misses when riding wheelies

[cals400ex]

my friends bike misses when riding wheelies at higher throttle positions. i don't know if this is normal or not?? by the way he is running a fcr39. at low throttle it is fine but when we get to close to full throttle it starts to miss. any suggestions?

[RMX500]

up the main jet i guess, does it do it all the time or just in wheelies?

[cals400ex]

it is actually a bit rich on the main right now. it does it a tad when riding normal but just sometimes. on wheelies it gets to the point where it wants to die almost.

[haywire4130]

it has nothing to do with your jetting... your float height is too high for doing wheelies or your overflow is clogged. the thing is flooding. when you tip the carb at extreme angles, the fuel will pour right into the motor or out the overflow if it's working correctly. picture a full glass of water. if you tip it 90 degrees, what happens to the water? my friend's ex pours fuel out the overflow when he does 12's on it. the float assembly is plastic on his (stock carb) so it's not really adjustable. p.m. me if you'd like a step by step on how to adjust it on your fcr carb. good luck

[Gatorman199]

Mine did that when my air filter got sick nasty. Didnt know it i run mine w/o the cover and i hadn't cleaned it ina while it ws sick looking BTW its a K&N w/ outerwear. Once i cleaned it it helped alot. This actually has nothing to do with anything lol. mine just sputtered a little bit and so i decided to post this anyways lol. Its your carb. lol

[Woodsrider]

If it was a float issue it would be too low, not too high. Here is why; the float bowl is on the back of the motor, not the front, therefore making the carb lower than the intake in a wheelie position. The float bowl is at the bottom of the carb, and the fuel tips away from the pick up.
On the top end the quad misses or cuts out and wants to die because it is drawing fuel from the bowl faster than the bowl is refilling.
The mainjet would cause it too miss on the top end if it was too lean, but would not affect how it runs in a wheelie position.

This is how I see it, and if I am wrong someone some one please school me;)

[cals400ex]

i know the mainjet for sure is a little big. i was thinking the float too. however, i am not sure what it needs to be adjusted at on the fcr 39.

[Woodsrider]

I would suggest calling the place it was purchased if that possible. If not I'm sure that there are enough riders on here that run that carb, someone can tell you what the float hight should be.

[haywire4130]

woodsrider is correct in theory, but when it is tipped backwards, the float will open the needle and dump in loads of fuel, making your fuel level way too high when it starts to come down. if you are perfectly steady in your wheelie, you might be right, but if it's choppy, the fuel will slosh into the cylinder. i'm just going by experience, because as a test on my buddy's ex, which dumped fuel from the overflow, we tried blocking the line with a small screw. when it went up in a wheelie, it would sputter and flood out and stall, and we needed to clear it out with full throttle to get it started again. to adjust the float height, you just carefully bend the little metal tang on the float assembly that closes the needle so it contacts the needle. to measure it, you hold the carb upside down and measure from the bowl gasket surface to the top of the float. i will post a link when i find one. woodsrider: does this sound right? i'm not trying to be a knowitall, but i think i'm right

[haywire4130]

http://www.factorypro.com/ go here, click on "mc tech" in the left column, then go to "keihin flatslide carb technical info". this is the most complete page you could ever ask for regarding the fcr carbs. everyone running these carbs should read this. this is a streetbike page, but the same primciples apply to all fcr carbs. note: i don't recommend actually changing the float height to make it wheelie good, because it will run like crap on flat ground. i was just trying to explain why. enjoy

[cals400ex]

i didn't see flat side carbs on that site. maybe i skipped over it.

[haywire4130]

scroll down the menu on the left, it's the second one from the bottor "mc tech" then go to the flatslide carb page, it's very well written, and i have used tons of street bike parts from these guys, they know their sheet!