Project Stumpbroke How I do it

[deye223]

What's that long thing stuck in the bore?

if it's red i'd say a boring bar

 

[Stihlman441]

Nice work, rep sent.:msp_smile:

 

[Jim Timber]

What compression ratio do you bump these up to?

 

[imagineero]

Rep sent (don't do that very often!) and subscribing. Best pics I've ever seen on porting, really felt like I was there. Thanks for sharing your knowledge!

Shaun

 

[sefh3]

Thanks for taking the time to post this. A few questions. Can you acheive close to the same gains without lower the cylinder base? Also, what kind of bit are you using.

 

[ptjeep]

Nice pics stumpy, I enjoy the step by step shots. I got a question, I've used a ring to make my horizontal marks before but never used a piston. Do you care to explain how you hold, measure, and mark using a piston?

 

[imagineero]

Thanks for taking the time to post this. A few questions. Can you acheive close to the same gains without lower the cylinder base? Also, what kind of bit are you using.

That's a pretty standard tungsten carbide die grinder bit, 6mm by the look. If you find a good tool shop they usually have a small case full of them, you get what you pay for and the good ones aren't cheap. Last a long time though, especially on aluminum. They have about a dozen shapes usually, that one's called a 'Round Cyllinder'. it's one of the more useful shapes. The square ended cylinders are prone to gouging, the elyptical ones are difficult to get a flat edge from, spheres are pretty concentrated and triangles are just plain weird to keep under control.

Shaun

 

[Bluefish]

I love reading about all the porting jobs but have never really understood what was going on. This explanatory thread has made a light bulb go on in my mind. This site is awesome and you are not just an artist and technician Stumpy, you are now also a teacher. Thank you very much for this thread, I think it will be referred to by many for a long time. Russ

 

[mweba]

if it's red i'd say a boring bar

Was just poking fun :msp_wink:

 

[deye223]

Was just poking fun :msp_wink:

you dirty old man you :haha:

 

[jerrycmorrow]

SUB scribing. excellent post stump. lots of grass

(muchos gracias)

 

[Mastermind]

Good stuff Strumpet. :msp_biggrin:

 

[Isna]

opcorn:

 

[jasper89]

This is great stuff. Very interesting and thank you for taking the time to post!

 

[sunfish]

Well done Stump! So far...

Thanks for this!

 

[Stumpys Customs]

Thanks for taking the time to post this. A few questions. Can you acheive close to the same gains without lower the cylinder base? Also, what kind of bit are you using.

Yes, you can get respectable gains without all the machine work.
The bit is a 5/16" x 1/4'' carbid, round nosed cylinder.

Nice pics stumpy, I enjoy the step by step shots. I got a question, I've used a ring to make my horizontal marks before but never used a piston. Do you care to explain how you hold, measure, and mark using a piston?

I slide the piston in upside down with the crown facing the the bottom of the cyl. I clamp the cyl in the vice horizontally so the piston doesn't move. Then I set my caliper to the desired measurement & push the piston in the bore with the depth gauge "stick" on the caliper. I have to hold the piston in place with my finger through one of the ports & then make a mark. I'll try to get a pic of this in a bit.

 

[milkman]

You're tempting me again, nice explanation and pics, looks like you remove a lot of meat. Are those pics of the finished porting, or do you polish them up after grinding, or is there a need to polish? These picture threads are getting right up there with my other picture sites.

 

[cheeves]

Thanks Stumpy!! Really appreciate your taking the time to show an old wood cutter how to get more out of these amazing machines!! This Thread is Bookmarked!!!

 

[Stumpys Customs]

I'll be out in & out for a while today. So bear with me.

 

[Hedgerow]

Yes, you can get respectable gains without all the machine work.
The bit is a 5/16" x 1/4'' carbid, round nosed cylinder.

Those carbide bur bits are awesome! And they come in all shapes and sizes. And your oil trick works good too...
This is the tapered type.