Solo 681 vs Makita 6401 Big Bore aka DCS 8401

[dean06919]

With ten takes of a gas through the Home Depot-Bailey's Big Bore Makita, I headed out to compare it against my well broken in Solo 681 on a freshly cut Black Oak that was 36"-52" across. Both wore the same 36" bar, same new Oregon chain, with the Makita running a 7 pin sprocket and the Solo running a 8 pin sprocket. The results were rather surprising as the Makita struggled the entire time and would accept almost no downward pressure while the Solo willingly accepted the downward pressure.

The Solo is completely stock with the exception of the 8 pin sprocket, while the Makita wears a Bailey's 84cc Big Bore kit installed without the base gasket with a heavy duty air filter kit. The compression difference is noticeable also, with the Solo making more than the Makita.

Any suggestions as to why such a big difference in performance? I was thinking about replacing the compression relief valve on the Makita in case it was leaking. The jetting seems to be fine on the Makita, it starts great, idles, doesn't bog when hitting the throttle and seems to be hitting the rev limiter under no load testing. I tuned both saws in wood and the Solo's Walbro carb did seem to allow for more H speed adjustment, while the Makita's Zama carb did not adjust out as far.

I would have imagined that they would have been closer in performance. I question now if I should have purchased the PS 7900 kit instead. So what do you guys think?

 

[blsnelling]

Did you retune the carb? It should not be weak like that. The one I ran was slightly stronger than a stock 7900.

 

[volks-man]

there is a lot of mystery and magic in port timing which man has yet to understand.

i would think that the solo is simply ported and timed (stock) in a hotter manner than the big bore kit.
likely also, is that the compression of the BB may be significantly lower than the solo even without a base gasket.

for giggles i'd run a compression test on both saws and i think i would have to try again with the same 7-pin on both saws. the sprocket is likely not the source of your troubles but may contribute to a perceived difference.


edit: i'd fatten up the BB saw a bit more as i would not want the saw bouncing off the limiter. do a search.... member andyshine shows how to tune a 7900 in the wood for peak power.

 

[blsnelling]

edit: i'd fatten up the BB saw a bit more as i would not want the saw bouncing off the limiter. do a search.... member andyshine shows how to tune a 7900 in the wood for peak power.

+1. If it's bouncing off the rev limiter, you really have no idea how lean it is. But then again, you ported it, so it's likely to turn more RPMs than stock. I'd still start by bringing it down to the edge of the limiter, and then tuning in the cut.

 

[scotvl]

whats the squish and compression?

 

[WoodChuck'r]

Always seems like there's something good to say about those 681's.

 

[dean06919]

Did you retune the carb? It should not be weak like that. The one I ran was slightly stronger than a stock 7900.

Yes, I tuned it in wood according to Andyshine77's video. Whereas the Solo 681 would adjust to allow a blubber when richening the H screw and then clean out as the screw was turned to the right, the Makita's H screw simply hits both stops with no change in sound. Should I trim the limits on the screw and see what happens? Is the general consensus that it is running too lean?

there is a lot of mystery and magic in port timing which man has yet to understand.

i would think that the solo is simply ported and timed (stock) in a hotter manner than the big bore kit.
likely also, is that the compression of the BB may be significantly lower than the solo even without a base gasket.

I wonder if that is the case.

whats the squish and compression?

I'll try to make it to the dealer on Wednesday to have these two things checked, unfortunately I don't have the necessary tools to check these things. Not yet anyway.

Always seems like there's something good to say about those 681's.

I've ran the Solo against my friends Husqvarna 394XP and found that with a 24" bar, the Solo is only a second slower. I have ran both with 36" bars at different times and really think that the Solo isn't that much slower. Add to this it's lighter weight and I'm starting to think it's the best big saw on the market.

 

[WoodChuck'r]

Yes, I tuned it in wood according to Andyshine77's video. Whereas the Solo 681 would adjust to allow a blubber when richening the H screw and then clean out as the screw was turned to the right, the Makita's H screw simply hits both stops with no change in sound. Should I trim the limits on the screw and see what happens? Is the general consensus that it is running too lean?



I wonder if that is the case.



I'll try to make it to the dealer on Wednesday to have these two things checked, unfortunately I don't have the necessary tools to check these things. Not yet anyway.


