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Porting! Techniques and advice requested.

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I just took delivery of a full-on porting kit from CC Specialty Porting Tools. I had been itching to blow some cash on something that was purely for myself and not something I would have to share with the wife. And seeing as she isn't as interested in two-stroke motors as I am, I made the jump and bought a porting equipment set.

Anyone in the club using this stuff? I've got my iron barrel coming off and planning on reworking it and doing two Imola kits.

What I'm trying to figure out now is how to measure port angles accurately. I also need some guidance on how to best approach getting good port maps (rubbings?).

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A plastic ruler works for measure port widths if you chose to do it that way. Calipers gives you a straight line measurement. Piece of paper rolled up into a tube and stuffed down the cylinder and the pressed against the walls of the cylinder will give a decent imprint. Heights for top and bottom of ports to top of cylinder is easy, steel machinist rule in metric.

 

Generally, getting things smooth is what helps the most.

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Chris do you know Guido ("Geedow") up in Canada

he is a racer of lambrettas in the NW, is the fastest dude around, does all his own tuning and I bet would be happy to provide you with some tips

 

he is FB

PM me if you want his contact info

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One of the major things to remember is to give the cylinder a hone after porting, or just port before boring. When you work the ports it actually moves some material in to the cylinder. Nice sloping angles, watch for divots and high spots, and above all CLEANER THAN A CLEAN THING when you are done.  

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I've been porting and studying two stroke theory for a number of years. Here's some basics that I've learned....

 

Port maps- Learning to do port rubbings by putting a tube of paper in the barrel Isn't too hard, just takes a few tries to get the hang of it.

                  A few tips- make the paper long enough to just over lap itself. 1/4" -1/2" is best. Too much overlap and the seam will run into a port rubbing. Then when you undo the paper, the port will                   be split in half. Also, make your tube longer than the barrel by at least an inch. Leave the extra stick out of the top of the barrel, and cut two tabs in it. Then you can fold the tabs down                     tight against the head gasket face and tape them down to keep the sleeve in place. This extra also allows you to get a rubbing of the line at the top of the barrel. If you plan on                                 measuring port heights with the map, it's essential that you have this frame of reference. I made a light box so I could easily trace the rubbings into a notebook for future reference. 

 

I use this to convert my measurements into degrees-  http://www.lambretta-images.com/archive/porttiming.php#.U7U87_ldXT9

 

 

Not sure exactly what the top tool is officially called (besides just a caliper), but I use these to measure port widths. Line it up with the port, then measure with a micrometer. Reversible too...I use the 65% rule for port width. Take the bore diameter x 0.65 and that's the max width, provided that the ports are shaped correctly. Adjust the caliper to that measurement and you can use it to mark out the new port.

ku1_12.jpg

 

 

For measuring heights, I use the depth bar of a venier micrometer. Using the piston inside the bore helps you get an accurate stop. The piston also helps to scribe a straight line around the bore, as needed. A square is helpful for lines parallel to the stroke. 

 

I use carbide bits for hogging out larger amounts of material from ports, the hard stones for smoothing everything out, then the sanding drums for polishing. With aluminum barrels, low speeds on all three types of bits is important. The CC tool is great for that because it has good torque at low speeds. The sanding drums seem to give a better finish at low speeds than at high speeds.

 

 

One of the major things to remember is to give the cylinder a hone after porting, or just port before boring. When you work the ports it actually moves some material in to the cylinder.

This is ideal, but whether porting or honing (which gives a sharp edge in the opposite direction), a good chamfer on all ports will clean up the sharp edges. 

 

Never touch the transfer windows, its too easy to ruin them completely. Making the exhaust port shape symmetrical is important. If it's not, it can ease the rings back into their grooves more on one side, leading to ring peg failure. 

 

I love discussing two stroke tuning theory, so if you decide to go further down the rabbit hole, feel free to bombard me with questions.

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It gets sticky at port measurement. A straight line measurenment is going to be shorter than a measurement taken following the curvature of the bore.

A digiltal caliper can actually be used for the inside measurements so there is no disrepency when measuring from one tool to another. Simply cut the side off that is used for OD measurements(the big fingers), then the ID side(small fingers) will fit directly down into the bore. That way you can also check to make sure the port is the same from inside the cylinder to the outside, where the manifold sits. If you want the port to be shaped like that ;) 

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Got cutting on a little bit tonight. I'm modifying a Casa kit to run reed. It is the easiest kit to modify like this because of the way the intake port is already shaped, with a small boost cut-out above intake port. Just remove that "island" in between and shape a second finger port. And slap a kit on it!

 

These are the two handpieces I have to work with:

 

14416011639_109b835ff4_z.jpg

182-AMC handpiece by SFvsr, on Flickr

 

14416068459_e92796589b_z.jpg

44MC handpiece by SFvsr, on Flickr

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I have an Imola kit getting ready to go onto a Serveta Li engine. I started cleaning it up.

 

First job was to do something about the internal lines of the transfers at the bottom of the cylinder:

 

14469448560_c5e8befbd9_z.jpg

Correcting case transfer shape - Imola cylinder by SFvsr, on Flickr

 

 

14652893041_36e72697d9_z.jpg

Correcting case transfer shape - Imola cylinder by SFvsr, on Flickr

 

14469503259_455dcb0271_z.jpg

Untitled by SFvsr, on Flickr

 

14676339673_cc8fccbf25_z.jpg

Correcting case transfers shape - Imola cylinder by SFvsr, on Flickr

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Ha. That sketch is not exact. I was just trying to show what I was thinking. Man, those Imola cylinders are ROUGH! The nikasil covers up a big amount of the internal transfers. There were globs of aluminum down in the ports. I think I got the kit cleaned up pretty well for my first shot at using these sorts of tools. I can see where I'll need lots of practice. I was surprised at how high the Imola cylinder sits, placing the piston below the ports at BDC. I would have liked to bring the cylinder lower or use a different crank with a longer conrod, but the owner of the engine is on a bit of a budget. Also, the piston rings were originally at 0.19mm and 0.21mm end gap right out of the box. I had to file them to get a bigger number. Squish was 1.80mm using the middle thickness gasket (0.71mm), so I put in the thinnest one (the kit came with three different size paper gaskets) and came away with 1.32mm squish.

 

 

I just ordered some diamond coated cutters for use on hard stuff like iron and nikasil.

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I wonder if that is why the lip at the top of the transfer, to force the mixture to that divet and then it is forced into the cylinder? If the little bump at the top is removed, perhaps the gas won't flow through the port as it is supposed to.

I'd be tempted to rmove the bump too at first look...

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I wonder if that is why the lip at the top of the transfer, to force the mixture to that divet and then it is forced into the cylinder? If the little bump at the top is removed, perhaps the gas won't flow through the port as it is supposed to.

I'd be tempted to rmove the bump too at first look...

Wait  - you mean at the intake finger port on the left side?  That is because I was holding the barrel at and angle. Straight on and it isn't like that. I was trying to get light to reflect off the polished exhaust port surface.

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The very first picture is a before picture. The second picture is an after picture.

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I understand that UJ. What I am trying to get across is that perhaps the bump at the top of the transfer may actually be there for a reason, the reason being to direct the mixture in a certain direction.

 

At first look, I would want to remove it also, but perhaps Imola want it there. Can't see them doing all the R +D and then leaving a bump for no reason. In which case you "may"(don't now how to bold type on purpose :o ) have just messed up the kit. Maybe you haven't messed it up, who the frig knows.

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Christopher, The area you removed from the transfers is there to assist the tumbling,

 

The imola transfers are pretty darn nice for a road going machine right out out of the box so they can use a light sand to removed the rough casting seen in some.

 

Also, the exhaust port walls appear as if they need to be straightened. Take a straight edge and apply it to the inside walls of the Ex and see where the high spots are and remove them. For flow the exhaust walls need to be as straight as possible from the interior to the flange surface. 

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Not only straight as possible but that line needs to continue past the flange right down into the wall of the downtube is what I'm learning. I have grinded the entrance of the tube waLl as smooth as possible where there is optimum flow. That one thing has provided great results for me.

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Not only straight as possible but that line needs to continue past the flange right down into the wall of the downtube is what I'm learning. I have grinded the entrance of the tube waLl as smooth as possible where there is optimum flow. That one thing has provided great results for me.

Right on the money Jimmy. The inner lip on a stock downpipe can be open right out to take a fairly big port. The pipe to flange weld is on the outside, so the strength is still there.as long as the pipe is not mounted under stress, it's golden.

 

No one seems to belive that 70+ is doable on a stock carb and exhaust(clean) set up(200cc), well, it is, I have built many that go that fast and get good fuel consumption. 175's, 60-65 all day long...Why people are only getting in the 70's with kits, pipes and carbs is beyond me. Seems like either it's an ego thing to have the latest or greatest, a fixation for stopping at gas stations, a desire to throw good money after bad or perhaps a combination of all three

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Christopher, The area you removed from the transfers is there to assist the tumbling,

 

The imola transfers are pretty darn nice for a road going machine right out out of the box so they can use a light sand to removed the rough casting seen in some.

 

Also, the exhaust port walls appear as if they need to be straightened. Take a straight edge and apply it to the inside walls of the Ex and see where the high spots are and remove them. For flow the exhaust walls need to be as straight as possible from the interior to the flange surface. 

I fully agree, that is what I was trying to say. Good eye on the exhaust port.

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I did go back and follow your advice on checking the straightness of the exhaust walls. I got it kinda straight, but since the port is slightly angled away, it is difficult to get rid of that "dip."

 

As for the changes to the transfers that are on the bottom of the cylinder... Too late! I'm grinding away on everything! It's like fuckin Purple Rain up in this joint!

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 It's like fuckin Purple Rain up in this joint!

Didn't realise you were into have colored genitals as well Chris :wacko: . Heard of blue balls, but purple?

 

Go on, you can do it, glue those grindings of tranfer back onto the transfer wall ;)  :)

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I haven't dropped in a while but I bet purple grindings and trippin would be cool.

 

I don't think I ever had a bad trip.

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