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Illegal modification: 50cc class

Joined
Dec 29, 1999
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#1
In considering my five year old's next bike (current one: PW50), my head is swirling over the different versions and models all these mini bike manufacturers offer...juniors, seniors, works, standards, kings, big wheels...and then sub versions of these versions!

I was just wondering if I would have the option to make certain parts swaps among models and keep the bike AMA legal. Specifically, in digesting all the models for Polini, I was wondering if the Standard L3 would still be legal if I were to swap the smaller carb on the Standard L3 for the larger carb on the Works L3.

I believe that the AMA rule book says that carbs are one of the parts that must remain stock, but I'm not clear if that pertains to swaps between like models from the same year from the same manufacturer. Would this prevent me from doing the carb swap discussed above?

Note that I haven't bought him his next bike yet. I'm just trying to get all my options straight before I make the call.

Thanks!

James
 
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#2
I'm with you. I have been trying to figure out my son's second bike
for awhile and after having looked at new bikes and talked with used
bike owners I decided on a KX65. The little 50's are very labor and cost
intensive. The 65 will be a little harder transition but it will be alot
more usable bike for trail riding or racing. mxextreme.com has some rules
updates,try them. Don
 

wardy

2005 Lori Nyland Award Winner
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#3
Boy that didn't take long.......the 50cc class is the most hostile class we have but the kids hopefully get alot of fun out of it.

Here is what i hope will answer your question. Modifying a 50cc bike in any way even cross over things from the same manufacturer is a NO NO. BUt AMA has a current list of things that are legal and accepted for the 50cc bikes. THis list is long and quite detailed but should help you make a deciscion in what to buy.

One might think that all the effort to keep the fifty class stock is unwarranted and i was thinking the same thing back like 8 years ago.
BOy was i wrong they will modify them to the max then put their 4 year old on it go figure.

Here is a link where you can find most of that information also..... http://www.ama-cycle.org/rulebooks/index.html
or call Roger Ansel at AMA 614-856-1900 he is the head of this department and can fax or send you a complete list of the legal things to do on a 50cc machine.
Hope this all helps

wardy
 

AJ Waggoner

Crash Test Dummy
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#4
In an un related but sort of related topic..

I just had a call today on boring the 50cc bikes in the Stock classes.

the polini if it is a borable cylinder can be bored .080 over
and my understanding is a certain model already comes bored over?

but ANY of the other 50's that are nikisil CANNOT be bored .080
over and re-Nikisiled.

the rule is in stock that a minicycle can be overbored .080 but ANY cylinder that is Nikisiled or similar coated cannot be overbored and relined.
 
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#5
The impetus for the original question was that the only differences between the Polini Works and Standard models are that the Works has adjustable damping on the rear shock, a larger carb and neater graphics. Oh yeah, and it costs $1,000 more. If legal, I thought one of my options might be to get the Standard model and swap in the larger carb. But I guess the answer is "no," especially since my district MX director moderates this forum (doh!).

I have the AMA rules from the March issue and off the Web site. If you look on page 48 of the list of things that can be changed in the stock class, the carb is not mentioned (although the jetting is). Also, at the bottom of page 47, the rules say "Effective 2001, newly approved machines are required to have carburetors that meet the specifications of the minicycle class, i.e., Class 1 - 14mm, Class 2 - 19mm, Class 3 - 12mm."

Then, on page 17 for the youth rules, the classes are broken down into 1, 2 and 3 with other criteria (3 obviously is for PWs while 1 and 2 seem to be for the "racing" 50s, i.e., Cobras, LEMs, Polinis, etc.), but with the same carb size restrictions. Why, then, does it say the carb sizes are effective in 2001 in other sections of the rule book if the same sizes are listed in the criteria valid for 2000? I'm sure I'm missing something obvious.

Another question: Is it typical for Districts to run the minicycle classes as broken down above? Knowing this will definitely help in selecting junior's next bike. I'm specifically interested in D17.

