MillerModSaws and the PS-7910

Arborist Forum

Help Support Arborist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
With the tight crankcase volume would raising the upper transfers higher than 129 be beneficial or not?
Unless it runs out of go go. On the second saw I will most likely go 2 degrees higher so it will have 25° blowdown. If it goes backwards I will raise the exhaust to 100 to get my blowdown back.
 
Unless it runs out of go go. On the second saw I will most likely go 2 degrees higher so it will have 25° blowdown. If it goes backwards I will raise the exhaust to 100 to get my blowdown back.
Blowdown and degrees of crank case compression are important on these saws.. But so much is still unknown on them... Even saw builders who are well versed are confounded by them.. They run very well in stock form, and are very tough to improve on..

Those folks at Dolmar sure didn't leave us any low hanging fruit!!
 
Blowdown and degrees of crank case compression are important on these saws.. But so much is still unknown on them... Even saw builders who are well versed are confounded by them.. They run very well in stock form, and are very tough to improve on..

Those folks at Dolmar sure didn't leave us any low hanging fruit!!
I agree. If u notice I havnt faired to far off a 7900s numbers. This saw may be a real good canidate for the epoxied intake due to its need for cranckcase pressure. Also Andyshine has give me a couple helpful warnings on this saw.
 
I agree. If u notice I havnt faired to far off a 7900s numbers. This saw may be a real good canidate for the epoxied intake due to its need for cranckcase pressure. Also Andyshine has give me a couple helpful warnings on this saw.
Andy is as crazy as a shithouse rat...
Gotta watch that guy...
 
Why does this particular saw require so much more blowdown than another similarly designed quad port like a Husky?

My blowdown on a Stihl is 16-18*. What's the reason for the vast difference?
 
Why does this particular saw require so much more blowdown than another similarly designed quad port like a Husky?

My blowdown on a Stihl is 16-18*. What's the reason for the vast difference?
Some say Stihl transfers are a bit lazy and require more time open..
A head start you could say..
But that varies from model to model..
 
Blowdown and degrees of crank case compression are important on these saws.. But so much is still unknown on them... Even saw builders who are well versed are confounded by them.. They run very well in stock form, and are very tough to improve on..

Those folks at Dolmar sure didn't leave us any low hanging fruit!!
Your red one has 30° of blowdown. if I remember right it has 45° of crankcase compression.
 
In my limited experience with these, they need LOTS of blowdown. And, simply raising the exhaust up to remedy transfers that were raised too much, doesn't work that well.

What's the stock exhaust port timing on a 7900?
 
In my limited experience with these, they need LOTS of blowdown. And, simply raising the exhaust up to remedy transfers that were raised too much, doesn't work that well.

What's the stock exhaust port timing on a 7900?

I agree, it doesn't.

The transfers will still be too high..
 
In my limited experience with these, they need LOTS of blowdown. And, simply raising the exhaust up to remedy transfers that were raised too much, doesn't work that well.

What's the stock exhaust port timing on a 7900?
I'll agree to however. In building these I want to try a 100 degree exhaust height. See how that works. So I would be at 100/127 if I tried that. Stock exhaust height from what I've read is 105 on the 7900 with 27 blowdown.
 

Latest posts

Back
Top