Aftermarket Cylinder Quality

[slackinoff]

@isaaccarlson - Oh wow! Nice job! I might look at trying that. The "wings" seem overkill with how thick the casting is behind them.

@Ketchup - Excellent info thank you brotherman. Definitely food for thought.

 

[NateSaw]

White box 460 Big Bore:
View attachment 398780View attachment 398781View attachment 398782View attachment 398783

The foredom should be able to clean up the rough edges and improve the ports where necessary. I might have to epoxy the transfers to improve the exit angles. $27

I have one of those. I expect it to flake.

 

[isaaccarlson]

Yeah, it wasn’t my thread but I think he mentioned it as though a normal 268 slug cut to a popup would be lighter than the one he cut out of a Hyway 268 factory popup. Seems to me the squish dynamics would be more of an issue with a tall popup.

I’m all for lightening pistons. I agree that you can take a surprising amount off without negative consequences. It can be important how the shapes of the piston push the case charge and contribute to case volume. I’m a big fan of eliminating piston skirts that obstruct transfer lowers. In my mind the piston stroke creates a pressure wave that continues downward after the piston achieves BDC. Many people disagree.

Pressure waves in a 2 stroke move at the speed of sound. That's why we can tune the exhaust and intake. If the waves moved any slower, you'd never get 'em to run. The port's are not open very long at 12-16k rpm. At 14,000 rpm, one full turn of the crank only takes 4 THOUSANDTHS of a second. That means the ports are only open for about .0015 seconds. At 12,000 rpm, the ports are open for .002 seconds. It's amazing how enough air gets through them even at mach 1. To put that in perspective, that's less time than it takes for the firing pin to move in a pew-pew OR about the same amount of time that it takes for the bullet to leave the barrel once the powder has been ignited.

 

[Ketchup]

Pressure waves in a 2 stroke move at the speed of sound. That's why we can tune the exhaust and intake. If the waves moved any slower, you'd never get 'em to run. The port's are not open very long at 12-16k rpm. At 14,000 rpm, one full turn of the crank only takes 4 THOUSANDTHS of a second. That means the ports are only open for about .0015 seconds. At 12,000 rpm, the ports are open for .002 seconds. It's amazing how enough air gets through them even at mach 1. To put that in perspective, that's less time than it takes for the firing pin to move in a pew-pew OR about the same amount of time that it takes for the bullet to leave the barrel once the powder has been ignited.

Mind blowing stuff. I love it.

 

[hacskaroly]

Where I worked, we sold a MS 261c to a customer who later brought it back after running it for an hour on straight gas...muffler was bright blue and the piston had detonation marks on it. Cylinder had some scoring, but not bad. Customer did not like this his error was not covered under the warranty and did not want to pay for the repair, so just abandoned the saw.

The store sold it to me for $50 and due to available funds at the time, I installed a Mtanlo piston and cylinder kit (Mtanlo Piston and Cylinder Kit - Amazon) from Amazon for $50. I did a little bit of clean up on it and installed it. It fired right up and so far I have run about 6 tanks of fuel through it so far and its still going good. I still have the original cylinder and I think that I can get it cleaned up and use it again if needed.

 

[isaaccarlson]

Where I worked, we sold a MS 261c to a customer who later brought it back after running it for an hour on straight gas...muffler was bright blue and the piston had detonation marks on it. Cylinder had some scoring, but not bad. Customer did not like this his error was not covered under the warranty and did not want to pay for the repair, so just abandoned the saw.

The store sold it to me for $50 and due to available funds at the time, I installed a Mtanlo piston and cylinder kit (Mtanlo Piston and Cylinder Kit - Amazon) from Amazon for $50. I did a little bit of clean up on it and installed it. It fired right up and so far I have run about 6 tanks of fuel through it so far and its still going good. I still have the original cylinder and I think that I can get it cleaned up and use it again if needed.

Crazy

 

[Woodslasher]

Good eye. That’s pretty bad.
View attachment 398788

I've got what I believe is a 460 BB kit, if you want it just cover the shipping. A guy gave it to me saying it was a 660 BB kit but the stroke is way too short.

 

[Ketchup]

Good deal. PM inbound.

 

[Outback]

I would think the windowed 268 would create less bottom end primary compression. It would seem to me the harder it pushes up the transfers the better.

slackinoff. I do like that laser cylinder. Looks like a score.

 

[slackinoff]

I would think the windowed 268 would create less bottom end primary compression. It would seem to me the harder it pushes up the transfers the better.

slackinoff. I do like that laser cylinder. Looks like a score.

Yes I agree on case pressure with windowed 268… especially since this laser cylinder has fairly big upper transfers compared to oem. It might even have lager tunnels as well. Hard to say without an oem 372 cylinder. Decent used ones keep getting snatched up on eBay within hours of listing. Arg.

I would still like to try it one day just to play with and see. But anyways, I’m excited to try this Laser. I just got the cylinder on and also the modified Zama C3M twin jet. Tomorrow we will see!

 

[Ketchup]

If it goes good you should upgrade it to Rancher Boss.

 

[slackinoff]

If it goes good you should upgrade it to Rancher Boss.

Lol - you caught my goofball sticker. I was actually considering a Super Pro Rancher Boss.

 

[slackinoff]

First run with Laser cylinder. Way way way better already. It never ran anywhere close to this (even without b&c....I've built enough 70cc saws I can tell).

The only problem I had was my modified Zama C3M was having low jet problems. I expected this because of an isssue JB welding and re drilling a passage. It's fixable, but for now it wearing an Un-Modified Zama C3M Twin Jet and that's ok.

I'm going to test this un-modified Zama C3M twin jet against an oem Walbro HD12, then finally against a properly modified C3M Twin Jet.

 

[isaaccarlson]

That cylinder sound like it runs real nice.

 

[MG porting]

Well, I finally found a victim to put this cylinder in, and while it was not a port job, I was curios to know just how the plating would react to being cut, so I lowered the cylinder extension notch by the lower transfers a little bit with a carbide burr bit followed by beveling and all went well just like it should. Here's it running in some pine. @Duke Thieroff

Next time use a light.

 

[Stump Shot]

Next time use a light.