ESE's works engine tuner

[Frits Overmars]

The TZ250G... when you got it to rev, the pistons would fall into the idiot designed inlet port and would destroy themselves in about 100Km -
the whole team that designed that piece of shit cylinder should have been shot.

That's one way of looking at it Wob. I'd say the TZ250G had by far the best gometry of all the 2-in-1 cylinder blocks.
You'd only have to shoot the Jap that fitted it the wrong way around. With the carbs up front all piston problems were gone.

[peewee]

I tried almost your way wobbly, just a couple of minutes ago.
I didn´t reach as you describe so i just started to weld,(material was about 1mm thick) and i pushed in a lot of weldingrod and heated and heated so it 'sinked' down into the waterjacket, had the cylinder upside down.

In middle of progress:
Attachment 335502

have you a tig welder ? ive found it to be a priceless tool and you can make many things

[wobbly]

Yes I agree Frits the duct geometry was well ahead of any other parallel twin,and that is why we started the LSR 350 engine with one.
Once you turn it around ( as we did for years in Superkart racing } as well as the LSR then the intake issue is null,as well as making really nice pipes easy to fabricate.
Luckily the earlier F model heads bolt straight on, and or hoovering out the G cover and adding inserts got rid of the dumb arse Dr Joe money making enterprise of offset combustion.
The last thing to try on the LSR 350 is to use 400 cases, shunting the case volume thru the roof, as well as NO chance of flywheel parasitic radial drag.

[husaberg]

Yes I agree Frits the duct geometry was well ahead of any other parallel twin,and that is why we started the LSR 350 engine with one.
Once you turn it around ( as we did for years in Superkart racing } as well as the LSR then the intake issue is null,as well as making really nice pipes easy to fabricate.
Luckily the earlier F model heads bolt straight on, and or hoovering out the G cover and adding inserts got rid of the dumb arse Dr Joe money making enterprise of offset combustion.
The last thing to try on the LSR 350 is to use 400 cases, shunting the case volume thru the roof, as well as NO chance of flywheel parasitic radial drag.

How move bigger volume are the cases?
I actually thought that once you go over 1-2mm clearance between the crnk wheels and the cases you will get boundary friction drag.
I ask this as i assume the crankwheels on the RD400 are quite a lot bigger than the 250/350 DS7/TZ/rd cases but i always thought most of the volume was from the taller deck cases.

[Haufen]

Port flow

Looks like it would be a good idea to make the duct straight and angle it more downwards. The RSA is at 25° iirc (for a square engine, that is. will be less for a big bore and vice versa).

[ken seeber]

Ken Seeber, the DiTech SR 50 has a domed piston.

Johnny, you're right. I googled for a pic and came up with this one of the head. Certainly spherical, but does feature the characteristic offset bowl and varying squish areas.

[Muhr]

Looks like it would be a good idea to make the duct straight and angle it more downwards. The RSA is at 25° iirc (for a square engine, that is. will be less for a big bore and vice versa).

I think so too! I would like to use a shorter conrod i have as I get 13g less balanced weight. Perhaps it was a bad decision.
Tried to adjust some angles and get a little bit better, but I don't know.

[SwePatrick]

have you a tig welder ? ive found it to be a priceless tool and you can make many things

Yes, since i bought my first tig welder the old MIG/MAG is left dusty in a corner =)

[Frits Overmars]

Yes I agree Frits the duct geometry was well ahead of any other parallel twin,and that is why we started the LSR 350 engine with one....
The last thing to try on the LSR 350 is to use 400 cases, shunting the case volume thru the roof, as well as NO chance of flywheel parasitic radial drag.

With the bigger case volume, your porting layout and the really fat pipes on the LSR bike, it should fly, Wob!

How move bigger volume are the cases? I actually thought that once you go over 1-2mm clearance between the crnk wheels and the cases you will get boundary friction drag. I ask this as i assume the crankwheels on the RD400 are quite a lot bigger than the 250/350 DS7/TZ/rd cases but i always thought most of the volume was from the taller deck cases.

Boundary drag between crank wheels and cases rises steeply when you go under 1 mm clearance, Husa. But that's not the case here; the crankwheel diameter of the RD400 may be quite a lot bigger, but when you put a TZ350 crank in the RD400-cases, everything is fine.

[peewee]

Yes, since i bought my first tig welder the old MIG/MAG is left dusty in a corner =)

you can also get micro torch for weld inside exh port. i got this one new helmet yesterday. optrel made in switzerland

[Frits Overmars]

you can also get micro torch for weld inside exh port. i got this one new helmet yesterday. optrel made in switzerland

Careful now, Peewee. If you carry on like this, you cannot blame the equipment any longer .

[SwePatrick]

you can also get micro torch for weld inside exh port. i got this one new helmet yesterday. optrel made in switzerland

I´ve got a Speedglas helmet with my own graphics on it, had it for 15years i guess.
Must be the most quality weldinghelmet ever, never lets me down =)

Yes, i´ve seen those microtorches, i just about reached with my wp9 with stubby setup into exhaustport also, i welded up the floor a bit.

[Muhr]

If try continue from where Jan stopped, why not to try exhaust bottom at transfers upper edge level, and then grinding in small steps.
Interesting how bottom exhaust duct shape should look like with this configuration, parallel with upper and oval cross-section or something different,
of course with ......G, H,.......

Haufen had a point! maybe this is the way to go even from start.

[wobbly]

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.

[husaberg]

Boundary drag between crank wheels and cases rises steeply when you go under 1 mm clearance, Husa. But that's not the case here; the crankwheel diameter of the RD400 may be quite a lot bigger, but when you put a TZ350 crank in the RD400-cases, everything is fine.

Hanks Frits Well i sure had that backwards.
I remember you mentioning the TZ with RD400 previously, so how much extra power are you talking here?