Stella 2T highway/performance upgrades
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Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Wed Oct 30, 2019 8:18 pm quote
charlieman22 wrote:
Swiss,
Here is an article that may be helpful: https://scooterlab.uk/vespa-px-gear-selector-boxes-part-1-workshop/

At issue is not the xmas tree and drive shaft gears alignment.
Its where the selector box places the shift cross.
A few millimeters apparently makes a big difference.

Thats why Sime noted that simply shimming the total drive shaft stack to take out slack - would get rid of play - but not necessarily align that gear with the cross.

For what its worth - which is very little - I like the short 4th. won't matter what gear your in - you will have get up and go in your right hand. To Jack's point - if you undershoot and really want lower RPM, you can always just alter the clutch primary = don't have to split to adjust.
CM, yes that link is helpful. Thanks. I have come to the same conclusion at the end of my hour playing with gearboxes like legos. It will stick now that I saw it physically instead of just reading it.
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Thu Oct 31, 2019 7:21 am quote
and here is the "final" exhaust profile to grind for. I left some space above the blue piston line as I will grind to the red level now and then get cylinder re-bored and chamfered, and when I mount everything back in engine I will finish lowering the exhaust line flush with piston after knowing the exact location of that line.

mal166ports_02_portingtemplate.jpg
20mm width flat added to the top and bottom line.

Addicted
Joined: 26 Jan 2019
Posts: 689
Location: california
Thu Oct 31, 2019 7:27 am quote
Swiss,
If I had the Dremel in my hand - I would make that bottom curved the entire length.
Reason - The radius are sharper there vs the top - so the transition for rings is quicker and more aggressive as they meet the end of the hole.
Even a slight radius over all for the bottom line would be more ring friendly.
As for the top - will let Jack comment on the 20mm width of the flat.
Visually - seems like a lot to me with such a wide ex. port.
No experience of course with this particular job on my side - so consider that.
However - decent understanding of material properties and mech. eng. side of it.

My $.02 - take that flat on top down to about 10mm and get rid of it on the bottom with long sweeping line - if it were me...
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Thu Oct 31, 2019 7:39 am quote
alternative more rounded less flat width both top and bottom. this is now a fat wide opening with tons of grinding to do. ha. still slightly trapezoid shaped.

mal166ports_02_portingtemplate.jpg

Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Thu Oct 31, 2019 8:18 am quote
If this is the stuff you guys are talking about.. I'll order a tube!

https://www.amazon.com/Permatex-29132-MotoSeal-Ultimate-Gasket/dp/B000HBGHKE
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3990
Location: San Diego, CA
Thu Oct 31, 2019 8:30 am quote
that's the one, great stuff!
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Thu Oct 31, 2019 8:31 am quote
you use that on base and head even with metal gaskets or rubber gasket on the head present?
Addicted
Joined: 26 Jan 2019
Posts: 689
Location: california
Thu Oct 31, 2019 8:36 am quote
General rule is - no sealant on the head gasket.
Can't recall - do you have some sort of O ringed head?
If not - good lap job and use of dry gasket should be all you need - based on Forum experts.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3990
Location: San Diego, CA
Thu Oct 31, 2019 8:38 am quote
I use Motoseal on base gaskets. For head gaskets I use copper spray sealant, though others are not so keen on it. My experience with it has been very good though, so I keep on keepin' on.
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Thu Oct 31, 2019 9:05 am quote
rubber o ring head on mine.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3990
Location: San Diego, CA
Thu Oct 31, 2019 12:11 pm quote
rubber o-ring head is great if you have no need for head gasket. if you do, I only put the copper stuff on the side that will be going onto the barrel.

swiss - can you post a link for the timing calculator you are using? I've only seen it in 100% German, here:

http://ddog.at/stz/rechnen.php

BTW I don't know how I didn't read this thread until the last 2 pages, but I started at the beginning today and it's been pretty epic. Lots of good info and learning and a few mishaps makes for a great read.
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Thu Oct 31, 2019 12:45 pm quote
sdjohn wrote:
rubber o-ring head is great if you have no need for head gasket. if you do, I only put the copper stuff on the side that will be going onto the barrel.

