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doofy doofy
8/10/2017 6:09 PM

alright, I have a limited understanding of the rules - but as far as I know here in the states the mfg's are limited to using oem cases, frame and swingarm and in Europe its anything goes correct? I don't read too many tests of GP bikes but I wonder how big a difference there is between Cairoli and Herlings KTM vs Marvins.

I could be totally wrong about this, someone smarter than me help me out

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David934 David934
8/11/2017 2:06 AM

I think Marvin must have standard oem frame, while Tony and Jeffrey have frames on request (no frame rules)

18 Yamaha YZ450F
94 Honda CR 500
90 Honda CR 500
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69 Triumph Tiger 100

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UpTiTe UpTiTe
8/11/2017 6:38 AM

The biggest difference is the frame, on faster tracks the Euros are allowed to use longer frames and on slower tracks with turns shorter frames. They get to have foot Peg placement rake all seat height and other stuff built into the frame.

The other difference is a Transmissions, a lot of the factory bikes use two and three speed transmissions in Europe.

Most American teams don't exactly follow the rules to the T, but they can't outright build a different frame.

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Wandell Wandell
8/11/2017 7:44 AM

My understanding is that today, it's the Japanese National series that has the really exotic, one off stuff.

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Rooster Rooster
8/11/2017 4:42 PM
Wandell wrote:

My understanding is that ...more

That's always been the case. Like the 125 twin cylinder ribi lever Hondas. I think the Japanese series is for experimentation whereas a works bike is no place to experiment with stuff that may or may not work right. They have too much invested to lose races due to experimental equipment in a major racing series.


Empty a bag of skittles into the toilet and then flush. It's like watching a five second long nascar race.

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loftyair loftyair
8/11/2017 5:00 PM

Different fuel use also contributes to different engine configs.

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kzizok kzizok
8/11/2017 6:15 PM
Rooster wrote:

That's always been the ...more

The American works bikes often had experimental equipment. Heck, the whole bike of the first Yamaha fourstroke was experimental. Disk brakes, radiators and their placements and sizes, low boy gas tanks, frames, carbs, FI, transmissions, etc.

much ty. How to spot a paid forum poster/artificial forum traffic producer (see list of actions/phrases below):

Copius pattern amounts of phrases like “Anyone have”..., “Anybody know?”.... and their variations.

Any help is appreciated!
Thanks in advance!

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doofy doofy
8/13/2017 8:13 PM

I assume the GP guys are allowed to use their one-off equipment in the MXON?

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doofy doofy
8/13/2017 8:14 PM
loftyair wrote:

Different fuel use also ...more

I think I remember RV saying he thought the engine package was terrible when he went over there - and attributed it to the fuel used. Is it an octane thing?

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scott_nz scott_nz
8/13/2017 8:22 PM
doofy wrote:

I assume the GP guys are ...more

yes the rules are MXGP rules, which means different fuel, and more stringent noise regs, along with no production rules,

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dilligaf dilligaf
8/13/2017 8:56 PM

I'm sure this has been answered many times in the past but a short list:
AMA bikes
production base frame (that can not have material removed only added support)
production base swing arm (a grey area if you ask some)
cylinder, head and case casting need to start life as a production unit
bore x stroke the same as the homologated unit
Transmission needs the same amount of gears as the homologated unit.
Ti axles and pivot are allowed in AMA (not allowed in gp's)

GP bikes
Frame : anything goes
Engine: anything goes displacement needs to be under the CC limit
Steel axles and pivot
Fuel is of FIM motocross regulations (a little more rescrictive than ama).The reality between the two series is the fuel rule is a bit tighter, sound limit is a bit lower and enforced a bit harder. 4 speed transmissions are a bit more common with VERY few using the 3 speed set up as it is tricky and the engine needs to operate in much wider rpm window. As for the engine packages the 250's tend to be a bit more high rpm top end focused in Europe with a bit of focus on keeping the rev's up. Rumors fly all over the paddock on engine set up with bore and stroke figures sounding more like Moto 3 than a MX set up.

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kiwifan kiwifan
8/13/2017 9:12 PM
UpTiTe wrote:

The biggest difference is ...more

'Most American teams..' ...really? Does that imply some are breaking the rules?

Current rides: 2020 CRF450RWE and 2019 TC300
Occasional ride for VMX: 1985 CR500RF
Adventure/Road bike: CRF1000L

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