Getting Rid of the 3120 Rev Limit

As many of you know, later models of the 3120 XP have rev limiters built into the CDI/coil. On my 1999 model, the thing cuts in at about 11,500 RPM. On newer models, Ken has told me that he's seen something like 9,000 RPM! This really sucks when you're looking for any edge you can get on a screaming, unlimited 088 KD at close to 15 grand. In a large fir log, this isn't necessarily a problem because the revs of both saws fall below this in the wood. In smaller logs and cants, however, the inertia carried into the first few inches of the wood by higher RPM can mean the difference between beverages all around or a lengthy trip behind the bushes for some relief.

So here's what I did for my '99. First you order up a "-02" suffix flywheel for a 3120. Watch out if you have a 2000 or beyond model as you may not have to change the flywheel. More on that later. This is about $100 US. Then get hold of a 394 coil, which has no rev limit. These are about $75 US or so. The 394 coil has a two-legged pole piece, while the 1999 3120 coil has three legs. It is because of this that the position of the flywheel magnet relative to the crankshaft keyway will be different between the two. For models after 2000 or so, this will not be the case. As to when the changeover was made, I don't know, but you can look at the attached picture to see the relative positions of the magnets on the flywheels. The 1999 original flywheel and coil are on the right and the -02 flywheel and 394 coil are on the left. Note that the keyways are at the 3:00 position. The coils were placed so that they are in the position where they would just pick up the magnet for a counterclockwise crank rotation.

How I got the flywheel off

I first called Ken when I wanted to pull the flywheel as I didn't want any surprises. He offered to mail me a puller across the country, which I was thankful for, but told him I'd first look into alternatives. Next, I called Dennis, who told me I could use a harmonic balancer puller, which I thought I might have, but later found out that I couldn't locate it for some reason. I missed leaving the office in time to buy one at an auto parts store, so when I got home, I took some advice from Dennis, and figured I'd build my own. First, I dragged out the plasma cutter to cut off a hunk of 1/4" steel for the puller plate. Since I had done up a few cocktails before this, I was feeling no pain and ended up cutting a 6 inch gash in my steel tablesaw top before I even realized what I was doing. After this, I threw up my hands, said "%^$# it" and called JD Lambert. I'll tell you what, that JD Hotsaw guy sure knew what he was doing. I had the flywheel off in less than 45 minutes!

On a slightly more serious note, 1/2" aluminum plate is what I use for pullers. Cuts well with a hacksaw or bandsaw and it's easy to tap.

I got a few stihl pullers, or well most of them.


Rest i pry and beat.


works 99.9% of the time.

Doug, what is your 3120KD revving at now with the limiter removed?

So, doug, if I understand correctly...what you are saying is that your 3120 wsnt performing at peak performance when it nearly beat that 088 of Lamberts to death?? And now that you have it finely tuned..., it should kick anything llamabert brings to the plate?? I would presume you should now be able to enter the log at about 14k instead of the 11k or so you were...and kick some of that Ontario @ss??

Alright, Ive just about had it! Dennis, I will straighten you out later!
Doug, you putz! You didnt listen correctly to my instructions!
In the picture you posted it is more than obvious you didnt do what I told you to do. You were suppose to use two wedges and two Hodads ( Matocks) so as to apply equal force to the flywheel!
Please dont ask for my instructions if you are not going to follow them!
And might I add, it would appear you have a drinking problem as well. Doug, you are dumber than a sack of hammers!
Humphrey Dumbroski

Nice use of the polaski Ive used those things for many aplications. Trenching , popin out small stumps, . never thought that using it along with a BFH would be able to remove fly wheeles . ya learn something new everyday !

John,
To me it doesn't seem like Doug has any kind of drinking problem, in fact, he seems to be good at it.

Art Martin

Hi Art, I think you are correct. I have done DB a severe injustice.
He drinks, he gets drunk, he falls down, no problem!
I guess I will get mine now. I'm sure he is conjuring up an appropriate comeback. Does anyone want to bet DB will post a picture he manipulated to make it appear I was passed out on the floor after JB fed me some "truth serum?"
John

Art..I concur...Doug never had a problem in clearwater either...except keeping his cup full...

Gypo...you? passed out? never!!

Dang. I open this thread to see about a 3120, next thing you know Lambert is nekkid. Yikes.

Hey ginger, 'weetie, how's it hangin'? Long time no see ya!

How bout some Turkey day fixin's/!!

Hope Llamabert has his mukluks on today, it's a mite colder up that way these days... I'd hate to see him all shriveled up to less than the nothin he's hangin in that pic.

lambert you redneck!

Oh well, if you ever need another husky case to hold you 088 I have one for sale. My saw does not fit in it so I must sell.

Hi Folks, I honestly didnt make that post or attach that picture.
I was read the riot act a while back about posting nudity and have since advised Darin to ban Ginger, so that others who have her password will not abuse it.
And by the way, be careful who you trust with a camera if you dont want the picture to show up on arborist site.
If anymore pictures appear here of my lil white @ss, you can rest assured who it is.
Gypo

one of the guys that i know who has been running a lawn and garden shop for about 25 years uses an air hammer to get flywheels off. he too the single pointed bit for it and ground a 60 degree taper on it which is what is in the end of the crank shaft and he hits the end of the crank witht he air hammer a couple of times and the flywheel comes off no problem and it dosen't damage anything in the engine. it was the slickest thing i had ever seen the first time he did it.

You can, of course, damage bearings by striking the end of the shaft too hard. But its hard to explain what is too hard.

I sometimes tap (I said Tap not give it hell) on the meatiest part of the flywheel at about 45 degrees downward opposite side from the keyway. Some times wedge some thing a little under the flywheel if access is available. Many will come off that way. There is risk, but I take em every day anyway.