New to Porting

[Nutball]

Hello from Middle TN.

I would like to be able to port my own saws, and any other equipment that could use it. I think it would be fun doing it myself, and the wait time to get someone else to do it is often more than I want to wait.

My plan for this thread is to show you my progress while gathering much needed help and wisdom from you guys.

I have some tools from CC Specialty on the way. I have a wore out 391 cylinder to use for getting a feel for using the tools, it looks like a bit of a hard to work on cylinder design. I also ordered a few cheap chinese cylinders at a greater discount to practice on before working on my own more expensive equipment. The design of the chinese cylinders look really easy to work on, but in my opinion they need very little modification. Most of the ports look bigger than one might see on a stock saw, some even too big.

I'm meticulous, and have a good sense of figuring flow characteristics, but need a starting point for port dimension proportions and techniques.

 

[huskihl]

Maybe this will help. Lots of useful tidbits

http://opeforum.com/threads/part-one-the-exhaust-port.7279/

http://opeforum.com/threads/part-two-the-intake-port.7290/

http://opeforum.com/threads/part-three-the-transfer-ports.7306/

http://opeforum.com/threads/part-four-compression.7318/

http://opeforum.com/threads/part-five-ignition-timing.7331/

http://opeforum.com/threads/part-six-the-exhaust-system.7372/

http://opeforum.com/threads/part-seven-carburation.7395/

 

[Nutball]

Thanks so much for those links, they look very useful. I've already read through some of the links CC Specialty had. I thought I noticed a conflict between 2 links though. I thought one said flow across the piston (instead of aimed more vertical towards the head = more RPM while another said it gives more torque and less RPM.

Has anyone here had experience porting or just plain using chinese replacement cylinders for Stihl saws, so they can share their experience on their fit, performance, and what they changed?

BTW, if I've posted in not the best section let me know and please move the thread. Just making sure.

 

[beaglebriar]

Maybe this will help. Lots of useful tidbits

http://opeforum.com/threads/part-one-the-exhaust-port.7279/

http://opeforum.com/threads/part-two-the-intake-port.7290/

http://opeforum.com/threads/part-three-the-transfer-ports.7306/

http://opeforum.com/threads/part-four-compression.7318/

http://opeforum.com/threads/part-five-ignition-timing.7331/

http://opeforum.com/threads/part-six-the-exhaust-system.7372/

http://opeforum.com/threads/part-seven-carburation.7395/

That guy's a hack...

 

[Dub11]

That guy's a hack...

Which one?

 

[beaglebriar]

Which one?

Yeth..

 

[huskihl]

Which one?

Yeth..

Below me

 

[beaglebriar]

Below me

Uncalled for

 

[beaglebriar]

Thanks so much for those links, they look very useful. I've already read through some of the links CC Specialty had. I thought I noticed a conflict between 2 links though. I thought one said flow across the piston (instead of aimed more vertical towards the head = more RPM while another said it gives more torque and less RPM.

Has anyone here had experience porting or just plain using chinese replacement cylinders for Stihl saws, so they can share their experience on their fit, performance, and what they changed?

BTW, if I've posted in not the best section let me know and please move the thread. Just making sure.

I had a Hyway cylinder that was nice enough and ran well with a little work.

The Cross Performance kit that I have here looks ok also. That's about all I have to offer...

 

[Nutball]

I got a couple 56mm 660 kits. The piston is capable of traveling high enough to allow a large opening below the piston in the exhaust port. I don't know if the piston can go that high when the engine is assembled. I might have to end up plugging the lower part of the port. It's a cheap part I know, but I would like to learn and practice even less usual skills such as repairing bad porting (or just simply altering ports by adding material) if at all possible. I want to treat these parts as if they will be used so I can practice doing it right. They might get used too, there's a 660 at work that's getting weaker.

 

[wcorey]

The piston is capable of traveling high enough to allow a large opening below the piston in the exhaust port.

The common term for that is freeporting, sometimes also caused after the fact by machining/lowering the cylinder to gain compression. A little is acceptable (like maybe .060") but at some point it must be detrimental to performance.

