Mastermind
Work Saw Specialist
Ya'll need to cool it with the BS!!! How you gonna make a two-stroker four-stroke???? :msp_sneaky:
Checking your tune in the wood
- Thread starter blsnelling
- Start date
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Put in high performance cams. Duh! :msp_thumbsup:
J.W Younger
ass kissing impaired
You'll just have to overlook us moobs, we've inhaled too much 2-stroke exhaust...
Eccentric
Mister Wizard
It loads up and doesn't always fire every revolution.......duh...
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Either that or you can lube the muffler bearings.:jester:
Stihlman441
Addicted to ArboristSite
This is a Snellerized 660 ported pop up and so on,and tuned to 13900 w/o and in the vid you will hear it still 4 strokes when the load is taken off.With stock saws tune them to what ever is recomended and the play in the cut,there is nothing wrong with being a little rich with a work saw infact i found it the way to get the best torque out of them.Check out the sap pockets in this wood its a pain in the a_ss this Stringybark,very thick bark that seam to grip ya chain and slows ya down and the white ants love it drowing up sand and rubbish to stuff ya chain,at the end i show one of those Works Tachs.
[video=youtube;Ums0wyb8eOE]http://www.youtube.com/watch?v=Ums0wyb8eOE[/video]
[video=youtube;Ums0wyb8eOE]http://www.youtube.com/watch?v=Ums0wyb8eOE[/video]
MCW
Somebody's talking crap here & it ain't the tree!
Actually if you'd have read my post properly (quoted below), you'll notice that I said "11-12k rpm in the cut (maybe less)". I also stated that my modified 7900's sit on around 12,000rpm in reasonable wood but this does vary a bit and certainly no higher than 12,000rpm.
In the context of the original poster he was asking about 4 stroking in the cut or if it's hitting the limiter. If you can hit a 13,500rpm limiter in the cut on a 7900 I want one
My main point originally being that you won't hit the limiter in the cut with a stock 7900.By the way I wasn't misleading at all - I've seen rpm's like that in an actual cut, on an actual stock 7900, with an actual tacho. These were with a 20" bar, semi chisel chain, and a 7 pin rim in Casuarinas. DISCLAIMER: Results may vary from user to user.
I can assure you 10,000rpm IS NOT too high. When my stock 7900 was running even a 32" bar it would just hold over 10,000rpm in the cut - dropping it below that would result in far more stalling, regardless of what the factory torque figures may suggest. I wasn't leaning into it as this simply slowed it down too much. I'm not trying to be a smartarse or stir up a hornet's nest but how many stock 7900's have you run and checked with a tacho? I didn't do it for fun, I did it because I was interested in what the saws were doing in the cut.
If I had a stock top end on hand for my 7900 I'd fit it this weekend and do a few videos, but then I'd probably be accused of doctoring the results. I've spent far too much time on 7900's in actual work conditions to not know what rpm they cut most efficiently at - I don't think I could ever be accused of having poorly cutting 7900's. If somebody else here would like to do some vids on a 7900 or have some input please do.
I can see where you're coming from Steve in regard to peak HP and torque, I used to have a lot to do with modded cars, but it's not always as simple as the figures would suggest. Apart from some facts and figures I'd like to know where else your facts on the 7900's are being gathered from? I don't claim to be a guru on any saw but if it's one saw I know a lot about it's the 7900's.
NORMZILLA44
Addicted to ArboristSite
Good stuff Matt! I learne'd something new from ya tuning in the cut. I like it make's sense. Alot of people don't understand a two cycle torqe curve. It is not like a 4 stroke low to mid range. Two cycle has to get to high speed reach a certain speed to get it. Shiat seen your'e stuff your'e a cutter, and walk the walk. I'll vouch for ye!
MCW
Somebody's talking crap here & it ain't the tree!
Hi Norm. I don't want it to look like I'm a know all or being a smart arse but coming from a completely mathematical standpoint like Steve above I can certainly see why he'd think that the 7900 will cut faster at it's peak torque and HP rpm rating. Unfortunately that hasn't been the case and if I hadn't done so much cutting with a 7900 and played around with tachos, rpms, sprockets, chains, tuning etc etc what he's said does make sense from a technical standpoint. From a practical standpoint however it is not the case at all.
To have a slower chain speed yet cut faster on the same saw a couple of factors have to come into play for that to happen. You either set your chain up very aggressively where you'll need very good torque to pull it or you lean on the saw harder, also needing very good torque to offset the extra friction. Neither are good from a cutting speed standpoint, even less so with a stock saw.
Just watched some of Brads vids on youtube, I'll keep running my 7900 loading the engine in the middle , not too many RPM's and not to few. Steve
MCW
Somebody's talking crap here & it ain't the tree!
Hey I agree Steve. I just think we have a different opinion of where the middle is. Not a biggy mate and certainly not worth arguing over. If we all agreed 100% of the time AS would be pretty boring. By the way Brad's vids on Youtube involving a 7900, 7901, 390XP, and a couple of MS660's were possibly my saws he built for me.
deye223
Addicted to ArboristSite
Actually if you'd have read my post properly (quoted below), you'll notice that I said "11-12k rpm in the cut (maybe less)". I also stated that my modified 7900's sit on around 12,000rpm in reasonable wood but this does vary a bit and certainly no higher than 12,000rpm.
In the context of the original poster he was asking about 4 stroking in the cut or if it's hitting the limiter. If you can hit a 13,500rpm limiter in the cut on a 7900 I want one
By the way I wasn't misleading at all - I've seen rpm's like that in an actual cut, on an actual stock 7900, with an actual tacho. These were with a 20" bar, semi chisel chain, and a 7 pin rim in Casuarinas. DISCLAIMER: Results may vary from user to user.
I can assure you 10,000rpm IS NOT too high. When my stock 7900 was running even a 32" bar it would just hold over 10,000rpm in the cut - dropping it below that would result in far more stalling, regardless of what the factory torque figures may suggest. I wasn't leaning into it as this simply slowed it down too much. I'm not trying to be a smartarse or stir up a hornet's nest but how many stock 7900's have you run and checked with a tacho? I didn't do it for fun, I did it because I was interested in what the saws were doing in the cut.
If I had a stock top end on hand for my 7900 I'd fit it this weekend and do a few videos, but then I'd probably be accused of doctoring the results. I've spent far too much time on 7900's in actual work conditions to not know what rpm they cut most efficiently at - I don't think I could ever be accused of having poorly cutting 7900's. If somebody else here would like to do some vids on a 7900 or have some input please do.
I can see where you're coming from Steve in regard to peak HP and torque, I used to have a lot to do with modded cars, but it's not always as simple as the figures would suggest. Apart from some facts and figures I'd like to know where else your facts on the 7900's are being gathered from? I don't claim to be a guru on any saw but if it's one saw I know a lot about it's the 7900's.
your to polite
More than can be said for you. Steve
NORMZILLA44
Addicted to ArboristSite
Good deal Matt, I guess with some it is a personal preference. Around here the normal has been either tune it until it four stroke's, or the guy's that just run them lean the pro's I know who crank em up, and real lean they sing chain speed like a sum biatch. No good on the stump. Gotta hand it to the 660 to take that abuse, leane'd out, leane'd on abuse'd, and they get 6 months out of em in the wood's, before they start to slow down. Then they get a new saw, the old one's still run. Tough saw I have argue'd the torque curve with them, and just gave up won't change em, and they won't me LOL! So far the 4cycle on the no load has been pretty good to me. Sometime's thought about getting a tach. Like what you said, and make's sense and new to me. Norm........
deye223
Addicted to ArboristSite
Link fixed.
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