Spuds Porting and Tuning Thread

[arbormonkey]

hi spud do you think a 261 is worth porting

[spudulike]

hi spud do you think a 261 is worth porting

 

I take it is a MS261? Autotune?

[wyk]

Looking, I think it is an auxiliary transfer??

 

Yup, just an auxiliary. This thing has 6 ports. Which would be great if they were closed. But with open ports, it usually means loads of torque and not much top end, and that's a lot of what ya get here. Though she is quite a bit faster than stock, I didn't put her next to my 241 in the video - that thing has a screaming top end

 

I just port matched the bottom of the jug to the chassis in the first pic. Raised the transfers a bit and played with their direction some, and removed the cat and the louvres from the muffler, and made the intake and exhaust more generous. The thing is built like a freakin' tank.

[spudulike]

Yup, just an auxiliary. This thing has 6 ports. Which would be great if they were closed. But with open ports, it usually means loads of torque and not much top end, and that's a lot of what ya get here. Though she is quite a bit faster than stock, I didn't put her next to my 241 in the video - that thing has a screaming top end

 

I just port matched the bottom of the jug to the chassis in the first pic. Raised the transfers a bit and played with their direction some, and removed the cat and the louvres from the muffler, and made the intake and exhaust more generous. The thing is built like a freakin' tank.

 

I'm surprised that there was enough wall thickness to get it in - you wouldn't want to drill through that:blushing:

 

Interesting though, I guess the triple transfer just allows a change of scavenging & less fuel stacking but thought it may risk the exhaust gases being blown backward rather then upwards and down out of the port as normal. I know The MS200 benefits from more torque over the 020 from having split transfers - interesting stuff, guess it was a drill down through the cylinder and then breaking out in to the cylinder with a burr!

[wyk]

I'm surprised that there was enough wall thickness to get it in - you wouldn't want to drill through that:blushing:

 

Interesting though, I guess the triple transfer just allows a change of scavenging & less fuel stacking but thought it may risk the exhaust gases being blown backward rather then upwards and down out of the port as normal. I know The MS200 benefits from more torque over the 020 from having split transfers - interesting stuff, guess it was a drill down through the cylinder and then breaking out in to the cylinder with a burr!

 

It's main problem is the chassis is large, the transfers are large, and not really designed well, so there's no velocity. Add in the fact you can't remove the gasket for more compression and less volume, and you just are not gonna get more top end out of this one unless you lathe it. The 7900 big brother has a much smaller chassis to displacement, and better designed transfers, for much better top end.

[wyk]

I'm surprised that there was enough wall thickness to get it in - you wouldn't want to drill through that:blushing:

 

Ah, just realized ya thought I added it, or maybe funnin me. No, for some unknown reason, Dolmar put that in. I think it's a mistake in this chassis - but only if you're gonna port it. Stock, it seems to help midrange torque a lot. But good factory ports to start would have done that...

[spudulike]

Ah, just realized ya thought I added it, or maybe funnin me. No, for some unknown reason, Dolmar put that in. I think it's a mistake in this chassis - but only if you're gonna port it. Stock, it seems to help midrange torque a lot. But good factory ports to start would have done that...

 

I thought you had added it TBH, thought it pretty radical and had only come across extra ports added to the back of the cylinder to aid the direction of the scavenging transfer of fuel air mix - closed when factory or open like on your 044 and other saws!

 

Not seen triple transfers like this before but not done many Dolmars! Extra ports bored in to the cylinder wall are a bit radical on long term work saws IMO - bit heavy on the rings!

[wyk]

That 420 and the 7900 are the only modern saws I know that have them. Some older McCullochs had loads of ports, though.

[spudulike]

This weekends Pleasure, a 395XP in splendid condition, very low hours and in for porting which I dis as shown.

 

Lowers opened and flowed, uppers swept back and re-profiled, inlet and exhaust reshaped, more inlet duration added. I also have changed the ignition timing advance. Will run it up over the next few days but it sounds very nice:thumbup:

 

Did a nice up and over shotgun muffler on it:thumbup:

[spudulike]

And another....from the same guy, a new MS150 with a sting. Fully ported, ignition advance and muffler mod...nice:thumbup:

 

This is it cutting through a solid lump of 11" Oak.....yup, I like to REALLY test em:thumbup:

 

[ame]

[/ame]