7900 is running 13,520 rpm...that ok?

[robby26wi]

Just got a new (really good) pulse tach and i picked up the 7900 and got it good and warm and pinned it till max rpm and it was 13,520...is that ok? i have heard to run a bit under there reccomended but who knows...

 

[rahtreelimbs]

The 7900 is rev-lilited at 13'500 I believe. Since this is a new saw I would back it down to around 13,000 rpm and go from there. I set my 7900's at 13,300.......just shy of the limit!!!

 

[robby26wi]

ok will do...prolly 1/8 turn or so i would guess...

 

[Lakeside53]

Be careful.. chasing rpm on a rev limited saw is a good way to mess it up... The 13530 is basically the same 13,500.. the ignition doesn't have a real time clock so it's just guessing.... and "limiting" will be plus or minus a few hundred rpm at best.

Exactly how does Dolmar say to set the max rpm?

I suspect it's working just fine as is.. as for guessing at 1/8? might be a 1/32... and it will be different tomorrow, so why...

 

[robby26wi]

It sounds pretty snappy right now so maybe i should fatten it up a bit anyways...

 

[Lakeside53]

Can't hurt, but if you wanted a less powerful saw you could have bought a smaller one

Seriously... look at the Dolmar recommended procedure for tuning a rev limited saw.

 

[robby26wi]

dont really want a less powerful saw...Just want a happy saw and lean isnt happy...Its just snappy till it goes tight lol...

 

[Lakeside53]

well.... the "right" lean is a happy saw...

 

[robby26wi]

true....

 

[Cut4fun]

if you are setting with a tach and you hit the rev-limiter it will start jumping around on the tach, mine drops to 12,700 and back and forth when hitting the limiter. Once you have it set a tad under limiter you will see a steady reading on the tach. I have to re-adjust for major weather changes too.

 

[Lakeside53]

if you are setting with a tach and you hit the rev-limiter it will start jumping around on the tach, mine drops to 12,700 and back and forth when hitting the limiter. Once you have it set a tad under limiter you will see a steady reading on the tach. I have to re-adjust for major weather changes too.

If you really have to adjust it for weather, you are probaly too close for comfort then.. Unless it's just bouncing off the limiter which might not be an issue for mixture anyhow - just the tach..

How does Dolmar say to adjust the H mixture?

 

[grandpatractor]

I set my 2171 by tuning to just under the rev limiter and then til it just (bounces) off of it. I couldn't get my 7900 to quit hitting the rev limiter. had the screw against the stop tab. I might have to trim it. The book doesn't give a very good procedure for setting it. How do the rest tune a rev limit saw:monkey:

 

[Cut4fun]

I try to keep mine between 13,300-13,400. a major weather change from lets say 75* to 30* and back again. I want all she has to give and then some.

 

[stihl 440]

rpm

I would say 13,530 is fine for it. A little lean won't hurt it. I run my 440 and 460 at 13,900. A couple other guys on here do it too, you get more performance. Just don't be pegging it no-load WOT all the time, just like any other saw.:hmm3grin2orange: :biggrinbounce2:

 

[rahtreelimbs]

I would say 13,530 is fine for it. A little lean won't hurt it. I run my 440 and 460 at 13,900. A couple other guys on here do it too, you get more performance. Just don't be pegging it no-load WOT all the time, just like any other saw.:hmm3grin2orange: :biggrinbounce2:

The problem there is you can be WAY lean and the tach will still read 13,520 as it is right up against the limiter. Better to be on the safe side and set it at 13,300. A little rich is far better than a little lean!!!

 

[MAG58]

The problem there is you can be WAY lean and the tach will still read 13,520 as it is right up against the limiter. Better to be on the safe side and set it at 13,300. A little rich is far better than a little lean!!!

+1

 

[stihl 440]

tach

The problem there is you can be WAY lean and the tach will still read 13,520 as it is right up against the limiter. Better to be on the safe side and set it at 13,300. A little rich is far better than a little lean!!!

I know what you're saying, but my tach reads 13,900 while WOT no-load B&C on. Which is probably what you meant. I don't know if dolmars are any different than stihls (on tuning) or not but.....:hmm3grin2orange: :biggrinbounce2:

 

[Lakeside53]

The problem there is you can be WAY lean and the tach will still read 13,520 as it is right up against the limiter. Better to be on the safe side and set it at 13,300. A little rich is far better than a little lean!!!

Yes... but also at limit the tach may read a LOT lower than reality as the way it limits is to skip sparks... and you're counting those left...

 

[Lakeside53]

I know what you're saying, but my tach reads 13,900 while WOT no-load B&C on. Which is probably what you meant. I don't know if dolmars are any different than stihls (on tuning) or not but.....:hmm3grin2orange: :biggrinbounce2:

Modern Stihls (other then the 880) aren't rev limited. The tuning is completely different with a rev limited engine.