Rules re engine mods?

[Scotty595]

Hey,

Am looking at what option i should go down for a bucket engine. I am just trying to clarify the rules regarding engine modifications. What are the rules regarding larger cylinders/pistons on an engine. ie if i got a 100cc engine and put a 125 top end on it?

Scott

[Henk]

It's all in the MNZ rulebook. I'd recommend you download a copy and get familiar with it.
As far as I'm aware you can do pretty much anything you like as long as you don't use any competition engine parts so no MX, go cart or RS125 engine bits. You can slap a 125 top end on a 100 as long as it falls withing those rules. So a DR125 top end would be OK but CR parts aren't as an example.

[Deano]

From my experience in racing in NZ, it seems to be whatever you can get away with. I have heard so many stories about mods done that are in breach of MNZ rules.

[bucketracer]

The MNZ rulebook

F4 rules http://www.motorcyclingnz.co.nz/down...oad_Racing.pdf

And the complete list http://www.mnz.co.nz/competitionrules.aspx

[Scotty595]

It's all in the MNZ rulebook. I'd recommend you download a copy and get familiar with it.
As far as I'm aware you can do pretty much anything you like as long as you don't use any competition engine parts so no MX, go cart or RS125 engine bits. You can slap a 125 top end on a 100 as long as it falls withing those rules. So a DR125 top end would be OK but CR parts aren't as an example.

How do you classify competition parts over just normal performance parts?

[Scotty595]

I had a look over the rule book before i posted but still was a bit confused about the competition parts etc

[bucketracer]

Some where Skunk has posted a list of eligible bikes/engines

.

[Scotty595]

Some where Skunk has posted a list of eligible bikes/engines

.

This one ????

[Henk]

How do you classify competition parts over just normal performance parts?

I think the way it works is that if the donor bike is intended as a race bike it's out. So soggy old trail bikes like XR200s are fair game but MXers aren't road bike bits are a bit easier, if you could register it you're fine. If you could use anything that fell within the capacity restrictions we'd have quite a few RS125 frames with CRF150 engines in them by now at a guess.

[Scotty595]

This one ????

So if i got one of them on the list (lets say for example the TZR50 or RG50) and put a 80/100cc top end on it, would that be legal?

[Henk]

That will depend mainly on where the top end comes from.

[Bert]

I had a look over the rule book before i posted but still was a bit confused about the competition parts etc

I'm sure others will have a lot to say on this matter (and generally do). Basically the classes (f4 & F5) are sourced from non-competition bikes i.e. small road bikes & farm bikes. Originally summed up as no aftermarket parts or performance part + racing parts (the challenge was to build something out of nothing – review the history of bucket racing and you will find that it all started on/around our Air force bases and is somewhat about engineering more than $$$); other the years this had been some what diluted: but the rules still stand for the following:
The motor chassis and transmission (i.e. what it stated its life as).
The rest is quite open:

24-2-4 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, which may be turbo or supercharged.

F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm
carburettor,

though not fully defined in the rules: aftermarket / performance parts are somewhat frond upon i.e. boyson reeds / hot rods cranks etc (as they could be deemed as a race parts) which fall back into rule clearly stating non competition source.
parts like pistons / chambers / electrics (24-2-4 defines this list) are open slather to after market parts or performance parts if it is on the list in 24-2-4.

if you want to chuck a 125cc two stroke barrel on to a 100cc chassis you can (I'm assuming you are thinking of a TS125 barrel onto a TS100 or something like that), the rules clearly states that it has to be air cooled and has to have a carb no bigger than 24mm and start its life as a non-competition motorcycle, there is no limit to the engineering that could be undertaken. I would recommend reading through all of ESE's tread about what they are doing with the GP125s all within the rules & some great ideas.

blabla sorry this has got quite long in terms of such a short question.

[bucketracer]

So if i got one of them on the list (lets say for example the TZR50 or RG50) and put a 80/100cc top end on it, would that be legal?

The best way to stay legal and be competitive is to get yourself a Suzuki GP, everything else is pretty much a wast of time ..........

[Scotty595]

That will depend mainly on where the top end comes from.

So if it was an aftermarket top end - ie didnt come off a bike originally it would be a no?

BUt you could essentially take a top end off a road bike, and engineer it to be exactly the same as said aftermarket top end, and it would all be legal?

[Henk]

That's pretty much it.