The cheater MX85 argument. I might be changing my mind.

[Drew]

So to summarise the MX85 proposal as there are about 50 versions in this thread
F4
MX engines, limited to 85cc no other restrictions
100cc 2t no other restrictions max overbore 107cc if new rulechange allowed
125cc 2t carb restriction 130cc max over size (considered dangerous in Australia)
150cc 4t no other restrictions 158.6cc max oversize

Looks good to me in this form , plenty of choices, cream always rises to the top

Where were you twenty pages ago? That's simple and succinct, (which makes typing 'simple' a wasted effort...and this too...and that...oh Christ this is ridiculous).

[Mental Trousers]

Legal 2 stroke engines that are the equivalent of a standard FXR.

There are way more 2 strokes on Tradenme than FXR150's. I only did the Suzuki's and got bored about half way through, someone else can do the other makes.

Clearly if there are this many new and secondhand legal bikes on Trademe then there must be a lot of serviceable engines lying about.

These farm/trail bikes are 12-14 or so rwhp std same as a std FXR and they can be developed to mid 20's no problem. The ESE thread has all the info you need and you will learn a few things and pickup a skill or two along the way.

A TS/TF125 is the engine Rick peddles and with low 20's hp he is right up there at the sharp end. There is nothing special about the rod/bigend/piston or any other components Rick uses, its all simple (mostly original) stuff, anyone could do it.

Sorry but you seem to have missed the bit about not being tuners.

I'm a system admin but no matter how well I document things your average person couldn't even get close to what I do. Just because the documentation gives you exact details about how to do things doesn't mean you're capable of being a sys admin. Likewise not everyone can learn to tune engines no matter how basic it is or how well documented.

Whether it's being a sys admin or tuning 2T engines there's a certain mindset, background knowledge and skill set required before you can even start to think of doing either.

EDIT TZ350 and I were obviously writing replies at the same time. See http://www.kiwibiker.co.nz/forums/sh...post1130724010 for his counter to this

Also, simply getting people involved and racing gets them on the path to tuning engines.

But suggesting that everyone should learn to be an engine tuner is not really the go, it's not everyone's interest or skill set nor should it have to be. A MX85 does not compare to a "hot" FXR150 it compares to stock FXR150 with a muffler and carb which is perfect.

Again the MX85s are not to fix buckets, nor take over buckets they are to allow a choice of a modern motor that is a good base package for those who want a 2T without learning the fundamentals of 2T engine development.

Same thing said a different way.

But the other point I forgot to add re the MX80/85 thing is what are the rules actually trying to achieve.
Get more 2Ts into a bucket field, or just get more " people " involved in the sport, or what ?

Both in my perspective.

Thing is that it would be very easy to shove a small MX engine in a bucket frame,with dead stock pipe etc and have a hell of alot of fun without investing a shitload of knowledge,time,cash.

Bingo - Total agree with that statement.

I agree with both of those as well.

EDIT

So to summarise the MX85 proposal as there are about 50 versions in this thread
F4
MX engines, limited to 85cc no other restrictions
100cc 2t no other restrictions max overbore 107cc if new rulechange allowed
125cc 2t carb restriction 130cc max over size (considered dangerous in Australia)
150cc 4t no other restrictions 158.6cc max oversize

Looks good to me in this form , plenty of choices, cream always rises to the top

Yay!!

[TZ350]

F4 rules I would like to see:-

MX engines, limited to 85cc no other restrictions

100cc 2t no other restrictions max overbore 110cc to allow for all the common makes of 2T to use the KX100 52mm piston as 107 only allows the Honda MB100 to use it.

Non Competition engine based.

125cc 2t 24mm carb no other restrictions 138cc (10%) max over size. allows for the 4 common 0.5mm over bore steps.

150cc 4 valve 4Ts (10% max oversize)

200cc 2 valve 4Ts (10% max oversize)

[husaberg]

F4 rules I would like to see are:-

MX engines, limited to 85cc no other restrictions

100cc 2t no other restrictions max overbore 110cc to allow for all makes of 2T to use the KX100 52mm piston as 107 only allows the MB100 to use it.

Non Competition engine based.

