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

[chrisc]

I voted no. Even though I would really love to build a RS with a 85mx engine, I don't think it would be good for F4. The last thing I want to see is less riders turning up and competition decreasing.

My understanding is that letting in FXRs revived buckets giving people an easy, reliable and fairly cheap way to go racing with enough scope to build, develop and learn. I think eventually F4 will change to allow something similar to these engines because as time moves on, bikes become obsolete, parts harder to find and more expensive as demand increases whilst supply decreases. If there isn't anything to replace FXRs directly, I think we will be forced to look for their replacement which is likely to be something along these lines.

I don't think having to build a one off bike to compete in F4 is good for the class and will likely result in less riders due to the amount of effort required to race.

If riders REALLY wanted to build a solid, legal, 2 stroke RS package, going down the Derbi 85cc engine route is there as an option already, which we can all see is a worthwhile project. All it takes is for the builder to put the effort in.

[Bert]

Did you stop disount to consider i was not talking about you.............

Misunderstanding your quote purpose Husa???


Ok, so it's not the time apparently (it's ok, it comes up every 2-3 years and has done for a while now)...
I've even had my own team mates............... Not in the sprit of the class.
Apparently engineering is the primary purpose not racing, nor empowering others (old or young) to join in on the fun.
For those unskilled or time limited Go buy a FXR or if you want a two stroke go import in a derbi and 85cc non-race kit...

So, I'll put this out there for others to consider, all cylinders must be OEM not aftermarket.
And Anything that has "racing" cast into it should be outlawed as well.... Performance or not...

Gearboxes, fk me let's not go there. My second bike turned out to have a 6speed RM125 box in it (still sitting in a bag under the bench removed, as I felt it didn't meet the rules; back in the day): so where did this engine come from and how many other TF100s back in the day had them..... The rules were never really that well Enforced. And I'm bet money there were MBs with CR boxes as well.

Each club should be stripping down the class winners to check rule conformity (just write it into your supplementary event rules, no need to pay your $50 for a protest)...

It all seems somewhat strange that so many are opposed to this. next time I hear people bitching about four strokes or no other real options other than FXRs or the cost of pistons for two strokes, I'll bring it up again...
They are a worthless motor, there is a good supply of them and parts are cheap. They don't make as much power as te bullshit dyno graphs have been showing. The right rules could be applied to manage the integration without upsetting those whom have spent the time building weapons to the rules...

It doesn't really worry me, I've built a tzr100 (while awaiting sleeve repair) and a new pipe and it should be a better motor than I will ever need (with no compromises to the current rules). It produced 24 no problems with the great big hole.
And I've got a FXR... So this really has no effect on me anyway except for the fact that I could have had ~ten MX motors for the same price (I don't have the skill or the tools so had to stop racing and save to pay others to do my work; I just wanted to race, as that's what I felt the purpose&sprit of the sport was actually about).

Personally I'm not going to vote. Everyone whom has been around this forum for more than ten minutes, knows my long held views on this topic...

[Sketchy_Racer]

Well there's quite a lot of interest in this isn't there!

There's a lot of really good inputs and point of views on this, and thankfully largely constructive!

I think there is still a lot of misconception about the 85 MX engines let me clear some of these up.

First of all, in the case of the RM85, it is not fast, not hot rod bucket fast that is for sure! It could hold Fishies FXR motor in a straight line and that is all. So bullshit dyno numbers aside that is the reality of its power output. I'm not sure what level of tune Fishies FXR is, but I know it has a carb and exhaust done, it may have cams??? Some of the numbers being thrown around here are bloody laughable! 30HP out of a 85 MX engine are you kidding me? The damn things would have more power than a 125cc 2T MX bike. There is a very very big difference between road HP and dirt HP, and please NEVER quote a damn power graph off of the internet, it will be as bullshit as the Motomart Dyno.

The major over sight here is that while reasonable power levels are possible, it comes at a cost. At only 85cc you are getting some pretty peaky power outputs and makes the things damn hard to ride, well in comparison to the FXR150s. But that is part of the fun of 2Ts they are hard to ride but can be awesomely rewarding!

