How to make your 7900 or 681 NON rev-limited

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Andyshine77 said:
Hi Scott. I was referring to WOT, in the wood it was mostly 4 stroking. It may have hit the limiter a bit because it wasn't under much load, but it was mostly 4 stroking..:cheers:
Click to expand...

Ok i misunderstood:bang:
Wheres the vid gone?

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Hey guys this is my 262 vs my muffler modded 036:)
The 036 is a QS you can see the brake come on just before i swap saws.
The Dawgs on the 262 seem to be a real bad design on the last cut they touch the wood and it just stops cutting.

Sorry for hyjacking your thread Brad:)
 
After running better than a tank of fuel through this saw since setting the timing, and multiple cold starts, I was curious to see if it had slipped. The only way to do that was to see if it would still turn the same RPMs. It does. Leaned out, this saw will turn 16,000. No kidding! Before I run it again, I'm going to mark the crank, flywheel nut, and flywheel so that I can visualize that they have not moved. I don't care to be spinning this thing that fast. I don't want to be the second to have one come apart:dizzy: It runs great anywhere between 14K and 15K. I don't know where I'd get the fastest cut times, but for a work saw, I'll probably leave it around 14K. No reason getting it too lean when you're just cutting firewood.
 
I was just looking back over this thread. It appears that I put bad info on what coil to use. I said to use the unlimited coil that fits saws like the 346, 357, 359, 372, 385, 390 etc. Obviously, that's not what's pictured on the Solo. I believe the coil you need is for 50,51,55,61,254,261,262,268,272,394.

Just a reminder. Any time you run without a key in the flywheel, you run the risk of it slipping. I believe that did indeed end up happening to this saw. When that happens, the saw will loose significant power and RPMs. Once you have the timing dialed in, perhaps a little Loctite would be in order. But that's up to your discretion. I've not tried it and don't know how it would work on the tapered shaft.
 
Last edited:
blsnelling said:
I was just looking back over this thread. It appears that I put bad info on what coil to use. I said to use the unlimited coil that fits saws like the 346, 357, 359, 372, 385, 390 etc. Obviously, that's not what's pictured on the Solo. I believe the coil you need is for 50,51,55,61,254,261,262,268,272,394.

Just a reminder. Any time you run without a key in the flywheel, you run the risk of it slipping. I believe that did indeed end up happening to this saw. When that happens, the saw will loose significant power and RPMs. Once you have the timing dialed in, perhaps a little Loctite would be in order. But that's up to your discretion. I've not tried it and don't know how it would work on the tapered shaft.
Click to expand...

My biggest problem when running a saw without a key is making sure to keep it aligned when tightening the bolt. On a few occasions I have tightened the bolt only to have the flywheel move a little with it. Once that taper is set and tight, it wouldn't be going anywhere.
 
blsnelling said:
Just a reminder. Any time you run without a key in the flywheel, you run the risk of it slipping. I believe that did indeed end up happening to this saw. When that happens, the saw will loose significant power and RPMs. Once you have the timing dialed in, perhaps a little Loctite would be in order. But that's up to your discretion. I've not tried it and don't know how it would work on the tapered shaft.
Click to expand...


Then why does it run better with a new stock cylinder and new stock muffler??
 
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epicklein22 said:
My biggest problem when running a saw without a key is making sure to keep it aligned when tightening the bolt. On a few occasions I have tightened the bolt only to have the flywheel move a little with it. Once that taper is set and tight, it wouldn't be going anywhere.
Click to expand...

When you locate your position, tap the flywheel using a deep socket etc over the crankshaft.
 
thanks for this thread. Romeo sent me his directions several months ago. i was not in any hurry, and i don't have timing light. i like the way you go about doing this mod. i have wanted to port one of my 7900 or the 8401, but i didn't want to mess with the limited coil and i just hadn't gotten up the nerve to try Romeo's method. this one looks simple enough for me.
 
Here's a vid of this saw shortly before I sold it. It's wearing a 28" B&C. The 7900 at the end is stock but only wearing a 20" B&C. Despite the longer B&C, the 681 is still about 30% faster.

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Here's another of it.

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This is what it sounded like with the stock limited coil.

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blsnelling said:
Just a reminder. Any time you run without a key in the flywheel, you run the risk of it slipping. I believe that did indeed end up happening to this saw. When that happens, the saw will loose significant power and RPMs. Once you have the timing dialed in, perhaps a little Loctite would be in order. But that's up to your discretion. I've not tried it and don't know how it would work on the tapered shaft.
Click to expand...

Remember, the key locates, the taper holds. It's a misconception that the key holds. Never rely on the key to hold or you will loose it. The flywheel nut is one that you should torque to spec. Ask me how I know? :mad:
The taper is somewhere I wouldn't like to use loctite.
:cheers:
 
In a perfect world, the taper does lock it down. But it doesn't take much for it not to hold too. I've ran a couple saws without keys. Some have held, some haven't. I seriously prefer to leave them in. It's a huge hassle trying to dial in the tuning on a saw with no key. I never alter the timing on saws I build for others. It's not worth the risk of having it slip. It's another thing if I do it to one of mine and I can deal with it if it happens.
 
My concern about using loctite on crank tapers is the possibility of not being able to remove the flywheel without damaging the end of the crank.

I have thought seriously about using it when not using a key, just couldnt bring myself to do it.
 
Woodchucker, I think that you just pretty much said exactly what brad was refering too. The timing hasn't budged but the saw runs better stock than with the port. Brad is saying the timing needed to be advanced a smidge for the port, solidified by the fact that putting the stock jug and exhaust actually made an improvement on the saws performance meaning that the timing was set better for stock than a port job. :cheers:
 

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