swiss - can you post a link for the timing calculator you are using? I've only seen it in 100% German, here:

http://ddog.at/stz/rechnen.php

BTW I don't know how I didn't read this thread until the last 2 pages, but I started at the beginning today and it's been pretty epic. Lots of good info and learning and a few mishaps makes for a great read.
That is the same timing calculator I use, but I have my Chrome browser set to auto translate international pages so it gets translated somewhat poorly to english. only the right side doesn't really get translated.

I will keep the head clear of gasket sealant and trust the rubber o ring.

And thanks for the review of the thread. Its been quite costly mistakes for my first time.. but luckily I got this scooter for free from my uncle and bought the cheapest cylinder kit that apparently is really fast. So after the seize and new piston/bore my cylinder will be equivalent to spending money on the most expensive MHR!

I hope I can complete it and not destroy it further once its back together cause I would love to "get it" finally on all things vespa tuning and be able to move on to my p200 project and eventually start looking for some nicer models like an SS180 or GL or sport. I would love to eventually have a vespa with trapezoid head. not one of those bodges, but the original style.
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Thu Oct 31, 2019 4:51 pm quote
I was able to get the matching front shock barely used off an MV user in Cali who was reading this thread and had almost the same issue happen probably a year earlier when he ordered the front shock.. rear out of stock indefinitely. Thanks user VSX1T for passing it along for good price with only around 200 mi on it before he replaced with the BGM equivalent. I didn't even put a call out, he contacted me after reading on sunday night. By Tuesday I had sent money and received it tonight 2 days later all the way from Cali. That is awesome!

What I noticed and VSX1T mentioned is that sticking with production batches matters if color matching is important to you. The front shock is slightly lighter of a titanium color than the rear I ordered. Once I got them together they are actually not very far off, but what I did notice is that his front shock was manufactured in Dec 2017 and the metal had a smooth surface with slightly lighter color. The rear shock I ordered this month was manufactured in Dec 2018 and the metal has slight ridged ring texture around the surface and barely noticeable darker tint to the color. They are the same product code/color though. I'm happy with it so far and can't wait to actually have a running scooter to throw them on. For now they will go on this stella, but was planning on having them end up on the p200 since the shock color goes much better with the burgundy p200 than this red stella. In person they look more purple tinted than photographed.

This community amazes me the willingness to help each other out on a regular basis! I should also mention my appreciation for Rowdyc who hooked me up a month or two ago with the correct indicator lights with text printed on them for my p200 headset. Those things are only available without the text printed on them from SIP now. Also all the intellectual assistance from everyone who has chimed in on threads sharing their knowledge. It is great to learn from experienced people about a topic which seems to be fading from general knowledge within society (maybe not in Europe, but more so in US). Especially when you don't really have a lot of people to turn to locally for help.

IMG_20191031_203400.jpg

Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Thu Oct 31, 2019 6:18 pm quote
By the way.. tonight my neighbor referred me to possibly the best option for getting a re-bore done only a few miles away!

Finally can stop worrying about finding a place that will do that.

http://www.newyorkspeedandmachine.com/

So now I've found local places that will do machining, powder coating and vapor blasting. Everything I may need for this and the P200.
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Fri Nov 01, 2019 6:50 am quote
I angled out that little section of overlap on the cylinder gasket face while leaving the cylinder wall intact. one side is very narrow close to the stud hole now. Will need to make sure I get a good gasket sealant layer at that spot.

IMG_20191101_100444.jpg

IMG_20191101_100404.jpg

IMG_20191101_100520.jpg

IMG_20191101_100514.jpg

Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3990
Location: San Diego, CA
Fri Nov 01, 2019 6:53 am quote
could you could blend the outside corner of the cylinder wall to avoid the sharp edge going from cylinder to port?
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Fri Nov 01, 2019 7:03 am quote
Keeping this separate so the topic flow is easier to follow.

