First time porting

[merc_man]

 

[merc_man]

 

[merc_man]

i think i got it figured out. takes a long time to up load. the vid with snow is before and no snow is after.

let me know if it worked

thanks randy

 

[XP_Slinger]

So in the interest of learning, lets talk about everything that you did to this saw. What was stock timing? How much did you raise the transfers, how much did you raise the intake and exhaust?

 

[merc_man]

So in the interest of learning, lets talk about everything that you did to this saw. What was stock timing? How much did you raise the transfers, how much did you raise the intake and exhaust?

All i did to the saw was gasket delete and widen the transfer. Muffler was already gutted. I added the pipe to muffler. Just wanted to try and keep it simple for the first time but really not much for gains. Might have to learn more about timimg and how to determine how much you can rais top of ports.
The intake port the ring ends are close to the edge so never wanted to widen them.

 

[Keith Gandy]

All i did to the saw was gasket delete and widen the transfer. Muffler was already gutted. I added the pipe to muffler. Just wanted to try and keep it simple for the first time but really not much for gains. Might have to learn more about timimg and how to determine how much you can rais top of ports.
The intake port the ring ends are close to the edge so never wanted to widen them.

Just dont overdo the porting too quick. Its easy to wanna grind away!!

 

[merc_man]

Just dont overdo the porting too quick. Its easy to wanna geind away!!

I went about. 65% of the bore.
Before i do anymore i gotta learn more aboiut the timing and how it will affect it.

 

[XP_Slinger]

If I may humbly suggest the "porting theory" thread on here. It's a long read at this point (38pages) but I learned a TON.

 

[merc_man]

If I may humbly suggest the "porting theory" thread on here. It's a long read at this point (38pages) but I learned a TON.

I been reading it since beginning. Lot of good knoledge on ther.

 

[merc_man]

I still havnt been able to find info on how to determine how high you can take an exhaust port or intake port. Is it a certain amount of degreese for a max on degree wheel.

 

[drf256]

I still havnt been able to find info on how to determine how high you can take an exhaust port or intake port. Is it a certain amount of degreese for a max on degree wheel.

No.

Exhaust roof does three things. It determines when compression of charge begins, it determines the amount of trapped volume, and it determines when combustion pressure is vented.

There are some general rules on this. In my mind you want it to open at the very point where pressure from combustion becomes close to parasitic drag losses. That's the theory at least. The actual amount that's best for any individual saw varies because of design and stroke.

A lot of guys use a rule of thumb of exhaust opening based on displacement for a worksaw. 105 on 50cc, 103 on 60cc, 101 on anything larger. But no one fits all in this game. If you have too much compression, somethings you want a higher roof. If you want more rpm and less lugging power, sometimes you want a higher roof. Etc...

The more you learn in this game, the more confusing it becomes. I hope the above helps.

 

[merc_man]

No.

Exhaust roof does three things. It determines when compression of charge begins, it determines the amount of trapped volume, and it determines when combustion pressure is vented.

There are some general rules on this. In my mind you want it to open at the very point where pressure from combustion becomes close to parasitic drag losses. That's the theory at least. The actual amount that's best for any individual saw varies because of design and stroke.

A lot of guys use a rule of thumb of exhaust opening based on displacement for a worksaw. 105 on 50cc, 103 on 60cc, 101 on anything larger. But no one fits all in this game. If you have too much compression, somethings you want a higher roof. If you want more rpm and less lugging power, sometimes you want a higher roof. Etc...

The more you learn in this game, the more confusing it becomes. I hope the above helps.

Thanks. That helps a little i think lol.

 

[merc_man]

So the 105 is kind of a starter point for my 50cc saw

 

[XP_Slinger]

The best thing you can do is make small changes. It's much more time consuming and involves a lot of tear down and rebuild sessions but it's the best way to develope what works best for you.

 

[merc_man]

If you raise exhaust do you have to raise intake. And do you raise them the same height.

 

[wcorey]

Normally you would only lower the intake port, to obtain more opening duration (or alternatively trim the piston skirt). Often deleting the base gasket and/or cutting the cyl base get you as much as is desired, sometimes more than...

One trade off to more intake duration is less case compression, 40 degrees seems to be the number many shoot for there. The height of the upper transfers is the other factor that dictates this and changing that then also effects blowdown. Changing the exhaust height can fix that but as you can see, everything interacts and has consequences downstream... round and round we go...lol...

You can raise the intake roof some as long as the ring ends don't hang down into the port at bdc.
The only real advantage here is if the piston skirt goes past the roof at tdc, you can gain additional time/area by bringing the roof up to the bottom of the skirt.

 

[jmssaws]

Your biggest gains will come from compression and a good muffler mod,most saws a ignition advance is a big mod also. The biggest gains from a grinder will be timing changes,widening and smoothing things will gain but not like the others. All things piled together though make a saw run the way it should.

Two people can port two saws to the same numbers and they can run very different, you have to find what works for you and it will be obvious when you do cause it will just be free,a completely free running saw is a beautiful thing and easily felt by anyone who runs it.

It varies from one saw to the next,I can build to saws the same and one run much better than the other,no explanation for it,it just does.

 

[merc_man]

Im in trested in trying tyming advance. Would five degrees be ok to start. What would be a max.

 

[jmssaws]

What saw?

010 to 020 off the key,some saws will take more.

 

[merc_man]

The husky 353. If ok i will try .010