Rule change submissions close 1 March 2016 - be in to win.

**TZ350** · 8th February 2016, 20:37

Help .... I have been unable to get onto the MNZ site to download the latest 2015 version of the rules to work with. Is this just me or is it MNZ's website?

**husaberg** · 8th February 2016, 20:48

Originally Posted by TZ350

Help .... I have been unable to get onto the MNZ site to download the latest 2015 version of the rules to work with. Is this just me or is it MNZ's website?

Chapter 24 – Road Racing – Miniature
24.2 - Engines must be derived from non-competition motorcycles. Motocross, Road Racing, Enduro
and Go Kart motors and transmission parts are not permitted. There shall be no restriction on the
make, type or design of carburettor, ignition, exhaust, piston, cam, valve springs or cooling system
except for class eligibility. All engines must be normally aspirated except F4 4 stroke engines of less
than 100cc capacity and F4 2 stroke engines of less than 70cc capacity, which may be turbo or
supercharged. F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single
24mm carburettor, F5 4 stroke engines over 53cc are restricted to carburetion equivalent to a single
20mm carburettor

https://www.mnz.co.nz/regulations/Mo...d-rule-changes

**koba** · 8th February 2016, 21:17

I think the rules are largely OK, we are all managing to build bikes that are quite close and most paths that one can choose are workable within the rules, with some pros and cons. Brilliant.

What I would like to see is one change to the status quo that is more inclusive.

There are A LOT of air-cooled 2 valve singles in our capacity range. There are lots of old Hondas and newer Chinese and other cheap engines available.
Currently they are screwed as they have to fit in with the other 4 valve 4-strokes yet will never keep up.

I'm all for giving them more capacity.

The only question in my mind is; how much?

175?
180?
190?
200?

The objective would to be to get one to be competitive with what we already have.
Horsepower may not be the full story here either, as we know it's not about the total number.

Grumph, what's your opinion?

**TZ350** · 8th February 2016, 21:57

Originally Posted by husaberg

Chapter 24 – Road Racing – Miniature
24.2 - Engines must be derived from non-competition motorcycles. Motocross, Road Racing, Enduro
and Go Kart motors and transmission parts are not permitted. There shall be no restriction on the
make, type or design of carburettor, ignition, exhaust, piston, cam, valve springs or cooling system
except for class eligibility. All engines must be normally aspirated except F4 4 stroke engines of less
than 100cc capacity and F4 2 stroke engines of less than 70cc capacity, which may be turbo or
supercharged. F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single
24mm carburettor, F5 4 stroke engines over 53cc are restricted to carburetion equivalent to a single
20mm carburettor

https://www.mnz.co.nz/regulations/Mo...d-rule-changes

Thanks Husa. You know, that link does not work for me, strange!!!!

Ok so now we have the up to date 2015 text with the rule change possibilities and an S after the word "Kart motor".

Option 1, a refined definition of 24mm carb equivalent that takes into account EFI and throttle plate carbs like the Tillotson pumper carb.

Chapter 24 – Road Racing – Miniature
24.2 - Engines must be derived from non-competition motorcycles. Motocross, Road Racing, Enduro
and Go Kart motors and transmission parts are not permitted. There shall be no restriction on the
make, type or design of carburettor, ignition, exhaust, piston, cam, valve springs or cooling system
except for class eligibility. All engines must be normally aspirated except F4 4 stroke engines of less
than 100cc capacity and F4 2 stroke engines of less than 70cc capacity, which may be turbo or
supercharged. F4 2 stroke engines over 104cc ; At some point in the inlet tract(s) between atmosphere and crankcase or barrel, the inlet tract(s) shall not exceed an area of 452mm2 (24mm equivalent) in total. For the purposes of measurement, EFI throttle body idle air circuit if any and carburettor air bleed jets and orifices shall be ignored. F5 4 stroke engines over 53cc are restricted to carburetion equivalent to a single
20mm carburettor

