3120 Gone BAD

[Cantdog]

Thoughts to consider

First I am not as experienced as some on porting. Just from the pictures it looks like there is no or not enough bevel on any of the ports/transfers it's a wonder that it didn't catch a ring and this wouldn't even be an issue!! I don't know any of the players so I hope that my observations do not offend anyone. Here is how I see it, first you have a poor porting job that seems to fly in the face of any thing that I have learned. Raising and lowering as opposed to widening. Then we have the sheared flywheel key. What caused this??? Stopping to quick (seizing) or loose on the shaft?? Low comp (110-115) Now in my experiance a two ring piston will pull (by hand) better comp # than the same size single ring piston and those numbers you can almost get without rings at all! From what I have read, when you raise the exhaust port the saw responds with higher RPM and less torque so we have to assume that this saw really screamed!!
So we have, poor porting, perhaps shoddy assembly, a very high RPM capable saw and massive heat but no scoring as such and a ruined saw.
I would have to say that the owner seriously overrevved a cold saw with no load that was not ported correctly and caused the rings to overheat and warp loosing temper and ring tension and glazing the cyl walls at the same time. Don't know but my best guess. The sheared key is still not accounted for, unless it seized so suddenly that it sheared the key??? Interested to hear what you come up with, I'm sure you will get to the bottom of this Brad. Good luck

 

[blsnelling]

SO you won't tell us who did this porting origionally can you at least tell us which ones saws to stay away from? I mean if I bought a used saw that was professionally ported and that is what I got I would be pissed.

I've been here 3 years and had not heard of him. I'll let the owner of the saw speak up if he so chooses.

 

[Former Saw Builder]

Brad it's looking good - Do you ever put those tools down -

 

[blsnelling]

There was NO bevel on any of the ports. And the entire port job does fly in the face of what most would do.

 

[blsnelling]

Brad it's looking good - Do you ever put those tools down -

When I'm done I didn't do any saws for anyone else last week because of the GTG. Now this week I'm trying to catch up. This is saw #4 for the week. They haven't all been port jobs though.

 

[4mocajuns]

I've been here 3 years and had not heard of him. I'll let the owner of the saw speak up if he so chooses.

Jeeze I've been here nearly that long and you have nearly 15000 posts! Impressive!
I must edit because my join date doesn't jive with my actual arrival. I was under another user name for a while.

 

[blsnelling]

Jeeze I've been here nearly that long and you have nearly 15000 posts! Impressive!
I must edit because my join date doesn't jive with my actual arrival. I was under another user name for a while.

Three years in November.

 

[Cantdog]

Brad You've got me hooked!!

Rereading this more it occured to me, which way was the key sheared?? Did the flwheel shear it from decelerating (in other words sheared in the counter clockwise direction) or was it sheared in the clockwize direction??
What I'm getting at is, if the flywheel key was sheared in the clockwise direction from running loose and would that not advance the timing even further and could this not cause the heat and near siezure?? Not nesessarly an over zealous trigger finger?

 

[breymeyerfam]

did i meantion pipe it....:monkey:

 

[parrisw]

Man that was a terrible looking job, my first wasn't near that bad.

 

[blsnelling]

I finally got it running! At first it wouldn't start at all. Then when it did, it couldn't get enough fuel to even idle. Long story short, the fuel line was badly cracked. Who'd a thunk it on a saw that's hardly been used? Anyway, it now starts and idles like a dream. Throttle response is electric. After warming it up, I put a tach on it and pulled the throttle. 14,500!!!!!!!! Woah. From what I've read, a 3120 doesn't like much of that. I let off instantly. It's time to ream out that fixed jet. Obviously, this saw is not rev limited. How that was accomplished, I'm not sure.

The carb is a Walbro 030. That's the only marking on it. The jet has a 1 on top of the screw slot and a 12 below it. Any idea what size that is and what I should drill it to? Man I had fixed jet carbs! It makes no sense at all!

The coil is marked:
SEM
AM 44
809 204 16

Port timing is now:
Exhaust 95°
Transfers 113°
Intake 80°

I'll check the compression again after I get the carb fattened up and a little time on the rings.

 

[wigglesworth]

I'll check the compression again after I get the carb fattened up and a little time on the rings.

Can you tell a difference on the rope end?

 

[blsnelling]

The size of the jet is stamped right into the jet itself. My saw is fairly new and it had a 1.12mm jet in it. The non-epa saws sold in the ROW come with a larger 1.16mm jet. If I were only doing the coil change, I would have wanted this 1.16mm jet. Since I was going to open up the muffler a little as well, I decided to go a little larger. Warbo jets can be bought, but I didn't have one on hand (this was kind of something I just decided to sit down and do yesterday), so I reamed out my factory jet to about .0465", which is about 1.18mm.

I used the numbered bits as an index. I have had the reamers for years, sorry I have no idea where they came from as I bought them off a retired machinist. The jet as you know is brass and very soft. You can probably turn a 57 and 56 bit into the jet by hand (or with pliers) and not remove any excess material if you don't have reamers. Ive done this before with excellent results.

These are quotes from the "Basic 3120 Mods" thread. Some excellent info there.

 

[blsnelling]

Can you tell a difference on the rope end?

It was still only about 125 PSI hot. My experience has shown that it should be 135 cold. The cylinder is freshly honed, and the rings still have the factory ridges on the surface. So there's a fair amount of breakin that has to happen here. I would be tickled to end up with 140 PSI. If more is required, it'll take a popup piston to get there. I really think it's going to run fine though.

 

[wigglesworth]

That was probably the worst job i'd seen from a payed builder. That looked like crap. You cleaned it up nicely though. I hate going in behind somebody to fix crap.

 

[RRSsawshop]

Jeeze I've been here nearly that long and you have nearly 15000 posts! Impressive!
I must edit because my join date doesn't jive with my actual arrival. I was under another user name for a while.

I dont think he ever SLEEPS thats why he has so many...But he is one of the BEST guys on here...KEEP post'n Brad!!

 

[Wild Knight]

Let's see some video and cut times.

I like Levi's idea about putting a pipe on it. Could be a screamer...

 

[2000ssm6]

Please tell me it wasn't Ben.

 

[epicklein22]

Please tell me it wasn't Ben.

LOL

 

[blsnelling]

Thanks for filling us all in Dan. I knew you'd be around shortly to do so. There were several things stacked up against this saw.

1. It was ported, kind of
2. The ignition was advanced
3. It has an unlimited coil
4. It's running the stock 1.12mm jet!!!!!!!!!!! The carb was never fattened up. It was doomed to die.

I found a paper clip that measures 0.044" and it's a tight fit. That's the same as 1.12mm, so I know it had not been drilled. I'm going out today to find a 3/64" drill bit. That's the same as 1.20mm or 0.047" or a #56 drill. I'll give that a whirl and see how it does. With this carb not being adjustable, I've got to jet it a little on the fat side of perfect, since you can fatten it up when it needs it, like a dry cold winter day.