ESE's works engine tuner

[RAW]

I have heard of late model TZ250s have an issue with piston burning due to excessive retard ( like after TDC ) when in the overev - as well as having the powerjet switch off , but its usually
too much advance at some point lower down in the rev range that tears up the ring lands.
If its too much timing at peak, you will hole the piston.


Here is the link to the Frepin TZ400 startup and first dyno session

https://www.youtube.com/watch?v=p8ZJCPXAIyA

Cheers Wobbly

Yeh the ring land reference was just to let you know where the piston was eroding / melting away
It's just below the ring groove, we actually burnt a hole through the piston wall, it kept running just down on power with a slight nip up type feel to it

I will hopefully get down to the Island to see the machine in the flesh

[wobbly]

Na, the RS125/250 never had a factory curve that ended after TDC.
It simply wasnt needed when the "new " powerjet system ( as Yamaha had used for years , to pump up the stupid 50.6 stroke engines )
was introduced when leaded race gas was banned in 1998.

[senso]

As said, here are some photos about the sachs finned cases:








Edit: Corrected the links, now showing the 4 photos as supposed.

[TZ350]

Thanks, that is very interesting as my problem is being able to reject enough waste heat through air cooling.

[senso]

Have you tried glass bead blasting the cylinder and the head?

[F5 Dave]

While we're getting desperate, maybe a coarse sand would give it that weathered look & expose even more surface area?

[Frits Overmars]

While we're getting desperate, maybe a coarse sand would give it that weathered look & expose even more surface area?

I fear that as long as the coarseness (coarsity?) is less than the boundary layer thickness of the air clinging to the surface, it will only create an isolating air blanket....

[Flettner]

Enter the transfer port master and transfer core box.
Water core box next, then all will become clear, as to how it all fits together.

[F5 Dave]

I fear that as long as the coarseness (coarsity?) is less than the boundary layer thickness of the air clinging to the surface, it will only create an isolating air blanket....

Ok I can believe that. Nice word evolution.

[husaberg]

As said, here are some photos about the sachs finned cases:


Edit: Corrected the links, now showing the 4 photos as supposed.

I see your Sachs and I raise you a Penton.....which could be a sachs. also think the DKW and the Zundap were similarly finned

[senso]

From a lot of photos(from this epic topic), it seems like the sachs engine is almost a copy of the dkw ones.
The finning on the zundapp engines are not as big/long, they only span around the crankcase, nothing or almost nothing under the gearbox.

[Drew]

The good folk at mini seemed to think it was worth it too. Suppose it's a bit different on a four stroke with the oil being pumped through the motor though.

[FastFred]

Enter the transfer port master and transfer core box.
Water core box next, then all will become clear, as to how it all fits together.

I can't quite picture it yet but I am enjoying seeing this pattern coming together, thanks.

[F5 Dave]

I see your Sachs and I raise you a Penton.....which could be a sachs. also think the DKW and the Zundap were similarly finned

I was going to say Penton was the Amorican distrubutor of KTM & badged them as such, but a quick Google sez the first Pentons ran Sachs engines.

[Yow Ling]

I can't quite picture it yet but I am enjoying seeing this pattern coming together, thanks.

I cant quite picture it either but was scared to tell the Emperor he had no clothes.
Even simple moulds are not so simple once the cores turn up