mnz rule changes

[PeteJ]

the rule as published said
twin cylinder four strokes up to 650 cc standard engines,
(only oem engine parts for that model maybe fitted).

so some race engine builders say to remove your exhaust camshaft and replace with oem inlet camshaft in its place. its a oem part from that model,

the clarification says camshafts must remain as fitted standard ie inlet cam must be fitted to inlet valve and exhaust cams to exhaust valves...

i think its a big change !

Just seen this one. Having had a lot to do with MNZ/NZACU rule drafting in the past, my take is that "OEM" means what it says - OEM part for OEM place.

The artistic intentional misinterpretation failed, and deservedly so. It's not at all a change.

This is the problem with trying to explain and clarify rules - you just provide more chances for aforementioned artistic misinterpretation.

[twinshock750]

When you stop and think about it, it's kind of pointless if you're allowed to swap out the exhaust cam, because then everyone one will do it, and then we'll all be back to equal performance again - only the costs have gone up.

Incidentally, I've asked them about the Tyre Safety Rating rule as well. Limiting to V or Z makes it very hard to get a decent tyre, most modern tyres are now 'W'. (The W Rating is better/safer than V or Z.) Mr Stewart was going to look into it prior to the final rule being published, but nothing changed.

My understanding is that almost all tyres you are likley to find will be V or Z rated. The W rating is an extension of Z ie you will see 180/55ZR17 83W

The numering meaning 180 wide 55 profile, Z for 240 plus, R for radial, 17 rim dia, 83 is the load rating (ie how much weight it can carry) and the last one being the actual final overall speed rating.

Z 240+ thus you may see also the following letters.
W 270
Y 300

A racetec rear in 180 is 180/55 ZR 17 M/C 73W TL

[ajturbo]

is it possible to change the rules in a new class after july and before the nationals ???

hahahahaha...

at least you get more than 12hrs notice of a rule change...

this year the rules for the SS class changed in an afternoon... WHILE they were racing!... beat that!

[johnsv650]

biggest two improvement on motor (dyno results) have been pipe and then power commander, both in allowed to do list , cam timing was next (it was a wee way out from f/specs) then oem cam...

[johnsv650]

safety issue,
they don't want you guys in ss on the best tyres,
just expensive road only tyres, what wear out quick,

[Tim 39]

safety issue,
they don't want you guys in ss on the best tyres,
just expensive road only tyres, what wear out quick,

that was our argument, MNZ had different ideas. well not realy actualy, doing justice to them, they had to make the ruling that they did because of politics in the new zealand justice system unfortunately

[codgyoleracer]

I stated here a long time ago in another thread - it will require more $ & more cunning to build a slightly faster protwin than many F3 bikes under the current rules.
Based on the current rules - I dont think the pro twins class was started as a low cost beginners class - As far as I can tell its been started to ultimatly & logically replace F3 (which is fine by me).

On the cam thing - my "safe" interpretation would be yes you can dial in the original cams & do cam timing - but no you wouldnt be able to swap out "other model" cams. If a manufacturer has released a higher spec cam (that is slightly different) - it will not have the same part number, therfore it may not be fitted in any other model of the same series.

On the airbox/filter thing, dont risk changing or modding them it s very easy to see & check & you will definatly have them checked at nats meetings.

I wouldnt be surprised at all under the current rules to see a well piloted protwin giving top F3 bikes a hurry up - engine wise we are not talking massive differences in HP, weight wise the F3 bike should be a little lighter (unless its got a fat ginga like me on board)

Gary H is right - there are endless options to be played with & adjusted on a road going machine to make it more track friendly & still be within the pro-twins rules. It just take time, money & testing to find out what works & what doesnt.

Glen W