 

[Nutball]

I would have called it sub piston induction, but that's only beneficial to Cox style engines. I guess the only way to find out would be to test fit it in a 660 since adding material to the bottom of the piston might not clear the inside of the crank case. Anyway, it has ports to practice on, and I know the transfers are way too small on these cylinders.

 

[Deets066]

I would suggest getting a timing wheel setup before you do any grinding.
Also I would never consider adding anything to the bottom of a piston skirt.

 

[Al Smith]

A few suggestions on the net --Macdizzy --- Jennings two stroke tuners hand book ---A. Graham Bell two stroke performance tuning ---Fox Valley kart --British MC sites --many RC sites ---
While it can be interesting quite honestly you won't find much on chainsaw sites being very specific . Keep in mind it's not all just the porting .There's other factors,cutting system ,ignition timing .Conditions,work saw,cookie cutter ,alkie burning hottie etc .
It's not the rocket science some profess it to be ,not voodoo ,not black magic .It is physics .Some can,some want to and some pay somebody else to do it .Good luck

 

[smokey7]

If using a aftermarket part co pair it to the oem version and think about why things are made that way and what they were trying to accomplish. Then think about how it ran berore and then think how you want it to run. I aim for a saw to feel free when running when everytging is working in concert. I tend to like a saw with torque and keeps pulling when lugged down. I would hate to fall a large tree with a saw that waa all revs and constantly had to be feathered to keep it cutting vs a saw that i could start and stop in the cut easily that didnt live and die revving to the moon.

 

[Nutball]

I kind of like how my 2188 runs, as well as a stock 661: a decent bit of low end torque, but could be better, and lots of power in higher revs. I wouldn't want the power band any higher though.

I got my CC Specialtools. I'll get started on a wore out 391 cylinder to get a feel for handling the tools.

Do I need any special lube while grinding? Or should it be done dry ?

 

[Nutball]

After reading some of the porting threads I guess I'd port my saws towards how I would use them. And since I know how to run a chainsaw (finding and maintaining optimal rpm) and not see how hard I can push before it stalls (like I see almost everyone at work do), I will probably aim for a high rpm saw most times for more power and faster cutting speed.

 

[huskyboy]

I kind of like how my 2188 runs as well as a stock 661: a decent bit of low end torque, but could be better, and lots of power in higher revs. I wouldn't want the power band any higher though.

I got my CC Specialtools. I'll get started on a wore out 391 cylinder to get a feel for handling the tools.

Do I need any special lube while grinding? Or should it be done dry ?

I would first see if you could get away with deleting the base gasket (use 1184 threebond or similar gas/oil resistant sealant) or make a thinner one. You will get a little bump in torque from that from the increased compression. When you have the head off, use the old gasket to see if the lower transfers match the base or not. Use the gasket as a guideline to match (I use a sharpie to mark where on the cylinder to grind). After that look at the intake boot and see if the spigot on the cylinder matches the boot or not. After going through this try fitting a black unlimited coil to make tuning easier and advance it 1/3 of the key on the flywheel. Don’t advance it if you keep the blue coil. I gutted the muffler under the stock deflector. The 390 I had with a hyway cylinder liked to be tuned around 13,200 with these mods and it was faster than a stock 661 by a bit. Run 40:1 or 32:1 gas mix. If you find yourself wanting more than these simple mods get you, you can go back in for more. You might be surprised how much simple mods wake up a saw. Some more than others. I haven’t gotten into porting other than mess with intake timing or widen the ex because I don’t really have the right tools or knowledge for it.

 

[Redfin]

Do I need any special lube while grinding? Or should it be done dry ?

You dont “need” any but some lubricant will keep the burr from filling up with shavings.

I have been using a dielectric grease, seems to work well.

 

[mdavlee]

You dont “need” any but some lubricant will keep the burr from filling up with shavings.

I have been using a dielectric grease, seems to work well.

I used Belray H1R for a long time for bits. Couldn’t stand the smell to burn it. Bits last longer the cooler they stay