First Graduate

[timberwolf]

You are correct sir, taking some of the skirt would be effectively moving the port down. And I will take your other remark as a compliment, I would much rather be accused of overthinking than underthinking.

As far as doing 2 things in isolation and expecting the result to be the sum of the two, still need convincing here, depends. Take widening the intake and raising the exhaust. should work, but if the raised exhaust and resulting RPM conflicts with the changes in Intake resonance you might not be getting all that is available, maybe a bit mor of on and a bit less of the other would net more.

My point is just looking at things symbiotically as opposed to in isolation. Maybe I am jumping ahead, that is saw building 201 Right?

 

[timberwolf]

Reflecting on the "Overthinking" and it occured Jennings referenced the deceptive apparent simplicity of two strokes in the Tunners Handbook.

Mechanically, the two-stroke engine is very simple and, unfortunately, on too many occasions this apparent simplicity has fooled would-be tuners into believing that this type of engine is easy to modify. Just a few hours with a file in the exhaust and inlet ports can change the entire character of the engine for the better, but if you go just a few millimeters too far you could end up with a machine that is slower than its stock counterpart.

This book details in layman terms various methods used to increase speed in two-stroke engines. Although his directions are easy to understand, the author goes to great lengths to make sure every detail is covered in his instructions. A great book on getting maximum performance from two-stroke motorcycles.

Now says a few mm could be too much but on a motor a fraction of the size the margines would be smaller.

 

[buck futter]

There is some good info getting kicked around here.

MS-310, Grab a seat and get comfy.
The Ms-310 was built with a horizontally split crankcase which means that the whole motor comes apart at the crankshaft bearings. From what I understand, mind you I am still a knowledge hungry novice, when modifying a saw it is very important to raise the compression which is most commonly accomplished by removing the gasket at the base of the jug on a vertically split crankcase. This more traditional construction is actually a three piece design. Left, Right and the Jug itself. On exception that I know on is the husky 350 which has a hybrid of these two designs, horizontal split bottom with a traditional jug siting on the top. Now if one had access to a milling machine, the proper size endmill and plenty of machining knowledge. I believe it would be possible to increase compression of a horizontally split crankcase by milling the base of the jug the amount you want to raise the piston ( say .020") off the bottom of the jug. Then place the jug and bottom plate together without the crank of course and resize the hole with either a cnc mill or the proper size endmill. It sounds like alot of work and certainly there is alot of ways things could go wrong. That said Gypo is going to work on a ms250 soon which has the same engine design. So be patient and Gypo will show the way. You may be able to do some modest porting with out changing the compression like if you lowered the intake .020-.025" raised the exhaust by .020" and you can't go wrong by removing casting flaws. By all means do a muffler mod. You can also take the carb off and pull the choke and throttle plates out relieve the screws holding the plates in and reinstall everything. It may help some or not at all but I figure I can't hurt anything.
As for the husky what model is it?


Lucky

 

[buck futter]

Gypo has revolutionized this site by releasing information that seemed to be off limits. Myself for example, I have two small kids, my wife and I are both in school and I am providing the only income. If I could justify spending an extra 2-300 bucks I would definately have a saw modded by one of the pros. Realistically I would be stuck with a stock saw for a long time. Thanks to John I have gained some HP on the cheap and learned alot about saws/2-stroke motors in general. I know that what I gained is modest in comparison to the pros but I am very impressed with the improvement.

Dennis,
You said to lower the intake and not raise it, I understand that lowering the port is like turning on the valve sooner to get more gas in. As far as raising the port it would be like leaving the valve open longer, correct? When I ported the 357/359 I lowered the port .0385" and I noticed that skirt of the piston went past the top of the intake port. The base of the jug to the top of the intake port measured 1.1745", I calculated the piston length plus squish clearance at tdc the bottom of the skirt would be 1.2505 from the base. so I move the top of the intake port up to 1.2000" reasoning that it was like opening the valve more. Is there anything that I am missing on this? Could I move the top up an additonal .0505?

Quick recap I lowered the intake .0385 and raised it .0255" the exhaust I raised .0375"

Lucky