Makita DCS6400, 7300, 7900

[joe_indi]

All these three models differ only in their cylinder/ piston sets.
Which would be the best option considering the ideal combination of power, speed and durability.
The stroke of all the three models is 37mm.
I dont know the bore size of the 6400, but the 7300 and 7900 have bores of 50mm and 52mm respectively.

Joe

[chevytaHOE5674]

The 6400 IMO is underpowered for its weight. But the 7300 and 7900 are much more competitive for their power to weight ratio. Personally I love my 6400 converted to a 7900. From what I've seen and read durability is right there with any of the top of the line pro saws.   

[nmurph]

i own three 7900's. two were born as 64cc saws and morphed into larger saws. the other one was genetically superior from the start. they are indistinguishable in terms of performance. i would definitely go for the 79cc. if you are going to tote the weight, you may as well have the maximum power.

[stonebroke]

Baileys has a 84cc big bore kit for the 6400, I bet it would rip then.

Stonebroke

[joe_indi]

..... From what I've seen and read durability is right there with any of the top of the line pro saws.  

..... i would definitely go for the 79cc. if you are going to tote the weight, you may as well have the maximum power.

Is the extra power of the 7900 at the cost of crankshaft life.
That is what I would like to know.
Also, when this saw was available as the Dolmar PS7900, there was also a problem of the crankcase developing cracks.
Have you faced any similar problem?
Or could it have been caused by wrong usage.

Joe

[chevytaHOE5674]

I've had no issues with the crank shaft. I'm sure the 7900 will have a slightly shorter life. But since its more powerful slightly more work will get done in slightly less time.

[joe_indi]

I've had no issues with the crank shaft. I'm sure the 7900 will have a slightly shorter life. But since its more powerful slightly more work will get done in slightly less time.

How slightly, that is the question.
Slightly as in hours, days or months.
Or, looking at it from a different angle, how does it compare in performance and life compared to the Stihl MS460?

Joe

[chevytaHOE5674]

My 7900 is a makita 6401 home depot rental saw, that the top end was shot on. Got a 7900 P&C and it has probably a hundred or so hours on it and the lower end is tight as can be. If the saw can suffer through rental saw abused and still keep ticking that means something.

[nmurph]

Also, when this saw was available as the Dolmar PS7900, there was also a problem of the crankcase developing cracks.
Have you faced any similar problem?
Or could it have been caused by wrong usage.

Joe

this is the first time i have heard of this problem. i have had zero issues with my saws.

[Rocky_J]

I've never owned or used one, but I've been reading the saw forums for about 10 years now and I've never heard of the 7900 saws developing cracks in the crankshafts. I'm not saying it hasn't happened, but I've never seen it mentioned or discussed on the forums. If it were a problem then it would have been brought up. On the other hand, some people could break an anvil so I'm sure at some point somebody has managed to break a 7900 crankshaft.

The ONLY reason to buy this saw in any configuration but the 7900 is to save money on the purchase price. And for anybody who plans on using the saw more than a few hours per year, that is false economy in my mind. But then some people here think a Poulan from Wal Mart is economical, so we are not all on the same page anyway.

[John Mc]

I've never heard of the 7900 saws developing cracks in the crankshafts.

He was talking crankcase cracks, not crankshaft. Though I suppose if you'd heard of any problems with that, you'd have mentioned it?

[Cut4fun]

Just to show you what a 6401 could become with a OEM 79cc topend.

Top video is stock 7900 that is one of the strongest stock ones with 185psi from the factory. Not all stock ones run like this one. Only seen one other run like this in the last few years.

Then if you chose your builders wisely  , the ones that know what they are doing you can end up with a 7900 with over 30% gains  and not crap 15% like some others achieve  .

stock



woods ported




I have never heard of cracking crankcases either.

[joe_indi]

Some years ago the Dolmar PS 6400, 7300 and 7900 made their debut here.
The 7900, according to the users used to develop cracks near the bearing seats.
The reason at that time was attributed to the  stress of the extra power imposed on the 6400 crankshaft and crankcase when it was the 7900.
The PS7900 therefore was considered a 'failure' or 'bad buy' and lost the battle and departed the scene.
Before some of you start rising up in arms against me, this was what happened here in India.Remember, its a different country, different user (abuser?), different usage.

Up to a point the 385XP too had the problem of cracking crankcases.Again, I repeat, here in India.
This used to happen on the starter side and was caused primarily because users dont bother about the starter screws.That is, they only do something when they are down to just a single screw.They cannot start the saw at that point.
But, by then the damage would have already occurred. The area around the loose screws would have already developed cracks.

Back to the Makitas.
Now The PS 6400, 7300 and 7900 are coming back here with the  DCS prefix.
Memories of the PS7900 are still fresh in the minds of the users.
Though I never was involved with Dolmar saws, I might get a bit of involvement with the Makita saws.
I was going through the specifications of all three. I did not see any figures that could possibly crack crankcases.
Quality of manufacture was then the question.I dont see the Germans cutting essential corners at the price of reliability.
Design? If such a thing as a fault in design existed, it should be there everywhere.That is why I started this post.
And going by the responses, I dont see any clues to that having happened.
So, the only possibility is that my fellow countrymen, who were just getting to know the proper use of chainsaws wrecked those Dolmars out of inexperience.

Joe

[Rocky_J]

We have inexperienced dolts who can break an anvil here in America also. I don't think they are limited to just your country, they are a world wide phenomenon.

That said, I cannot possibly see how a crack that is a direct result of neglect/abuse could possibly be considered a 'failure'. Those magnesium cases probably won't hold up too well to being smacked with a baseball bat either, but beating on one until it cracks doesn't indicate any sort of defect or failure on the manufacturer's part.

[joe_indi]

We have inexperienced dolts who can break an anvil here in America also. I don't think they are limited to just your country, they are a world wide phenomenon.

Well I think  I'll accept  that every country has its share of  'heroes'.

That said, I cannot possibly see how a crack that is a direct result of neglect/abuse could possibly be considered a 'failure'. Those magnesium cases probably won't hold up too well to being smacked with a baseball bat either, but beating on one until it cracks doesn't indicate any sort of defect or failure on the manufacturer's part.

How about:
# Fuel setting lean like Audrey Hepburn.
# Rakers filed right to tie strap level.
# Chain tension similar to some torture device from the Inquisition.
# Topped off with a death grip on the throttle till the engine dies out of fuel or the crank burns  out.



Joe

BTW My age changes from 54 to 55 next Tuesday