While out there, I took a look at the stud locations in relation to where I am expecting to grind out the exhaust port. I am a little concerned now that if I widen as much as suggested, I will break through to the stud holes. There does not seem like there is a lot of leeway between the exhaust port and cylinder stud.

I traced the arc of the closest point of contact of the stud to the exhaust opening (which is a little misleading because the exhaust opening is slightly further forward into the cylinder than the studs). Bright yellow is the center of the stud hole mapped to the arc of the cylinder bore. Dark yellow lines mark the outer profile of each stud hole.. which are not as close to the cylinder wall as the center of the stud hole due to geometry of the stud hole in 3d space.

Side view shows that the stud holes are fully encased in the cylinder from the bottom through about the middle point of the exhaust port. At about the halfway point, the exterior of the cylinder narrows a bit leaving the studs exposed and just passing through fins, not cylinder body. This means that I lose some extra cutting space in the exhaust walls about halfway up the exhaust port opening, exactly where I need all the space I can get.

So what I am concerned with is that I can get the exhaust profiled properly at the bore opening, but there is very little room to work that opening back into the exhaust port to smooth out that transition. Specifically at the top half of that tube. And if I go too far.. the cylinder is ruined.

What is the performance difference if port is left stock width or only slightly widened, but the top and bottom heights are only changed to currently suggested profile? So instead of a wide and deep opening, just a deep opening that is stock narrow?

IMG_20191101_095412.jpg

IMG_20191101_095306.jpg
upside down view of the cylinder showing the spot where the exterior of the cylinder narrows leaving studs to pass only through fins and not cylinder body.

IMG_20191101_095318.jpg

IMG_20191101_094854.jpg
gross estimate of the thickness of material between the exhaust opening and the stud opening at its current state.

mal166ports_02_portingtemplate_stud_warnings.jpg
bright yellow.. stud center (closest to exhaust port). dark yellow stud outer edges (slightly further away from port). This shows along the bore edge, but the studs are inset a few mm distance probably only 5-15mm max.

Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Fri Nov 01, 2019 7:06 am quote
sdjohn wrote:
could you could blend the outside corner of the cylinder wall to avoid the sharp edge going from cylinder to port?
I don't think that would add anything as the piston skirt is the same width of that cylinder wall. So, even with rounding it, the airflow still hits a wall from the few mm overlap of cylinder wall/piston skirt to that port opening coming around that corner anyways. How I visualize the airflow is that the air is coming through piston and cylinder wall at that spot. The case/cylinder are wider behind that wall/piston opening.. so the air will curl around that blockage when entering, and now with the gasket face rounded the way it is... that air that curls around along that length of opening will be guided and aimed with more force deep into the transfer ports instead of hitting the gasket face like a wall and squeezing back in a perpendicular towards the center of that opening which would bounce around screwing up the airflow within the main section of that opening. Air is flowing from bore to this opening, not the other way around.. which would require smoothing to increase airflow if that were the case. At least that's how I think it is working.

It was suggested not to widen that wall/skirt section as it won't improve performance enough to offset the increased piston slap from widening. I think this is an ok compromise to deal with leaving the width alone. Better than stock!
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Fri Nov 01, 2019 7:42 am quote
I just remembered I recently bought a kit of various measurement tools from Harbor Freight which might help me measure the thickness between stud hole and bore wall as well as bore/exhaust to outside world. And there was one caliper very useful. After using this long thin analog caliper to get that thickness at the wall, I think it alleviated some of my serious concerns because it made it easier to actually visualize at the point of grinding where the stud sits and how much room is around there and in which direction the stud is in relation to grinding in 3d space.

