carb question need help soon!!!!

[harrisky]

I just got my motor sleeved to a 240 with a 3mm stroker stuffer crank. i was wondering if the carb from a 1987 Polaris Cyclone 250 would work after I adjust the jetting?

[tyephoon]

Originally Posted by harrisky

I just got my motor sleeved to a 240 with a 3mm stroker stuffer crank. i was wondering if the carb from a 1987 Polaris Cyclone 250 would work after I adjust the jetting?

well to be honest i'm not really sure but i do know that 250r's use the same carbs and so do banshees. they're interchangealble. do you have a picture, brand of carb, size. that would help a little more. i'm not familar with the cyclone at all.

[harrisky]

It is a Mikuni 34mm I think

[tecateboy]

im sure you can get it to work, you just have to get the jetting correct.

[swrbansheeboy]

Originally Posted by tyephoon

well to be honest i'm not really sure but i do know that 250r's use the same carbs and so do banshees. they're interchangealble. do you have a picture, brand of carb, size. that would help a little more. i'm not familar with the cyclone at all.

well i hate to dissagree but the 250r's run a 34 mill keihin pj carb stock and the banshee's run 26 mill mikuni's stock as do the blaster's....

from what i have read the cyclone came with a 38 mill carb but the easiest way to tell what size carb you have is to take a micrometer and mic the inlet side of the carb, that will let you know what size it is... i know that the hot swap wth alot of blaster guy's who have went to the bigger set up's is the stock 250r carb. a buddy of mine has a ported piped blaster and he loves his r carb on his bike...

as for the "im sure it will work just get it jetted right" approach, it's not that simple, ever carb has a sweet spot it work's best in. on up-stroke your motor pull's x-amount of cfm and with a smaller carb it will have a ton of velocity going through your carb so it's natural that if you build your motor you will have to up the volume of air your carb can flow, the downside is that if you go to big then the velocity of the air slows down and wont pull the fuel from the jets right, at low r's it wont get enough fuel, at high r's it will over fuel and run rich...your best bet is to start talking to people and find someone who has the same set up as you and find out what has worked for them...

[tecateboy]

Originally Posted by swrbansheeboy

well i hate to dissagree but the 250r's run a 34 mill keihin pj carb stock and the banshee's run 26 mill mikuni's stock as do the blaster's....

from what i have read the cyclone came with a 38 mill carb but the easiest way to tell what size carb you have is to take a micrometer and mic the inlet side of the carb, that will let you know what size it is... i know that the hot swap wth alot of blaster guy's who have went to the bigger set up's is the stock 250r carb. a buddy of mine has a ported piped blaster and he loves his r carb on his bike...

as for the "im sure it will work just get it jetted right" approach, it's not that simple, ever carb has a sweet spot it work's best in. on up-stroke your motor pull's x-amount of cfm and with a smaller carb it will have a ton of velocity going through your carb so it's natural that if you build your motor you will have to up the volume of air your carb can flow, the downside is that if you go to big then the velocity of the air slows down and wont pull the fuel from the jets right, at low r's it wont get enough fuel, at high r's it will over fuel and run rich...your best bet is to start talking to people and find someone who has the same set up as you and find out what has worked for them...

well my figureing was that since a stock 250 is running a 38mm carb, it shouldnt overcarb a 240bb with a 3mm stuffer....and i dont see how it would run lean on the bottom and rich on top, thats why you rejet the carb so it isnt lean or rich.
but i am sure you know more on this subject than i do, so ill belive you on it unless someone else comes in and proves one of us wrong.

[swrbansheeboy]

i'm not saying you cant get it to run with a carb thats too big or too small, but your going to go through alot of headache to wind up with a bike that only run's so-so, since our carb's relly on the air flowing through them to pull the fuel from the jets there kinda size specific depending on how much air your motor can draw through the carb. too small a carb you have to have big pilots, huge main's, aftermarket needles, aftermarket slides and all this big stuff to make it work. too big you have to undersize everything cause theres not as much air running through the carb...anyway, it's kinda hard to type out an explanation but the shortest explanation i can give is that if it were all in the jetting we would all be running 20 mill carbs because we could re-jet them to make them supply more or less fuel for our application...

for a 240 blaster with a 3 mill i would be looking in the 32-34 mill carb range...

[Ed Gein]

33 or 35mm Keihin PWK.......

[BlueDiablo]

GO with what you what but i havent had a single problem with my 38mm. Works great had a huge improvement over the 35mm i had on there. But its up to you.

[tyephoon]

hey just thought i'd throw this out... the bigger the carb the more tempermental the jetting is. i've heard that if you have a bigger carb, changes in the air, temp, elevation effect it more because of the huge amounts of air that have to flow through. Any way you look at it though jetting can be kind of a pain. i have a 34mm pj on mine with the same setup (changed from stock 26mm) and it took me awhile to get it right. Bottom line is you want less time working more time ridding. The 34mm works great, but i hear the pwk are better because there more updated. either way you can pick one up for fairly cheep. i got mine for 175 on ebay.