390XP Limiter Caps...Just the facts...

[double clutchin weasel]

I'm looking at picking up a new 390XP in the next few weeks. When I get it home, the limiter caps will undoubtedly have to be removed to tune the saw correctly...particularly to perform a slightly rich run-in. I have already ordered some of the new-style limiter caps. Maybe they'll be here by the time I get the saw!
The last 390 I worked on had a Tillotson carb & a different type of cap. These new Walbro-equipped models look different. In particular, the limiter caps seem to be recessed into the carb body. And, there is some sort of plastic retainer device (#42) in there as well. The guide tube device (bushing) looks very similar to the 372, & I hope is as easily removed (push in, lift up, pull out) to access the screws.
I am seeking information from anyone having first-hand knowledge of how to safely remove these particular caps. The more detail, the better. Pictures are even better. I would like to leave the carb in place, if possible.
So, who knows what about the details of this particular setup?

Thanks!



 

[Andyshine77]

The limiters can be deleted quite easily. Remove the carb, take a small pin or whatever will fit, and push down the ring "part #23" between the needle screws and carb body. This will allow you to turn the needles 360° remove both needles this way. Now simply grind off the lobes on the metal limiters aka part #23. Reinstall everything and open both screws 1 1/2 turns. I know this sounds complicated, but it's not. They make a spline carb screwdriver that will also work, if you don't feel comfortable doing the modification.   

[NCFarmboy]

Poulan splined carb tool is the one.  Push in w/tool turn screw.  If it has to have limiter caps this style is the easiest to deal with.  Same tool for 365-372 XT w/RWJ4 carb.  You can still get tool on Ebay but price gouging since the EPA ban on the carb adj. tools
Shep

[double clutchin weasel]

The limiters can be deleted quite easily. Remove the carb, take a small pin or whatever will fit, and push down the ring "part #23" between the needle screws and carb body. This will allow you to turn the needles 360° remove both needles this way. Now simply grind off the lobes on the metal limiters aka part #23. Reinstall everything and open both screws 1 1/2 turns. I know this sounds complicated, but it's not. They make a spline carb screwdriver that will also work, if you don't feel comfortable doing the modification.   

Thanks for the input.  I hate to sound dumb, but I am a little confused.  Are these particular limiter caps plastic or metal?  Or, are they part metal?

I think I see what you are saying about prying the flanges down, which will allow the needles to unscrew.  The caps could then be trimmed, and the needles replaced, without even removing the caps from the needles...if I understand you correctly.

Have you actually done a 390 set up this way?  Sounds like you might have.

Any thoughts on the retainer (part #42)?  Does it just pull out?  Is it "on top of" or "under" the limiter caps.  The drawing LOOKS like it in underneath, but that makes no sense.

I am going to try to stop at a local shop and look at a 390 later in the week.  Maybe I can tell more about it if I can see one.  And, again, I have ordered a couple of caps so I can see what is what.  Figure they'll be here before I get the saw anyway.

Thanks again.

[double clutchin weasel]

Poulan splined carb tool is the one.  Push in w/tool turn screw.  If it has to have limiter caps this style is the easiest to deal with.  Same tool for 365-372 XT w/RWJ4 carb.  You can still get tool on Ebay but price gouging since the EPA ban on the carb adj. tools
Shep

Not familiar with that tool.  On my 372, I was able to trim the protruding tabs on the limiters with everything still on the saw.  I just kept trimming a bit at a time until I got the needle rich enough to run at the correct RPM.  So, as it sits, it is correctly tuned, and the needle is against the rich stop.

Got any more info regarding the use of the tool?

[Den-Den]

The drawing looks like the limiters on my 455, it was not necessary to remove them.  I pressed the limiter in with some tweezers while adjusted the jets.

[double clutchin weasel]

The drawing looks like the limiters on my 455, it was not necessary to remove them.  I pressed the limiter in with some tweezers while adjusted the jets.

Pushed them inward, toward the carb?  Or squeezed the outside diameter inward, against the needle?

[double clutchin weasel]

The drawing looks like the limiters on my 455, it was not necessary to remove them.  I pressed the limiter in with some tweezers while adjusted the jets.

Here is a clearer picture of the same part number caps, but from a slightly older saw.

This looks like the caps are UNDER the needles, not OVER them.  Furthermore, it almost looks like the springs are under the caps, not under the needles.