I think it is possible to do the suggested super wide/high exhaust port, with most attention paid during the profiling at the opening and a few mm back from the opening face. Once you get past that point, the stud no longer plays into it, just the shallow exterior wall. So the upper corner and exhaust inner side wall profile would need to be a sharper gradation back into the port than the bottom extension. The thickness from exhaust to outside world actually lines up with my stud center line drawn as an arc at the bore surface.. so the yellow lines do in fact show the danger to outside world from the exterior thickness, as well as from the stud.

IMG_20191101_112938.jpg

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IMG_20191101_114655.jpg
measuring the top corner of the exhaust to the exterior surface of cylinder.. prior to widening.

IMG_20191101_114705.jpg

IMG_20191101_114719.jpg
top corner of exhaust to exterior surface of cylinder. prior to grinding

IMG_20191101_114944.jpg
8.63mm thickness before breaking through to outside world.

IMG_20191101_115057.jpg
measuring thickness in middle of port right before the exterior gets thicker and studs stay inside the cylinder instead of going through fins only

IMG_20191101_115118.jpg
and showing where in the middle of the exhaust port this thickness is.

IMG_20191101_115223.jpg
the middle has less at 7.01mm thickness before breaking through to outside world. this is where the risk comes in.

mal166ports_02_portingtemplate_topleftcorner_outsideworldrisk.jpg
top left corner of exhaust. Green marks show two points of each caliper measurement. Green marks on left are the outside world thickness to avoid. I think there is enough room to grind to the 42mm width safely as long as I be very deliberate.

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Fri Nov 01, 2019 7:50 pm quote
I think now you understand about keeping in mind where the stud holes are. If you think the 166 is close have a look at your 200 cylinder. Now that's a real issue to get more width out of. Whoever designed that 200 stud pattern in the 60's really screwed up. The narrowest studs are at the exhuast port. With the main transfers through the piston the studs could have gone anywhere. Smallies and Lammys have an open goal when it comes to 50bhp cylinders.

You will have no issue making that wider port in that cylinder. Just be careful to follow the shape you drew.
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Fri Nov 01, 2019 8:50 pm quote
Jack221 wrote:
If you think the 166 is close have a look at your 200 cylinder. Now that's a real issue to get more width out of. Whoever designed that 200 stud pattern in the 60's really screwed up. The narrowest studs are at the exhuast port. With the main transfers through the piston the studs could have gone anywhere.
I will take a look at this on Sunday when I get a chance. Just to see how much worse it is than what I'm dealing with currently.
Jack221 wrote:
Smallies and Lammys have an open goal when it comes to 50bhp cylinders.
This makes me wonder about how widening each dimension affects performance.

I know already two of those dimensions:

1.) raising the exhaust port raises RPMs
2.) lowering the exhaust port increases torque

But this last statement makes me wonder if:
3.) widening the exhaust port helps increase horsepower.

It was a nice surprise to find out the other day that 1 and 2 together increase both, and not the opposite of canceling each other out. But if 3 is also true then that is pretty awesome you can eek out every last bit of HP by larger bore/longer stroke and wider exhaust port.

This stuff is sinking in now that I've done it for real. I'm gonna go back and re-read the Jennings chapter on port timing and exhaust profiling to see what he says about widening the exhaust in relation to RPM/Torque/HP.