Thanks,
James
 
- a d v e r t i s e m e n t -

wardy

2005 Lori Nyland Award Winner
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#6
Your gonna love this, I was the committe chairman for the technical committe at last years congress. That carb deal has been before my committee for four outa the last five years. We instituted restrictors three years ago and now have set a time limit for the manufacturers to make the carbs the smaller size in hopes to slow these bikes down. I would tell you that if somthing is not listed on ama list to be able to change then it prolly can't be.

I realize that alot of this stuff don't make sense but let me give you an idea what happens here. We try to set down rules to keep these classes and playing field level, the manufactuers have sat right at these committee meetings to influence how we judge this stuff. THen after we feel that we have a working situation, the bikes are built using every little angle and every option avaible to make thier bike a little better. Basically they are trying to have the best bike. So you can see that it is real easy to make a huge mountain outa a few rules since the very second we make the rule, it starts to get undermined.
ANyway class structure for the 50cc class is class 1, 2, and 3

Most d-17 tracks only run two classes jr and sr. Buffalo is the only one i know of that runs the pee wee class or i think its class 3. If you want tracks to run a pee wee, you need to organize a bunch of guys and ask them to do it......i am sure they will.

hope this helps

wardy

James you mite want to call me on this so i can explain it to you better or try to it can get very complicated. my number is 815.539.9021.
i am usually here alot but if i am gone leave a message.
thanks<p align=right> 03-07-2000 :Edited
[ By Moderator ]
 
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#7
It is pretty clear in the AMA rule book where the criteria are listed for each class. I was just confused when the same carb restrictions were part of the criteria in the class breakdown for the current year (2000), and then it says elsewhere that these don't go into effect until 2001.

In any case, my son will only be racing his PW this year (looks like at Buffalo Range). He won't be ready for a larger 50 until next year, or possibly this fall. And he definitely won't be racing in 50 Class 1 until 2001, when the carb restrictions go into full force.

Thanks,
James

PS: Thanks for working on slowing these things down. The mini bikes really come out for BR's peewee track on open practice days and boy do those Cobras fly!
 
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#8
Once those carb restrictors go into effect chemical horsepower should kick into high gear. I'll bet I can make some good consulting money helping those mini-Dads who just HAVE to put Junior on the fastest bike in the class. You guys need to put that fuel check in place NOW&nbsp;&nbsp;




------------------
Rich Rohrich

"If we all worked on the assumption that what is accepted as true is really true, there would be little hope of advance."
    -- Orville Wright
 
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#9
Ok, then once that's done, I'm sure we mini-dads will come up with something else. Hmmmmm...Is there a rule against me using one of the old inner tubes out of the CR as a big rubber band to catapult my boy over the whoop section at Casey? Please let me know ASAP because once we get that down, I might try doubling up on the rubber and seeing if we can't clear the tabletop that just follows as well.

Thanks,
James
 
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#10
Nothing can be Mini-Dad Proof because Mini-Dads are so ingenious




------------------
Rich Rohrich

"I have no special talents. I am only passionately curious." - Albert Einstein
 
- a d v e r t i s e m e n t -

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#11
We're also handsome, friendly, good-natured and funny. The only virtue we lack is wealth because of all the damn 50s we have to buy for all these mini bike classes.


In fact, the only people nicer than mini bike dads are Honda riders.

James
00CR250
 
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#12
OK, the Polini X1 has the right seat height to fit the Class 1 designation for 2001, but it comes stock with the 19mm carb, which would force it into Class 2. But, a Polini dealer tells me that there is a restrictor available that makes this bike legal for Class 1.

Is this true or is this guy just trying to sell me a bike?

Thanks,
James
 

wardy

2005 Lori Nyland Award Winner
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#13
Restrictors are legal as far as I know, one thing you have to understand is ama makes the bike rules with most of the manufacture dudes sittin right behind us in the committee room. They know what the rules are, that doesn't mean they always will build bikes to comply.
I would double check with roger ansel on the restrictor, but i am sure its fine.
wardy

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"the older i get, the shorter i want the moto!"