1996 xp bogging on low rpm but runs fine on high rpm

[mikidymac]

@mikidymac do you know where i can buy a set of needle and seats?

Search for Mikuni part number 786-35018-1.5 or 786-35015-1.5. You can get them from Amazon but make sure it says sold by and ships by Mikuni.

NEEDLE VALVE SQUARE PUMP 1.5
by Mikuni
4.9 out of 5 stars 15 customer reviews

List Price:$21.95 Price:$17.49 FREE Shipping on orders over $25 shipped by Amazon or get Fast, Free Shipping with Amazon Prime& FREE ReturnsYou Save:$4.46 (20%)
Note: Available at a lower price from other sellers that may not offer free Prime shipping.

• Made by Mikuni
• Mikuni # 786-35015
• 38-46mm Square Pump Super BN watercraft carbs.

New (15) from $16.65 & FREE shipping.

 

[rubves]

okay, i ordered from osdparts.com the same day i asked but forgot to update sorry.

 

[R-u-n2it]

"If i dont Get it to start and pull the plugs they are wet so i think the cut spring gave it too much fuel so its drowning. Ive always had this problem but the mid - high end is good now."

I doubt cranking the engine would build enough fuel pressure to "pop-off" before engine would start, think about it, if ignition was good somewhere in between dry plugs and wet as you indicate the engine would fire if all other components/systems were functioning as intended, and your choke system doesn't rely on that metering system.

If you still have the no start problem clean the plugs and try again with no choke, if you were using the choke to begin with and got the wet plugs. If still no start before using choke look at plugs to see if wet like before or dry, if dry you might rethink the prior no start was from "flooding with fuel".

 

[rubves]

oaky, i did use choke so thats probably why they were wet. my bad.

 

[R-u-n2it]

follow through with dry plugs and no choke, crank a reasonable enough time that it will start if it's going to start, look at plugs, dry or wet like before?

 

[rubves]

have the carbs apart and waiting for new needle and seats but i will defently try that if this doesnt fix the problems

 

[R-u-n2it]

If I remember right you said the battery was 12.5, so hook up a charger when you try to start to eliminate it from being a possible problem.

 

[rubves]

i got the new needle and seats, now how do i adjust the pop off pressure? it pops at 15psi and 18psi.

 

[mikidymac]

You have the wrong springs if it is popping that low.

You don’t technically “adjust pop off”. You can only use the correct needle and seat size, correct spring and only make very fine adjustments bending the lever one a millimeter each way.

 

[rubves]

Okay now i have the 80g black ones so which should i get now?

 

[mikidymac]

Those are the correct springs so if it’s poping that low it’s either the needle and seats, the lever arm or the lever pin causing it.

 

[rubves]

The needle and seats are new, 1.5 push in type. So can it be that its not worn in yet?

 

[mikidymac]

No. Wearing in has nothing to do with it.

All genuine mikuni parts?

 

[rubves]

I bought the spring and needle & seats from osdparts.com

 

[rubves]

Is that okay or do i need to order from somewhere else?

 

[mikidymac]

OSD sells good parts.

I would try a new lever arm and pin to be safe.

 

[rubves]

Okay will do, any other parts which can be the problem that i should order at the same time too?

 

[mikidymac]

Nope, the only things that change pop-off are the needle & seat, spring, arm and pin.

 

[rubves]

okay, is there only one arm and pin that is the right one or is there multiple options?

 

[rubves]

turns out it was a bad seat, as i switched the seat to the old one and left the new needle and it jumped to 20ish psi instead of 14psi.