125cc 2t 24mm carb no other restrictions 138cc (10%) max over size. allows for the 4 common 0.5mm over bore steps.

150cc 4 valve 4Ts (10% max oversize)

200cc 2 valve 4Ts (10% max oversize)

This is looking betterer with maybe the parts to sort as well.
125 2t air cooled you mean 24mm carb.......

[TZ350]

This is looking betterer with maybe the parts to sort as well.
125 2t air cooled you mean 24mm carb.......

I was just thinking NC (non competition) 125 2T but may be NC air cooled no other restriction and NC 125 2T water cooled with a suitable carb restriction.

Thoughts.....

Maybe by the time for the next rule submissions we could have a well thrashed out Bucket application that is supported by pretty much everyone.

[TZ350]

Sorry but you seem to have missed the bit about not being tuners....not everyone can learn to tune engines no matter how basic it is or how well documented....simply getting people involved and racing gets them on the path to tuning engines.

My post showed there were plenty of good std reliable readily available and legal 2T's to be had without going to MX85's.

And I see the ESE thread as less about documentation and more about insights into the science and art of 2T tuning, things for the practitioner to absorb and apply in their own way.

Participation in Buckets has always accommodated those who starting out lacked basic tuning knowledge and mechanical skills but racing success there does not accommodate those that do not want to or can't learn or don't want to make the effort and that is how it should be, there are other classes for that.

But I am beginning to see how the proposed MX85 thing could help get people started and maybe hooked on 2t's.

[Drew]

Participation in Buckets has always accommodated those who starting out lacked basic tuning knowledge and mechanical skills but racing success there does not accommodate those that do not want to or can't learn or don't want to make the effort and that is how it should be, there are other classes for that.

You have built a potential weapon. You don't ride it though. Are you saying Av can't have another go untill she fully grasps the way it is built?

Doesn't leave a lot of room for me. I enjoy the engineering of the bike. Setting up geometry and suspension, and trying to lose weight from the machine. I am not inclined to do a great deal of work on motors, though I am appropriately skilled that I could learn to.

[F5 Dave]

F4 rules I would like to see:-

MX engines, limited to 85cc no other restrictions

100cc 2t no other restrictions max overbore 110cc to allow for all the common makes of 2T to use the KX100 52mm piston as 107 only allows the Honda MB100 to use it.

Non Competition engine based.

125cc 2t 24mm carb no other restrictions 138cc (10%) max over size. allows for the 4 common 0.5mm over bore steps.

150cc 4 valve 4Ts (10% max oversize)

200cc 2 valve 4Ts (10% max oversize)

52mm piston only takes many engines to 106.something, not just the Hondas

[TZ350]

52mm piston only takes many engines to 106.something, not just the Hondas

Here is a 1mm OS KT100 piston.


Sure 52 gives 106, but don't these pistons come in 52+somethings out to 2mm OS?

Suzuki TF/TS/GP100 50mm bore 50mm stroke.

50mm bore 50mm stroke (5x5x3.1416x5)/4 = 98.18cc

52mm bore 50mm stroke (5.2x5.2x3.1416x5)/4 = 106cc

53mm bore 50mm stroke (5.3x5.3x3.1416x5)/4 = 110cc


Ok I have named the three most common engines and they don't fit the 106 limit with all the oversize KT100 pistons available, your turn now, name some other common engine that would only be 106cc with oversize KT100 pistons in it, may be a 1mm or better yet 2mm OS piston.

[Yow Ling]

Here is a 1mm OS KT100 piston.


Sure 52 gives 106, but don't these pistons come in 52+somethings out to 2mm OS?

Suzuki TF/TS/GP100 50mm bore 50mm stroke.

50mm bore 50mm stroke (5x5x3.1416x5)/4 = 98.18cc

52mm bore 50mm stroke (5.2x5.2x3.1416x5)/4 = 106cc

53mm bore 50mm stroke (5.3x5.3x3.1416x5)/4 = 110cc


Ok I have named the three most common engines and they don't fit the 106 limit with all the oversize KT100 pistons available, your turn now, name some other common engine that would only be 106cc with oversize KT100 pistons in it, may be a 1mm or better yet 2mm OS piston.

