300/440/550 650sx carb issues

[herbnerd]

ok i bought a 89 650sx hull it had no motor so i bought a 650 ts engine with electronics. i tore the whole motor apart ported and polished my exhaust , bored out my stock intake manifold to 44 mm with and adapter plate wit a sbn 44 and the f/a is a stock with madified holes. other than that motor is pretty much stock. about 2 weeks ago i was running the ski on the stand no water and i was looking down the carb body and noticed fuel dripping so i changed out my pop off sping until it quit i have a 1.5 needle and seat with the stiffest spring. not sure of my jets but the carb came off a yamaha 650 couch.after doing changing the pop off i started to get a back fire at high throttle. now if i punch it the ski it dies .also trying to take off and plain takes for ever.guessing because i dont have any top end.any help would be great.

 

[WFO Speedracer]

You are running too much popoff pressure,and your needle and seat is bad.
Popoff controls from around 1/4 to 1/2 throttle, what you described the ski doing is a dead giveaway that you have the popoff set too high.
The popoff spring that came in carb as it was on the yamaha should have been dead on the money.
Put a new needle and seat in the carb and reinstall the popoff spring it came with, the needle and or seat in your carb now is bad, you only masked the problem and created another by jacking the popoff pressure up.

 

[herbnerd]

should i go with a larger needle a seat. 2.0 instead of a 1.5

 

[WFO Speedracer]

You can but then you have to guess at the popoff pressure.

 

[herbnerd]

is there any benefit to it .im installing a west coast water box and im doing the stock pipe mod and extending the cone 4 inches.

 

[WFO Speedracer]

I would say at that level of mods no there is no benefit to it.

 

[slipmag]

right on! def needle and seat! had the same issue a while back...

 

[herbnerd]

thanks for the help.

 

[herbnerd]

im going to replace that and drop my pop off pressure back down.

 

[herbnerd]

ok since my last reply on this issue i have re worked my carb i have 120 low jet 150 main 2.3 needle and seet and 22 psi on my popoff. i took it out yester day and the ski runs much better ,but still has problems .i have good low and mid throttle but it bogs and dies at wide open.also when i start it after it sits for about 5 min it will have wide open throttle but it goes away after 20-30 feet of riding.can this be pop off pressure too high or low or a jetting issue.also the water coming from the pisser is pretty hot.thanks in advance

 

[herbnerd]

i really want to get it going this weekend.i have been out 3 times this summer and no enjoyment of a good running ski.

 

[herbnerd]

bump