The biggest advantage I believe that these motors offer is a replacement to the long extinct "non competition" two strokes, such as the MB100s GP125 etc. I'm sorry if anyone disagrees with my opinion with this but they are old obsolete motors that you can no longer buy new parts for it's as simple as that.

Parts supply is one of the bigger factors of appeal with the MX 85 motors.

Even the FXRs are getting more more scarce as they are no longer imported into NZ, are they still even manufactured?

As for ruling I think it is an easy one, if you want to use competition derived engines or any engine parts you are simply limited to 85cc and go for you life. If you want to put a CR85 gearbox in a MB100, great but you better make it a MB85... so go get a MX85 motor.

The part I am struggling is with the four stroke equivalent and how that fits into the picture. I'm not sure how that works in? My hope for the 85s to be made legal is to bring back the two strokes before the entire field becomes 150 4Ts.

as stated, we already have a MX80 under the name "derbi" cleaning up in Auck, for two reasons, 1 it's a good bike and 2 it's got a fucken good rider on it but the fact of the matter is that it is of the same breed as the MX85 motors.

[Sketchy_Racer]

Deleted.....

[kel]

I voted no. Even though I would really love to build a RS with a 85mx engine, I don't think it would be good for F4. The last thing I want to see is less riders turning up and competition decreasing.

My understanding is that letting in FXRs revived buckets giving people an easy, reliable and fairly cheap way to go racing with enough scope to build, develop and learn. I think eventually F4 will change to allow something similar to these engines because as time moves on, bikes become obsolete, parts harder to find and more expensive as demand increases whilst supply decreases. If there isn't anything to replace FXRs directly, I think we will be forced to look for their replacement which is likely to be something along these lines.

I don't think having to build a one off bike to compete in F4 is good for the class and will likely result in less riders due to the amount of effort required to race.

If riders REALLY wanted to build a solid, legal, 2 stroke RS package, going down the Derbi 85cc engine route is there as an option already, which we can all see is a worthwhile project. All it takes is for the builder to put the effort in.

Chris, Im not following. Do you believe the 85's will make the FXR and everything else obsolete and as such everyone will just stay home?
Why do you feel the Derbi kits are legal while so many argue otherwise?

ps. The effort to build a Derbi is not much more than opening your cheque book

[Sketchy_Racer]

My understanding is that letting in FXRs revived buckets giving people an easy, reliable and fairly cheap way to go racing with enough scope to build, develop and learn.

Yes you are right, that is what revived buckets, but only after it got to the point where it was almost completely dead! I believe that it is important to keep the class alive and not wait till it near on dies. Lets keep it alive and well with new and intersting stuff!

[chrisc]

Chris, Im not following. Do you believe the 85's will make the FXR and everything else obsolete and as such everyone will just stay home?
Why do you feel the Derbi kits are legal while so many argue otherwise?

ps. The effort to build a Derbi is not much more than opening your cheque book

"Chris, Im not following. Do you believe the 85's will make the FXR and everything else obsolete and as such everyone will just stay home?"

No. I doubt it will make a huge impact for some time, you still have to ride it after all. Over time it might change the perception of the class however and if that ends up discouraging a bunch of people then it's definitely a loss for the class.

"Why do you feel the Derbi kits are legal while so many argue otherwise?"
I don't believe the race derbi kits are legal. The [usually] steel bore, mildly ported, twin ring piston kits, I believe are legal. These would still require tuning input to build a fast one.

"ps. The effort to build a Derbi is not much more than opening your cheque book"
Agreed, but only for the race cylinders which I don't consider legal. The diprose derbi's wouldn't be where they are without tuning and development. I doubt just slapping on a 80cc 'street' cylinder kit will yield much power, at least not an amount which would easily get away from the usual crowd of FXRs on a kart track. Again, you still need to race it.