So, given that, are you saying that the caps are actually spring-loaded, and they can be "depressed" while turning the needles?  And then, after adjustment, the springs will push the caps back into position on the needles?  If so, that makes some of the other posts make more sense!

Oh.  By the way.  The limiter cap IS the same part number as on at least some of the 455s (544 97 08-01)!

Sorry everybody, for the multiple posts!  Had a little "glitch"! Fixed by Admin



 

[double clutchin weasel]

Stopped by the local Husky/Stihl dealer today.  Asked the man if the limiter caps on the 390 could be depressed with a tubular tool to allow adjustment of the needle.  He said that is exactly how it worked.

So, thanks to you guys and him, I think I know what to expect there.

Still, if anybody has any more thoughts or input, please lay it on me!  Never too old to learn something new...

[double clutchin weasel]

Poulan splined carb tool is the one.  Push in w/tool turn screw.  If it has to have limiter caps this style is the easiest to deal with.  Same tool for 365-372 XT w/RWJ4 carb.  You can still get tool on Ebay but price gouging since the EPA ban on the carb adj. tools
Shep

And, you're 100% correct. That is the same part number as on the 372XP "X-Torq" models with the RWJ4 carb.

Thanks again!

[Andyshine77]

If you look at part #23 one side is open the other isn't. When you push them in they no longer move and catch on part #42 I think part 42 acts line a spacer and seat for the screw springs, so I didn't mess with it. I simply ground the lobes off part 23, they became nothing more than seats for the springs. You don't want to completely remove them or the springs, if you do the screws will turn on their own do to vibration. Remember this is much easier than it sounds, and you'll see what to do when you get in there, it's a 15 minute job at best.   

[double clutchin weasel]

If you look at part #23 one side is open the other isn't. When you push them in they no longer move and catch on part #42 I think part 42 acts line a spacer and seat for the screw springs, so I didn't mess with it. I simply ground the lobes off part 23, they became nothing more than seats for the springs. You don't want to completely remove them or the springs, if you do the screws will turn on their own do to vibration. Remember this is much easier than it sounds, and you'll see what to do when you get in there, it's a 15 minute job at best.   

Gotcha.

Hopefully, when I do this, I'll get some good pics & help out the next poor slob who does it!

[SawTroll]

Poulan splined carb tool is the one.  ....

Poulan???  I got mine from my friendly local Husky dealer.

[Andyshine77]

Poulan splined carb tool is the one.  ....

Poulan???  I got mine from my friendly local Husky dealer.

Niko right now local dealers are not allowed to sell the tools, Ebay is a good option, or deleting the issue all together.

Merry Christmas to everyone!!! 

[SawTroll]

Something like that....

[Maine logger88]

Why aren't the dealers allowed to sell them?

[ChopperDan]

The EPA

[Maine logger88]

Really! the epa needs to quit getting in the way of people trying to make a living

[double clutchin weasel]

Why aren't the dealers allowed to sell them?

This is great example of governmental stupidity. The EPA thinks melting a $1000 chainsaw is a great way to reduce pollution.
That is idiotic & not big-picture thinking.
In addition to putting a saw in the trash, people will drive to the dealer to buy another saw, and produce more pollution on that one trip than the saw would produce.
Then we have to mine and process more metal, & mold more plastic to make a new one.
Then we ship the new one to the dealer & produce more pollution.

Like I said...idiotic!

Rant over...

[Andyshine77]

Why aren't the dealers allowed to sell them?

This is great example of governmental stupidity. The EPA thinks melting a $1000 chainsaw is a great way to reduce pollution.
That is idiotic & not big-picture thinking.
In addition to putting a saw in the trash, people will drive to the dealer to buy another saw, and produce more pollution on that one trip than the saw would produce.
Then we have to mine and process more metal, & mold more plastic to make a new one.
Then we ship the new one to the dealer & produce more pollution.

Like I said...idiotic!

Rant over...

Some truth there, it does help keep things moving which isn't bad. Truth is the OPE manufactures were caught sitting on their backsides, not investing anything in R&D for far too long. In a few years time, no one will want to run a saw with a carb at all IMHO.     

Take into consideration 99.9% of people who buy saws, or any other OPE, don't know they have to tune the carb, and even less know how. Limiters on carbs are nothing new and have been used for decades to prevent people from messing with the needles and killing their equipment. I have dozens of orange Stihl screw driver, get them free from my dealer, they don't give them to any other costumers because they're clueless.       

[double clutchin weasel]

Why aren't the dealers allowed to sell them?

