3120xp - 50in bar - skip chain?

[mdavlee]

These have a passage to connect the H and L if I remember right.

 

[Hedgerow]

These have a passage to connect the H and L if I remember right.

I've not been into one...
I just know fixed jets make my ass pucker...:msp_scared:
They can and do work, but not having control of such a high dollar saw...
Well???
:msp_scared:

 

[mdavlee]

I think they do it hoping no one will lean seize one. It is a bad design but I guess they think that's the best. I guess autotune on it would be better than that.

 

[excess650]

The first year or so of 3120s in the USA had fully adjustable carbs. Mine is a '94 model with 12K coil and no H adjustment, and it seems fine at less than 1000' elevation. It came through with a 30" .404 full comp B&C, but is being swapped out for a 42" 3/8 .063 for more use on my mill.

 

[Alex D]

A business down the street from me just had a 14 foot bar made for a 3120 to buck old growth redwood stumps. Can't wait to post pics. They said it took a few minutes for the chain and bar to break in then it cut good.

Are they running two powerheads on that bar?? As if i ain t mistaken on a signle powerhead the biggest bars they run in the PNW for the giant OG was 10 or 12 foot and thats on the huge OG. A 7 foot bar is extremely unweildly i cant imagine 14 the sag would be huge.

 

[zogger]

A business down the street from me just had a 14 foot bar made for a 3120 to buck old growth redwood stumps. Can't wait to post pics. They said it took a few minutes for the chain and bar to break in then it cut good.

I want to see that! Plus the guy running it!

 

[Redoakranch]

They ran it with one power head and a cheesy helper handle. They are going to fab a new helper handle. They are going back to the 7' bar until it's done. I told them I HAVE to see it the next time they run it. That redwood is really soft...

 

[zogger]

If you have a saw with a fixed high jet, it would not be wise to run more oil in the mix than what the jet is sized for... If it's meant for 50:1, running 25:1 will make it run lean...
Not a good scenario... On an adjustable carb, no sweat, but if not, beware...:msp_mellow:

Its the same volume of mix per air volume going in. Normally we think of lean meaning less mix, more air. In this instance, it is the same, just more oil, less gas, with the same air volume. Exact same ratio of mix to air. I cant see this being called lean, I think better just call it richer in oil.

With the same exact carb settings, have you ever seen a saw run hotter with 25 to 1 versus 50 to 1? Or lean seize running that ratio, given an appropriate carb setting?

I am just asking, I dont know, I have just read that description here before with higher oil ratios being lean..aint seeing it, you havent changed the air volume.

I dont know where semantics leaves the engineering here.

Way back we were running dino oil at 16 to 1, (or the heavy glug glug glug measuring method...) why no lean seizes then? It was smoky and stinky, but no lean seizes if it was adjusted correctly.

I dont have enough experience with modern saws running different oil ratios. Just wondering is all. Be interesting with a infrared thermometer reader toolm whatever those things are, I dont have one..

 

[Hedgerow]

Its the same volume of mix per air volume going in. Normally we think of lean meaning less mix, more air. In this instance, it is the same, just more oil, less gas, with the same air volume. Exact same ratio of mix to air. I cant see this being called lean, I think better just call it richer in oil.

With the same exact carb settings, have you ever seen a saw run hotter with 25 to 1 versus 50 to 1? Or lean seize running that ratio, given an appropriate carb setting?

I am just asking, I dont know, I have just read that description here before with higher oil ratios being lean..aint seeing it, you havent changed the air volume.

I dont know where semantics leaves the engineering here.

Way back we were running dino oil at 16 to 1, (or the heavy glug glug glug measuring method...) why no lean seizes then? It was smoky and stinky, but no lean seizes if it was adjusted correctly.

I dont have enough experience with modern saws running different oil ratios. Just wondering is all. Be interesting with a infrared thermometer reader toolm whatever those things are, I dont have one..

Oil does not flow through the same size hole at the same rate as gasoline... When the oil ratio is raised, your liquid to air ratio is cut, you get a lean condition... Remember, the fuel mixture doesn't just lubricate, it cools...
Lower the ammt of liquid, and cooling is reduced... "lean condition" and aluminum transfer can happen due to temps... Old saws ran fine at 14:1... Because that's what they were jetted for. Mix em a batch of 50:1, and see what happens without the ability to lean out the high screw...
Fat as hell...

 

[2dogs]

This might help.

