390xp

[NORMZILLA44]

I would be lying Will, if I said all this was not over my head, but I still enjoy the thread, had to cover over and say hello to my loyal friend!! P.S 390, and all husky muscle saws are way cool:msp_thumbup:

 

[jropo]

Once again, I am sorry. I do not want to derail Op's good thread. If I still have that many questions I have more reading to do. And I do appreciate all of the further assistance. I have imposed on the op enough.

 

[Mastermind]

All this thinking makes my head hurt. :msp_unsure:

I'm just going back to hogging everything out and hoping for the best. :msp_ohmy:




:hmm3grin2orange::hmm3grin2orange::hmm3grin2orange:

 

[parrisw]

Ya no worries guys. I've still got lots to learn just like most of us. The more you think you know, you realize how much your really don't know.

 

[jropo]

I hope Will don't care, But this is a 066 cylinder Im getting ready to port.

That upper mark is when the Intake closes, the lower one down next to the lip is when the transfers open.......marked off the bottom of the piston skirt. I laid it out like this because it was easy to tell what was what just by eyeballing it.
Intake is at 160 stock. If ya lower the intake more, its gonna move that upper line closer to the bottom line.

Transfer are at 114. Raise them and its gonna move that bottom line closer to the top line. The closer them lines get, the less case pressure you have. Am I making any sence?


Now I have no idea how much is enough, or how much is not enough.......:msp_confused: But the lower the intake gets, and the higher the transfers get, the less case pressure you have. The area between them 2 lines is what ''Im gonna call" the compression stage for the crank case....which don't look like much anyways.





BTW, all of this is just thinking out loud.

I still do not want to derail op thread.
But I now want to take a stab at this.

Why would you even want to mess w/ the intake? Unless your raiseing it, and maybe filling the bottom.
More case pressure more Torque?
I get messed up when it comes to the transfers, but if you raised the intake and the transfers the same......... no change?
More the cylinder compression the less the case pressure you need?
The closer the intake and transfer times are togather the more rpm?
The further they are apart more torque? Its just the matter of weighing it out.
Now the (on my screen) vertical lines are how far you are planning to widen and blend? Seems like alot.

Please let me know if I'm even in the Ballpark..

 

[jropo]

So how about this ........... what if you don't raise the uppers to compensate for dropping the jug, widen them towards the intake as much as possible. Does this not help to "save" some c/c pressure & if you raise the ex. up this will increase the blowdown. By widening the uppers only, will this not help in the port/time/area to sweep out the old gasses & fill the cyl. with the extra charge from the added intake dur.

Also just thinkin' through the keys.........

Steve

No loss in torque added rpm?

More directed volume?

 

[jropo]

All this thinking makes my head hurt. :msp_unsure:

I'm just going back to hogging everything out and hoping for the best. :msp_ohmy:




:hmm3grin2orange::hmm3grin2orange::hmm3grin2orange:

My too. I thought they were talking nonsense until I did a little more reading, it still makes me a little but its starting to make some sense now.

Thats what I say hog'em out! More the better!

 

[parrisw]

You don't raise the intake, you lower it. Intake opens from bottom to top, ex opens from top to bottom.

 

[komatsuvarna]

I still do not want to derail op thread.
But I now want to take a stab at this.

Why would you even want to mess w/ the intake? Unless your raiseing it, and maybe filling the bottom.
More case pressure more Torque?
I get messed up when it comes to the transfers, but if you raised the intake and the transfers the same......... no change?
More the cylinder compression the less the case pressure you need?
The closer the intake and transfer times are togather the more rpm?
The further they are apart more torque? Its just the matter of weighing it out.
Now the (on my screen) vertical lines are how far you are planning to widen and blend? Seems like alot.

Please let me know if I'm even in the Ballpark..

Dont raise the intake. You run the risk of dropping a ring into the intake port,,, which isn't a big deal as long as its not the ring ends. Alot of saws have rings that drop in the intake, but the ring ends cant be in there.

