Question on Pro Twin front forks

[Ivan]

Hey someone in the know

Would youplease beable to explain what is the best option to do to a SV650 front end for when I get myne to still be able to race it under Pro Twin rules.

What would be the best valving kit to get for it
And what other internal mods can you do I have had aread through rules but currently cant view PDF files so cant re read and there are a few guys who have actually developed protwins so just wondering

Ivan

[speights_bud]

APPENDIX F
650cc PRO TWIN
This class rules will apply to all National Championship and Endurance championship races.
At other meetings these rules will apply unless varied in the supplementary regulations, but
not contradicting the class rules.
Capacity Group
This class of motorcycle requires an MNZ Homologation with a minimum of 10 units sold of

that model per year.
This class to be called the 650cc Pro Twins.
All items not mentioned in the following articles must remain as originally produced by the
manufacturers remain fitted and operational for that homologated model.

1. Twin cylinder four strokes up to 650cc standard engines. (Only OEM engine
parts for that model may be fitted).

2. Number Plate Colours – Orange background with black numbers.

3. Fuel
This class must function on normal unleaded fuel with a maximum lead content
of 0.013g/l (unleaded) and a maximum RON of 98.

4. Tyres
Tyres V or Z rating must be used. Only tyres on general sale to the public in
New Zealand as road legal fitment will be permitted. For all events other than
endurance races only one set of tyres per meeting will be allowed for races
counting towards the MNZ championship.
Tyre warmers are allowed.
Wet tyres.
In the event that the track is damp/wet the choice of tyre is at the discretion of
the rider.
The DOT rule requirement for sports production wet tyres is suspended.
A full race wet tyre marked NOT FOR HIGHWAY USE may be used providing
that the tyre has a moulded tread pattern, any number of wets may be used.
Hand cut DOT approved sports production tyres and hand cut slicks may not be
used.

5. Machine Specifications (General)
All machines must comply with the relevant general competition Rules such as
Chapter 10.
Machines with rebored cylinders must remain within that models OEM
capacity limits (ie: second oversize, .5mm).

6. Modifications Allowed
a. The front fork inner (slide pipe stanchion) and the outer (outer stanchion)
must remain as per the original manufacturers OEM parts for that

[speights_bud]

homologated model. Damper Rods, fitment of emulators, springs and valving
may be changed for suspension timing purposes.
Complete cartridge replacement with non-OEM parts is not permitted.
Quality and quantity of oil in forks.
The height and position of the front fork in relation to the top yoke (fork crown)
is free.
b. Cam wheels (sprockets) may be slotted.
c. Undercutting and shimming of gearbox.
d. Rear Suspension unit (Rear Shock) may be replaced. The link arm may be
changed or modified but the suspension linkage must remain standard,
original attachments to the frame must be used.
e. Exhaust system
f. Drive sprockets
g. Steering damper
h. Handle bars
i. Instrument panel
j. Foot rest/Foot controls, must be mounted to the frame at the original
mounting point.
k. Small protective cones may be fitted to minimize accident damage.
l. Brake disc pads.
m. Brake lines front and rear.
n. Spark plugs
o. Carburettor jetting and slides
p. A fuel tuning device ie Power commander may be used.
q. Ignition, Engine control module/unit (ICM, ECU, ECM) and wiring loom
must remain standard.
Fairing/Body Work
Accessory aftermarket fairing, front guard and bodywork may be fitted.
The use of carbon fibre is restricted to the reinforcing mounting parts (area) only.
Windscreen may be replaced.
The original combination instrument/fairing brackets.
The following items must be altered or removed
Passenger footrests/grab rails, chain guard
Safety bars, centre stands (fixed welded brackets must remain)
Where breather or over flow pipes are fitted they must discharge via existing outlet. The
original closed system must be retained; no direct atmospheric emission is permitted.
Headlight, rear light and blinkers must be removed.
Horn
Licence plate bracket

[speights_bud]

The following may be removed
Instruments, brackets and associated cables
Toolbox
Speedometer
Radiator fan and wiring
Items not allowed
No Data logging
Additional equipment not on the original homologated motorcycle may not be added (ie; data
acquisition computers, recording equipment)
The fitment of aftermarket Traction Control units is not permitted.

[Robert Taylor]

Hey someone in the know

Would youplease beable to explain what is the best option to do to a SV650 front end for when I get myne to still be able to race it under Pro Twin rules.

What would be the best valving kit to get for it
And what other internal mods can you do I have had aread through rules but currently cant view PDF files so cant re read and there are a few guys who have actually developed protwins so just wondering

Ivan

Essentially for that bike you are allowed to fit emulators and springs but are not allowed to fit aftermarket cartridges.

This is a relatively low cost mod but its also easy to do it badly. Enlarging and adding extra holes in the bottom of the damper rods ( as per Race Tech suggested method ) MUST NOT be done in this way as you actually end up with a dead area of high speed rebound damping. Dirt bikes with 300mm of travel can get away with it, but not road race bikes with 120mm of travel. I have had this conversation directly with Paul Thede and he agrees with what I have stated.

As a brazen pitch for my business doing the job we supply Ohlins superbike springs as part of the package, the advantage here being is that we stock all the rates. If you find that you end up needing a slightly different rate to those supplied we exchange at no cost excepting courier recovery costs. Further advantages of these springs is that they are highly polished so there is less internal wall rubbing friction and they are very short but still with adequate stroke integrity. Short springs means less coils to rub and create friction and rapid oil contamination, also weight reduction.
Another thing to bear in mind is that damper rod forks are very viscosity and ambient temperature sensitive. Because there is so much badly controlled bleed they must neccessarily run around 15 weight oil in winter and 20 weight in summer, although personally I prefer to see only what centistroke rating the oils are as the only true indicator of flow rate. Such relatively thick oils can vary in characteristic enormously over the course of a day. First thing in the morning the rebound speed can be very lethargic, and yet in the middle of the day when the suns out the rebound speed is appreciably faster. For that reason dont fill it with a cheap oil that has widely varying flow chracteristics according to temperature. I dare not say it in print but there is also one high profile brand of oil that a lot of people have been duped into using in their forks that has very poor corrosion resistance properties.
The set up we provide is very well dialed and we are always available for set up advice.

