FCR acclerator pump duration?

[Scott in KC]

I am helping a buddy of mine jet his 400ex quad that he just built up and added a FULL race, slant FCR carb from Sudco. The carb body is different than my Yamaha FCR, no choke, no hot start and (most important) NO Tab to do the "BK" mod!! The TIMING of the squirt can be adjusted and is fine, but the duration of the squirt is like 2 full seconds and just dumping too much fuel. I know there is the P-38 Lightning deal, but I'm wanting to get that squirt tunable and down to .5 sec like my WR. Looking at the carb body, I'm sure I could manufacture a piece to keep the pump arm from returning as far, thus shortening the squirt. BUT, it would be pretty vulnerable to movement and debris.

Rich??
Anybody??

 

[wayneo426]

Hey Scott-
Isnt there a cam or pump actuator on that thing? Or even possibly a timing screw?
I know you can find a way to drill some holes in it, and cure the prob. :scream: ;)

 

[VintageDirt]

Would a bigger leak jet help?

 

[Scott in KC]

Wayneo, it's a totally different carb body than what we have. It does have a cam that actuates the pump (where we did the BK mod), but there is no tab to put a screw in AND there isn't a hell of lot of the cam sticking out to get a stopper on. You'd have to see it.

Vintage, I think you're on the right track. There must be someway, internally, to cut the duration down. I don't know why they don't make this adjustable from the get-go??!! Or at least put the tab there like they did on the Yamaha carbs.

 

[Boozer]

hmm. i think i remember a fellow named Taffy on thumpertalk.com had found a mod for this particular model. these are all i could find.
scroll down half way on this link to find the Taffy mod.
http://www.thumpertalk.com/bike/ubb/ultimatebb.php?ubb=get_topic&f=3&t=006382
http://www.thumpertalk.com/bike/ubb/ultimatebb.php?ubb=get_topic&f=12&t=005018

are these of any help? i'm just guessing your carb is the same as the one being discussed.

 

[Scott in KC]

Boozer, thanks for the heads-up! I kind of overlooked all those threads because they were for older YZ's & WR's, but that's the mod I needed!! Same, basic carb body on the full race FCR as the early YZ/WR carb.