3 outlet Mikuni fuel pump on Polaris SL650

[kevmor99]

I installed the 3-outlet mikuni fuel pump on a Polaris SL650 and now it runs like it has too much fuel. Some times it won't rev up past 1/2 throttle and if you're idling and punch the throttle sometimes you can kill the engine.

I've read on here that "you can't feed too much fuel to the carbs" and that no jetting is necessary to change with this fuel pump. Isn't it putting out more fuel pressure than the stock one, so shouldn't it require smaller jets?

[kevmor99]

Re: 3 outlet Mikuni fuel pump on Polaris SL650

Also, I believe it is a 1994, do I have a restrictor in the return line? I'll check... but should this be made larger with the higher volume fuel pump? Would this fix my problems without messing with the carbs.?

[scottso]

Re: 3 outlet Mikuni fuel pump on Polaris SL650

A higher volume pump will not feed too much fuel to the carbs. Your upgrade by itself did not cause problems. Though I am not an authority on this, I believe the pop-off is what governs the amount of fuel flowing to the carbs. I would think testing the pop-off pressure is your next step - but maybe someone else can direct you from here.

[kevmor99]

Re: 3 outlet Mikuni fuel pump on Polaris SL650

It was running fine before the pump switch though. First I thought pop-off pressure, but after working on another ski w/ SBN 38's, pop off only effects the lower end of the throttle opening range.

If I wait long enough, it will slowly start accelerating to full speed. If I check the pop-off pressure, what should I be looking for, the stock psi?

I'd put the original pump back on to test if it was easy, but each carb. has it's own fuel line now.

[kevmor99]

Re: 3 outlet Mikuni fuel pump on Polaris SL650

What if I try some higher gram springs?

[addicted]

Re: 3 outlet Mikuni fuel pump on Polaris SL650

Did you do a plug chop to verify that you are in fact running rich? It is possible that the old fuel lines that you replaced left some gunk in the carbs and the filter screens are plugged up.

[kevmor99]

Re: 3 outlet Mikuni fuel pump on Polaris SL650

It wouldn't rev up most of the time past idle, but I took the plugs out later and they were all black and wet.