cap pulling tool to do the H screw.

Additionnal question:
I replaced the original muffler cover with a hyway DP and I enlarged the original port. Does that changes anything in how I tune the saw? Does the idle/max rpm stays the same, or do I need to make it more lean/rich?
 
SteveSr

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I replaced the original muffler cover with a hyway DP and I enlarged the original port. Does that changes anything in how I tune the saw? Does the idle/max rpm stays the same, or do I need to make it more lean/rich?
This is highly likely why it is lean up top. OEM carbs are calibrated to run properly with a stock exhaust system. Hopefully you haven't done any damage to the saw yet.
 
Maxi5566

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This is highly likely why it is lean up top. OEM carbs are calibrated to run properly with a stock exhaust system. Hopefully you haven't done any damage to the saw yet.
i do not think I damaged it, I only started the saw to tune it.

is there anythig special I should do while tuning a saw with a muffler mod?
 
SteveSr

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is there anythig special I should do while tuning a saw with a muffler mod?
The limiter caps will have to be removed and new ones reinstalled after tuning or just removed. The issue is that if the caps are completely removed the stock settings printed on the saw will no longer be accurate and if someone else tried to tune to these stock settings they will burn up the saw. There is a certain amount of bias built into the needle positions before the caps are installed. These pre-settings are carb specific and have also been changed by your non-stock exhaust.
 
trains

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Thanks guys. I was able to tune the LA and L screws (it idles @ 2500 rpm and the chain doesnt move at all).

I will order a limiter cap pulling tool to do the H screw.

Additionnal question:
I replaced the original muffler cover with a hyway DP and I enlarged the original port. Does that changes anything in how I tune the saw? Does the idle/max rpm stays the same, or do I need to make it more lean/rich?
Did you not read my post ?
just use a 2mm allen key, and give yourself an 1/8th of a turn richer, or whats required, no need to pull the limiters.
 
Maxi5566

Maxi5566

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Did you not read my post ?
just use a 2mm allen key, and give yourself an 1/8th of a turn richer, or whats required, no need to pull the limiters.
I didnt understand where the 2mm allen key is supposed to go. Do I need to pull the carburetor?
 
DND 9000

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The 2mm allen key would go through the limiter Cap into the screw for tuning it. But this will not work in your case, because you have seated caps and not pre-seated ones.
 
stihl86

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It your caps are red, you have to pull them. There is a special puller and also small square screwdriver to make the adjustment. If you pull the cap out completely, you can use a regular screwdriver.
If I remember correctly, a MS461 has a Walbro HD series carb.
 
drf255

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The 461 has a limited coil, unless you replaced it. It will make rpm reading difficult with some tachs and also make it difficult to hear 4 stroke vs limiter.

Im not certain exactly how a 2mm Allen wrench would do anything here. It’s difficult to move a screw through the caps. You’ll see a slot where each cap is on your HD50 carb. The screw slot needs to line up with that to pull the cap. That’s generally accessed by rotating both screws counterclockwise all the way, then the Stihl OEM tool is just a fine L hand thread screw attached to a handle. It pulls the cap out as you twist counter clockwise Without rotating the cap away from the egress slot.

BTW, once you mess with a saw, the factory setting go out the window. You need to tune that saw by ear now.
 
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