Honda TRX250R Forums banner

1 - 9 of 9 Posts

·
Registered
Joined
·
91 Posts
Discussion Starter #1
So i am building a atc500R with a 1986 cr500 motor and would like to know what size carb would work good on this engine.. Currently it is running a stock PJ series carb.. I havent been inside the motor so i don't know the extent of the internal work, however what i do know is that it has been port and polished, the head has been shaved i assume because the guy i bought it from say's it runs on half 91 octaine and half 110, he said it has high compression although i can not confirm because i don't have a compression tester. i will be running a CPI inframe drag pipe and no air box of coarse.. i am building this bike for all around dune riding and not just a dragger.. so to the question, what carb would really open this motor up for midrange and top end?? I have a stock cr500 pj carb on my atc250r also and it runs amazing so im thinking that this cr500 should run better, Less restricted with a bigger carb?? any help would be awesome and thanks in advance, if you need more info let me know..
 

·
Registered
Joined
·
13,273 Posts
For the CR500R Honda use a 39MM Keihin...you can use a 40.5MM Keihin (bored out 39MM) and get a bit more mid to top end. On the CR500R, you can go bigger than 40.5Mm well into the high 40's lke a 48MM, however; not really needed for the use you described.

Carlos
 

·
Registered
Joined
·
13,273 Posts
You can go bigger, like I said high 40MM or 48MM Lectron if it makes you feel better. On a CR500R engine that is set-up half way decent, the 39MM or 40.50MM for an "all around Duner" is a better choice on Pump Gas as far as ease of tune-ability IMO.

Carlos
 

·
Banned
Joined
·
565 Posts
My Lectron is stupid simple to setup and tune a monkey could do it. Plus I like the fact that I can adjust the Power Jet while out riding. 1.5 turns out for just general riding. Want to line up and race at the strip just turn it in and lean it out some. And I am just on gas as well. Throttle response is fine for dune riding as well.

Plus it picked up some HP over the 40.5mm I have.
 

·
Registered
Joined
·
91 Posts
Discussion Starter #7
Awesome! I will look into a few carbs describe above.. And i am pretty confortable tuning a carb, i just am not good (yet) at choosing what size jets to start with.. So may need some help when putting the new carb together. So these 500 motors being known for the bottom end grunt and all would i loose much if i were to go with say a 44 lectron or something like that?
 

·
Registered
Joined
·
91 Posts
Discussion Starter #9
Would i be able to bore a stocker to 40.5mm and get the same benefits as a 40.1 pwk?
 
1 - 9 of 9 Posts
Top