Combustion chamber shape, squish, compression

Ok, I could raise the transfers to 130 to make it more even, but
maybe from what tiba mentioned that would be too much? I was
also thinking about raising the exhaust another 1/2mm, which would
make exhaust duration around 190. This would also lower compression
a bit, which I think might help.

Ever had one of those weekends where you have so much to do, you
end up doing nothing? :)
 
Ok, I could raise the transfers to 130 to make it more even, but
maybe from what tiba mentioned that would be too much? I was
also thinking about raising the exhaust another 1/2mm, which would
make exhaust duration around 190. This would also lower compression
a bit, which I think might help.

Ever had one of those weekends where you have so much to do, you
end up doing nothing? :)

130/190 is almost Speed2 timing:p
You defently gonna need a new exhaust + carb if you gonna use that timing.
Beter get a new cheap imi stock cylinder and report it.
 
Big B, that sounds like something I should leave for the next
stage project then. I bought a used NCY 47mm cylinder on Ebay.
Liner looks great, and porting is just like my stock cylinder was.
Will try to get better tools before attempting that one :)

I'm a little bit stuck in thought experiments, about how to tilt
the reed cage. I have a spacer under it now, made from the
base of the original reed cage. If I grind that into a wedge,
I'm afraid it might crack.

I have some black rubber (2 part) potting compound which might
work. With this I could also try filling in the case a bit, around the
sides of the reed cage... might help lower crankase volume.

And I could cheat a little, and put in a Koso intake manifold.
This doesn't fit right though, and would have to be fudged in there.
It's frustrating that the Vino has a slightly different mounting pattern
that the normal Minarelli cases. There's very few intakes that will
fit. The only one I know is one from MRP.. some rebranded junky
looking chrome thing.

For my education :) what rpm do speed2 specs give, on a properly
ported engine?

Also I was asked this question in a message:
"Is your reed box tuned to carb´s 90% area?..."
I don't know what this means. It was also suggested that
I try thicker reeds. Right now I'm usind standard VForce reeds,
haven't measured their thickness.
 
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I'm a little bit stuck in thought experiments, about how to tilt
the reed cage. I have a spacer under it now, made from the
base of the original reed cage. If I grind that into a wedge,
I'm afraid it might crack.

You need something like this, this one is for piaggio, get it done in a machine workshop for a few $.

ResizeofDSC04868.jpg
 
don't bother putting thicker reeds it will only make it worse, i find 0,30 reeds more than adequate for competion use even on high end racing cilinders, for your type of setup a 0,25 reeds will give better response since you're setting up a restricted engine.

for porting it's better you get another cilinder & do it differently, staged transfer openings give best powerband & topend, like Big B said open the main transfer first then the secondaries & finally the boost port, let the secondaries open a few degrees later than the main transfers (130/126), leave the boost port alone for now.
 
Thanks tiba, I'll take note of those numbers, and try them
on the 70cc cylinder. I've put so many hours into this 50cc
cylinder, that I don't see myself doing it over. I only need 3
more mph from it. Should be able to get that with intake
and transmission tweeks... like maybe the new belt.
 
hey stepvino, pardon me asking you but what are your tools for making engine ports? do you use a dremel kit? if yes then what make and what head dremel sizes. frankly to be honest with you, you're turning a 2$ cylinder into a 2million racer (that's a saying here :)) i love your work man you have got to teach me some of this, i'd like to get some custom stuff going for my bike too, since i got a PGO scoot and not very many tuning parts go with it, not to mention the reed cage and the intake manifold which is really rare to find cause it's a unique type.

do you use stock cylinders? or do you buy cheap 40mm, 47mm cylinders from the market. Here in Madagascar they sell a whole slew of cylinders ranging from real makes to real fakes (pure chinese and taiwanese brands that you could get for 10~25$) one thing i did notice tho is that heat dessipation of these cheap cylinders are pretty good.

cheers :)
 
Big B, that sounds like something I should leave for the next
stage project then. I bought a used NCY 47mm cylinder on Ebay.
Liner looks great, and porting is just like my stock cylinder was.
Will try to get better tools before attempting that one :)

I'm a little bit stuck in thought experiments, about how to tilt
the reed cage. I have a spacer under it now, made from the
base of the original reed cage. If I grind that into a wedge,
I'm afraid it might crack.

I have some black rubber (2 part) potting compound which might
work. With this I could also try filling in the case a bit, around the
sides of the reed cage... might help lower crankase volume.

And I could cheat a little, and put in a Koso intake manifold.
This doesn't fit right though, and would have to be fudged in there.
It's frustrating that the Vino has a slightly different mounting pattern
that the normal Minarelli cases. There's very few intakes that will
fit. The only one I know is one from MRP.. some rebranded junky
looking chrome thing.

For my education :) what rpm do speed2 specs give, on a properly
ported engine?

Also I was asked this question in a message:
"Is your reed box tuned to carb´s 90% area?..."
I don't know what this means. It was also suggested that
I try thicker reeds. Right now I'm usind standard VForce reeds,
haven't measured their thickness.

A full ported speed2 setup does around 14.5k RPM (depends alittle how it's tuned). The old speed 6T setup was around 13.8k RPM.
But these figures are just "relative" it depends alot on timing/exhaust/carb/volume/reed/combustion head etc etc

With that message you got it ment that your reed surface should be 90% of your total venturi surface, this is for giving the mixture flow/speed.

90% is also just a number, it depends alittle on what setup etc.

