Chainsaw porting

[Snedding_J]

New to the site. Just wondering if anyone has any information on chainsaw porting? Not for a racing saw, just to get a bit more performance out them. Is there any guidelines to follow on how much material to take out? Got quite a lot of mechanical experience, just not on porting. What kind of small die grinders do people use? Hope I've posted this in the right place, new to the forum stuff.

Thanks in advance

[Stubby]

1 hour ago, Snedding_J said:

New to the site. Just wondering if anyone has any information on chainsaw porting? Not for a racing saw, just to get a bit more performance out them. Is there any guidelines to follow on how much material to take out? Got quite a lot of mechanical experience, just not on porting. What kind of small die grinders do people use? Hope I've posted this in the right place, new to the forum stuff.

Thanks in advance

@spudulike   Spud ported most of mine .

[Snedding_J]

21 minutes ago, Stubby said:

@spudulike   Spud ported most of mine .

Great, with a bit of luck he might see this post. I'm keen to have a go at my own. What models have you had ported? Did you get good improvements?

[spudulike]

Yes, there are guidelines as to how large ports can be made, restrictive elements that can limit port size, minimum clearances piston to squish etc. I learnt some by looking online, some from reading a couple of books that I purchased and some by just developing my own techniques.

Just use a dremel with a carbide burr or diamond burrs for lighter work.

You can't put metal back on once you have ground it off so don't just think "wider the better" as many seem to think.

[Stubby]

34 minutes ago, Snedding_J said:

Great, with a bit of luck he might see this post. I'm keen to have a go at my own. What models have you had ported? Did you get good improvements?

Spud did ...346XP 372XP 390XP  . Petemate did my 560XP  and the Walker saw shop my 395XP . Yes vast improvement . Picks up quicker drives harder , runs cooler ( helped by MM ) and just as , if not more reliable .  EG my 346XP runs a 15" bar , full chiz chain driven by an 8 pin powermate rim .

[Snedding_J]

7 minutes ago, spudulike said:

Yes, there are guidelines as to how large ports can be made, restrictive elements that can limit port size, minimum clearances piston to squish etc. I learnt some by looking online, some from reading a couple of books that I purchased and some by just developing my own techniques.

Just use a dremel with a carbide burr or diamond burrs for lighter work.

You can't put metal back on once you have ground it off so don't just think "wider the better" as many seem to think.

Great, cheers Spudulike. Do you get good results, more torque and RPMS? Yeah, definitely a little material removed goes along way. Is there a certain percentage of the bore/stroke dimensions the ports can be enlarged too? I've been reading about squish, have you decked the bottom of a cylinder to raise compression? If there's any books you could recommend, it would be much appreciated. Sorry for all the questions, not too many people this side of the pond interested in porting chainsaws.

Many thanks

[Snedding_J]

4 minutes ago, Stubby said:

Spud did ...346XP 372XP 390XP  . Petemate did my 560XP  and the Walker saw shop my 395XP . Yes vast improvement . Picks up quicker drives harder , runs cooler ( helped by MM ) and just as , if not more reliable .  EG my 346XP runs a 15" bar , full chiz chain driven by an 8 pin powermate rim .

Impressive collection, all ported too. I've read that the 372xp responds well to porting. Hoping to port my 560xp in the near future.

[spudulike]

1 hour ago, Snedding_J said:

Great, cheers Spudulike. Do you get good results, more torque and RPMS? Yeah, definitely a little material removed goes along way. Is there a certain percentage of the bore/stroke dimensions the ports can be enlarged too? I've been reading about squish, have you decked the bottom of a cylinder to raise compression? If there's any books you could recommend, it would be much appreciated. Sorry for all the questions, not too many people this side of the pond interested in porting chainsaws.

Many thanks

The results are more torque, aggressive in the cut, higher revs in the cut, shortens cutting speed, you can lean on the saw more with less bogging etc.  Varies from saw to saw, there are always models that turn out better than others.

Yes, there is a percentage that most accept as the maximum you can go on port size but it doesn't work like that if there are other constraints of the engine design that stops you going to the maximum size - you have to understand how two strokes work and how the piston works in conjunction with the port openings and crankcase.

I have done a few saws with pop up pistons and turned down cylinder bases, they are an expensive option due to the machining so tend to keep it simple to keep costs acceptable....get 75% of the easier gains rather than spending days trying to get the last 25% for 3X the cost!

The only book that makes good reading is by Gordon Jennings, it gives a few pointers but is mainly aimed at motorcycle porting although it gives a good overall look at the subject.

[Snedding_J]

48 minutes ago, spudulike said:

The results are more torque, aggressive in the cut, higher revs in the cut, shortens cutting speed, you can lean on the saw more with less bogging etc.  Varies from saw to saw, there are always models that turn out better than others.

Yes, there is a percentage that most accept as the maximum you can go on port size but it doesn't work like that if there are other constraints of the engine design that stops you going to the maximum size - you have to understand how two strokes work and how the piston works in conjunction with the port openings and crankcase.

I have done a few saws with pop up pistons and turned down cylinder bases, they are an expensive option due to the machining so tend to keep it simple to keep costs acceptable....get 75% of the easier gains rather than spending days trying to get the last 25% for 3X the cost!

The only book that makes good reading is by Gordon Jennings, it gives a few pointers but is mainly aimed at motorcycle porting although it gives a good overall look at the subject.

It does make sense, got to way the costs against the performance gains. I'll look up the book by Gordon Jennings. Think I'll start by cleaning up the ports and removing any imperfections (lumps and bumps) in the casting. That should make a difference. I'm quite interested to check the squish and hopefully turn down the base of the cylinder (roughly the thickness of the gasket) to see if it raises the compression much and what the gains will be. Thanks again, might pick you brains again I'm the near future

[Wonky]

it’s a start

Gordons book

http://www.amrca.com/tech/tuners.pdf

 

and google mcdizzy,, maybe I’d better point you 

 

MacDizzy's Two Stroke Technology Exchange - TRX - YFS - YFZ - Glamis Sand Dunes

MACDIZZ.COM

---

Two Stroke Engine Technology Database, Large Two Stroke engine building / porting section. Visit the Glamis...