EDIT: I assume the 20mm flat top is safer now in 2019 because the ring materials are much better than when this was written in 1973? In his diagram of exhaust profile for 70% width, it is elliptical with no flat section.
Jennings 2 stroke tuning page 109-110 wrote:
Even assuming that no change is made in exhaust-port
timing, simply widening the port window will result in a power increase; it also can result in drastically-shortened ring life, amounting in extreme examples to outright and nearly-instant breakage of the rings, and/or severe overheating of the piston crown.
Jennings 2 stroke tuning page 109-110 wrote:
A relatively mildly-tuned engine will have an exhaust port width
equal to at least 50-percent of its bore diameter (which is to say, a 3-inch cylinder bore would have a 1.5-inch exhaust port width) and that is enough to allow the ring to spring out into the port window very perceptibly. Make that port square, with sharp comers and sharp edges, and the ring will be destroyed very quickly. And if you enlarge the port so that its width represents 70-percent of cylinder-bore diameter, ring failure would almost
certainly occur during the first revolution of the crankshaft. Yet, racing engines have been run quite successfully with 70-percent port widths, and while I cannot recommend that kind of extremity for modified production-type engines, the mere fact that it has been done tells us that techniques exist to make it possible.
Jennings 2 stroke tuning page 110 wrote:
Assuming that the port width does not exceed 60-percent of bore diameter, the radii at the port window's corners should be about 15- or 20-percent of the port width, and that is just what you will find in most engines. But as the port is widened, those corner radii have to be made larger - to about 28-percent of port width when the latter approaches being 70-percent of cylinder
diameter. Actually, even these very large radii will not completely prevent ring snagging if they are not joined by straight-line edges. The upper and lower edges of the port window should be arched, on a radius equal to about twice the port width, in ports having a width that is 60-percent of bore diameter or less. Unfortunately, these simple rules-of-thumb are not adequate at port widths above the 60-percent level - and such widths are
becoming very common. With the rings we had a decade past, which were relatively thick, axially, and quite narrow, radially, (not to mention being made of ordinary and rather brittle cast-iron) the upper limit for port width was 62-percent of cylinder bore diameter; now, with our vastly improved rings it has become possible to widen the port out to 70-percent of bore, or slightly more, if we are very careful in shaping the port window.
Also relevant info:
Jennings 2 stroke tuning page 84-85 wrote:
Taking each port individually, there is every reason to make any port as wide as possible, acquiring the necessary time-area value in this manner instead of extending the port-open duration. Reasons for moderating this approach do exist, however, in the interaction between ports and in the effects exaggerated exhaust port widths have upon pistons and rings. These reasons are discussed in detail in the chapter titled, ďScavengingĒ, but I will I include a brief reminder here. A too-wide exhaust port will cause rings to snag and break, or wear very rapidly, and if the widening brings the exhaust port window's sides too near the transfer ports, there will be an increased tendency toward short-circuiting of the incoming charge. Obviously, excessive widening of the transfer ports can also result in ring-trapping and/or charge short-circuiting. You should also understand that widening an engine's exhaust port, increasing its time-area
value without actually increasing its open duration, has much the same effect as obtaining the same increase by raising its height and thus increasing both time and area: that is to say, widening the exhaust port increases the engine speed at which maximum power is realized, while reducing low-speed power. And the same pattern is to be observed in increases to transfer port time-area, though in the opposite direction. These effects should become familiar to you, particularly as regards the exhaust port, for any increases in exhaust time-area should begin with widening the port to the maximum tolerable to the piston and rings, moving on to the business of raising the top of the exhaust port only after the limit for width has been reached. There is good reason for taking this approach, for while increases in exhaust port time-area, gained by whatever change in the port-window's shape, certainly will have the same general effect, increasing width to get more time-area has a much less narrowing effect on the power band than increases in height.
All of this talk about ring wear has me wondering what the avg lifespan of modern rings in a modern cylinder are with exhaust width 60% or less vs 70%? how often do you need to change your rings?

I am sticking with the 70% exhaust width and profile.. as it seems this is well worn path I am merely following down after others trial and error... just curious what you guys think about all of this info?

jennings-70percent-exhaust-profile.jpg

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Fri Nov 01, 2019 10:20 pm quote
Yes, all very interesting but often misleading. Jennings published this book in 1973 based on his work over many years through the 60's. A lot of it still relevant but dare I say it certain parts are just history.
I am sure Jennings would be quite excited about what he could do with modern 0.8mm semi trapezoidal chrome-moly rings.