This is great example of governmental stupidity. The EPA thinks melting a $1000 chainsaw is a great way to reduce pollution.
That is idiotic & not big-picture thinking.
In addition to putting a saw in the trash, people will drive to the dealer to buy another saw, and produce more pollution on that one trip than the saw would produce.
Then we have to mine and process more metal, & mold more plastic to make a new one.
Then we ship the new one to the dealer & produce more pollution.

Like I said...idiotic!

Rant over...

Some truth there, it does help keep things moving which isn't bad. Truth is the OPE manufactures were caught sitting on their backsides, not investing anything in R&D for far too long. In a few years time, no one will want to run a saw with a carb at all IMHO.     

Take into consideration 99.9% of people who buy saws, or any other OPE, don't know they have to tune the carb, and even less know how. Limiters on cabs are nothing new and have been used for decades to prevent people from messing with the needles and killing their equipment. I have dozens of orange Stihl screw driver, get them free from my dealer, they don't give them to any other costumers because they're clueless.     

Some truth to yours, too.

However, not all dealers will let those tools out. Because it can get them in a ton of hot water. So, be thankful your dealer will.

And, at some point, the electronic engine management systems will evolve into a fine system. But, like the early emission controls on automobiles, the current systems on saws are not all that great.

But, my point is still that destroying an internal combustion engine by running it too lean is not a valid way to reduce pollution. Also, causing more manufacturing by destroying the product is false economy, at best. Try telling professional loggers that destroying thier equipment is good for the economy! The cost they incur goes into the cost of everything they produce. If their operating costs go up, the cost of their product (lumber, right-of-way, etc...) goes up. And, that cost is eventually passed on to the consumer.

You are also correct that many people cannot properly tune a chainsaw.  But, that is because most purchases are of consumer-type units, and that weights the averge heavily toward a "consumer".  Most professional saw users CAN properly tune their equipment.  In fact, I find that on pretty much anything I own, I take better care of it, and pay more attention to it, than most service centers. 

Oh, and by the way, we have been defeating limiters as long as they have been in existance!

[double clutchin weasel]

Keep in mind, nobody defeats limiters to try to increase emissions. They do it to tune the saw as described in the factory service manuals. But, since those same manuals detail how the caps are installed in the full-rich position, while the mixture is borderline on being too lean, how exactly can one tune the saw 6-700 rpm rich for the initial break-in period? That's what the manuals say to do. But, this is physically impossible without messing with the caps.

A good dealer might be able to help out there. But, I prefer to do my own work, when it needs done, wherever I happen to be at the time, and know it is done correctly.

Fuel varies. Temperature varies. Barometric pressure varies. Humidity varies. And elevation varies. All these things require adjusting the saw to compensate. And, I'm pretty sure the local dealer's tech won't be willing to follow you all over the country to tune your saw!

So, until the next generation of closed-loop engine controls arrive, we gotta keep tweakin' on these!

Sorry this post took a detour! As originally titled, I just wanted to know how to adjust the caps on a new 390, IF they needed it! Maybe I'll get lucky & they won't need any adjustment. Of course, if that's the case, it'll be the first time...

Merry Christmas to all!
And a Happy New Year!

[double clutchin weasel]

The drawing looks like the limiters on my 455, it was not necessary to remove them.  I pressed the limiter in with some tweezers while adjusted the jets.

Did a little more research. I think I get it now. If so, there's absolutely no need to delete these. Just need to re-index them to put the needle in the correct position.

Did you just press in with tweezers and turn the needle to put you in the correct position?

[Den-Den]

The drawing looks like the limiters on my 455, it was not necessary to remove them.  I pressed the limiter in with some tweezers while adjusted the jets.

Did a little more research. I think I get it now. If so, there's absolutely no need to delete these. Just need to re-index them to put the needle in the correct position.

Did you just press in with tweezers and turn the needle to put you in the correct position?

That is exactly it, I now have some room to adjust and the limiters are still there.

[double clutchin weasel]

The drawing looks like the limiters on my 455, it was not necessary to remove them.  I pressed the limiter in with some tweezers while adjusted the jets.

Did a little more research. I think I get it now. If so, there's absolutely no need to delete these. Just need to re-index them to put the needle in the correct position.

Did you just press in with tweezers and turn the needle to put you in the correct position?

That is exactly it, I now have some room to adjust and the limiters are still there.

Many thanks!
This is exactly what I needed to know.
I don't really want to remove them. I just want enough adjustment to set them correctly.
Thanks again.