Option 2 same as 1 but without the F5 4T 20mm carb restriction

Chapter 24 – Road Racing – Miniature
24.2 - Engines must be derived from non-competition motorcycles. Motocross, Road Racing, Enduro
and Go Kart motors and transmission parts are not permitted. There shall be no restriction on the
make, type or design of carburettor, ignition, exhaust, piston, cam, valve springs or cooling system
except for class eligibility. All engines must be normally aspirated except F4 4 stroke engines of less
than 100cc capacity and F4 2 stroke engines of less than 70cc capacity, which may be turbo or
supercharged. F4 2 stroke engines over 104cc ; At some point in the inlet tract(s) between atmosphere and crankcase or barrel, the inlet tract(s) shall not exceed an area of 452mm2 (24mm equivalent) in total. For the purposes of measurement, EFI throttle body idle air circuit if any and carburettor air bleed jets and orifices shall be ignored.

Option 3, no carb restrictions at all.

Chapter 24 – Road Racing – Miniature
24.2 - Engines must be derived from non-competition motorcycles. Motocross, Road Racing, Enduro
and Go Kart motors and transmission parts are not permitted. There shall be no restriction on the
make, type or design of carburettor, ignition, exhaust, piston, cam, valve springs or cooling system
except for class eligibility. All engines must be normally aspirated except F4 4 stroke engines of less
than 100cc capacity and F4 2 stroke engines of less than 70cc capacity, which may be turbo or
supercharged.

Now if we could have no restrictions on fuel type or additives for 4T's of less than 100cc and 2T's of less than 70cc then we could see some very interesting machines indeed.

**TZ350** · 8th February 2016, 22:24

Originally Posted by koba

What I would like to see is one change to the status quo that is more inclusive. There are A LOT of air-cooled 2 valve singles in our capacity range. There are lots of old Hondas and newer Chinese and other cheap engines available.

Yes it would be good to get them included, some cheap but usable engines are excluded because they are 155cc to start with.

**jasonu** · 9th February 2016, 03:32

Originally Posted by TZ350

some cheap but usable engines are excluded because they are 155cc to start with.

Then why not increase the upper limit to say 300cc to include them as well.
Hell why not just make it all comers run what you brung...That way every time some old/obscure or newly imported motor comes out of the wood work or if someone runs out of oversizes or finds cheaper larger pistons from the space shuttle they won't have to worry about the rules because there won't be any. While you are at it make it open fuel incase someone has a jug of old rocket fuel or some plutonium in the back yard.

**Grumph** · 9th February 2016, 05:59

Originally Posted by koba

I think the rules are largely OK, we are all managing to build bikes that are quite close and most paths that one can choose are workable within the rules, with some pros and cons. Brilliant.

What I would like to see is one change to the status quo that is more inclusive.

There are A LOT of air-cooled 2 valve singles in our capacity range. There are lots of old Hondas and newer Chinese and other cheap engines available.
Currently they are screwed as they have to fit in with the other 4 valve 4-strokes yet will never keep up.

I'm all for giving them more capacity.

The only question in my mind is; how much?

175?
180?
190?
200?

The objective would to be to get one to be competitive with what we already have.
Horsepower may not be the full story here either, as we know it's not about the total number.

Grumph, what's your opinion?

I know that without much development - but quite a lot of clever fabrication - 20plus(a little) HP is available from a legal 2 valver. 185 would be an easy build but IMO would only see maybe another 5HP or so. Better torque though which for kart tracks may be a factor. 2V really need alcohol to go against 4V on equal capacity terms.

Originally Posted by jasonu

Then why not increase the upper limit to say 300cc to include them as well.
Hell why not just make it all comers run what you brung...That way every time some old/obscure or newly imported motor comes out of the wood work or if someone runs out of oversizes or finds cheaper larger pistons from the space shuttle they won't have to worry about the rules because there won't be any. While you are at it make it open fuel incase someone has a jug of old rocket fuel or some plutonium in the back yard.

Oh certainly. But I'd point out that the bucket rules have been one of the most stable classes over the years. This may be the last chance for some time to do an "adjustment".
Personally I like Rob's three proposals as it mandates rider involvement in any changes. Note that as a non licence holder, currently I won't get a say.
And yes, i know i can get a vote but I feel i'm better to just stir as I'm currently doing.