ESE's works engine tuner

[Muhr]

Looking at the latest 125 TM kart cylinders I have been working on,the best power is had from using the Aprilia 25* down angle on the roof that ends in a hump
just past where the Aux port exits into the duct.
The floor is horizontal to the same point,than ramps down.
This is keeping the duct volume down, especially where the Aux ducts intersect with the main duct.
As far as lifting the floor above BDC is concerned, just remember that Jan found power I believe at 2mm,then the tests ended.
So this is as far as has been dyno proven in a really well developed cylinder like this.
Another point re the water - after my tests on the ceramic coated duct I believe that you should have water right up to the flange face,and I go one further
and mill slots thru the flange face to cool the back of the bolt on spigot.

Thanks wobbly I'll look into it. Just raise the bottom made surprisingly little change on the flow image

[SwePatrick]

Looking at the latest 125 TM kart cylinders I have been working on,the best power is had from using the Aprilia 25* down angle on the roof that ends in a hump
just past where the Aux port exits into the duct.
The floor is horizontal to the same point,than ramps down.
This is keeping the duct volume down, especially where the Aux ducts intersect with the main duct.
As far as lifting the floor above BDC is concerned, just remember that Jan found power I believe at 2mm,then the tests ended.
So this is as far as has been dyno proven in a really well developed cylinder like this.
Another point re the water - after my tests on the ceramic coated duct I believe that you should have water right up to the flange face,and I go one further
and mill slots thru the flange face to cool the back of the bolt on spigot.

Yes, I have drawn a pic of how i´m designing my new cylinder, it is very similar to your drawing actually.
Then i drew that idea of water all into the flange, roostcylinders for scooters have this design.

Then also another thing, i altered the auxports on picture to be more similar to my porting.
I don´t want the wristpin to pass over the port to much as it is expensive to laserweld the wristpin shut in the ends like Aprilia did.

[Frits Overmars]

I don´t want the wristpin to pass over the port to much as it is expensive to laserweld the wristpin shut in the ends like Aprilia did.

The wristpin passing over the auxiliary exhaust windows need not be a problem Patrick. The problem arises when the wristpin passes over those aux windows and the transfer windows simultaneously, as indicated by the yellow circle in the first picture. That is why the aux ports in the Aprilia cylinders have sloping undersides in order to minimize the port area in the 'danger zone'.
Laserwelding the wristpin ends is not the most effective solution. You might want to try the type of synthetic plug that I developed.
They are closer to the cylinder bore and fairly easy to produce, although the necessary material, Torlon, is not cheap.

[SwePatrick]

Nice Info Frits, Thanks.

I had the problem in an earlier build, long time ago, thereby my caution.
It was like a handgrenade in the crankhouse, it flew reedpetals all over the garage, and it actually chopped off the needle in the carb =)

[Frits Overmars]

I remember you mentioning the TZ with RD400 previously, so how much extra power are you talking here?

I don't remember Husa; it was about 40 years ago, when the TZs still came with 34 mm Mikunis. In combination with the bigger crankcase volume we fitted 38 mm carbs to the TZ250 and 40 mm to the TZ350. With hindsight that should have been about 44....

[JanBros]

someone asked me if it was possible to switch of the wobbly-duct for 2/3stage in my FOS excel. it wasn't so I changed it now.
also added volumes.

http://users.telenet.be/jannemie/FOS...E%20black.xlsm

[lodgernz]

Never seen this before. Usually it's the rear skirt that breaks, as it's the thrust face.
From my 50 after 10.2 hours thrashing at race pace. Not all at once of course. Over a year or so.
Any comments? Looks a bit like fatigue.

[Muhr]

Thanks wobbly I'll look into it. Just raise the bottom made surprisingly little change on the flow image

I can not manage to get any circulation when I try to approach the flange, I've tested a lot of different variations but the only thing that gives results is area and that's something I haven't got. It's easy to forget how small it is when sitting in CAD

[husaberg]

Never seen this before. Usually it's the rear skirt that breaks, as it's the thrust face.
From my 50 after 10.2 hours thrashing at race pace. Not all at once of course. Over a year or so.
Any comments? Looks a bit like fatigue.

Why is the gudgeon bore so black? Actually looks sooty.

[tjbw]

Never seen this before. Usually it's the rear skirt that breaks, as it's the thrust face.
From my 50 after 10.2 hours thrashing at race pace. Not all at once of course. Over a year or so.
Any comments? Looks a bit like fatigue.

Looks brittle! Is there a polished fatigue surface in the shadow?

[F5 Dave]

Measure bore wear Roger. Usually takes out inlet but vould gave been weak in that piston front.

[katinas]

.........
Laserwelding the wristpin ends is not the most effective solution. You might want to try the type of synthetic plug that I developed.
They are closer to the cylinder bore and fairly easy to produce, although the necessary material, Torlon, is not cheap.

Yellow Torlon plugs looks nice, simple and effective.
Long time ago, made wirstpin plug in more complicated way. Found 25 year old piston with this plugs.
Torlon is fantastic material. Once made thrust washers for small end bearing from Black Torlon and they work fine.

[lodgernz]

Why is the gudgeon bore so black? Actually looks sooty.

No, just sort of cast-piston-grey.

Looks brittle! Is there a polished fatigue surface in the shadow?

Well spotted! Looks like a very slight polish there. Maybe where the breakage started?

Measure bore wear Roger. Usually takes out inlet but vould gave been weak in that piston front.

Bore is all good I think, 0.06mm clearance at the bottom. I'll check it all around in case there's an ovality somewhere.

[katinas]

Never seen this before. Usually it's the rear skirt that breaks, as it's the thrust face.
From my 50 after 10.2 hours thrashing at race pace. Not all at once of course. Over a year or so.
Any comments? Looks a bit like fatigue.

Maybe, squash gap is too small and sometimes piston touching the head.

[Muhr]

Never seen this before. Usually it's the rear skirt that breaks, as it's the thrust face.
From my 50 after 10.2 hours thrashing at race pace. Not all at once of course. Over a year or so.
Any comments? Looks a bit like fatigue.

I've seen it before on cast iron sleeve cylinders probably because of pistonclerence. I have thought it was because of curb jumping