400 CM Build

[Duane(Pa)]

Stihl moar

 

[Duane(Pa)]

Base

 

[Sloughfoot]

Is plating holding up to the alumahawg?

 

[EFSM]

@drf256 Did you enlarge the curved cutouts at the bottom of the cylinder walls? I’m not sure that I understand what their function is.

 

[Duane(Pa)]

@drf256 Did you enlarge the curved cutouts at the bottom of the cylinder walls? I’m not sure that I understand what their function is.

 

[Duane(Pa)]

He dropped the jug (machined base) I think this accounts for that. Doc can answer…

 

[huskihl]

Doc, the cylinder extension won’t fit all the way down in after you machine the base without removing this area on each side where the flat spots are on the extension. You either have to grind away the case or remove some material in this area to get it to sit down and not rock

 

[EFSM]

Doc, the cylinder extension won’t fit all the way down in after you machine the base without removing this area on each side where the flat spots are on the extension. You either have to grind away the case or remove some material in this area to get it to sit down and not rock

I figured it had something to do with the bearings or pockets, but I’ve never lowered the cylinder on a Stihl of that style.

 

[huskihl]

I figured it had something to do with the bearings or pockets, but I’ve never lowered the cylinder on a Stihl of that style.

My post was different than what they were talking about previously. Those arches that Al probably cut deeper are to make room for the bearing pockets after lowering the cylinder. The area I have marked out is from the crank case not being wide enough to fit a 50 MM round cylinder extension down into it, so they have flat spots machined into the side of it. Once you cut the base, you have to remove the material within the confines of that flat spot as it does not get removed with the lathe

 

[EFSM]

My post was different than what they were talking about previously. Those arches that Al probably cut deeper are to make room for the bearing pockets after lowering the cylinder. The area I have marked out is from the crank case not being wide enough to fit a 50 MM round cylinder extension down into it, so they have flat spots machined into the side of it. Once you cut the base, you have to remove the material within the confines of that flat spot as it does not get removed with the lathe

Makes complete sense now. I hadn’t seen the flat spots until now.

 

[fredx]

This forum is loaded with knowlegeable fellas willing to help

 

[Redfin]

looks like you had a little chatter toward the bottom

This forum is loaded with knowlegeable fellas willing to help

You seem completely willing to help.

 

[Redfin]

Doc, the cylinder extension won’t fit all the way down in after you machine the base without removing this area on each side where the flat spots are on the extension. You either have to grind away the case or remove some material in this area to get it to sit down and not rock

You knock them down when cutting base Kev?

 

[huskihl]

You knock them down when cutting base Kev?

Can’t. The lathe stays outside of it

 

[Hinerman]

Can’t. The lathe stays outside of it

How do you do it? Flat file by hand? Belt sander, lol?

 

[huskihl]

How do you do it? Flat file by hand? Belt sander, lol?

Tiny pointed and/or flat burs. It’s not crazy important to have it perfect, it just can’t be high. I try to make certain I’m at least low enough with it so that it doesn’t hit. Plenty of room outside for the cylinder base to seal

 

[drf256]

Doc, the cylinder extension won’t fit all the way down in after you machine the base without removing this area on each side where the flat spots are on the extension. You either have to grind away the case or remove some material in this area to get it to sit down and not rock

Thank you Kev. I will show pictures of it relieved as I go forward. Time has been the biggest hindrance for me.

Hoping to get final squish measurements and hit the ports this coming weekend.

 

[jurchybald]

This is how I did many of them without a problem.

 

[jurchybald]

But don't worry. 400.1 is much simpler)

 

[Redfin]

How do you do it? Flat file by hand? Belt sander, lol?

Man, its been awhile I shook your hand. Hows tricks?