The 50

**TZ350** · 30th December 2015, 17:42

Originally Posted by wobbly

Previously I said I would post pics of the mods done to the TZ400 that won at the Shorai Challenge, so here are some of the modified head and new water circuit.

From the pump water enters the rear of the cylinder below the welded on top plate, this forces flow around over the transfers then up into the front of the head via holes on each side of the Ex duct.

This water is then forced to flow around the inserted head, and out at the highest point, with an auto air bleed back to the top of the crossflow rad.

Follow the link to read Wobs post on his water circuit and to see the pictures.

**cotswold** · 31st December 2015, 07:23

Originally Posted by richban

I will never race a 2 stroke without one. Saves engines and body parts.

I just bought a couple so when they arrive I will be asking dumb questions

**F5 Dave** · 31st December 2015, 07:29

Only thing I learnt was on a 50 the header is so narrow you have to be careful not to stick the probe in so far (said the alien to the farmhand) as to overheat the fat edge. Do a dyno run without it and then fit it. Make a blanking plug so it can be removed for the test.

Temperature reading just kept climbing and lost 3hp. Went back next day once I'd fashioned a plug and hp came back. Put on the shelf and forgotten. Wish I'd tried pulling it out a bit further. Oh well.

**richban** · 31st December 2015, 07:34

Originally Posted by cotswold

I just bought a couple so when they arrive I will be asking dumb questions

Good move. They don't tell the full story but it will make jetting a lot more simple. And when you see the temp go down rapidly pull the clutch in.

**richban** · 31st December 2015, 07:39

Originally Posted by F5 Dave

Only thing I learnt was on a 50 the header is so narrow you have to be careful not to stick the probe in so far (said the alien to the farmhand) as to overheat the fat edge. Do a dyno run without it and then fit it. Make a blanking plug so it can be removed for the test.

Temperature reading just kept climbing and lost 3hp. Went back next day once I'd fashioned a plug and hp came back. Put on the shelf and forgotten. Wish I'd tried pulling it out a bit further. Oh well.

Good point! I wonder if just fitting it futher down the pipe would be the way to go. The reading would not be as fast maybe but with the data logged it should still tell the fuelling story. It would be interesting to here from anyone running an etg in a 50?

**jasonu** · 31st December 2015, 08:53

Originally Posted by cotswold

Mainly because the man that owns NZ's winningest 50 .

Who is this man? Pete Sales perhaps?

**cotswold** · 31st December 2015, 11:19

Originally Posted by jasonu

Who is this man? Pete Sales perhaps?

I am talking in living memory, modern times, this century though 7 times is a touch impressive, the last time was a quarter of a century ago.

**cotswold** · 31st December 2015, 13:31

50 cc with a 12 mm carb
http://youtu.be/q6FJ0vbUj6c

**jasonu** · 31st December 2015, 14:30

Originally Posted by cotswold

I am talking in living memory, modern times, this century though 7 times is a touch impressive, the last time was a quarter of a century ago.

Cheeky buggar.
Who then? David/Nathaniel Diprose comes to mind.

**cotswold** · 31st December 2015, 15:55

Originally Posted by jasonu

Cheeky buggar.
Who then? David/Nathaniel Diprose comes to mind.

yes David took a look over my very buckity 50 and said the engine was exceeding my radiators ability to remove the heat.

**richban** · 5th January 2016, 18:04

OK, so the motor is out and on the bench. With the cast barrel and gear oil its weighing in at 15.5kg. I think I can knock a couple of kg of that.

Looking at the cases down the intake duct I can see lots of sharp edges that I will attack soon. Before I do I will measure the case volume and see where its at. Just waiting on the gaskets and seals to turn up and away we go.

**TALLIS** · 5th January 2016, 18:52

Originally Posted by richban

OK, so the motor is out and on the bench. With the cast barrel and gear oil its weighing in at 15.5kg. I think I can knock a couple of kg of that.

Looking at the cases down the intake duct I can see lots of sharp edges that I will attack soon. Before I do I will measure the case volume and see where its at. Just waiting on the gaskets and seals to turn up and away we go.

Did you manage to get a dyno run in as is?

**F5 Dave** · 5th January 2016, 18:57

No he had some excuse or other. The other 50 we put on we found 2hp in 20 minutes before running out of adjustment.

**richban** · 5th January 2016, 19:44

Originally Posted by F5 Dave

No he had some excuse or other. The other 50 we put on we found 2hp in 20 minutes before running out of adjustment.

Plenty of excuse to burn. Did you measure the case volume of your Derbi dave?

The first dyno will be the base line. It would have been maybe 8 or 7 hp.