Dasa/carb tuning

[Ochocoronas]

My setup is a 7 port Dasa 900 10mil, full spec 49s, Bpipe 50mil bore, 148 Krash pump and a 10-16 thin blade 5 mil cut back with 4 1 mill washer.

Almost sitting still I have a low end hesitation when I give it gas. It then clears and rips nice and crisp. If I have a little speed and give it full throttle it rips just fine.

Jetting....125L 140h 2.3 n-s 22 popoff.

I tired 125,127.5, 130,132 L jets and hesitation was still there. When I went to the 10-16 from the 11-17 the hesitation did get a little better. I would think a 900 could spin a 10-16 in a 148 no problem. My hull is around 290lbs
Any help would be great.

 

[krash45p]

I would think you need to lower your popoff a lb or 2 when you have more of a load on motor with bigger prop you need more fuel thats y when you went smaller it got better less load on motor ! Have you tried adjustments of needles?

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[D-Roc]

if it hesitates, it is lacking fuel for a split second, increase pilots or reduce pop off to find the balance

 

[krash45p]

Hsve you tried 2.0 needle seat combination

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[D-Roc]

looks like you did increase your pilots, i miss read your post, I would try playing with pop off like Krash45p is suggesting.

 

[Just4Fun]

Try Reducing the amount of water to your waterbox. Are you running a fcv before the stinger inlet?

 

[CARBONX2]

What ignition are you runnung?

 

[Ochocoronas]

Running a MSD.

Yes on the FCV

Going to get popoff at 18-19 psi. I was also told to see what a little more water on the head pipe does.

So far consensus says lower the pop off. So I will start there.

 

[Ochocoronas]

SOB....Sometimes the answer is so easy.... My breather tubes ID was only 39mm each and my carbs are 49mm. Never really thought about it DUH... replaced them with 50.8 mm ID tubes now. Have not had a chance to run it but it explains why I had the same problem no mater the jetting. My plugs also always read rich no mater what. Choking the carbs would cause all my symptoms? Will I need bigger tubes?

 

[x2mafia]

you could vent the hood and run a frogskin on the outside. The fact that it burbles then picks up tells me its not the vents or lack of air. Ask @chrisgrace if he had extra venting. He had an 1100 tpe if im not mistaken

 

[Ochocoronas]

It's a lean hesitation no gurgling. Chris ran RRP tubes that are 2.25 and mine are now 2 Vs 1.5.

 

[37]

Almost sitting still I have a low end hesitation when I give it gas.

Jetting....125L 140h 2.3 n-s 22 popoff.

I tired 125,127.5, 130,132 L jets and hesitation was still there.

Sounds like your jetting is backwards. Try 140 pilots and 125 mains, but close the high speed adjusters while trying to tune the low. This will reduce errors. Open them back up when tuning the mid/high range. You might not need 125 mains and could end up in the 105~110 range depending on how your plugs look.

Stick with the ~22 PSI popoff. I take it this is 2.3mm seats + 115g springs?

SOB....Sometimes the answer is so easy.... Will I need bigger tubes?

Physics says otherwise (being serious here). It's not likely your tubes. Difficulty to pull air volume would enrich your low end and cause a bog from being fat, not a hesitation from being lean. Airspeed would simply increase through the smaller tubes, not choke off your engine. You'd need really small tubes to choke it and even that would be on a top-end run, not low/mid throttle blips. Bigger tubes won't hurt but I doubt that's related in any way to your jetting issues.

 

[x2mafia]

try my jetting specs I gave you im telling you dude your jetted fatter than ALL of my friends that have bigger motors than you

 

[37]

try my jetting specs I gave you im telling you dude your jetted fatter than ALL of my friends that have bigger motors than you

Keep in mind that bigger motors (especially strokers) can pull more vacuum and get away with smaller jetting. Jet size isn't a 1:1 ratio with engine displacement. You can definitely have an 800~900cc engine with larger pilots and an 1100~1200 with smaller pilots, same carbs on each.

 

[x2mafia]

Keep in mind that bigger motors (especially strokers) can pull more vacuum and get away with smaller jetting. Jet size isn't a 1:1 ratio with engine displacement. You can definitely have an 800~900cc engine with larger pilots and an 1100~1200 with smaller pilots, same carbs on each.

i want to argue with you SO bad right now but im not going to lol

 

[Ochocoronas]

135P 1-1/2 turnout

135M 1/2 turnout

22 psi pop-off 2.3ns

Is working very well. Plugs still read a little fat. Problem now it's burning the prop some. Time to remove a couple of the spacers. I have 4 1 mil spacers on a 5mil cut back. Maybe start with 2 and see?

 

[37]

Given those results, try the following and see if things improve:

• 140P at 1 turn out (dial in/out as needed to tune for smooth idle)
• 125M at 2 turns out (dial in as needed to tune for best RPMs)
• 22 PSI (again, curious if this is using 115g springs, if so leave this as-is)

The fact that you're at 135M at 1/2 turns tells me your mains are too big. Going smaller on the mains will affect your pilots, so the pilots might need to increase. This is why I think the 140/125 combo will work. It's only 5 jetting points smaller than what you're running now and your current settings clearly need to come down.

Worse case you can go back to where you are now.

Get your jetting fixed before you mess with the prop. Prop changes will affect jetting. You'll be chasing your tail if you change both at the same time. Take it one at a time.

Edit: formatting

 

[Ochocoronas]

Given those results, try the following and see if things improve:

• 140P at 1 turn out (dial in/out as needed to tune for smooth idle)
• 125M at 2 turns out (dial in as needed to tune for best RPMs)
• 22 PSI (again, curious if this is using 115g springs, if so leave this as-is)

The fact that you're at 135M at 1/2 turns tells me your mains are too big. Going smaller on the mains will affect your pilots, so the pilots might need to increase. This is why I think the 140/125 combo will work. It's only 5 jetting points smaller than what you're running now and your current settings clearly need to come down.

Worse case you can go back to where you are now.

Get your jetting fixed before you mess with the prop. Prop changes will affect jetting. You'll be chasing your tail if you change both at the same time. Take it one at a time.

Edit: formatting

Thanks for the info!

Need to order in some more jets. As far as the springs I used what I had to make the popoff 22 psi.I am going to order a set of springs just to have them.