carb to big?

[TheX1992]

me and my father got into a little discussion at dinner tonight. he was watching those 'chopper build off' shows on tv. he said:

The guy had the same problem as you. The bike runs, but once you give it gas it dies. He said if I wanted to drive to the corner and buy a pack of cigarettes it would be fine but if I was to take it on the highway it would die. Sounds like the exact same problem you're having. His solution was to get a small carburator.



i have a 400ex carb now. mods are in my sig. do you think its too much? im not sure what the jets are. its running way to lean i believe. when i start it (if it starts) the rpms skyrocket until i kill it. havnt had enough run time to take a plug check yet. all i know is i bought it with a dial a jet and no choke. i run B-32 (118octane) straight.

now i do know it will be running lean. when i attempted to boil and stretch my stock 250x airboot to fit over the 400ex carb, it ripped. i have a good 1 inch rip in the boot. it wont fit right to save my life. so there is a few decent sized gaps at the inlet of the carb. would that make that much of a difference? a little air leak? thanks for any of your help. i appreciate it.

[Greg Z]

When i had my banshee it use to rev up when i first started it

the problem was an air leak..

check if you have an air leak going on

air leak = Lean condition..

check it dont ride with an air leak.. I had one didnt no until my engine seized.

[TheX1992]

do you believe the story about my carb being to big though? i see alot of people running 400 carbs on their 250x.

[Texan32]

with the mods you have, i wouldn't think the 400 carb would be "too big". But to answer your rev questions, any air leak between the carb and the engine itself will cause big (even damaging) effects to the engine.

The FIRST thing you need to do is get the boot fix/repaired/replaced. There needs to be NO air leaks before you can even start thinking about tuning the carb! Also, when you do tune the carb., be sure to tune it as if you were riding it...i.e. filter in place, airbox lid on/off, seat on....some guys try to tune the carb with crap still taken off. Then, when they load up and go ride, it fowls the plug:rolleyes:

edit....yes, it is possible to have a carb that is too big. Would you stick a Holley 1100 cfm Double Pumper on a stock Chevy 350 c.i. motor? Nope!

[TheX1992]

Originally posted by Texan32
,any air leak between the carb and the engine itself will cause big (even damaging) effects to the engine.



this is between the box and the carb, not the carb and the motor. no difference though im guessing. still has a leak. am i right? i am looking for a 350x boot for it now.

[cals400ex]

no need to get a smaller carb in my opinion. i would make sure you don't have an air leak. also, you need to jump in and fine tune that carb!!! ;)

[TheX1992]

i need a starting point for jet sizes. with my mods, what do you think i could start at? i hear a 42 pilot is good for not having a choke. i was also thinking maybe a 140-150 main jet. 3rd clip on the needle also? what do you think? i just need to get it running (somewhat correctly) to do a plug check at least.

[cals400ex]

i would start around a 140 mainjet. its hard to tell with out ever having that setup. i would leave the clip on the 3rd for starters. you need to make sure you don't have an airleak first especially if your putting a carb in that wasn't in from the factory. is it actually running that bad???

[TheX1992]

yes. as of now it wont even start. im not sure if its just the cold weather or not. im going to work on fixing that air leak

[300exOH]

stick with the 400ex carb and get a 350x airboot from eBay or the for sale section and jet it right and you'll be good to go:cool:

[Greg Z]

if you wanna check if you haveb an air leak start her up and start spraying starter fluid all over on the boot / carb area. Then you will hear the engine revving possibly bubbles from the air leak.