[cowpoos]

Hey someone in the know

Would youplease beable to explain what is the best option to do to a SV650 front end for when I get myne to still be able to race it under Pro Twin rules.

What would be the best valving kit to get for it
And what other internal mods can you do I have had aread through rules but currently cant view PDF files so cant re read and there are a few guys who have actually developed protwins so just wondering

Ivan

I got a question for you...why don't you keep racing your rs125?? like so many people reckon you should??..and save any money you have for the mean time??

[Ivan]

I got a question for you...why don't you keep racing your rs125?? like so many people reckon you should??..and save any money you have for the mean time??

Ive talked to a few people and they believe its the right step for me to take.
Also its alot more practical for me. me being 6"1 and 67kgs on a 125 is INSTANT horsepower loss the power to weight ratio is set against me big time.

I also want the challenge of a new bike and working with it and plus I dont own my 125. but I will own this bike and I wpuld preferto own my own race bike.

[Ivan]

Essentially for that bike you are allowed to fit emulators and springs but are not allowed to fit aftermarket cartridges.

This is a relatively low cost mod but its also easy to do it badly. Enlarging and adding extra holes in the bottom of the damper rods ( as per Race Tech suggested method ) MUST NOT be done in this way as you actually end up with a dead area of high speed rebound damping. Dirt bikes with 300mm of travel can get away with it, but not road race bikes with 120mm of travel. I have had this conversation directly with Paul Thede and he agrees with what I have stated.

As a brazen pitch for my business doing the job we supply Ohlins superbike springs as part of the package, the advantage here being is that we stock all the rates. If you find that you end up needing a slightly different rate to those supplied we exchange at no cost excepting courier recovery costs. Further advantages of these springs is that they are highly polished so there is less internal wall rubbing friction and they are very short but still with adequate stroke integrity. Short springs means less coils to rub and create friction and rapid oil contamination, also weight reduction.
Another thing to bear in mind is that damper rod forks are very viscosity and ambient temperature sensitive. Because there is so much badly controlled bleed they must neccessarily run around 15 weight oil in winter and 20 weight in summer, although personally I prefer to see only what centistroke rating the oils are as the only true indicator of flow rate. Such relatively thick oils can vary in characteristic enormously over the course of a day. First thing in the morning the rebound speed can be very lethargic, and yet in the middle of the day when the suns out the rebound speed is appreciably faster. For that reason dont fill it with a cheap oil that has widely varying flow chracteristics according to temperature. I dare not say it in print but there is also one high profile brand of oil that a lot of people have been duped into using in their forks that has very poor corrosion resistance properties.
The set up we provide is very well dialed and we are always available for set up advice.

Cool I may have a bike already set up but I may get hold of you about it and send up and get you yo pull it down and service it and also set it up if you can for my weight etc?

[speights_bud]

i rode a completely stock SV650 (naked Version) except for a short scorpion ex pipe , at manfield a few weeks ago, it was my first time on a big bike at manfield and first time riding since december.
I was doing 1:20's on it. whats that like for pro twins?

The bike was running lean from about 10k to the red and suspension was stock/nothing flash, not to mention the stock brake pads .

[Shaun]

1 23 Karl Morgan 1:15.419 15 144.775 15 -
2 45 Tom Bos 1:17.693 7 140.538 2.274 2.274 11 -
3 12 David Cook 1:17.802 5 140.341 2.383 0.109 5 -
4 67 Geoff Booth 1:17.993 6 139.997 2.574 0.191 8 -
5 212 Anthony Stephens 1:18.677 6 138.780 3.258 0.684 16 -
6 210 Alan Zitnik 1:18.826 8 138.518 3.407 0.149 8 -
7 217 Paul Barnard 1:25.149 14 128.232 9.730 6.323 14 -
8 204 Raymond Nairn 1:28.131 5 123.893 12.712 2.982 13 -

[johnsv650]

hi ivan,
good luck with protwins, theres about 4 or 5 more down in the south island, some older guys and some from the super strong streetstock class....
robert Taylor and shawn on kb will helping you with suspension, just one tip , get the best first time, helps develope faster......dunlop tyres also.

[Ivan]

My tires will be Conti Race Attacks

[speights_bud]

1 23 Karl Morgan 1:15.419 15 144.775 15 -
2 45 Tom Bos 1:17.693 7 140.538 2.274 2.274 11 -
3 12 David Cook 1:17.802 5 140.341 2.383 0.109 5 -
4 67 Geoff Booth 1:17.993 6 139.997 2.574 0.191 8 -
5 212 Anthony Stephens 1:18.677 6 138.780 3.258 0.684 16 -
6 210 Alan Zitnik 1:18.826 8 138.518 3.407 0.149 8 -
7 217 Paul Barnard 1:25.149 14 128.232 9.730 6.323 14 -
8 204 Raymond Nairn 1:28.131 5 123.893 12.712 2.982 13 -

Cheers Shaun,
I've got a bit of work to do then a challenge is always good!

[Ivan]

Yeah I am only worried about getting the front end set up as i have said I am going to buy and race a Penske in the back and believe from waht have seen the Conti Race Attack tires are the bees knees as well.
Hoping to have me a bike soon and get some pre season Testing done.

[quallman1234]

Don't be blaming the bike now Ivan, Might pop round on friday with glen. Catch ya.