Anyone port a Makita 6421 cylinder?

[Wood Chopper]

About 5-6 seconds slower than a ported 500i. Consecutive saws in my YouTube a day or 3 apart in the same log.

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[huskihl]

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Lol

 

[Wood Doctor]

After I installed a Big Bore P/C kit onto a straight-gassed Makita 6401, it ran like gangbusters and still does after 12 years:

Whale of a saw. I think your 6421 would respond the same way. The Pic shows a 32" bar and chain that it pulls without batting an eye.

 

[Stevetheboatguy]

I know it's going to be a waste of time. But I've got a 6421 that is getting a 7900 top end a friend is working over. I'm going to see if I can gain anything with my limited tooling. Nothing to loose. Just going to be sitting on a shelf otherwise.

Steven

 

[Shane¹]

After I installed a Big Bore P/C kit onto a straight-gassed Makita 6401, it ran like gangbusters and still does after 12 years:
View attachment 359543
Whale of a saw. I think your 6421 would respond the same way. The Pic shows a 32" bar and chain that it pulls without batting an eye.

I like the big bores I have one and I leave a 28 on it it pulls it great as well as a 7900 sitting on the shelf I just have a 6421 cylinder sitting here and had thoughts of messing with it some if it sucks I am out nothing

 

[computeruser]

Dave Neiger had ported some 6400s back when the 6400/7300/7900 first came out. They ran very well.

 

[Ford3000]

No porting will make a open port 64cc saw perform close to or as well as a stock closed port 79cc saw - You are looking at a 15cc gap to make up for.
I do believe gains can be achieved though as a stock 6400 is quite conservative.

I love my PS-6400.
Curious to see what You can get out of Yours.

You answered my question, which was with the same stroke, what was
so different with the port layout, excluding the obvious cc difference.

 

[whitesnake]

After I installed a Big Bore P/C kit onto a straight-gassed Makita 6401, it ran like gangbusters and still does after 12 years:
View attachment 359543
Whale of a saw. I think your 6421 would respond the same way. The Pic shows a 32" bar and chain that it pulls without batting an eye.

Which bb kit do you have? I have a couple new ones in the box that hl supply sells. I have a nice dolmar 6400 sitting here. Nothing wrong with it but figured for the price what did I have to lose? Did you use the rings and clips that came with the kit? Thanks!

 

[Shane¹]

Which bb kit do you have? I have a couple new ones in the box that hl supply sells. I have a nice dolmar 6400 sitting here. Nothing wrong with it but figured for the price what did I have to lose? Did you use the rings and clips that came with the kit? Thanks!

I put an hl supply big bore on mine used everything in the kit no base gasket. Have no idea what squish or any numbers on it are but it's a torque monster slightly slower than 7900 with a short bar but pulls a 28 with authority and is my go to saw

 

[WKEND LUMBERJAK]

After I installed a Big Bore P/C kit onto a straight-gassed Makita 6401, it ran like gangbusters and still does after 12 years:
View attachment 359543
Whale of a saw. I think your 6421 would respond the same way. The Pic shows a 32" bar and chain that it pulls without batting an eye.

Has that been 12 years? Man time flies

 

[whitesnake]

I put an hl supply big bore on mine used everything in the kit no base gasket. Have no idea what squish or any numbers on it are but it's a torque monster slightly slower than 7900 with a short bar but pulls a 28 with authority and is my go to saw

Sounds good. How long have you had it on service? I was just curious if I should get some different clips and a caber ring.

 

[Shane¹]

It has been on there for a couple years but I don't cut too much I would say maybe 40 tanks or so? As far as clips I can't remember if I got different ones or not if it had ears on it I may have or cut the ears off I can't remember. I would just run the ring that came with it or get a dukes ring I have had good luck with them. I don't see the need for a caber ring but again I don't cut that much

 

[Wood Doctor]

Has that been 12 years? Man time flies

Yes it has, and yes, time does fly. That was a fabulous learning experience that you gave me, and I have installed new top ends on at least 40 saw engines since then. Thank you so much, Kenneth, and Happy New Year!

