Play time?

[huskihl]

Would you would have to do a popup on the hood of that badboy to get that Dolmar to fit?
That would be cool

We could call it a Dorko

 

[Red97]

Would you would have to do a popup on the hood of that badboy to get that Dolmar to fit?
That would be cool

I looked inbthe past, it is s good bit too large to fit this chassis, hood, case, everything lol

We could call it a Dorko

Might end up being pretty Dorko anyway...

 

[RI Chevy]

Dolcho

 

[mdavlee]

The 620 (45mm bore) is 77,105,125 those are not exact but in the ball park and around where I like my ported 590's. Again a 45mm bore.

Trimming the piston was my plan once I get the 54mm running.

If the case is indeed tighter that means higher pressure. Typically the higher the pressure the more peaky an engine becomes....
I don't really feel a peak in the saw yet. Could the little carb and restrictive filter be mellowing out the powerband.

I plan on testing lots of things, I just thoroughly enjoy the discussion.




I didn't realize I hadn't posted any numbers.

It has been a while, butbibreally need to look at the 7910 ports.. Don't they have a smaller ex than the 046? Could that along with the long stright trans play a role in why they like the longer be?

I've never messed with the short bd. But even the shorter bd would be more piston travel vs the 046.

View attachment 227637

I raised the ex to 100 intake and ex are 65%

Upper trans are untouched.

Exhaust size is pretty close. I port mapped the 46, 372, and 7900 once after porting. The 372 had the biggest transfers.

 

[Red97]

Exhaust size is pretty close. I port mapped the 46, 372, and 7900 once after porting. The 372 had the biggest transfers.

I can see that. This is a 7910 jug with the step in the exhaust. For the muffler tube thing... maybe that why it is smaller?

 

[mdavlee]

I can see that. This is a 7910 jug with the step in the exhaust. For the muffler tube thing... maybe that why it is smaller?

It is for it to extend into the jug. If you blend it open all the way it can free port

 

[huskihl]

It is for it to extend into the jug. If you blend it open all the way it can free port

I leave just a little ramp on the bottom. And open the rest up

 

[MG porting]

Grins and giggles here are the transfers the saw/case was designed for. At 45mm bore.

What stile of piston does the echo run I've never worked on one that deep do they have Windows or not?

 

[Red97]

What stile of piston does the echo run I've never worked on one that deep do they have Windows or not?

Full circle. No windows or slab sides

 

[MG porting]

Full circle. No windows or slab sides

Ok that makes things make more sense with them transfer's.

 

[Red97]

Ok that makes things make more sense with them transfer's.

Stock is a bottom fed quad port.

But 7mm larger than stock bore size now. Next will be 9mm...

Maybe I jb weld the transfer cutouts and tighten the case even More?

One cylinder will be converted to bottom fed... Maybe quad port too...

 

[MG porting]

Stock is a bottom fed quad port.

But 7mm larger than stock bore size now. Next will be 9mm...

Maybe I jb weld the transfer cutouts and tighten the case even More?

One cylinder will be converted to bottom fed... Maybe quad port too...

That sounds like a plan will be interesting.

 

[Red97]

Well the mandrel came out, and the plating stayed on. 86cc is looking good..


Piston even fits the bore...

 

[Stihlbro]

Joe, got any pictures of the piston on the rod at bottom dead center? Any pictures of piston in cylinder of piston in position of ports opening or closing?

 

[Red97]

Joe, got any pictures of the piston on the rod at bottom dead center? Any pictures of piston in cylinder of piston in position of ports opening or closing?

In my haste to get this first one together, I only checked bdc and tried to match the lowers to the piston windows.

Never bothered to check any other spots...

But that is a good idea for the 54mm one.

 

[Red97]

Had planned on getting the 54mm case together this morning.. Found a nice little surprise.

Had some rot on the gasket surface.

I'll dimple it and patch with in weld. Feel I will make a larger mess trying to tig it myself..

Still has a good bit of a ledge to hold the jb weld on the bottom. Don't see it being an issue.

 

[RI Chevy]

I never realized Magnesium was that corrosive.

 

[Red97]

I never realized Magnesium was that corrosive.

I think this saw fell in the drink at some point. Ring was rusted to the bore water was sitting in the case for a long period. I'm just using the case. I have another crank and new bearings.

Wanted to use this case because it has the larger 38mm od bearings.

 

[RI Chevy]

Ahhh. OK. Thanks Joe.

 

[srcarr52]

Had planned on getting the 54mm case together this morning.. Found a nice little surprise.

Had some rot on the gasket surface.

I'll dimple it and patch with in weld. Feel I will make a larger mess trying to tig it myself..

Still has a good bit of a ledge to hold the jb weld on the bottom. Don't see it being an issue.View attachment 227854

I can weld that for you.