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Carburators Reply:

Hey guys,

Your selection on a carb applies to what parts your running on your

motor. BIGGER is not better. A properly jetted carb. is the key. I ran

a lite bore 88cc kit on my fiddie ( cylinder, flat top piston and rings, and

a BBR pipe) I used my stock carb jetted it correctly and wow!! I then

changed my gear to 15/36 to compensate for the power gain lots of

low to midrange power, and with the gear change got some more top end.

If i went with a 18mm carb it would have improved the mid to top end a

little bit more... well then i decided to go with a ultra head. alot bigger

valves, HD.springs ect.. went with a popup or dome piston, and got a

TOURING cam setup " just under a race cam". and went with an 18mm

and 20mm carb. to see what kind of gains i would get. first i took a look

at the intakes. and noticed the one that came with the 20mm carb.

matched the head better and the openings were considerly bigger. So I

went with the bigger intake, and use the 18mm over the 20mm it works

better for me and my riding style. I get more out of the 18 then the 20mm

the 20mm was overkill for me.. a little more top end. I think any bigger

carb size 22mm or 24mm would be for a road race application. but I dont

run a super head or a DOHC head, were a bigger carb. could apply.



Thanks hope this helps Kevin a.k.a. OLDSCHOOL
 

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What Carb would you guys suggest for a bike with a UNI clamp on filter and a BBR pipe ? i want to run the stock class so i won't be getting any big bore kits. and will the carb help out the BBR pipe because right now i can't tell any gains from my pipe its only louder ,,lol, how much of a difference will a carb make ? and would you guys recommend a fast 50s speed cam ? i want my bike to have some power it kinda lugs in the bottom of all the gears
 

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Carbs.

Hey Six,

If your going to run the stock class then you got to run the stock Carb!!





Example: I ran my stock carb and had a BBR pipe and an 88cc lite bore

and Takegawa cdi box and my bike flew....

This only goes to show you that your stock carb will work even with a BBK







Try running 97 octaine and change your gearing and get someone to match your intake to your head.... remember the bike is stock dont

exspect a miracle..... Anybody else have any stock suggestions???



Hope this helps man.... OLDSCHOOL
 

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do u think higher octane would help? Even on stock compression? I run super in it now (about 92 octane) and i found a gas station that sells 100 and 110. Maybe ill try it out. What gains would you see? I didnt think there would be any benefit. Fill me in. Thanks
 

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gas

Hey six,

you wont get much if any gains it would just make the motor run more

efficiant. dont run over 97 octaine. the 100 and 110 are slower burning

fuels we need a faster burning gas like 87 though 97 octaine



thanks hope this helps OLDSCHOOL



PS this will start a good DEBEATE
 

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you stock motor needs nothing better then 91 octane, or some lucky country people who get 93.



As for your carb a 17-18 carb is ideal for your stock bike. But then you cannot run the stock class.



As for running an ultra head and an 18mm carb? your starving yourself!! Ill run you with a 22mm on my race bike against whatever carb set up you have.



Bigger is not always better. but you at least have to go big enough
 

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Carbs

Hey XR,

I agree on the Octaine but I said Efficant sunoco 97 will burn better.

91 or 93 is good too.



Six wants to race the stock class so 17 and 18mm are out....



I do not agree on the size carb that you picked for the ultra head......

" My opinion only " if you have 100 yd straights and a 5 spd ya i'll agree.

but you give up lots of low end. On a fiddie track built for fiddies you

diffenitly dont need top end. any set up of a super head or bigger the

bigger carb would apply Im sure your bike runs but have you tried to

run a 20mm on your bike or did you just spend the $200 + on the bigger

set up.



I have a ultra head 88cc set up on my bike and run a 18mm carb and

BLEW away Extreme 107's, 95cc, and stroker 110's on a fiddie trk.

so bring it on.



Thanks OLDSCHOOL.
 

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yes ive tried smaller, the smallest i go is a 20 if the the track is real tight but i have a different bike for that. I dont run that big of a motor on a real tight track. youl be faster on a little bit slower bike.



Now come open straights and big track ill drop a 106 in the bike......
 

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Since when you do need the stock carb to run stock class? I alway assumed "stock" meant you had a 49cc piston and a stock head.
 

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Carbs

Hey xr,

Right on I knew you knew what I ment. Some how I dont think there is

enough gear in a stock fiddie 3spd tranny to hall you around on a 106cc.

You wont even come close to getting any power out of that animal..





As for you other guys Im done discussing that damn stock class.

nobody will ever be happy... If I were to race that class I would have the

BADDDEST stock motor............. You guys just dont get it.





Thanks Kevin a.k.a.OLDSCHOOL
 

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stock sugestions

For all you 50cc stock bores. Put a cam in the bike and run a xr70 carb and intake with the xr50 carb needle jet. Might need to buy heavy duty valve springs cause when I did this to my bike, it reved so high it bent the intake valve cause the stock springs couldn't return fast enough. Garaunteed to beat any other stock bike. Also had a fast50 pipe on it. Way faster than a stock bike, but still 50cc's.
 
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