I've ran the Solo against my friends Husqvarna 394XP and found that with a 24" bar, the Solo is only a second slower. I have ran both with 36" bars at different times and really think that the Solo isn't that much slower. Add to this it's lighter weight and I'm starting to think it's the best big saw on the market.

Other than the AV, which should be 7900 AV to make it better, it's a badass saw.

Horray for Dolmar!

 

[Jtheo]

I have owned both the Makita with a BB kit, and a 7900 both bought new.

No way would the BB Makita cut with the 7900.

I think the difference is the MAHLE cylinder and more compression in the 7900, plus it seems the German engineers built the 7900 to take down everything in it's class. I think they succeeded.

No timed cuts, just my take on the two. The Makita left, the 7900 stayed.

 

[dean06919]

I have owned both the Makita with a BB kit, and a 7900 both bought new.

No way would the BB Makita cut with the 7900.

I think the difference is the MAHLE cylinder and more compression in the 7900, plus it seems the German engineers built the 7900 to take down everything in it's class. I think they succeeded.

No timed cuts, just my take on the two. The Makita left, the 7900 stayed.

That's kind of what I was wondering. There might me a slightly used BB kit in the marketplace soon and an OEM PS 7900 kit on the way.

 

[Jtheo]

That's kind of what I was wondering. There might me a slightly used BB kit in the marketplace soon and an OEM PS 7900 kit on the way.

I am not going to knock the BB Kit, but when you think about it, $80 more gets you the Mahle P&C that comes on the 7900.

 

[volks-man]

That's kind of what I was wondering. There might me a slightly used BB kit in the marketplace soon and an OEM PS 7900 kit on the way.

see, now you've gone and done it!

you've opened the door.

if you are thinking of upgrading to the 7900 top end then you will have a lightly used BB kit sitting there taunting you.

send it to one of the machinists here on the forum and get yourself a pop-up and milled cylinder. try widening the ports and angling the transfers back toward the intake.

make a silk purse out of the sow's ear! what do you have to lose if you already have the 7900 top to replace it with?

 

[WoodChuck'r]

see, now you've gone and done it!

you've opened the door.

if you are thinking of upgrading to the 7900 top end then you will have a lightly used BB kit sitting there taunting you.

send it to one of the machinists here on the forum and get yourself a pop-up and milled cylinder. try widening the ports and angling the transfers back toward the intake.

make a silk purse out of the sow's ear! what do you have to lose if you already have the 7900 top to replace it with?

Spoken like a man with a brain!

 

[AUSSIE1]

see, now you've gone and done it!

you've opened the door.

if you are thinking of upgrading to the 7900 top end then you will have a lightly used BB kit sitting there taunting you.

send it to one of the machinists here on the forum and get yourself a pop-up and milled cylinder. try widening the ports and angling the transfers back toward the intake.

make a silk purse out of the sow's ear! what do you have to lose if you already have the 7900 top to replace it with?

For sure.

The aftermarket kit can be made to run at LEAST as good as the 7900 kit if the No's aren't more in the wrong direction.

 

[scotvl]

Yes, I tuned it in wood according to Andyshine77's video. Whereas the Solo 681 would adjust to allow a blubber when richening the H screw and then clean out as the screw was turned to the right, the Makita's H screw simply hits both stops with no change in sound. Should I trim the limits on the screw and see what happens? Is the general consensus that it is running too lean?



I wonder if that is the case.

I think that's part of the problem along with not knowing your squish and compression. Trim the caps and let the rings seat, the bb kit I just got looked pretty good before I ported it, better than some of the made in Brazil Mahle jugs Ive seen posted here.

 

[HEAVY FUEL]

I feel my BB cuts right with if not a hair faster than my stock 7900 AFTER about 5 tanks threw the BB. They maybe hit & miss on some. All said and done I would opt for the 7900 OEM if I had to do it again.

 

[madhatte]

I've had GREAT luck with myDolmar 6400 with the BB topend so far. Cuts like crazy, pulls forever and ever. Bone-stock. Might port it later, after the warranty runs out. Might get a HD Makita, put the BB topend on that, and a stock 7900 on the Dolmar. No matter -- either way, they're still the best bang for the buck on the market today.

 

[blsnelling]

Definately sounds like your 7900BB is too lean. Better trim those tabs before it's too late.

 

[rms61moparman]

My 7900 BB is stronger than my OEM topend 7900.
Both are wicked.

Mike