[Bert]

.....
derbi's wouldn't be where they are without tuning and development. I doubt just slapping on a 80cc 'street' cylinder kit will yield much power, at least not an amount which would easily get away from the usual crowd of FXRs on a kart track.

Again, you still need to race it.

Bingo.

Racing... Flag drops the bullshit stops (or just gos slow in my case)...

[CM2005]

The effort to build a Derbi is not much more than opening your cheque book

true story. same deal with RS frames, they've separated the field both in time and cash investment more than an old mx bike engine will!

[chrisc]

Bingo.

Racing... Flag drops the bullshit stops (or just gos slow in my case)...

true story. same deal with RS frames, they've separated the field both in time and cash investment more than an old mx bike engine will!

And yet riders like Tyler Lincoln still managed top 3 finishes (and even won a race) at Roy's Hill this year on Henk's FXR which I would guess to have 19-23hp?

[Bert]

Yes you are right, that is what revived buckets, but only after it got to the point where it was almost completely dead! I believe that it is important to keep the class alive and not wait till it near on dies. Lets keep it alive and well with new and intersting stuff!

Here's a plan Sketchy. I've got a TZ125 roller. How about I import in a derbi and 80 kit (and a race kit to copy). And you race it... Sponsored rider... Or maybe Tyler.

Likely similar people will say that's not fair as well, or not in the spirt....

[CM2005]

As you'd expect for NZ #2 125 class eh.

I think the argument against MX85 is about as clever as trying to set some capped budget rule.

the whole gbox swap argument - if someone really thinks it'll make the difference and wants to put in all the man hours to try and fit one then get amongst it. next some big budget guys will be asking TT industries for a CR 5 or 6 speed cnc 'box for FXRs at 6k a pop.
Kart engines aren't an advantage - the watercooled 125's would obviously be banned, KT100's don't have a gearbox and wouldn't really suit a bike.
Yes a good fast rider with a sorted MX85cc engine in a nice RS or similar frame would be very fast. But for others who pick up a $cheap KX85, give it seals, piston, front end wheels and some seat unit (or a different cheap road based frame i.e FXR, RGV or something) would just have a bike to have a fang on at limited cost (cheaper than an FXR probably). Remember that it wont suddenly turn the bucket meetings into a 200X's 85cc supermoto class, some people hate two strokes, and some will just see sense in buying an FXR, CBR150/building a honda 150 etc.

[avgas]

The point re the gearboxs alludes to the fact that the rules say
"Engines must be derived from non-competition motorcycles. Motocross, Road
Racing, Enduro and Go Kart motors and transmission parts are not permitted."

But an FXR 5-speed with a changed tooth ratio is fine........this just gets better and better.

Hang-on I will go get my popcorn and you can tell me how competition pistons, high-flow head, smooth bore carbs etc are not the same as having a "race engine" because you can't see it.

Carry on.

[cotswold]

I voted yes,

My F4 road bike 2T project was scrapped at the last post as I got bored waiting for work that I did not have the skills to do get done. If I could have just gone out and bought an 80mx I would still be racing in F4 as it is I switched to F5 on the worlds slowest 50 and am having a blast.

Oh and f#$@ yeh to KTM50's bring that on as well.

[F5 Dave]

true story. same deal with RS frames, they've separated the field both in time and cash investment more than an old mx bike engine will!

I've done 2 RS framed buckets. the first I believe, although it got stalled & only made it to the track a few years back. At the time it was the cheap option, certainly cheaper than an RGV or TZR roller esp when you considered the other bits you didn't need to upgrade. My 50 was a $300 upgrade when I found a frame, forks, shock, tank arrangement & swapped bits over from my RG50, paid a doz beer for some welding & was racing in 3 weeks.

Unfortunately for the late adopters they have started to run out & got more expensive. Biggest issue is they fon't fit many engines easily. One did pass through my hands a couple of years back losing some parts but went out the dor for a couple of hundy & swap for some engineering work. Bucket prices for the lads I believe. Btw they don't turn that sharply so kart track use is a compromise.