Fuel for Pro Saws

 

[zogger]

Oil does not flow through the same size hole at the same rate as gasoline... When the oil ratio is raised, your liquid to air ratio is cut, you get a lean condition... Remember, the fuel mixture doesn't just lubricate, it cools...
Lower the ammt of liquid, and cooling is reduced... "lean condition" and aluminum transfer can happen due to temps... Old saws ran fine at 14:1... Because that's what they were jetted for. Mix em a batch of 50:1, and see what happens without the ability to lean out the high screw...
Fat as hell...

Yes, but I think oil lubricates and cools as well. Lubrication is the oils job ater all. Not sure on the jetting and the flow, I imagine modern synthetics break down into rather small micrdroplets compared to old dino oil. Dont know if there is all that much difference in most newer saws where it would kill the saws shortly to run it oil rich. Maybe carbonization?? dont know how far you could push it.

With that said, I ran 50 to one for a long time, but 40 seems to work better, but I dont have anything to back that up accept what it feels like to me and how the saws run. I switched in that nasty heat wave last summer. I have read here some guys are running 32:1 in all their saws all the time, apparently without troubles. 25 to 1, dont know.

Id really like to see a proper test with some numbers. I have an old whatever kicking around, Ill do a small test tank at 25 to 1 sometime, if it seizes up, Ill post pics.

 

[tlandrum]

i had a fixed jet 3120 that had a great big sticker on it from the factory that said 25:1. yes it was a fixed jet saw. i happen to be one of the guys that can do an adjustable carb for the 3120 so i just fixed that little problem and continued on with my day. anyone needing a high speed screw put it to a non adjustable wg give me a shout.

 

[marti384]

i had a fixed jet 3120 that had a great big sticker on it from the factory that said 25:1. yes it was a fixed jet saw. i happen to be one of the guys that can do an adjustable carb for the 3120 so i just fixed that little problem and continued on with my day. anyone needing a high speed screw put it to a non adjustable wg give me a shout.

I have a fixed jet 3120 also, with the sticker that says 25:1. I have been running about 40:1 in it without problems. I would be interested in having it made fully adjustable. Is this something you could do a thread on how to do, or is it a service you provide? How much? I think I saw another person post that it isn't too hard to do, but they didn't give any explanation or instructions.

 

[Hedgerow]

Yes, but I think oil lubricates and cools as well. Lubrication is the oils job ater all. Not sure on the jetting and the flow, I imagine modern synthetics break down into rather small micrdroplets compared to old dino oil. Dont know if there is all that much difference in most newer saws where it would kill the saws shortly to run it oil rich. Maybe carbonization?? dont know how far you could push it.

With that said, I ran 50 to one for a long time, but 40 seems to work better, but I dont have anything to back that up accept what it feels like to me and how the saws run. I switched in that nasty heat wave last summer. I have read here some guys are running 32:1 in all their saws all the time, apparently without troubles. 25 to 1, dont know.

Id really like to see a proper test with some numbers. I have an old whatever kicking around, Ill do a small test tank at 25 to 1 sometime, if it seizes up, Ill post pics.

I guess, by this reply, I have utterly failed to convey this concept...
Yes, you can run 25:1 in a 50:1 saw and the other way around too...
As long as the saws carb can be tuned...
With a fixed jet carb, ya can't tune the high side...
The problem lyes with a fixed jet carb that's jetted for 40:1 or 50:1 and someone tries to be "helpful", and mixes their fuel at 25:1... Fuel is more viscous, therefore, will not flow as much through jet orifice, creating a lean condition...
Too lean???
Well??? That depends on how rich the saw was at with 50:1...
Sorry zog... I know I'm terrible at explaining stuff..

 

[nstueve]

Sorry zog... I know I'm terrible at explaining stuff..

nah... I got your point the first time. Sounds like the fix lies with tlandrum and fixing the "H" jet...

 

[Hedgerow]

nah... I got your point the first time. Sounds like the fix lies with tlandrum and fixing the "H" jet...

Yes, it can be overcome...:msp_wink:

 

[tlandrum]

I have a fixed jet 3120 also, with the sticker that says 25:1. I have been running about 40:1 in it without problems. I would be interested in having it made fully adjustable. Is this something you could do a thread on how to do, or is it a service you provide? How much? I think I saw another person post that it isn't too hard to do, but they didn't give any explanation or instructions.

i can and do provide the service of adding the high speed screw.