I cant speak about the case pressure.....I have no lies to tell when I say a lot of this stuff is over my head!!

The vertical lines.....The closest ones to the port is the piston skirt sides, the widest set of lines is the ring end pins. Ya probably cant see it in that picture, but the ring end pins is CLOSE to the upper transfer ports. Cant wrap them but a very very small amount. I may end up turning the piston around backwards so the ring ends will be on each side of the exhaust port. They will be ~ .100 on each side which should be fine, but I haven't made my mind up yet.

Like somebody said the other day, the more I learn, the less I know.

 

[wyk]

Thanks.

Supposed to be not too bad in weight for a 90cc saw.

The 390 weighs in about the same neighborhood.

 

[jropo]

You don't raise the intake, you lower it. Intake opens from bottom to top, ex opens from top to bottom.

W/ my eyes closed, I cut the motor/cylinder in half, ran the process thru slow in my head, and this is what I also came up w/. Why I thought raising the intake was ideal is beyond me now. If anything you would want to lower the intake to increase duration/charge, which would also get the charge in the cylinder earlier(if matters or not :dunno. Or raise the intake side of the skirt of the piston instead, (I guess this where a windowed pistion comes into play if needed) if you don't want to cut the cylinder. To make the exhaust port open earlier w/o cutting the cylinder, slope the crown on the exhaust side as long as there is enough material. Enrichen carb to pervent a lean mix due to the increased volume intering the c/c,transfers, combustion chamber. This is why the intake and exhaust are staggered, to reverse this makes no sense, to me, right now.

Also thinking out loud, thanks for helping me understand this a little more.
Once again not meaning to derail. :chatter:

 

[jropo]

Dont raise the intake. You run the risk of dropping a ring into the intake port,,, which isn't a big deal as long as its not the ring ends. Alot of saws have rings that drop in the intake, but the ring ends cant be in there.

I cant speak about the case pressure.....I have no lies to tell when I say a lot of this stuff is over my head!!

The vertical lines.....The closest ones to the port is the piston skirt sides, the widest set of lines is the ring end pins. Ya probably cant see it in that picture, but the ring end pins is CLOSE to the upper transfer ports. Cant wrap them but a very very small amount. I may end up turning the piston around backwards so the ring ends will be on each side of the exhaust port. They will be ~ .100 on each side which should be fine, but I haven't made my mind up yet.

Like somebody said the other day, the more I learn, the less I know.

Makes sense to me.
I forgot all about the ring ends.

 

[parrisw]

Makes sense to me.
I forgot all about the ring ends.

Search for the thread porting 101, lots of reading there.

 

[NORMZILLA44]

How we doing tonight? I been on the other new site. Liking it!

 

[parrisw]

Doing well.

 

[NORMZILLA44]

Sweet! And by the way just noticed your post count, never did before. Mother of god 11k!! Nice! I thought I reached another level 3k, but got a long way to go to catch ya buddy!

 

[tree monkey]

Sweet! And by the way just noticed your post count, never did before. Mother of god 11k!! Nice! I thought I reached another level 3k, but got a long way to go to catch ya buddy!

lol, i think he does more talking then working.

you got this thing running yet?

 

[parrisw]

Sweet! And by the way just noticed your post count, never did before. Mother of god 11k!! Nice! I thought I reached another level 3k, but got a long way to go to catch ya buddy!

LOL, thanks.

lol, i think he does more talking then working.

you got this thing running yet?

If you knew me, you'd know its the complete opposite.

No its not running yet. Still waiting on a few small parts, this is what happens when you build a saw from a box of parts.

 

[tree monkey]

LOL, thanks.



If you knew me, you'd know its the complete opposite.

No its not running yet. Still waiting on a few small parts, this is what happens when you build a saw from a box of parts.

lol "box-o-saw" been there, more then once:bang:

 

[parrisw]

lol "box-o-saw" been there, more then once:bang:

Yep, allot of my saws started this way.