359 port timing numbers

[jonsered 535]

Here's how we do the cat muffler....



Just make the outlet behind the plate, then cover it with a deflector. This is made from a piece of pipe.........probably an old bike frame.

That's perfect, nice, should I cap the top one off and how big of a hole did you drill there
I'd like to keep the stock one and put one like you did also???

 

[sunfish]

 

[Mastermind]

That's perfect, nice, should I cap the top one off and how big of a hole did you drill there
I'd like to keep the stock one and put one like you did also???

Everything under the deflector, and behind the cat plate is open. At least a 3/4" hole. Yes, keep the top outlet too.......we open that and make larger deflectors that protect the top cover better.

I'll find a pic soon......

 

[jonsered 535]

With the cat plate gone I could do like your top picture and put a rectangle hole and square deflector

 

[sunfish]

With the cat plate gone I could do like your top picture and put a rectangle hole and square deflector

Yes, the baffle is gone in both those. Big rectangle hole under the deflector.

Randy's way above is actually easier because you don't have to mess with the baffle. But since your baffle is gone there are many options.

 

[David Young]

 

[sunfish]

More wrong with that saw than port shape!

 

[David Young]

I think opening up the baffle is a big part of it. if you have a big enough muffler the outlet size is less important. look at the 7900 dolmar. They knew what they were doing. a smaller muffler is louder and will need a larger outlet, both of which will make it louder.

 

[David Young]

More wrong with that saw than port shape!

yeah I just found a picture from google images. I just wanted to show the crescent at the bottom.

 

[sunfish]

yeah I just found a picture from google images. I just wanted to show the crescent at the bottom.

Gottcha. But I don't see the crescent shape at the bottom of the piston doin anything more than increasing intake duration?

 

[David Young]

Gottcha. But I don't see the crescent shape at the bottom of the piston doin anything more than increasing intake duration?

Don Normally the port has some roundness to it or is narrow enough that the piston is supported and does not enter the intake port (like on Strato saws)
this port is like a port that is too flat not enough to push the piston back out of the port. you need the round shape somewhere. the only other way to do it is with the piston. what he can expect from my experience with the 372 is that it will only take 3-6 tanks before it looks like the pictures I have shown.

i hope what I have tried to describe is clear

David

 

[jonsered 535]

So

Don Normally the port has some roundness to it or is narrow enough that the piston is supported and does not enter the intake port (like on Strato saws)
this port is like a port that is too flat not enough to push the piston back out of the port. you need the round shape somewhere. the only other way to do it is with the piston. what he can expect from my experience with the 372 is that it will only take 3-6 tanks before it looks like the pictures I have shown.

i hope what I have tried to describe is clear

David

David do you want me to do that with my piston and leave the epoxy higher or something to get the same port opening as say 79* or what degree does everyone think I should make it now

 

[mdavlee]

Try 76 first.

 

[David Young]

So

David do you want me to do that with my piston and leave the epoxy higher or something to get the same port opening as say 79* or what degree does everyone think I should make it now

Yes that is my idea

I'd go 76-77minimum

You saw my suggestion if your mig handy I like the deflectors these guys have done some great jobs on the mufflers.

 

[jonsered 535]

Yes that is my idea

I'd go 76-77minimum

You saw my suggestion if your mig handy I like the deflectors these guys have done some great jobs on the mufflers.

what shape should I make the intake when I sand the liquid steel down, round down, round up, flat across??? at 76*

 

[jonsered 535]

I hate having to wait 16hrs for the liquid steel to fully cure so i'll get at the muffler this afternoon and that will keep me busy and away from it drying.

 

[David Young]

what shape should I make the intake when I sand the liquid steel down, round down, round up, flat across??? at 76*

I don't know and don't know how well the jb weld will hold on a bearing surface. I only have used jbweld for external transfers and for cutting through the sides of the cylinder to get more swoop on open transfer saws.
I think I would try to make it like a normal intake port and round it up on the corners. if you put in the epoxy it may support the piston enough and not need the half moon. now I am speculating. Maybe Mike can elaborate on his experience.

David

 

[David Young]

I hate having to wait 16hrs for the liquid steel to fully cure so i'll get at the muffler this afternoon and that will keep me busy and away from it drying.

heat hastens the process of curing.....

 

[jonsered 535]

I'll put the half moon a bit (maybe make it moon up a 1/16 high you think?) in the piston make the port like normal again and at 76

 

[David Young]

worth a shot, are you using the cheap piston? I think thats how I would go. also you only want it it in the very center.