Why would you want to run a 100 aircooled when you can run a 100 watercooled?
There are way more oversize steps on a kt100 not just 0.25mm steps like bikes.

The question was do we want 85cc mx engines , not do you want 4t 200s and 10% oversizes

the maths above is all wrong as suzuki stroke is 50.6mm

[husaberg]

Why would you want to run a 100 aircooled when you can run a 100 watercooled?
There are way more oversize steps on a kt100 not just 0.25mm steps like bikes.

The question was do we want 85cc mx engines , not do you want 4t 200s and 10% oversizes

the maths above is all wrong as suzuki stroke is 50.6mm

I think most of the major 125's and 100 are 50.6mm.

I was just thinking NC (non competition) 125 2T but may be NC air cooled no other restriction and NC 125 2T water cooled with a suitable carb restriction.

Thoughts.....

Maybe by the time for the next rule submissions we could have a well thrashed out Bucket application that is supported by pretty much everyone.

I don't quite go along with unlimited carb 125 air cooled cause they have already shown 30HP on a 24mm carb.
Being air cooled is not enough of a restriction. it just limits their ability to retain peak performance in longer races.
the 24mm carb rule has worked well. So far
I would like to see liquid cooled non comp 125's (Maybe for selfselving reasons) but they would have to be limited to around 30hp somehow.....
Maybe Wobs exhaust restrictor idea could work, on the LC125's with a carb limit to keep them 30hp ish.

The parts issues also need to be sorted before MX85's come in.........

[TZ350]

the maths above is all wrong as suzuki stroke is 50.6mm

Maybe true and I thought so too, but I got my figure for the 50mm stroke from the official Suzuki GP125 service manual. If you have a better source do tell as I think the 100 is the same, likewise the TF and TS.

Why would you want to run a 100 aircooled when you can run a 100 watercooled? There are way more oversize steps on a kt100 not just 0.25mm steps like bikes.

Too true, but like the old aircooled MB100's there are a few TS/TF/GP and a few RG 100cc engines around, or at least the parts for them. And we would like the same options for pistons as the MB boys.

There are way more oversize steps on a kt100 not just 0.25mm steps like bikes.

I understand this, but if people are using the KT100 piston then they can go 2mm OS.

The question was do we want 85cc mx engines , not do you want 4t 200s and 10% oversizes

True but I am allowed to express my opinion and now that we are opening the Bucket rules Pandoras box lets get it all out there.

[Sketchy_Racer]

A bit off the topic but relating to the 85. I have two videos from when I had the MB100 and then 85.

RM85




And then the MB100 (starts at 1:05)

[Bert]

F4 rules I would like to see:-

MX engines, limited to 85cc no other restrictions

100cc 2t no other restrictions max overbore 110cc

Non Competition engine based.

125cc 2t 24mm carb no other restrictions 138cc (10%) max over size.

150cc 4 valve 4Ts (10% max oversize)

200cc 2 valve 4Ts (10% max oversize)

I actually almost agree,

10% oversizes.
I think that gives enough fair options to everyone.
(I have to say I never really agreed with the over sizes given to the 150cc 4T. Anyone serious will take the hit and bore to maximum oversize anyway. sleeves are cheap).

but I'd be keeping the:

MX engines, limited to 85cc no other restrictions

Non competition derived engine, including the following:
transmission, blablabla.. (same as last 10year)
Exception of Pistons, pipes, blabla...(same as last 10year)

100cc 2t no other restrictions max overbore 110cc to allow for all the common makes of 2T to use the KX100 52mm piston as 107 only allows the Honda MB100 to use it.
125cc 2t 24mm Carb Restriction (10% max oversize). Aircooled
150cc 4 valve 4Ts (10% max oversize)
180cc 2valve 4Ts (10% max oversize). Aircooled

if you want to run watercooled engines (or competition derived engines or components), you have to run the smaller size.

Thermal constraint will level the playing field during a race; and it will make things interesting tactically during longer events...

[Mental Trousers]

A bit off the topic but relating to the 85. I have two videos from when I had the MB100 and then 85.

RM85

...


And then the MB100 (starts at 1:05)

...

I know which one sounds better.