Generally with exhaust ports bigger is more of something, in any direction. The shape does affect the powerband. A three port set up like the new Piansco 251 is my favorite exhaust arrangement but not spending 5 grand on a new engine just yet.
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Sat Nov 02, 2019 5:38 am quote
That's what I figured, 50 yr old technical information is outdated from 50 years of technical progress.. specifically ring materials and trapezoid shape probably helps retain shape to prevent bulging into ports while still being flexible enough to expand and contract with the bore.

Love that we have a two stroke tuners handbook 2019 volume in NSM!

There are a lot of little mistakes that can lead to disaster along the way, and you guys are priceless wealth of knowledge!
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Sun Nov 03, 2019 1:21 am quote
charlieman22 wrote:
General rule is - no sealant on the head gasket.
Can't recall - do you have some sort of O ringed head?
If not - good lap job and use of dry gasket should be all you need - based on Forum experts.
No sealant on head when using only rubber gasket on head by itself as CM suggested....

But I just remembered I need to use a 0.1mm head gasket to bring timings from 126 down to 125. If using head gaskets I will use sealant on the bottom of gasket to cylinder deck and then rubber o ring between metal head gasket and head as sdjohn suggests.

I'm thinking of using this material to make my own head gasket (0.003" thickness):
https://www.mcmaster.com/shim-stock-sheets
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Mon Nov 04, 2019 9:32 am quote
Setting up to start exhaust grinding...

Started with the scanned tracing of original exhaust. Scan was exactly same size so everything should line up in real world. Next printed the updated template out at 100% scanned size. Then I cut top edge to top of scanned tracing paper that was lined up exactly with top of cylinder, having scanned wider than original paper trace for exactly this reason.

Also left some of transfer ports in template to cut them out and use as locators for the whole template along the sides as another dimension from the top side since the exhaust template is wider than the original and I needed more reference points to line up the template into the cylinder.

Then I taped the template into cylinder being as precise as I can. I'll leave it here and use it as visual reference to cut to. Also with use marker to color in the excess metal to remove in case the paper template comes off. I also have extra copies to replace template if needed.

IMG_20191104_120243.jpg
Print out the template at 100% of scanned tracing. Multiple copies if one gets ruined.

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Cut out template.

IMG_20191104_122115.jpg
Position precisely into cylinder and tape it in place

IMG_20191104_122126.jpg
Ready to start grinding!

Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Mon Nov 04, 2019 11:23 am quote
exhaust grinding commenced
One hour and 45 min later. Almost done. I still need to shave a sliver off the top of the exhaust and a few spots around to remove what is slightly excess.

Probably spent the first 30 min really trying to figure out how to hold the tool and cylinder and use the tool inside the port to safely grind while under full control.

What I learned is that you really have to grind inside the port tube before you get to the face of the profile because the port is sharp angled about a half an inch into the face as its wider near the opening than it is inside the port tube. This prevents you from really getting a good angle on the face with the tool without the dremel hitting the exhaust tube and not being able to reach the face edges (dremel tool isn't long enough to really get the tip deep into the port unless you grind some space inside the port.

I also learned a trick where if I went slightly outside my garage on sunny day, if I positioned the cylinder in such a way that I could see into it, and the sun would shine down the other end, it would reflect off the excess material and not off the paper template. So this created a very visible outline of material still needing to be removed. I took many breaks and would check things constantly. This helped give my hands a rest so I wouldn't be shaking or tired when doing precise grinding.

Almost done. I want to replace the template and recheck as well as measure the depth from deck to top of exhaust port to make sure i am close or on. not over.

EDIT: just removed the template to take an accurate measurement of where the exhaust top stands. It's at 33.6mm now, so I can ease it up another 0.7-0.8mm to 32.8mm. really have to stay longer than 32.6mm or it will be higher than desired timing.

IMG_20191104_134126.jpg
showing the best angle to get a reflection of sun off material still needing removal.

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and when it was removed up to the correct edge of the template. no more shiny reflection.

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current state of port.

