Spuds Porting and Tuning Thread

[Graham]

To answer my own question. The modified hole as a rule of thumb should be around 70% of the size of the outlet port on the cylinder.

I understand that there will be lots of variations to this depending on what work has been done.

 

I've got no idea of the ratio but remember in the heyday of two stroke racing bikes the old TZ expansion chambers seemed to have a very small outlet compared to their cc. Couldn't beat that ear splitting crackle though:001_smile: They seemed to alter in size when mufflers were put on them.

[MATTMOSS]

I've got no idea of the ratio but remember in the heyday of two stroke racing bikes the old TZ expansion chambers seemed to have a very small outlet compared to their cc. Couldn't beat that ear splitting crackle though:001_smile: They seemed to alter in size when mufflers were put on them.

 

I know a few (old:001_tongue:) bikers who have mentioned this also.

[Graham]

I know a few (old:001_tongue:) bikers who have mentioned this also.

 

You're only as old as the bike you ride:001_smile:

[wyk]

To answer my own question. The modified hole as a rule of thumb should be around 70% of the size of the outlet port on the cylinder.

I understand that there will be lots of variations to this depending on what work has been done.

 

Sorry, I only skimmed through your posts because I thought someone else had answered them when I saw your answer to yourself.

 

The answer of course is - it depends. It is difficult to open a saw up too much, though. There's only so many holes one can put into a muffler before you have hot exhaust spilling into parts of the saw that aren't designed for it - like the brake handle or top cover. 70% is a good start. Make sure to retune/add a bit more fuel.

[spudulike]

I've got no idea of the ratio but remember in the heyday of two stroke racing bikes the old TZ expansion chambers seemed to have a very small outlet compared to their cc. Couldn't beat that ear splitting crackle though:001_smile: They seemed to alter in size when mufflers were put on them.

 

The mufflers on chainsaws are just small cans that try not ot restrict flow but do try to restrict noise. They use a mix of small outlet holes and baffle plates - all this restricts the flow of gasses through the engine.

 

A muffler mod is just a very basic way of improving this flow whilst trying to not make a saw damn well deafening:blushing:

 

Teh TZ you talk about will have had an expension pipe, this is a way of varying the power curve and torque of an engine with its exhaust. The science of the expension is exactly that, it is dependant on the engine and is then designed with a specific outlet length and diameter, length and diameter of the expansion chamber and same on the outlet pipe.

 

The expansion allows the shock wave of the engine exhaust to bounce back on the outer wall of the expansion and bounce back in to the engine, charging it with a slight mix of exhaust and unburnt fuel/air vapour....more charge = more power:thumbup:

 

Don't get mixed up between our compact mufflers and the racing TZs of the 1980s.

 

On a separate note - I saw a tripple engined drag bike once based on three TZ750s - that was nine expansion pipes and sounded.....pretty damn weird:thumbup:

 

Has anyone tried revving two saws together at the same time in unison....try it:thumbup: Pro Am 1980s starting grid comes to mind!

[wyk]

And the bar and chain are in from Rob. Ported and lathe worked MS361. Ending compression was about 195psi:

 

 

[Old Mill Tree Care]

Has anyone ever made their own full wrap handles?

Since they seem so hard to get and are not too cheap I'd think making one yourself may be an option?

 

I have a home made one on my 395xp.

It makes a massive difference up a tree!

 

 

Sent with my iPhone from me, to you!

[D A Tree Surgeons]

I have a home made one on my 395xp.

It makes a massive difference up a tree!

 

 

Sent with my iPhone from me, to you!

 

Got any pics

[Stubby]

Got any pics

 

Got a posh after market one on my 395 . Very good quality slightly fatter than standard Husky ./ Will post a pic tomorrow .

[D A Tree Surgeons]

Got a posh after market one on my 395 . Very good quality slightly fatter than standard Husky ./ Will post a pic tomorrow .

 

nice one:thumbup: