Modding a 7900

[manual]

Not wanting to throw you guys off your current path.. but... topic shift..


It's been said the limiter on coils is an "EPA thing". Not so sure... When a coil limits, it (the saw, not the coil) REALLY dumps unburnt hydrocarbons out... Spark skipping...

I think it's a design issue - make light components then make sure they don't do around too fast (I'm keeping it simple...)opcorn:

I'll go with you on that, However it would be interesting what the internal parts weight on the 575 vrs 372.

 

[04ultra]

I'll go with you on that, However it would be interesting what the internal parts weight on the 575 vrs 372.

Manual you buy the saws I'll take them apart and weigh each part and give you a full report....






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[manual]

I agree with the troublemaker part........But more are involved in the other part..


interesting part is there not all the for the same brand...





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Maybe the bylaws don't specify what you have to own.opcorn:

 

[04ultra]

Maybe the bylaws don't specify what you have to own.opcorn:

Did you look in your copy????? I thought you wrote it..... opcorn: opcorn:




.

 

[manual]

Manual you buy the saws I'll take them apart and weigh each part and give you a full report....






.

Ok I'll get right on that..........Not........I can only afford what I use.

 

[manual]

Did you look in your copy????? I thought you wrote it..... opcorn: opcorn:




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Nope can't spell.:rockn:

 

[sawinredneck]

Ok I'll get right on that..........Not........I can only afford what I use.

He'll be gentle and put them back to working order?

 

[manual]

He'll be gentle and put them back to working order?

Oh yea,:hmm3grin2orange: Are you going to help. Hmmm, What parts are you looking for ?

 

[drmiller100]

Nope - I'll stick with mine...

interesting.

on rotating mass, it is a lot easier to make ti heavier then lghter. But, on crankshsafts, rods, and pistons, you are RPM limited by weight.

So, if you go cheap, you went heavy.

If you made it lighter, you could run more rpm.

 

[sawinredneck]

Oh yea,:hmm3grin2orange: Are you going to help. Hmmm, What parts are you looking for ?

Hell no, I can't afford another saw right now, much less the impending D_I_V_O_R_C_E that would follow!!!!!!
Andy

 

[manual]

actually, what i posted was to ask if reading the wash on the piston wasn't a valid way to verify jetting.

I never got an answer. Search didn't help.

What could be simpler then to jet by ear under load, then pop the plug and verify?????

you guys DO know how to read wash, right??????

OK, wash would be the amount of fuel left in the cylinder after fire.
like being to rich.

 

[manual]

interesting.

on rotating mass, it is a lot easier to make ti heavier then lghter. But, on crankshsafts, rods, and pistons, you are RPM limited by weight.

So, if you go cheap, you went heavy.

If you made it lighter, you could run more rpm.

casting can be made lighter, like rods, fly wheels and you could cut cost

 

[drmiller100]

OK, wash would be the amount of fuel left in the cylinder after fire.
like being to rich.

hmmmm. Well, Nope.

Take a happy running saw. Run it full chat at a 40 inch log for 30 seconds and hit the kill switch.
Remove the jug for simplicity.

on the intake side of the top of the piston, there will be clean spots where the fuel has WASHED away the carbon off the top of teh piston. If it is too rich, the areas with no carbon will be huge. If it is too lean, the entire piston will be covered with carbon.

If it is even leaner, the carbon will get burned away.

leaner yet, and the piston will melt.

on my 7900, it had aeras the size of my little pinky with no carbon.

race gas and av gas takes longer to build carbon, as does synthetic oil.

 

[drmiller100]

casting can be made lighter, like rods, fly wheels and you could cut cost

if you make them lighter,then you must make them out of much better materials, or they will be weaker and break.

 

[sawinredneck]

Ok I'll get right on that..........Not........I can only afford what I use.

Do you have any idea how much azz I had to kiss to mod the 346 on the kitchen table!!!!!!!!!!:jawdrop:
Andy

 

[Freakingstang]

Thats because nobody made a thread on splatter shield. LOL
Hey freak go to farm and fleet and pick up a can of splatter shield,
spray it on and around the area you are going to weld so the spatter don't stick.




Atleast thats what the pros do. LOL

Sorry, NOT A PRO WELDER. lol.

Not a pro Anything. Thanks

 

[blis]

interesting.

on rotating mass, it is a lot easier to make ti heavier then lghter. But, on crankshsafts, rods, and pistons, you are RPM limited by weight.

So, if you go cheap, you went heavy.

If you made it lighter, you could run more rpm.

actually, its not the weight of rotation components that set the max. safe rpm, its the piston speed that affects it. Therefore, engine with shorter stroke will and can run in higher rpm than a engine with longer stroke... the safe limit of piston speed is around 20m/s in motorcycle and i believe its bit higher in chainsaws (smaller rotating masses)...

 

[Urbicide]

Do you have any idea how much azz I had to kiss to mod the 346 on the kitchen table!!!!!!!!!!:jawdrop:
Andy

How much Andy?

 

[manual]

Sorry, NOT A PRO WELDER. lol.

Not a pro Anything. Thanks

Homie

 

[drmiller100]

actually, its not the weight of rotation components that set the max. safe rpm, its the piston speed that affects it.

...... i believe its bit higher in chainsaws (smaller rotating masses)...

ummmm, i think you ended up making my point...........

the lighter the piston and rod, the faster you can sing them up.

To make them lighter costs money. go price a titanium rod for a saw.