IMG_20191104_140618.jpg
another view of current state.



Last edited by swiss1939 on Mon Nov 04, 2019 2:16 pm; edited 2 times in total
Addicted
Honda elite
Joined: 19 Jun 2007
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Mon Nov 04, 2019 12:00 pm quote
oh darn that looks good Swiss!
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Mon Nov 04, 2019 6:56 pm quote
hibbert wrote:
oh darn that looks good Swiss!
Thanks, Hibbert. BTW I love your blue bajaj! Be careful with jetting. Make sure you go grossly over rich before start working down as jack suggested. After my mistake I am terrified of jetting again. Costly mistake to make!

Also, Jack... I took a look at my p200 cylinder and you weren't kidding, the studs are essentially right on the edge of the exhaust port with probably less than 2mm thickness between them! Absolutely no room to widen that port!

Here is my exhaust port as it stands with measurements shown. Still a little bit to grind out. But it is close. I also want to try to remove most of the hump within the exhaust port tunnel to make a more direct wider passage into the exhaust once I'm done profiling the opening.

malossi166_grind_v01.jpg
red current. blue target.

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Mon Nov 04, 2019 7:04 pm quote
Sure that's not too big? sure its fine, should be somewhere near 46mm arc. Looks quite a size compared to the tiny Malossi port. I think it's quite an impressive job for a first go. If you do the rest of the cuts with something finer or a sanding drum it will clean up really well. Check the top is flat with the piston and the timing height is level across the flat part.

Last edited by Jack221 on Mon Nov 04, 2019 7:17 pm; edited 1 time in total
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Mon Nov 04, 2019 7:13 pm quote
swiss1939 wrote:
Also, Jack... I took a look at my p200 cylinder and you weren't kidding, the studs are essentially right on the edge of the exhaust port with probably less than 2mm thickness between them! Absolutely no room to widen that port!
They do go a bit wider but you have to be ultra careful. Malossi actually use much smaller stud holes, which is why they say they don't fit on some engines with bad tolerances. This gets another few mm. If they moved the studs apart another 5 mm it would have been a whole load easier.
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Mon Nov 04, 2019 7:17 pm quote
Jack221 wrote:
Sure that's not too big? sure its fine, should be somewhere near 46mm arc.
I thought my measurement was the arc. Its 42mm around the surface of the bore from edge to edge of opening. not the straight line across the two points passing through the open bore hole which would be the chord, correct?
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Mon Nov 04, 2019 7:23 pm quote
Jack221 wrote:
I think it's quite an impressive job for a first go. If you do the rest of the cuts with something finer or a sanding drum it will clean up really well. Check the top is flat with the piston and the timing height is level across the flat part.
Thanks! I was worried at first, but once I got into it I was pretty confident in what I was doing. Too much though, as when I got close, I kept going right up to the template and realized afterwards I should have stopped when not right up to the edge and taken some real measurements first. Luckily, my timing line at the top was not over, but under.. and as you can see its not entirely flat as left side is higher up at around 33.18mm with the right side slightly lower at around 33.4-5mm. I do need to even it out as well as round off the bottom left corner a little bit better. Hopefully I can get it smoother with the sanding disc. I should probably go buy some more sanding discs in different grits as I only have like 2 that came with the dremel tool and they seem to wear out really fast.

I did the whole port with just this one dremel bit pictured.

51YpHeIAynL._AC_SL1000_.jpg



Last edited by swiss1939 on Mon Nov 04, 2019 7:27 pm; edited 1 time in total
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Mon Nov 04, 2019 7:25 pm quote
oh 42mm arc is 62% on a 61mm bore. Looks big already. Could go to 46mm arc (42mm chord) The pictures make it look big already.
The original port must have been about 55%.

