[2 Stroke] Cagiva Mito Racer-new Exhaust

These are the images of Filandro:
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{mRk} a écrit:

I'll post the designs of a exhaust we use. The second exhaust is the result of the fos-pipe program.
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Some advice or recommendation?

The first design works good?

Work ... But I know, I can do better.
I have to work, try and try again. Now I work on exhausts, heads, reeds and ignition.

I have problems to solve, in particular with the carburetor VHST.
I also have to increase the distance of the spark plug from the piston.

{mRk} a écrit:

Work ... But I know, I can do better.
I have to work, try and try again. Now I work on exhausts, heads, reeds and ignition.

I have problems to solve, in particular with the carburetor VHST.
I also have to increase the distance of the spark plug from the piston.

You still work on a lot of variables.

Is your spark plug heating too mutch the piston?

Absolutely not.
This distance is too small:
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I was interested to improve acceleration out of corners. Thus the temperatures of the exhaust gases are low, changing the performance of the exhaust:
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To improve the performance of the exhaust were using the flanges with different lengths.

Now I work to maintain the same acceleration and improve performance at high rpm. I increase the squish area of ​​up to 50% of bore and will try to bring the distance to 8.2 - 8.3 mm.
I wanted to make new exhaust with de Laval nozzles. But this is more complicated, I don't have experience or references.
I don't want damage the engine For now I'll try to make a exhaust as indicated by fos-pipe.

You guys are racing the Mito so clearly you are further along than I am with my bike. I have a street based Mito out here in San Francisco. I've done a couple of interesting things with mine though, and I might have something for you. I noticed that you are chatting about carbs. Mine came equipped with the TM35 and I swapped it out for the PWK28. The throttle response is much nicer, and I got a bonus of getter better fuel economy than I get with my kitted Derbi GPR.

Here's the PWK installed (yeah I know I need a new intake manifold--parts are tough to get out here in the States, and this is the intake that showed up from my UK eBay purchase). The nice thing about these carbs, purchase wise, is that they are fitted stock on the Kawasaki KX85/100. You can walk into the local dealer and buy one for around $100USD. Yamaha also has these on the YZ85, but they cost more. The stock choke cable connects right up without need to change any fittings. I still run the oil pump so I had to add a fitting for the oil line.
I'm running the 73037 cylinder, with the H head. Piston wise I've had excellent results with the Wisco flat top
Here's a photo of it next to the stock piston
It's really great to see people still active with the Mito development.

Hi Tora, thanks for your interesting photos; question is, Jap spare needles and jets are far costly than Dell'Ortos.
Surely you fitted one of the best carbs now available!
But please, change that manifold.. .
If you can't find it, please send me a PM.
Ciao

ToraTora a écrit:

You guys are racing the Mito so clearly you are further along than I am with my bike. I have a street based Mito out here in San Francisco. I've done a couple of interesting things with mine though, and I might have something for you. I noticed that you are chatting about carbs. Mine came equipped with the TM35 and I swapped it out for the PWK28. The throttle response is much nicer, and I got a bonus of getter better fuel economy than I get with my kitted Derbi GPR.

Here's the PWK installed (yeah I know I need a new intake manifold--parts are tough to get out here in the States, and this is the intake that showed up from my UK eBay purchase). The nice thing about these carbs, purchase wise, is that they are fitted stock on the Kawasaki KX85/100. You can walk into the local dealer and buy one for around $100USD. Yamaha also has these on the YZ85, but they cost more. The stock choke cable connects right up without need to change any fittings. I still run the oil pump so I had to add a fitting for the oil line.
---
I'm running the 73037 cylinder, with the H head. Piston wise I've had excellent results with the Wisco flat top
---
Here's a photo of it next to the stock piston
---
It's really great to see people still active with the Mito development.

For the Mikuni TM35 you can try jet needle 6AEL01-61 and mainjet 290 or 300.

I tried the PWK28:
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It works well.
Yamaha and Kawasaki use different needle (NAPE, NAPF for KAwasali, NBKF for Yamaha) and needle jet.

I ran the tests on single ring pistons produced by Wiseco, Asso, Vertex and Prox. Wiseco, Vertex and Prox work fine. Prox and Wiseco provide good rings, Vertex not always. The Asso sinle ring pistons have bad profile and low rings quality.
With piston "profile" I mean this:
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{mRk} a écrit:

I'll post the designs of a exhaust we use. The second exhaust is the result of the fos-pipe program.
[Vous devez être inscrit et connecté pour voir cette image]

Some advice or recommendation?

What happens if I insert a de laval nozzle at the end of the exhaust and change Dtail in 25.5 mm? Should do this test or is time lost?

Oh hey guys thanks for the response.


