Dolmar 7900 carb tuning trick???

[mountainlake]

The L & H screws on the newer saw carbs are dependent on each other, if you adjust one it will effect the other.

Hi Frank.

The newest 7900's hit the limiter really fast, so I think the best way to correctly set the carb on a 7900 is while it's under load. Put a medium size bar on the saw, warm it up by making a few cuts in a good sized log, than that set the H dog rich. Now start making a cut without pushing down on the saw, as you're cutting slowly turn in the H speed screw until the saw just stops 4 stroking, or when it's bouncing back and forth between 4 and 2 stroking. The limiter tabs will need to be snipped off to do this.

Best of luck. Andy.

+1 Good way to tune any saw, in the cut when they pull the best. Steve

 

[blsnelling]

The newest 7900's hit the limiter really fast, so I think the best way to correctly set the carb on a 7900 is while it's under load. Put a medium size bar on the saw, warm it up by making a few cuts in a good sized log, than that set the H dog rich. Now start making a cut without pushing down on the saw, as you're cutting slowly turn in the H speed screw until the saw just stops 4 stroking, or when it's bouncing back and forth between 4 and 2 stroking. The limiter tabs will need to be snipped off to do this.

Best of luck. Andy.

Good advice there Andy. The only truely safe way to tune a saw with a limited coil.

 

[Maldeney]

Let me know when you wanna tune in the cut...(I will try not to burn this one up!)

 

[gink595]

Let me know when you wanna tune in the cut...(I will try not to burn this one up!)

LOL, Ahhh **** happens, junk big bore crap. BTW, were clearing fence rows so maybe after that we can get together and piss with the saws:greenchainsaw:

 

[gink595]

In your OP you say you can do 12.9k at part throttle.
Is it possible that you can't pull it down below limited RPM without taking the restraining cap off from the H screw?

Well I canned the limiter caps after the first try, thats what I was thinking also that it was restricting me from tuning it any farther. I will try some more. I just don't understand what could've changed, it went from screaming to blah... WTF! I just want my old Dolmar back

 

[cuttinscott]

If you can't get it figured out you can pack it up and send it to me I will fix it up N/C to you (warranty) all you have to do is pay shipping cost.



Scott

 

[blsnelling]

If you can't get it figured out you can pack it up and send it to me I will fix it up N/C to you (warranty) all you have to do is pay shipping cost.



Scott

And that my friend is what a good dealer is all about. Good on ya Scott.

 

[gink595]

If you can't get it figured out you can pack it up and send it to me I will fix it up N/C to you (warranty) all you have to do is pay shipping cost.



Scott

Wow!!!! What can I say that is generosity at it's finest, I just might have to take you up on that if I can't get it narrowed down...soon

 

[Andyshine77]

Here's a video I made yesterday of me tuning the carb on my ported 7900, it should give you guys an idea how to tune the saw while cutting. I think I've got her set spot on for a firewood saw with a 24" b&c, I would however run it richer if was running a longer bar. At times you can hear the saw hitting the rev limiter really hard, a stock 7900 won't do that as easily.

Don't I look cool wearing shorts and chainsaw chaps.

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[MCW]

If you can't get it figured out you can pack it up and send it to me I will fix it up N/C to you (warranty) all you have to do is pay shipping cost.



Scott

Would you like to open a Dolmar dealership in Australia?
Good stuff mate.

 

[Maldeney]

Here's a video I made yesterday of me tuning the carb on my ported 7900, it should give you guys an idea how to tune the saw while cutting. I think I've got her set spot on for a firewood saw with a 24" b&c, I would however run it richer if was running a longer bar. At times you can hear the saw hitting the rev limiter really hard, a stock 7900 won't do that as easily.

Don't I look cool wearing shorts and chainsaw chaps.

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Nice! (Shorts that is!) Very good example, now hopefully Ginks can run the same.

 

[Maldeney]

Here's a video I made yesterday of me tuning the carb on my ported 7900, it should give you guys an idea how to tune the saw while cutting. I think I've got her set spot on for a firewood saw with a 24" b&c, I would however run it richer if was running a longer bar. At times you can hear the saw hitting the rev limiter really hard, a stock 7900 won't do that as easily.

Don't I look cool wearing shorts and chainsaw chaps.

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Nice!.... Shorts that is!

Good example, hopefully Ginks will come back around now as well.

 

[scotclayshooter]

The tach is a DTI-20K.

That tach works fine with my 7900.
Mine was way rich when it arrived and would only pull 12,200rpm.

 

[Andyshine77]

I think this clip is better than the one I posted before, as you can clearly hear the saw lean out and hit it's sweet spot.

Andy.

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[Fl_Airboater]

Thanks for puttin those videos up. I'll use them as guide to tune mine.

 

[CHEVYTOWN13]

my ported 7900

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I have no idea how I missed this thread. I was doing some research on unlimited coils and came across this thread.

Andy, you have that 7900 snapping real nice in 4 stroke mode.

 

[CHEVYTOWN13]

I think this clip is better than the one I posted before, as you can clearly hear the saw lean out and hit it's sweet spot.

Andy.

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That's what I'm talking bout

 

[Andyshine77]

In the first video it was actually hitting the rev limiter in the cut. The second video is the better of the two because you're hearing the 4 stroke sound and not the limiter kicking in/out.

 

[gink595]

Very good video Andy, I actually went back out and fiddled some more with it. It's tricky for sure but I have made some progress tuning in the cut. I'm still not 100% happy with it, still not the same saw. Now back to the log

 

[CHEVYTOWN13]

second video is the better

I dig the way you started the cut and then stopped to get ready for adjustment. It also gave stability to the saw for a safe tune in the cut.