@tiba:
Are you sure that you use .3mm thichness reeds? Stock Vl14/VL13 are .25mm.
On 100cc gocart engine (18k rpm) they have around .22-.2 mm thickness.

On StepVino's engine I would something like .35 in.
 
@tiba:
Are you sure that you use .3mm thichness reeds? Stock Vl14/VL13 are .25mm.
On 100cc gocart engine (18k rpm) they have around .22-.2 mm thickness.

On StepVino's engine I would something like .35 in.

yup, positive about 0,30mm, malossi doesn't have 0,25mm reeds only polini sell them & i think top performance did have 0,25mm reeds back then.

0,35mm reeds on stepvino's setup would be overkill, the reeds would be too stiff & restrict the engine even further, i have tested 0,30 & 0,35mm reeds on my race engines & the thicker reed made my engine lose topend power contrary to what the common belief says so i put back 0,30mm reeds & it ran great.

ordered me 5 sets of polini 0,25mm reed sheets i'm gonna use them on my VL14 & VF3 reedcages as replacement petals, will let you know the results.
 
yup, positive about 0,30mm, malossi doesn't have 0,25mm reeds only polini sell them & i think top performance did have 0,25mm reeds back then.

0,35mm reeds on stepvino's setup would be overkill, the reeds would be too stiff & restrict the engine even further, i have tested 0,30 & 0,35mm reeds on my race engines & the thicker reed made my engine lose topend power contrary to what the common belief says so i put back 0,30mm reeds & it ran great.

ordered me 5 sets of polini 0,25mm reed sheets i'm gonna use them on my VL14 & VF3 reedcages as replacement petals, will let you know the results.

I thought I measured .25mm on the malossi plates... Gonna check that tonight.

About the powerloss, did you notice that only on your engine or was it the same at others?
 
I thought I measured .25mm on the malossi plates... Gonna check that tonight.

About the powerloss, did you notice that only on your engine or was it the same at others?

the thinnest malossi petal i measured with digital caliper was 0.28mm, these are the ones i set aside for our personal use, the others fall around 0.30mm to 0.32mm, those are the ones we use on our customer engines for durability purposes.

have tested a 0.35mm reed on my MHR Team engine & a MK Prorace engine for my customer, the actual thickness of the Polini "green" reeds is 0.38mm & not 0.35mm as advertised, at low to mid throttle openings the "green" petals are ok but when i slowly rolled on the throttle to wide open the carb made a "bwoooooaaahhhhhh" sound & bogged down like it was running out of fuel so i thought the main jet was lean so i increased the main jets but to no avail, the problem never went away.

so i decided to put 0.30mm reeds & the default mainjet size & the problem disappeared, the engine ran strong all the way to high rpm without so much as a hiccup.

i am no longer a big fan of thicker reeds i really avoid them as much as possible except for big engines (125cc & up) destined for street use where durability is concerned.

btw this was 2years ago & a certain Dutch tuner i was comparing notes with also agreed with me as he also encountered the same dilemma with thicker reeds.
 
have tested a 0.35mm reed on my MHR Team engine & a MK Prorace engine for my customer, the actual thickness of the Polini "green" reeds is 0.38mm & not 0.35mm as advertised, at low to mid throttle openings the "green" petals are ok but when i slowly rolled on the throttle to wide open the carb made a "bwoooooaaahhhhhh" sound & bogged down like it was running out of fuel so i thought the main jet was lean so i increased the main jets but to no avail, the problem never went away.

That's the problem with thicker reeds on high RPM setups.. They cannot keep up with the RPM, because of the stiffness.

In theory, smaller plates should open and close easier and that should be better on high rpm.

Oh btw, StepVino, if you just wanna reach that 3 extra miles, make your scooter lighter ;)
 
Spectro, yes I use a dremmel. It's good enough to make good
improvements over stock, but falls very short beyond that.

2ujp5ys.jpg


The easiest job is the exhaust port. Once you open up the flange
enough, you can get all the way in to the cylinder, and easily
make the inside port any shape you want. The transfers are the
tricky part. Can't really get good results with these tools.

Right now I'm using the stock cylinder. I don't really have a complete
picture, since I'm really just getting my feet wet.. but if you enjoy porting
and have a small budget, it seems like stock cylinders is the way
to go. You can buy them very cheap used, in good condition,
from people that have upgraded early to a bigger cylinder kit.

I've read bad stories about cheap cylinders, specifically Ruima
cylinder that you see on Ebay. I don't know if the bad examples
are from the seller having access to factory rejects, or really
all of them are that bad, but the cylinder skirts seem to have a
tendency to crack.

So, in summary, I'd say stay away from junk :), also I wouldn't
buy a nice name brand aftermarket performance cylinder, and try to
make it better. These tools are just not good enough. Stock
cylinders seem perfect for beginning porter, and you get good
results even with these crude tools.

@ Big B ans tiba

*blush* don't remind me of my weight. Just went to measure:
190lbs, 86kg. It's amazing how a piston the size of an espresso
cup can propel me to almost 100kph! :) :)

Thanks for all the great info on the reed petals.
 
I've measured the lips of a vl13 and those are exactly .25mm thick..

i see, hmmmm it seems malossi has come out with a new reedpetal thickness, when i kocht my VL14 i measured both sides, they came out .28mm & .32mm, i think it's the thickness of the clear epoxy resin they use & not the carbonfiber itself that varies the thickness.
 
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