Flat top or pop-up

[Mastermind]

We're always a day late and a dollar short in the saw modifying world......picking through the leftovers of motocross and road race bike theory.

Build your saw go cut wood. Run against other guys saws.....practice makes perfect.

I'm in the shop cutting squish bands today.

Just saying. :msp_biggrin:

 

[Trx250r180]

now i see why DC puts pipes and big carbs on his saws ,makin them into dirt bike engines :msp_wink:

 

[Dennis Cahoon]

We're always a day late and a dollar short in the saw modifying world......picking through the leftovers of motocross and road race bike theory.

Build your saw go cut wood. Run against other guys saws.....practice makes perfect.

You forgot about the most important part Randy!........A good kick@ss "CHAIN"......Hahahahahahaha!

 

[Mastermind]

You forgot about the most important part Randy!........A good kick@ss "CHAIN"......Hahahahahahaha!

Right you are Dennis.

 

[mile9socounty]

Thanks for all the good intel gentlemen. The insights discussed will help me decide on what to do when I have my saws ported.

 

[sachsmo]

I've seen many saws with dished pistons from the factory; like the Sachs-Dolmar 133, Husky 350/J-red 2150, and some of the Solo saws.

Them 133s are a kickin' Mule even with a dish!

 

[sachsmo]

I'm in the shop cutting squish bands today.

Just saying. :msp_biggrin:

Yes Sir, a pop-up seems to be such a waste,

just sayin'

 

[HuskStihl]

Flat- Pop.

You'd have to be really careful with a pop-up in a 346. If you don't get the timing chain and cam profile just right, you'll wind up crashing it right into the intake valves. Might be different with a pushrod chainsaw.

 

[cpr]

You'd have to be really careful with a pop-up in a 346. If you don't get the timing chain and cam profile just right, you'll wind up crashing it right into the intake valves. Might be different with a pushrod chainsaw.

They rev-gain a lot on the pushrod saws, so you need to switch to a roller and maybe girdle the rocker stands along with heavier springs to avoid float-induced free porting.

 

[Mastermind]

You'd have to be really careful with a pop-up in a 346. If you don't get the timing chain and cam profile just right, you'll wind up crashing it right into the intake valves. Might be different with a pushrod chainsaw.

They rev-gain a lot on the pushrod saws, so you need to switch to a roller and maybe girdle the rocker stands along with heavier springs to avoid float-induced free porting.

You guys are just being silly. This interweb chainsaw discussion is serious bidness.

 

[woodyman]

I put Roads lifters in my last saw and they really made the rockers quite

 

[tlandrum]

dont make randy mad, you wont like him if he gets mad. dont mess around with chainsaw bidness if your not prepared for it.

 

[Mastermind]

 

[HuskStihl]

I put Roads lifters in my last saw and they really made the rockers quite

Sorry Randy, I was feeling insecure because I had no idea what the heck anybody was talking about. I'm just relieved CPR thought I was joking! I'll go find a nice safe oil thread now

 

[cpr]

Wait, WHAT? That was a joke?

Oh. and stuff.

 

[Walt41]

Let's see, a 25 pound flywheel, jackshaft, belt, dial indicator, saw mount, safety screening and some fasteners and we are partially on our way to a chainsaw Dyno...any thoughts?

 

[blsnelling]

I have worked on and I have ran a few of the 346s. I have cut the chambers and I have done the pop ups. I still cant tell a difference performance. When I built my personal 346 I cut the piston and not the chamber. If I had thought that I would gain anything by cutting the chamber I would have done it.
Try to stay under 200 pound compression on the 346, anything over that and it will slow down.
Somehow your thread got changed from your original question on your 346 to flat vs domed piston in race saws and modern 2 stroke dirt bikes. On a woods ported 346 saw I dont think anyone can tell the difference.
Here is a quiote from Eric Gorr. Please google him if you dont know who he is. It will give you a good idea about domes vs flat pistons.

Later
Dan

Thanks for sharing Dan. I have a new 2153 here that I cut the squish band in. It has just shy of 220 PSI. It's still on it's first tank of fuel, so not even close to broken in. My 346 has a popup piston with just shy of 200 PSI. I'm anxious to get some time on the 2153 to make a fair comparison. It's not a perfect test for the popup/flattop debate. In addition to the piston difference, there's a 20 PSI compression difference, with the one getting past what you say is ideal. We'll see. Other than that, the two saws are close to identical in build.

Don't forget in this discussion, we're using chainsaws that run at WOT almost exclusively. We're not concerned with bottom/mid-range torque needed to come out of a corner.

Flat top with cut squish band. 220 PSI. First time to see wood. Pine log.
[video=youtube_share;p1OeCYOGElQ]http://youtu.be/p1OeCYOGElQ[/video]

 

[blsnelling]

Popup 200 PSI. Well broken in work saw. This is an Oak cant.

[video=youtube_share;bqF0u_ux0JM]http://youtu.be/bqF0u_ux0JM[/video]

 

[thomas1]

Thanks for sharing Dan. I have a new 2153 here that I cut the squish band in. It has just shy of 220 PSI. It's still on it's first tank of fuel, so not even close to broken in. My 346 has a popup piston with just shy of 200 PSI. I'm anxious to get some time on the 2153 to make a fair comparison. It's not a perfect test for the popup/flattop debate. In addition to the piston difference, there's a 20 PSI compression difference, with the one getting past what you say is ideal. We'll see. Other than that, the two saws are close to identical in build.

Don't forget in this discussion, we're using chainsaws that run at WOT almost exclusively. We're not concerned with bottom/mid-range torque needed to come out of a corner.

Just because the throttle is wide open does not mean you don't want as broad a range of usable power as possible. That's what makes a saw easier and more forgiving to run. Making a peaky top end screamer kinda defeats the purpose of a work saw.

 

[Dennis Cahoon]

.......We're not concerned with bottom/mid-range torque needed to come out of a corner.

Brad........Next time you push down on your saw, in the middle of a cut.......you'll be coming out of the turn.......Hahahahahaha!


"Morons, I've got morons on my team".....Strother Martin