262XP Day

[Marshy]

OK, I've checked the timing numbers. Stock Mahle jug, with a base gasket.

EX: 103.5
TR: 116
IN: 69

That means we have only 12.5 degrees of blowdown. Cool huh?

Case compression angle is 47 degrees.

No wonder these saws are factory hotrods.

I'm with Chris on this, a little green. Please explain how you measure these numbers. Maybe you have already taken the time to explain this? I think I get the gist of useing a timing wheel and the light trick at the port. What Im unsure about is, what is your 0 deg reference piont TDC or BDC. These measurements (assuming TDC=0 deg) are taken then the port opening (aka the ceiling/roof) correct? What about durration of the ports, how come you never comment on it, seems like port duration is equally important? Is this asking too much to share? I can respect that. Thanks!

 

[Paragon Builder]

I should'nt be reading this thread.............This **** is way over my paygrade..
Carry on..

Damn, you get payed to read???
I'm jealous!

 

[Mastermind]

I think I remember you mentioned the exhaust to displacement rule in another thread. Was it your trade secret or can you share it?

It's simple.

50cc = 105
60cc =103
70cc = 101

It gets weird after that........101 is good all the way to 120cc really.

I should'nt be reading this thread.............This **** is way over my paygrade..
Carry on..

I know better........you're smarter than any of us.

I'm with Chris on this, a little green. Please explain how you measure these numbers. Maybe you have already taken the time to explain this? I think I get the gist of useing a timing wheel and the light trick at the port. What Im unsure about is, what is your 0 deg reference piont TDC or BDC. These measurements (assuming TDC=0 deg) are taken then the port opening (aka the ceiling/roof) correct? What about durration of the ports, how come you never comment on it, seems like port duration is equally important? Is this asking too much to share? I can respect that. Thanks!

I measure opening points from TDC. That's the roof of the exhaust port, and transfers.......but the floor of the intake.

I don't worry about duration at all.

 

[skippysphins]

I am more a hands on type if learner .

 

[Mastermind]

Me too Chris.

I've completely destroyed a bunch of jugs.

 

[skippysphins]

Me too Chris.

I've completely destroyed a bunch of jugs.

I have a feeling I will be buying some I don't care about

 

[kz1000]

This is cool, I haven't seen this many questions about how it is, done since the scene in Jurassic Park about the baby dinosaurs.

 

[Paragon Builder]

It's simple.

50cc = 105
60cc =103
70cc = 101

It gets weird after that........101 is good all the way to 120cc really.

Wow! Thanks.
Does this follow true through all makes?

Is this an experience (trial and error) thing, or is there some kind of "science" behind it?

And how do you determine transfer and intake heights based on this?

 

[skippysphins]

This is cool, I haven't seen this many questions about how it is, done since the scene in Jurassic Park about the baby dinosaurs.

Ty kz I feel really stupid now lol

 

[Mastermind]

Wow! Thanks.
Does this follow true through all makes?

Is this an experience (trial and error) thing, or is there some kind of "science" behind it?

And how do you determine transfer and intake heights based on this?

It works for me.

I'm not smart enough to tell you why. I've only got an eighth grade education.

Now transfer ports are black magic. Their height depends on whether the engine is quad port, dual port, intake height, case volume, etc.

Intake heights can be very confusing too. Throttle plate size, transfer height, case volume, etc all play a role in that one too.

 

[Mastermind]

I'm done for today........

All the transfer ports are roughed in.......

 

[skippysphins]

Thanks again Randy!!

 

[skippysphins]

Could I use cheap aftermarket cylinders to try

 

[Duane(Pa)]

You poor bastard.....Meaning only I reallllly pity you.... I thought you were taking April OFF? My hands ache just looking at 9 jugs.....

 

[weedkilla]

I'll try Chris.

Remember, this are just my thoughts.....

In a two stroke engine the transfers are everything. The air/fuel mix has to get around the piston from the crankcase to get into the combustion chamber.

This saw has a very short intake duration, and a high transfer opening point. The intake being short is what allows the transfers to open as soon as they do.

People think about blowdown far too much IMHO. The transfers opening is what pushes the remains of the exhaust out........as long as the pressure is not greater than the transfer flow. If the intake is too low, then there isn't as great of a pressure when then transfers open, and the exhaust can travel down the transfer ports......

There's a hell of a lot more at play here, but that's the quick and dirty version....

I feel like I have my boots stuck in mud when it comes to really understanding transfers, but I think I just got how the 066 lit up after you filled the inlet floor.

Thanks - although I've said it many times - for the amount you've shared with so many of us.
Engine tuning has always been cloaked in secrets, yet you continue to prove that giving up your secrets just shows the difference between the professionals and amateurs.

 

[weedkilla]

My hands ache just looking at 9 jugs.....

Erm?

 

[bryanr2]

When these are done, hope you add the Poulan 3750 to the videos for comparison.

 

[Nitroman]

Or maybe I should have said days?

10 of them total. 7 on the bench and 3 being assembled......

View attachment 417386

I can't believe I blew right over it. There was The Big Hint right in front of me. Geez. See what adrenaline does to me?

I am trying to find an appropriate box to put that oil in to send to you. I have a postal nazi watching me closely at my local P.O. so I'll have to sneak it past them. Even though it will be packaged perfectly. Will get it out this week. You'll love it.

 

[fastLeo151]

When these are done, hope you add the Poulan 3750 to the videos for comparison.

That would be great to see that saw hang with a 262 but I don't see it happening.

Randy,
Need anymore poulan parts yet?

 

[Eccentric]

Here's some pics of what Jon has been doing.

First he heats one side so it's hot enough to just drop the bearing in the pocket.

View attachment 417463

View attachment 417464

Then he lets the bearing soak some heat out of the case half.....and then he slips the crank in.

View attachment 417465

Installs the gasket......

View attachment 417467
View attachment 417466

And heats the other half.

View attachment 417468

Slides it on.......bolts it all up.

View attachment 417469

And then centers the crank up with a brass hammer.

View attachment 417462

Ummmmm....................................


Whut about da FW side bearing Randy? Methinks you skipped a step or two and a couple pichurs.........