4mil stroker problem learn on WOT even with NO HIGH JET

[sambo]

I built a 4mil stroker with case porting and port matched sleeves bored to 760. Should be around a 800cc. On daul 46s with 18pai 2.3 135 low and 190 high and still to lean

I have a learn spot when hit wot. Was going up jet sizes all the way from 120 to a 190 even to the point I removed the jet and still it's not rich. It still pulls on 3 turns out on high speed and no jet at all. If even bypassed fuel tap and filter and still no luck

There is no air leaks engine holds 10psi over 30mins and only drops in 1psi over that time.

I have tried 2 sets of 46s even bought a brand new set. I ran my first set with 60 return jet in line. And new set are bone stock. Still the same symptoms. Engine runs ok on the 38s but feel more power to be had out the 46s.

I read a lot about fuel pressure and people are going up jets to 90 in the return line. But my carbs give a learn symptom not rich. Is it possible the fuel pressure is to high at WOT and matching my pop off pressure as it set low at 18psi on 2.3 ns. So not opening the needle fully.

I'm stuck been going round in circles for long time now and licoriceed off.

 

[Half flip95]

what does the the tach say?

if it is lean with a 190, that's a sign that fuel is not making it to the high speed circuit.

 

[Storbeck]

It sure seems like the signs point toward fuel not getting to the carb the way it's supposed to.

Assuming you've done everything you can to make sure the fuel lines from fuel tank to carbs are perfect (dual lines straight from carb to tank, fuel "clunks" fully inserted to the bottom of the tank, lines are in perfect new shape no cracks or leaks, no tight bends etc) so you are absolutely positive there is no leak and no restriction from the fuel tank to the carb. I would also be making sure the pulse lines are perfect (no leaks, no tight bends, double taps in the case not T-ed) so you know for certain there is absolutely no way that is an issue.

I would then be using the set of carbs with the drilled restrictors (you talk about a return line restrictor jet, which implies you have a set of carbs with drilled restrictors) I would put the size 60 jet in there, and I would put a fuel gauge on it and go try to get a reading on fuel pressure when you are having this issue.


Is there anything unusual about your setup? Are you using a strange pipe or a strange fuel tank or something? You have a pretty "normal" setup so it implies that you should be pretty close to "normal" settings otherwise there is probably something wrong.

 

[G-Body]

If it were me I would start by putting a T in the fuel line going to the carb, hook a fuel pressure gauge to it, tape/tie/etc it to the pole, hood, or wherever and take the ski for a ride to make sure you are getting proper fuel pressure at WOT. If you have a well sealed motor and have tried 2 sets of carbs it sounds like a fuel delivery issue to me.

 

[Storbeck]

Why are you expecting pressure in the line going TO the carbs?

 

[Harbor]

Why are you expecting pressure in the line going TO the carbs?

Good point!

 

[TheBuzzard]

I didn't really read this very carefully or I didn't understand your foreign language but I think you said when you stab the throttle wide open , it has a lean hesitation? why are you dicking with the main jet? you got a 135 low jet in there. put a 155 low jet in there and see what happens. you have to adjust the low speed circuit before dicking with the high speed circuit/ main jet.
I don't get it.
the first thing I do when I ride somebodys junk, is putt it at 2 mph for 30 seconds and then stab it wide open. if it hesitates, its lean. if its loaded up, its rich. in either case it goes right back to shore for some major low speed screw tuning to see if it can be tuned without changing jets. if its got a lean hesitation, I take the low screw all the way out to 3 turns and test it again. at that point I know if I can tune it by turning screws, enough to be ridden or the carbs need to be jetted before it'll run

 

[sambo]

The ski never loads up On high circuit even with a 135 low and no jet in the high with 3 turns on both screws. I will be checking the line pressure today.

Storbeck I'm not checking feed line pressure. I'm checking the return line pressure before the restrictor.

I think I have found the issue tho but not getting my hopes up just yet. I have noticed with my new build I used some new after market fuel lines for the pulse lines. I fink it is too soft. I will get a fuel pressure reading under load then I will try some oem pulse lines. I think the lines are expanding and contracting under full Throttle making the pump not work to it's full potential. I'll.let you know how I get on. Thanks for your input guys

 

[Storbeck]

Storbeck I'm not checking feed line pressure. I'm checking the return line pressure before the restrictor.

My comment was to G-Body who suggested checking the feed line pressure if I understood him correctly. I think you're plan is good.

But, after re-reading your original post and Buzzard's post there is some confusion here. Is your problem occuring during a prolonged high speed wide open run, or is it a lean hesitation from quickly applying wide open throttle?

My response was assuming it is a prolonged high speed run, Buzzard's response was about quickly applying wide open.

 

[Sparkplug]

The mikuni manual says exactly what the buzzard said. To ride the ski at 1/4 throttle for 30 seconds to a minute and then instantly go wot. If you fly over the front of the ski cause it died or lurched, your lean on the low. If it gurgles and pulls through, your fat. Its carb tubing 101. Perhaps you have other issues but it doesn't sound like it from this toilet seat I'm on

Sent from my SM-G930V using Tapatalk

 

[Big Kahuna]

My comment was to G-Body who suggested checking the feed line pressure if I understood him correctly. I think you're plan is good.

But, after re-reading your original post and Buzzard's post there is some confusion here. Is your problem occuring during a prolonged high speed wide open run, or is it a lean hesitation from quickly applying wide open throttle?

My response was assuming it is a prolonged high speed run, Buzzard's response was about quickly applying wide open.

Its in the title of the thread.
"4mil stroker problem lean on WOT even with NO HIGH JET"

 

[Storbeck]

Lean on wot doesn't tell you if it's a long pull or a sudden handfull of throttle. Sounds like long pull to me but about half of the suggestions on this thread are for sudden handfull, so apparently it's not obvious.

 

[Big Kahuna]

WOT translates to pull the gas........... Go Wide open........ He is feeling the motor lean out........ has nothing to do with throttle pull, off idle response. pulling through the low speeds.

 

[sambo]

I'll get some reading of today's test up later. But yes I was getting a lean hesitation when snapping open throttle from 1/4 throttle, falls on face then rips my arms off. Bit I thought a super large high speed jet would sort it or make splutter with fuel bit nothing changed when going larger jets.

 

[Vortex]

See last item

 

[Big Kahuna]

I'll get some reading of today's test up later. But yes I was getting a lean hesitation when snapping open throttle from 1/4 throttle, falls on face then rips my arms off. Bit I thought a super large high speed jet would sort it or make splutter with fuel bit nothing changed when going larger jets.

ok, in future, dont use WOT to describe what you got going on. It gives us wrong impression of what is going on.

 

[Half flip95]

are you sure its going lean?
can you be more descriptive of what happens when you ride it and what indications you are getting.

 

[TheBuzzard]

I'll get some reading of today's test up later. But yes I was getting a lean hesitation when snapping open throttle from 1/4 throttle, falls on face then rips my arms off. Bit I thought a super large high speed jet would sort it or make splutter with fuel bit nothing changed when going larger jets.

that's what I thought. put a bigger pilot jet in there or turn the low screw 3 turns out and see if it gets any better. stop dicking with the high side until it don't hesitate on the bottom.

 

[Storbeck]

Now that the problem is a little more clear, I would do what buzzard said.

 

[G-Body]

Why are you expecting pressure in the line going TO the carbs?

I just re-read that and realized my mistake. I meant to have you check for fuel pressure at the carb, but I guess there really isn`t a good way to do that on a SBN mikuni since it has the integral pump.