Porting 101
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Molto Verboso
Vespa GS150, Messerschmitt GS150
Joined: 21 Jan 2013
Posts: 1060
Location: Glasgow
Tue Feb 03, 2015 2:30 am quote
Thinking back, Im sure I was only to run 3% when running in the engine. Everyone always says, you never listen do you.
Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 7121
Location: Victoria, Australia
Tue Feb 03, 2015 2:41 am quote
GLscoot wrote:
Thinking back, Im sure I was only to run 3% when running in the engine. Everyone always says, you never listen do you.
You human!

Enthusiast
2007 Stella 150
Joined: 02 Nov 2019
Posts: 53
Location: Rochester, Minnesota
Wed Nov 27, 2019 5:56 pm quote
Talk about bringing up an old thread. How did the cuts and porting turn out? I have a 2007 that has a DR177 kit, I want to tinker with it a bit and see what happens.
Enthusiast
2007 Stella 150
Joined: 02 Nov 2019
Posts: 53
Location: Rochester, Minnesota
Wed Nov 27, 2019 6:18 pm quote
chandlerman wrote:
Now, it's time for some work on the airbox & reed block.

Based on what blake7even had to say in his sleeper thread, my plan is to port the reed block and cut out the center bar like so:

the airbox like:


And I'm guessing, just blend the cases here:


One thing I saw which is a bit worrisome is the lip of the reed rubber (Oh noes!) from when I ate a bit of piston ring and killed the motor:


How did this turn out? Working on mine right now, cut the center bar out and was thinking of doing this.

So this may all be a bit of a practice run anyway, but it's easy enough to replace (i.e. no case splitting) that I'm not concerned.
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2268
Location: Chicago. Well, Evanston, but that's almost Chicago
Wed Nov 27, 2019 6:46 pm quote
it was ultimately about 14-15 HP build, so not too shabby. Port matching is pretty easy, really. It's getting the port timings correct that make the biggest difference, I've since learned.
Enthusiast
2007 Stella 150
Joined: 02 Nov 2019
Posts: 53
Location: Rochester, Minnesota
Thu Nov 28, 2019 7:07 pm quote
I just measured up my reed block, it is actually equal all the way around at 3.5 mm, except the bottom side of base where the reeds screws down.
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2268
Location: Chicago. Well, Evanston, but that's almost Chicago
Sat Nov 30, 2019 11:24 am quote
I don't know if 3.5mm enough or not, to be honest. It's going to depend on how much of a gap you have between the outer edge of the block and the edge of the reed.
Enthusiast
2007 Stella 150
Joined: 02 Nov 2019
Posts: 53
Location: Rochester, Minnesota
Sat Nov 30, 2019 7:01 pm quote
This kind of answers my questions about what to remove. Would you still remove the same material?
chandlerman wrote:
I finally got around to tackling porting the cases and new head for my LML.

After a little over an hour with a carbide cutting blade in my dremel, things were looking good, even if my ears were ringing a little bit. I should have worn ear plugs, but if that was the biggest mistake I made today, I'm happy.

I was pleasantly surprised how easy this was. Lots of test fitting & measuring. Tons of WD-40 to keep the cutter lubricated.

My strategy was to match the smaller opening to the larger, but increase the openings beyond that. Even that resulted in removing a LOT of metal, though. The LML has some pretty big ports, even stock.

Head:

and third port:



And the casings. I opened up the main ports just a tiny bit on the casings. Seem to have not gotten a picture of that, though.

And the third port:


Here's the half-way point. That's looking at the un-ported side through the new ports:


and here's one comparing the ported top end to the un-ported, blown DR top end that was on the bike previously:
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2268
Location: Chicago. Well, Evanston, but that's almost Chicago
Sun Dec 01, 2019 7:19 am quote
Christopher_55934 wrote:
This kind of answers my questions about what to remove. Would you still remove the same material?
Yes, I would. You can check out my 1976 Sprint rebuild thread which has some similar cylinder mods on a Polini 177, too.
Enthusiast
2007 Stella 150
Joined: 02 Nov 2019
Posts: 53
Location: Rochester, Minnesota
Sun Dec 01, 2019 5:03 pm quote
What did you use for a base gasket? The DR177 base gasket isn't going to work, there isn't enough remaining material once I opened up the rest of the port. The Polini is supposed to be fit for the Stella any reason not to try it?
Enthusiast
2007 Stella 150
Joined: 02 Nov 2019
Posts: 53
Location: Rochester, Minnesota
Sun Dec 01, 2019 6:11 pm quote
I see you opened up the sides a few millimeters, that is easy enough.
The third port that you opened up, was it to match the size of the third port hole you opened up in the cylinder? Do you know how much you removed? I don't have the cases split to know how much it take off for perfect alignment.
chandlerman wrote:
Thanks for the clarification on what you did with the Green Circle. I figured it was just rounded off, but wanted to be sure I understood. You're right about fitting the crank in there. While all I have right now is the old LML crank, once I stuck it in place, things made a lot more sense.

For the piston, I only opened up the sides a little (maybe 2mm per edge ), but it matches the openings in the jug and the cases, so it will be enough.


(That's the new one on the bottom along with "Shiva, Destroyer of Engines" on the top with stock openings)

For the top port, I hadn't done anything with it yet. Fitting it along with the crank for alignment, there's some room for improvement there

so I've got it marked where I'll open it out:


(The mark along the base is just for alignment)

I probably won't take any metal out of the top of the main opening, though, because I didn't open up the ports themselves, so there's a limit for how much good it would do. The opening in the jug is already matched to the cases, so it will stay as-is.

This whole process has given me a new appreciation for the difference in design decisions between different top ends. I've always run either stock or just bolted-on kits in the past--I just wasn't at the necessary level to appreciate the engineering differences between them.

Thanks again, Blake, for your help with my project and also for blazing the trail with your well-documented Sleeper build.
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