 

[00wyk]

No porting will make a open port 64cc saw perform close to or as well as a stock closed port 79cc saw - You are looking at a 15cc gap to make up for.
I do believe gains can be achieved though as a stock 6400 is quite conservative.

I love my PS-6400.
Curious to see what You can get out of Yours.

I think if you added finger ports you could get an impressive machine.

 

[Mycamaro_68]

I think if you added finger ports you could get an impressive machine.

I have a BB kit that I plan on putting on my 6421. I have read a lot (just in general, not necessarily specific to these) that because of the bigger bore that the transfers are quite a bit smaller than factory. It looks to me that there is plenty of material available to do bridge ports which is what I plan to try.

 

[Wilhelm]

I think if you added finger ports you could get an impressive machine.

Nope!
Great saw factory stock, not gonna touch anything.
Maybe a muffler mod down the road, most likely not though.

Factory stock Dolmar PS-6400:
- not too loud (without MM)
- good power with high torque (better than stock PS-6100 in any way)
- wide power band, not peaky
- well mannered
- excellent fuel economy
- reliable
- a proven saw chasis that has been in production for 2 decades

 

[Shane¹]

What would you guys recommend for a fairly cheap set of burrs? The few I have are not very good. I don't plan on doing but a few cylinders and only once in a great while?

 

[00wyk]

Nope!
Great saw factory stock, not gonna touch anything.
Maybe a muffler mod down the road, most likely not though.

Factory stock Dolmar PS-6400:
- not too loud (without MM)
- good power with high torque (better than stock PS-6100 in any way)
- wide power band, not peaky
- well mannered
- excellent fuel economy
- reliable
- a proven saw chasis that has been in production for 2 decades

I was talking to Shane. I mean, you did see the thread title?
The problem the open port Dolmars(as well as about all other open port saws) is scavenging. Finger ports bring that back.
Ask Andrew, I can really wake up a 420 with finger ports. Though, technically, they are eyebrow ports, and aren't all that invasive.

 

[00wyk]

What would you guys recommend for a fairly cheap set of burrs? The few I have are not very good. I don't plan on doing but a few cylinders and only once in a great while?

If you are just gonna fiddle with porting any cheap set of carbide burrs off EBay will work to start. They are cheap enough you can simply replace them when they die.
Hell, some of them are so cheap I replace them after hogging out a pair of steel 365XT transfers. And I am using 1/4",6mm shank pneumatic die grinders following a cut-off wheel for that work.
There are loads of threads here and all around the interwebs for porting.
My quick take to start is simply opening the intake within 1mm of the piston skirt, and open the exhaust at the exit as much as you dare without blowing out the gasket to start.
This with a muffler mod and a timing advance of 6-8* makes the biggest difference over stock. Anything else is just adding to it in degrees.
If you can, subscribe to Donny Walkers channel on youtube. He has a wealth of knowledge. And even though he has some massive saws out there in the hands of BC fallers, he advocates for some surprisingly moderate tuning for most work saws. But more importantly, his channel is full of very good, hard-earned information.

 

[00wyk]

I have a BB kit that I plan on putting on my 6421. I have read a lot (just in general, not necessarily specific to these) that because of the bigger bore that the transfers are quite a bit smaller than factory. It looks to me that there is plenty of material available to do bridge ports which is what I plan to try.

I was mostly talking to Shane about his 6400 top end.
I think on the BB top ends, that simply working the existing transfers would do you good.
I am not a fan of bridge or finger ports on closed port cylinders for work saws. But for cookie cutters, they can be impressive.
For a work saw, I prefer to keep the power band well below 12k rpm in the wood. I find if you are at high rpm in the wood that you start to lose chains and bars and wear the saw at an alarming rate in my work. I favour going up in chassis size vs aggressive porting should the timber require it.