Filandro, yeah it's difficult to get tasty bits here in the States. I was surprised to read here that there might be a CR125 intake that might work with the Mito--is that what you were going to mention?

{mRk}, I see that you've also upgraded your shock--what did you install? I had read over on the 125cc Sportsbike forum that an Aprilia RS250 shock would work. So I sourced one and found that they are about the right length, but there was a bit of modification to get it to mount properly.

(I do need to mount the res better!)

Here's a mini table of the bits that come in the stock carbs on the YZ/KX bikes when buying a PWK

KX85....needle.....mainjet........pilotjet
............NAPE......#140............#45

KX100...needle.....mainjet........pilotjet
.............NAPF......#138...........#45

YZ85....needle.....mainjet........pilotjet
............NBKF......#138...........#45

Also, the OKO parts fit the PWK (because the OKO's are PWK copies), and I've found that the moped guys here in the States stock these parts at reasonable rates. Each of these kits sells for $24 USD. (click on the photos to go to the Treats website where I bought these.)

Nitron is great option

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Filandro, yeah it's difficult to get tasty bits here in the States. I was surprised to read here that there might be a CR125 intake that might work with the Mito--is that what you were going to mention?

MRK suggested me to fit the CR 125 reed cage; I've done this, with genuine HRC reeds .
Added two side triangle-shaped sheets to reduce crank volume (Honda cage is shorter than stock one).
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About the Aprilia 250 shock, you can fit it, but with a softer spring.
Send me a PM, there is a good UK shop for Cagiva parts.

ToraTora a écrit:

Oh hey guys thanks for the response.


Filandro, yeah it's difficult to get tasty bits here in the States. I was surprised to read here that there might be a CR125 intake that might work with the Mito--is that what you were going to mention?

{mRk}, I see that you've also upgraded your shock--what did you install? I had read over on the 125cc Sportsbike forum that an Aprilia RS250 shock would work. So I sourced one and found that they are about the right length, but there was a bit of modification to get it to mount properly.

(I do need to mount the res better!)

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I use kit SP shock (Sachs and Ceriani). My shock are modified and recalibrated.

The shock absorber RS250 is not good, it's too hard. You must modify it.
I use 5.2 kg/mm springs for a rider of 76 kg.

Does anyone know show me the relationship between wave speed and temperature of the gas?
Before building this exhaust must be certain of the operating temperatures of the exhaust gases:
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Setting wave speed 530 m/s measures change much (Lmax = 809.0mm) , I have to be sure about this parameter. I can vary the temperature of the exhaust gas only within a certain range.


Have any of you tried working with the de laval nozzles?

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I asked the same question here. It was explained by a few people.

Thank you!

Frits Overmars a écrit:

Thank you, Vagelis.
I wish to emphasize once more that this FOS exhaust concept is only meant to help beginning tuners on their way and a lot of important facors, like compression ratio, ignition timing, type of fuel, carburetter diameter, crankcase volume, and port angle*areas, are not taken into account. Instead of all those factors that I left out, I included one variable, the speed of sound. Starting with 550 m/s will get you in the right ballpark, after which you can vary this value according to your findings.
Final remark: the calculation of the tailpipe restrictor diameter is critical: you can only apply it to engines that are thermally sound. Air-cooled engines are not...

How affects on the FOS exhaust concept a small diameter carburetor (only 28mm)?
Thanks!

Come incide l'utilizzo di un carburatore piccolo (da soli 28mm) sul dimensionamento della marmitta con il FOS pipe? Quali correttivi si posso eventualmente introdurre?
Grazie!

A smaller carburettor will probably influence the engine power so it will probably also influence the exhaust gas temperature and thus the speed of sound, and it will influence the tailpipe restrictor diameter, as you can see in the formula for Dtailrestrictor.

Thanks for the reply.
I will create different test exhaust with different wave speed parameter: 550, 540 and 530. I'll try to find the best compromise.
I also would try different tailpipe restrictor and this de laval nozzle:
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I will try and try again, until I improve the performance.
Thanks for the suggestions.

{mRk} a écrit:

I will create different test exhaust with different wave speed parameter: 550, 540 and 530. I'll try to find the best compromise.

Initially, try bigger steps: 400 - 500 - 600. Then, according to your findings, you can take smaller steps.
If you start with the smaller steps, it may take forever to find the optimum.

Good idea!

I have been playing around with the numbers for my bike and couldn't decide which pipes to actually make.

Do you make all your pipes using the same formula or do you add in other information? If so, could you elaborate on other factors when you design pipes?

Okay, I'll try with bigger steps.

Hi again.

Filandro, Have you already builded the exhaust from Frits concept?

Hi, I'm trying to find a new argon tank for my TIG..