Cannot find the RPM - 026

[Jimmy in NC]

Okay...

I setup the wheel and got actual port opening numbers on the AM jug. I know most like duration numbers but my mathing isn't going real well right now.

TDC - 0°
Exhaust - 98°
Transfers - 120°
Intake - 73.5°

So with my head clearing and my stomach holding food... can someone tell me if I have the durations correct? Trying to learn the whole process here.

Intake - 147°
Transfers - 120°
Exhaust - 164°

 

[Jimmy in NC]

Can anyone comment on if I backed into duration correctly?

 

[srcarr52]

Can anyone comment on if I backed into duration correctly?

Yes, your conversion was correct.

 

[Jimmy in NC]

Yes, your conversion was correct.

Thank you sir.

 

[Jimmy in NC]

Squared up the intake a bit tonight...transfers tomorrow if time allows. Also have to pickup another fine tip Sharpe.

 

[Jimmy in NC]

A little more shop time...a little more grinding. Read around, talked to some people, and I decided to pick up the transfers a few degrees. Dremel and cut off discs were the tools. First time I have attempted this. Also I checked the timing once more and when I put the ring in for lay out I confirmed the factory transfers had a few degrees of stagger to them. They are much closer to even now.

 

[Jimmy in NC]

Just for reference...here is where I started.

 

[Basher]

Looking good Jimmy, remember the bevel.

 

[Jimmy in NC]

Looking good Jimmy, remember the bevel.

View attachment 170874

Limited time last night. I hope to get some bevels added tonight if time allows.

Ball burr time!

 

[mettee]

Looking good Jimmy, remember the bevel.

View attachment 170874

okay so wash is a new concept to me, I get what it is, but what I want to know is how to read it. I assume you are looking for the mix to travel evenly across the piston, and not follow too far right out the exhaust?

 

[mettee]

Jimmy I dig the progress. Very fun to watch the process

 

[Jimmy in NC]

okay so wash is a new concept to me, I get what it is, but what I want to know is how to read it. I assume you are looking for the mix to travel evenly across the piston, and not follow too far right out the exhaust?

You want the transfers to blow towards the back of the cylinder wall to help the exhaust to scavenge all of the previous charge out of the cylinder. Atleast that's what I think I am understanding. I'm learning.

 

[Jimmy in NC]

Jimmy I dig the progress. Very fun to watch the process

It's the most fun I've had with a saw in awhile. Those that have messaged me or added to this thread I appreciate the tips and advice. I will continue to add so helpfully others can learn to.

 

[Jimmy in NC]

So I got home a little early and found some time to add some bevels to the transfers. I started with a ball end burr and then worked them with 150 and 320 on my finger tip. I am fairly confident they will be OK at this point.

 

[Basher]

You want the transfers to blow towards the back of the cylinder wall to help the exhaust to scavenge all of the previous charge out of the cylinder. Atleast that's what I think I am understanding. I'm learning.

That is what I try for, that piston has 57 tanks of mix burned through it, the carbon on the crown could be rubbed off with my thumb but it looks like its breathing about right.

 

[Basher]

The bevel on ports in a small cc saw do not have to be very wide, I try to keep them less than .010, timing is much more crisp with just a narrow bevel.

 

[Jimmy in NC]

The bevel on ports in a small cc saw do not have to be very wide, I try to keep them less than .010, timing is much more crisp with just a narrow bevel.

I understand. With this P&C set... and using FarmerTec rings...well I am probably a bit carried away. I also did not raise the transfers as far as was suggested. Probably a degree or two short. If I want to raise further the bevel will already be there thus "crisping" the transfer opening.

 

[Basher]

I understand. With this P&C set... and using FarmerTec rings...well I am probably a bit carried away. I also did not raise the transfers as far as was suggested. Probably a degree or two short. If I want to raise further the bevel will already be there thus "crisping" the transfer opening.

You are doing fine for your first grind, just take what we tell you as a sort of guidance along your road to full time saw porter...LOL

 

[Jimmy in NC]

You are doing fine for your first grind, just take what we tell you as a sort of guidance along your road to full time saw porter...LOL

Not sure I am ready to go that far.

 

[Jimmy in NC]

Saw almost back together... maybe get to run it again this weekend.