Carb. adjustment

[Qatanlison]

Russ,

I think it was some article on forestapps that said the max rpms is without bar and chain - but I might have misunderstood -
Never the less, very interesting stuff from you all! Thanks!

Ola

 

[jokers]

Ola,

Now that you referenced that concept to Forrest Apps I think I recall seeing that in their last news letter. I still don`t agree with it though based on the other info I`ve got.

Russ

 

[cbfarmall]

I know Madsen's tuning section lists max RPMs for a few pro saws, and they erroneously state that these are with NO bar and chain installed. That may have been what you read. Threw me for a brief curve but I know better than to tune a saw without a B/C.

Chris B.

 

[bwalker]

Taching a saw without a bar and chain will result in a leaner hs screw setting vs taching with a bar and chain.

 

[mboln52000]

Originally posted by jokers
Ola,


Another thing that I can say is that a spec of 13,500rpm is a no load spec, ie: the saw is not expected to pull that in the cut with the porting that they leave the factory with. Max power is generally between 9,000-9,500 rpm and if your stock saw is pulling 13k in the cut, you need to lower your rakers or sharpen your chain, or both. BTW, this bit of wisdom is for mboln.

Russ

Why would i want to lower the rakers, or sharpen the chain???It is cutting like a mad...throwing chips a mile! I really dont think its possible for it to cut much faster. It is ported/polished, and muffler modded. It took me a few years to get the sharpening down, but i have it.

Thanks for the wisdom, and no disrespect, but pass it on to a newbie.

In my area, the local dealer services factory saws. If somebody is in, and wanting it faster, he sends them my way.

 

[Crofter]

"True, i should have put a statement in there, and your right, it isnt for everybody. If you get it a little too lean, you will score the cylinder, and probably wipe out the big and small end bearings too.

My set-up is not factory recomended, and it will void any and all warranties.

I only run that way because it really doesnt bother me if I trash a cylinder or bearing. I wrench for fun, its an outlet, a hobby. I have been doing small engines, or just plain engines for around 20 years now, and i pretty much know what i am doing." By Mbolyn


Mbolyn; You say the saw is ported and polished. Have you changed port timing or is it still Factory timing. If it is indeed changed, you could be running it at a higher rpm without it indicating lean mixture, but if you are simply gaining higher rpm operation by running lean mixture you are using up the safety margin. It seems you encourage people who are naturally interested in having a faster saw to achieve it by running a lean mixture.

Frank

 

[jokers]

Hi mboln,

I didn`t recall reading anything in any of your posts indicating that you were modifying your saws, hence this part of my statement,

"Another thing that I can say is that a spec of 13,500rpm is a no load spec, ie: the saw is not expected to pull that in the cut WITH THE PORTING THEY LEAVE THE FACTORY WITH. Max power is generally between 9,000-9,500 rpm and if your STOCK saw is pulling 13k in the cut,..."


So if you`re modifying those saws and getting those returns, more power to ya! (Pun intended). I do think that my comments are relavent to this topic so that a newbie does not expect to pull those speeds with a stock saw and if they do, they should know what to look for.

Russ

 

[mboln52000]

True Russ, I should have put a discplaimer on my first post. Yes it would a little scary for a newbie to tune it this way, leading to a very expensive lesson.

On the bright side...that would be one more saw i could pick up from the dealer needing a rebuild!

I need to work on the wording of my posts a little bit. I think I lleave a lot of people wondering

 

[mboln52000]

wow, the picture worked...How cool!

 

[046]

Originally posted by mboln52000
It is ported/polished, and muffler modded.

mboln, my 024 needs new piston/cylinder anyways. So I figure while I'm there, might as well port and polish.

I've polished and matched up the exhaust port on my 024. It's amazing how far off the stock setup is.

Polishing is fairly straight forward, but how much did you change the ports? Which direction did you enlarge and what was the effect on timing.

Did you increase the compression by using a thinner gastket?

13,500 in the cut is blasting...

 

[mboln52000]

046,
Changing the cyl base gasket from the .031 thk paper to the manilla paper makes a small, but i think noticible change in compression. Plus, thats a good mod to make if you are changing cylinder/piston anyway.

I have heard of people polishing both mating surfaces, and using a "dead" fit, but the manilla paper is only .005 thk, so its easier for me to run with that.

Merc Marine and Bombadier use it all the times, so its okay stuff.

Your totally right on the exhaust port and gasket, they can be pretty far off, so alittle time with a die grinder there is well spent, plus smoothing it out helps it flow a little better too.

Now, the intake. Depends on the saw,, but most can benifet tons just by checking all the intake ports and cleaning them all out. I have seen many with alot of molding flash, and sharp edges left in them. Just smoothing all those out will make 'er breath a lot better.

If you do these mods above, and open up that muffler, you will really bring that 024 to life! I have a 024 too, and it needs exactly the same thing. A dealer had it, with a bad piston, and slightly scratched cylinder. they tried to hone it,(bad plan) and it held for a while, but its getting replaced with a new piston and cyl before next season.


As far as changing port timing, thats pretty much for competition, and i dont go there...not much of that here in IN. I have some ideas there, but i havent unleashed them yet. But maybe, by the summers end, I may have taken the die grinder and either successfully modded the port timing, or trashed a cylinder and piston!

And now for the disclaimer, I gotta add it!

DISCLAIMER:
My 13,500 in the cut is a freakin blast but....I have only ran it for one season, 50 or so tanks of gas, so its still unproven and could result in a trashed saw!

 

[rahtreelimbs]

Mboln,

I can't see a saw running that lean to have enough fuel to make power.

I'm glad you think that carb tuning method works for you.

But count me out.

I won't risk that method on $900 worth of modified saw!

 

[046]

mboln, thanks for the tips on tuning my 024. What you described is what I normally do when ever I'm into something.

If I'm there there is no reason to leave casting marks, mismatched ports or any other minor obstructions to flow.

I've got several solid carbide bits just for polishing ports.

I wonder what tuners like Dozer Dan do on changing the timing via port changes?

I really don't want something too radical. I want a reliable saw with high output. Thanks,

 

[tony marks]

from u list o saws .. it sounds like u gottum already..

 

[046]

Thanks tonyM, I pretty satisfied with my humble collection.

Except for modding the mufflers and matching up the exhaust ports. I'm not tearing down my saws just to polish the ports.

My 024's piston is scored as viewed thru the exhaust port. It's running fine for now. but I figure soon, it's either rebuilt my 024 or get a new 026/260. Thanks,

 

[PetrolHead]

Tuning methods seem to be as wide a subject as fuel/oil mix.
I don't think any method is 100% because lets face it, you may tune your saw today and check it again tomorrow with a different result. The variables could be anything from different ambient temp to the fact that you may have tensioned your chain differently from the last test.
Have you ever noticed at WOT with a tach that the rpm can change as much as 2-300rpm if your game enough to hold it long enough?? Theres another variable in itself.
I remember in the good old days we used to check spark plug colour just for a very rough indication but I've noticed with the lean oil mix and unleaded fuel that this no longer seems to be an indication at all if your already somewhere near the mark (they seem to burn very clean nowdays).
I find with my saw that adjusting just into the rough is above max which I don't think means bugger all really, I usually tune by ear till it's there then go another 1/8 turn or so just to err on the safe side. Tach says pretty close mate after a 5 second burst or so.
I think thats why all these different methods mentioned here work, because they all mostly have the same outcome, the saw ends up somewhere near the intended carb setting.
Just my 2 cents worth.