Anyone port a Makita 6421 cylinder?

[Wilhelm]

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.

Ups!
Apologies, just reacted to a post without taking into account the entire thread.

Happy new year!

 

[Shane¹]

While I was doing the 7900 cylinder I bolted the 6421 cylinder on and got timing numbers. Numbers are at intake 72, exhaust 111 and transfers 130. Anyone have any ideas on where to start?

 

[davidwyby]

I have a spare cylinder if you want it.

 

[Shane¹]

I have a spare cylinder if you want it.

Possibly you still have that orange carb tray?

 

[farminkarman]

While I was doing the 7900 cylinder I bolted the 6421 cylinder on and got timing numbers. Numbers are at intake 72, exhaust 111 and transfers 130. Anyone have any ideas on where to start?

I haven't tried messing with one yet, but I would probably try ex: 105, tr: 122-125, in: 78. If you might do machine work on it in the future, then I wouldn't lower the intake too much. I have a 6400 that I need to get started on for the fundraiser....perhaps I will try machining & porting the 6400 jug before I do the 7900 top end.

 

[davidwyby]

Possibly you still have that orange carb tray?

Yep

 

[Shane¹]

Yep

Are you using that tray? Did you find a blue one?

 

[davidwyby]

Are you using that tray? Did you find a blue one?

Nope. Yep. I’m trading my spare blue saw for a red saw. Bottom ends anyway.

 

[Shane¹]

Nope. Yep. I’m trading my spare blue saw for a red saw. Bottom ends anyway.

You don't have another set of blue cases do you? I could use some

 

[davidwyby]

You don't have another set of blue cases do you? I could use some

No, sorry.

 

[Shane¹]

I was going to port the 6421 jug then started on the aftermarket 7900. Well decided to do the 6421. Ended up trying exhaust at 102 intake 75 and left transfers at 130. Got it running tonight but it seems kinda funky it spits into the intake a little and if I lean it out any it races like it is actually too lean. Any ideas? Did I drop the intake too much? Do I need to raise the transfers a little?

 

[farminkarman]

I was going to port the 6421 jug then started on the aftermarket 7900. Well decided to do the 6421. Ended up trying exhaust at 102 intake 75 and left transfers at 130. Got it running tonight but it seems kinda funky it spits into the intake a little and if I lean it out any it races like it is actually too lean. Any ideas? Did I drop the intake too much? Do I need to raise the transfers a little?

Try raising your exhaust side transfers to 122 and stagger them to open at 125 on the intake side. You might have an air leak if it is racing.

 

[Shane¹]

Try raising your exhaust side transfers to 122 and stagger them to open at 125 on the intake side. You might have an air leak if it is racing.

It doesn't really race just sounds lean if I try to get less spit back by leaning it out. I wouldn't really even noticed the wetness if I didn't start it without an air cleaner maybe I should check my other saw tomorrow and see if this is normal?

 

[Shane¹]

Well I have ran a little over 2 tanks through the 6421. Wow it is really coming into it I am impressed with how much it gained over stock

 

[Mycamaro_68]

Well I have ran a little over 2 tanks through the 6421. Wow it is really coming into it I am impressed with how much it gained over stock

Are you still at the numbers you posted before or did you go back in and change anything?

 

[Shane¹]

I really like it at these numbers I am not sure if I would want to change it now or not. Intake is at 75 exhaust 102 transfers 130 squish is at 25 thousandths.

 

[Shane¹]

Got the blue bottom end all together and ran 4 more tanks through this saw. It's actually surprising how much I like this saw

 

[Wood Doctor]

Here's the 6401 that WKEND LUMBERJAK and I rebuilt about 12 years ago. It was a great joint project and I learned a lot from him, enough to rebuild about 30 more saws:

This saw remains in my artillery and runs fine today. That's a 32" bar on board and it pulls it flawlessly.

 

[Shane¹]

I haven't tried messing with one yet, but I would probably try ex: 105, tr: 122-125, in: 78. If you might do machine work on it in the future, then I wouldn't lower the intake too much. I have a 6400 that I need to get started on for the fundraiser....perhaps I will try machining & porting the 6400 jug before I do the 7900 top end.

@farminkarman did you ever mess around with the 6400 cylinder or just go straight for the 7900? I am thinking about trying some different numbers but the first round runs so good I don't want to mess one up now

 

[farminkarman]

@farminkarman did you ever mess around with the 6400 cylinder or just go straight for the 7900? I am thinking about trying some different numbers but the first round runs so good I don't want to mess one up now

I didn’t end up having time, so I went straight to the 7900 jug. At some point I would like to try doing the 6400 jug.