My 500i porting recipe?

[Hoolio]

Hello guys and girls.

So I’ve finally pulled the 500i apart and am ready to start porting.

I’ve only ported a few saws and never with a timing wheel.
I have posted about this before but now I have a clearer plan, I’m hoping you can let me know if my plan is sound.

Stock timing is this

Ex 106

In 83

I’ve gutted and opened up the stock muffler.



My plan-

Take .040”off the base. (Is this too much? I’m worried about needing epoxy in the inlet, I don’t want to do this.)

Cut the squish to .020” or slightly bigger.

Raise the exhaust to 103 (this will be grinding off about .060”, seems like a lot? )



Any input would be very appreciated.
Thanks everyone.

 

[Lightning Performance]

Why are people afraid to fill intake ports?
What is your transfer port number and your goals?

 

[Hoolio]

Why are people afraid to fill intake ports?
What is your transfer port number and your goals?

Guess I’m just a rookie and it’s one less thing for me to learn. I don’t necessarily think filling the ports is a bad practice.

I can’t remember the transfer now, I didn’t touch them, I don’t have a tool for them and really don’t know much about directing them.
I think going off other builds standard Nos with similar cut off the base to me (.045”) you can end up with 124. Bit of a rough guess though.

Goals. Have fun learning and Ideally end up with a pretty snappy saw, that still pulls well in the cut.
I ended up going .045 off the base, .022 squishband, smoothing out the intake port but not changing the shape or timing and smoothing inside the injector housing a little.
Raised exhaust to 103 and slightly widened it, almost 60% of the bore.

 

[Lightning Performance]

Guess I’m just a rookie and it’s one less thing for me to learn. I don’t necessarily think filling the ports is a bad practice.

I can’t remember the transfer now, I didn’t touch them, I don’t have a tool for them and really don’t know much about directing them.
I think going off other builds standard Nos with similar cut off the base to me (.045”) you can end up with 124. Bit of a rough guess though.

Goals. Have fun learning and Ideally end up with a pretty snappy saw, that still pulls well in the cut.
I ended up going .045 off the base, .022 squishband, smoothing out the intake port but not changing the shape or timing and smoothing inside the injector housing a little.
Raised exhaust to 103 and slightly widened it, almost 60% of the bore.

Go to 65 or 67% on the exhaust. Ring wear comes into play after that. Not recommended for milling running those 75% ports. Most will not live long if the rings still fit. Many reverse pistons on older stuff.
Figure your transfer port became less as the jug went down. That alone won't kill it but your missing a large gain from the extra intake time available.
Any transfer roof can be cut with a tiny wheel and finish the blending area with a small ball bur.
You either grow a pair and go there or be happy with mediocrity. That is not a dump on anyone or you. Once you get the stones to destroy a cylinder you will move forward and may or may not ruin one.

Blowdown time being suitable is likely more important then widening ports imho. That is the porters choice or operator preference. Finding your own lane takes times. Recommending things to others comes with experience and trigger time just like seat time is autos. Most of my port work experience early on was a constant mix of two stroke reed valve, loopers and four stoke poppet valved heads. Auto/truck , boat and bikes with this and that tossed in.

 

[Hoolio]

Go to 65 or 67% on the exhaust.

500i is close to the ring end, that’s the only reason I didn’t go wider.

You either grow a pair and go there or be happy with mediocrity. That is not a dump on anyone or you. Once you get the stones to destroy a cylinder you will move forward and may or may not ruin one.

I really appreciate this comment! Most people I’ve talked to and on Facebook etc have told me the opposite. “If you don’t know a lot don’t risk the 500i.”
I asked the local stihl dealer if anyone around here mucks around with porting, he said some do, no on the 500i though that he know.
I understand what they’re saying but I agree with you.

I don’t think I’ve been too scared to have a go.

Never machine a base, never made my own mandrel and cut the squish, firsts for me. Never done porting with a timing wheel. Big learning curve.
As for the transfer, il look into transfer flow direction and maybe come back to that.

Thanks I really appreciate you sharing your knowledge.

 

[Lightning Performance]

500i is close to the ring end, that’s the only reason I didn’t go wider.


I really appreciate this comment! Most people I’ve talked to and on Facebook etc have told me the opposite. “If you don’t know a lot don’t risk the 500i.”
I asked the local stihl dealer if anyone around here mucks around with porting, he said some do, no on the 500i though that he know.
I understand what they’re saying but I agree with you.

I don’t think I’ve been too scared to have a go.



Never machine a base, never made my own mandrel and cut the squish, firsts for me. Never done porting with a timing wheel. Big learning curve.
As for the transfer, il look into transfer flow direction and maybe come back to that.

Thanks I really appreciate you sharing your knowledge.

Just pay close attention to those ring ends. You need more on some than others based on the port shape. I've never broken a ring land from a hung ring. That said I don't build race engines. They get critical on ring end points. Most use a tool steel grade ring at that point to mitigate flex around the port openings. You can move a ring pin but it's not recommended for work tools.

I've also never ported a 500I so knowing the ring limits isn't in my tool box for that model.

Ask yourself two questions about rings ends on the exhaust side.
How much is left to carry the radial load and is approaching 65-67% a feasible number.

Once you do the math the rest will fall in place. Being close is good. Being on the edge is bad long term. Offset ports are grossly overlooked in this way of thinking that everything must be semetrical. Many have never blueprinted anything to know most thing are offset during manufacturing. Don't get caught in that closed circle of thought with a port or port location. The window matters more than the crosssection area location.

 

[SeMoTony]

Guess I’m just a rookie and it’s one less thing for me to learn. I don’t necessarily think filling the ports is a bad practice.

I can’t remember the transfer now, I didn’t touch them, I don’t have a tool for them and really don’t know much about directing them.
I think going off other builds standard Nos with similar cut off the base to me (.045”) you can end up with 124. Bit of a rough guess though.

Goals. Have fun learning and Ideally end up with a pretty snappy saw, that still pulls well in the cut.
I ended up going .045 off the base, .022 squishband, smoothing out the intake port but not changing the shape or timing and smoothing inside the injector housing a little.
Raised exhaust to 103 and slightly widened it, almost 60% of the bore.

Intake port should be rough finish. Turbulence keeps air fuel mix from condensing on the wall making it seem crazy when ya try to tune. My 661 (ported before my buy) has polished/opened exhaust with MT muffler, loved it once it broke in. Din't seem better than muf modded ms-460 til break in was done. Have milled with 60" b&c have 72" on hand in case