Modding a Poulan Pro 475

[Deets066]

Meteor is may be wider but also much heavier

 

[Cut4fun]

Hopefully you know not to run the heavier meteor wrist pin in them.

 

[GoBigBlue1984]

@Cut4fun Thank you for taking the time to post all those specs. Very generous/thoughtful of you. Have you used the 272 personally in any of your builds? If so, what were some of your thoughts? What would you have changed or thought could've used changing?

@mdavlee besides bar/chain what do you suppose Tommy switched out on the 475 from cutting timber through the week to the races on weekends?

 

[GoBigBlue1984]

@Deets066 the next one I build in gonna try something completely different. Full circle crank or a stroker. Actually I think the 272 would've been a great option for a stroker. JJ is sending me a jug for the two piece. As soon as this one is finished and I get a few side projects taken care of I'll sit down and map out a plan. I want your input though.

 

[Four Paws]

Glad we cleared up the 7900 piston fitment - I suggested because they are so light. If you are going to run a head, that would be my pick!

I have built a few saws using the 272 piston and it's a good piston, it worked well. I like it in your build, too. You can cut the squish and likely net enough compression to run some fuel.

Lots to consider, isn't there?

 

[Deets066]

Hopefully you know not to run the heavier meteor wrist pin in them.

Yeah they are pretty stout pins

 

[Deets066]

I think you could stick with the 272 piston, it's a good option I think. And add a crank stuffer or a little well placed JB. What's the muffler like? Sounded like it could use a little more opening possibly.

 

[GoBigBlue1984]

I think you could stick with the 272 piston, it's a good option I think. And add a crank stuffer or a little well placed JB. What's the muffler like? Sounded like it could use a little more opening possibly.

I'll post some pictures of the muffler assembly. I think there is lots of room for improvement there. Pictures will tell the story. All I've done now is open up the outlet on the muffler cover from roughly 7/16"diameter to 1 1/8". There is a baffle plate that forces the exhaust to travel down towards the case and through a 1 1/4" hole before traveling back up to the outlet at the top of the muffler cover. I haven't tried running it without the baffle plate but I will. Interesting to see what variance that will give.

 

[Deets066]

I'll post some pictures of the muffler assembly. I think there is lots of room for improvement there. Pictures will tell the story. All I've done now is open up the outlet on the muffler cover from roughly 7/16"diameter to 1 1/8". There is a baffle plate that forces the exhaust to travel down towards the case and through a 1 1/4" hole before traveling back up to the outlet at the top of the muffler cover. I haven't tried running it without the baffle plate but I will. Interesting to see what variance that will give.

Fastest muffler for a cant saw is no baffle and straight out the front, in line with the ex port

 

[Deets066]

I haven't built a fully dedicated saw to the cant yet.

But that's what it will have

 

[GoBigBlue1984]

Glad we cleared up the 7900 piston fitment - I suggested because they are so light. If you are going to run a head, that would be my pick!

I have built a few saws using the 272 piston and it's a good piston, it worked well. I like it in your build, too. You can cut the squish and likely net enough compression to run some fuel.

Lots to consider, isn't there?

A whole lot to consider. Had a conversation earlier with young and I mentioned that thumping 4 stroke that tommy's 475 had. Perhaps it's just the addition of the finger ports getting that extra charge up ahead of the piston. His is a very healthy sounding burble in and out of the cut. But angry. If that makes sense?

By going with a bigger carb than stock I know it may fill the case too much. Shouldnt fingers counter act that.

 

[Deets066]

A whole lot to consider. Had a conversation earlier with young and I mentioned that thumping 4 stroke that tommy's 475 had. Perhaps it's just the addition of the finger ports getting that extra charge up ahead of the piston. His is a very healthy sounding burble in and out of the cut. But angry. If that makes sense?

By going with a bigger carb than stock I know it may fill the case too much. Shouldnt fingers counter act that.

I do think fingers would help if you are over stuffing the case. I would add the carb first and see how it runs, check spit back.

 

[Deets066]

Just to give you an idea of what I did to increase transfer velocity if you decide to add fingers.







Aimed the charge in the right direction, better flow, more velocity

 

[Deets066]

Those two little fillets of JB are bout the size of two finger ports.

 

[mdavlee]

@Cut4fun Thank you for taking the time to post all those specs. Very generous/thoughtful of you. Have you used the 272 personally in any of your builds? If so, what were some of your thoughts? What would you have changed or thought could've used changing?

@mdavlee besides bar/chain what do you suppose Tommy switched out on the 475 from cutting timber through the week to the races on weekends?

I would guess nothing but a tune and pulling the filter.

 

[mdavlee]

A whole lot to consider. Had a conversation earlier with young and I mentioned that thumping 4 stroke that tommy's 475 had. Perhaps it's just the addition of the finger ports getting that extra charge up ahead of the piston. His is a very healthy sounding burble in and out of the cut. But angry. If that makes sense?

By going with a bigger carb than stock I know it may fill the case too much. Shouldnt fingers counter act that.

You can't really fill the case too much. It will only hold what it holds. If you have a bigger carb you can feed it with shorter duration and a wider port.

Now on the other hand it could spitback a ton.

 

[GoBigBlue1984]

I agree, but could it not fill too soon

A whole lot to consider. Had a conversation earlier with young and I mentioned that thumping 4 stroke that tommy's 475 had. Perhaps it's just the addition of the finger ports getting that extra charge up ahead of the piston. His is a very healthy sounding burble in and out of the cut. But angry. If that makes sense?

By going with a bigger carb than stock I know it may fill the case too much. Shouldnt fingers counter act that.

i should've worded that differently, rather filling the case too soon.

As of now I don't feel as though my long intake is hurting me.

 

[GoBigBlue1984]

Definitely wanna try the larger carb though.

 

[GoBigBlue1984]

Glad we cleared up the 7900 piston fitment - I suggested because they are so light. If you are going to run a head, that would be my pick!

I have built a few saws using the 272 piston and it's a good piston, it worked well. I like it in your build, too. You can cut the squish and likely net enough compression to run some fuel.

Lots to consider, isn't there?

Josh, this will be my first 2 piecer. I'm gonna have lots of questions. Anything you have to add when that time comes please fire away. I'd like to pull from several different guys or more on the two piece. I don't wanna wear Joey out. I've talked to Mike some as well. There may be another guy coming after me interested in building a two piece head who knows. It'll be a good thread having all of you guys to pull from.

 

[Cut4fun]

2 styles of mufflers on these. I like the 2 piece better then the 1 piece ones.

This is 1 piece.

2 piece in back. Also showing stock exit in front. The back one is what I do for a stock saw.