Last edited by Jack221 on Mon Nov 04, 2019 7:29 pm; edited 1 time in total
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Mon Nov 04, 2019 7:29 pm quote
Jack221 wrote:
oh 42mm arc is 62% on a 61mm bore. Looks big already. Could go to 46mm arc (42mm chord) The pictures make it look big already.
What is the math to figure that out? I thought it was 42/61 = 68.85%. But I guess I was wrong.

And in fact, I took a real measurement of the bore diameter and it was 60.95mm so I thought my 42mm arc width was 68.90%.

I'll need to rework my template again if I am to go to 46mm arc width.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Mon Nov 04, 2019 7:33 pm quote
Maths is fine but exhaust port widths are in chord. 62% is ok. Think it might go any more?
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Mon Nov 04, 2019 7:48 pm quote
Here is the updated template with 46mm arc width. Getting much closer to the stud and outside world.

blue 46mm arc
red 42mm arc

I will think about this. If 42mm arc is definitely 62% and 46mm is definitely 70% then I will need to try to get a little closer. I'll print out the template and lay it over and just look to see how confident I feel in attempting it first.

EDIT:

Using online calculators I've got these numbers:

Diameter (measured): 60.95mm
Radius (online calculator): 30.475mm

Current Arc: 42mm
Current Chord (online calculator): 38.75mm
Current Exhaust port width as percentage of bore (using chord): 63.57%


Desired Arc: 46mm
Desired Chord (online calculator): 41.76mm
Desired Exhaust port width as percentage of bore (using chord): 68.51%

mal166ports_02_portingtemplate_46mmarc.jpg
these widths are arc, not chord.



Last edited by swiss1939 on Mon Nov 04, 2019 8:02 pm; edited 3 times in total
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3990
Location: San Diego, CA
Mon Nov 04, 2019 7:58 pm quote
What kind of cylinder is this again? Iíve lost track somehow... itís custom now, though!
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Mon Nov 04, 2019 8:01 pm quote
sdjohn wrote:
What kind of cylinder is this again? Iíve lost track somehow... itís custom now, though!
This is the recently discontinued Malossi 166 mk III kit. 61mm bore (60.95 measured).

But as it stands now.. its a swiss1939mkII and soon to be a swiss1939mkIII

If I widen to 46mm arc, that leaves approx. 2.412mm on each side before stud/outside world, when there is currently 4.38mm extra space.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Mon Nov 04, 2019 8:20 pm quote
I get similar calculated numbers (when being more accurate).

The choice is now, do you go all the way. When was going all the way ever a bad thing?

You have a GS piston with 1.0mm flat chrome-moly type rings? These will take 70%.

In defence of this last minute decision. On your diagram when you wrote 42mm the arrows didn't go to the full width. Thought you might be measuring chord with your fancy new gauges.

Last edited by Jack221 on Mon Nov 04, 2019 8:26 pm; edited 1 time in total
Molto Verboso
1980 P200E project, 2005 Stella Mal 177 MKIII in pieces
Joined: 20 Jul 2018
Posts: 1128
Location: Staten Island, NY
Mon Nov 04, 2019 8:24 pm quote
Jack221 wrote:
I get similar calculated numbers (when being more accurate).

The choice is now, do you go all the way. When was going all the way ever a bad thing?

You have a GS piston with 1.0mm flat chrome-moly type rings? These will take 70%.

In defence of this last minute decision. On your diagram when you wrote 42mm the arrows didn't go to the full width. Thought you might be measuring chord with you fancy new gauges.
I do not have a GS piston. I have the malossi piston with trapezoid rings.
https://sip-scootershop.com/en/products/piston+malossi+139166+cc+_3416170j

When I originally drew the red arrow width describing 42mm arc, I did not draw it to the full width. I was casual with it. I drew the blue arrows to exactly 46mm width.

Despite that, the red and blue outlines of the exhaust ports are exact to those listed numbers. In all versions of the template I posted.

EDIT: and these are the exact rings:
https://sip-scootershop.com/en/products/~/products/piston+rings+malossi+kdn5+_m351541240
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