Strange jetting. What were they thinking??!!

[jasonham41]

So I'm trying to chase a low down performance issue on my 98 Xpl.
Just stripped the carbs down and here is what I have,
Low 79.5
High 167.5
N/S 2.3
Silver springs
L\S 1.5 turns
H\S 0.25 turns
19psi pop off with arms level.
Accl' pumps removed
Choke spindles removed
Stock air box, with the plastic deflector bits missing or removed by P/O.
Can anyone shed some light on what dark forces might at work here. :facepalm:

 

[wfo speedracer]

I don't know for sure but I would put PRO K's on it and jet for those, try somewhere around 95 lows and 170 highs with the 2.3 needle and seats

 

[jasonham41]

Moving forward with this, What do you think to the 19 pound pop off? (With prok's)
Do I need to order springs aswell?

 

[jasonham41]

Can anyone confirm, the mikuni SBN jets fit the BN-I
I'm pretty sure they do but I intend on ordering a bit of a range so I have them ready.

 

[Matt Braley]

Yes SBN jets are the right ones.

79.5 lows? never hear of that size real Mikuni jets go from 77.5 to 80.

With 85 lows your jetted for a 97.5 GSX white pipe and aftermarket flame arrestors. If you have the stock black pipe you could get away with 165 highs.

 

[jasonham41]

As best as my eyes can see they are 79.5 I will check again though.
Accl pumps removed, so would be up on the 85 a little?
Yes running a black pipe, should I look out for a white pipe? Something worth doing?
Prok's and an assortment of jets are on order, hopefully arrive mid week.

 

[Matt Braley]

Oh yeah a white pipe is worth another 100 to 150 rpm. Be sure to get the manifold from the 97.5 with the # ending in 600 cast into it. It's 2mm larger internally.

 

[jasonham41]

Well look what just showed up!

 

[jasonham41]

So I've gone for 95 lows at 1.5 turns and the 167.5 highs at 1/2 a turn, just to start out.
Any thoughts on this before I fit the carbs back on tomorrow? [MENTION=75495]wfo speedracer[/MENTION] [MENTION=51824]Matt Braley[/MENTION]

 

[wfo speedracer]

The only suggestion I have is to start at two turns out and lean it out till it turns 7000

 

[jasonham41]

Found something rather annoying today, after fitting the carbs back on.
Evidently my eyes are not what they used to be.... :facepalm:
What I thought to be a 79.5 is actually some sort of symbol followed by a 95...
So I've fitted prok's and replaced my 95s with some more 95's.
I'll run the boat next week and see how it goes. I've got some 100's here already, which I imagine is going to be the next job, but I will adjust up the lows and see how it picks up off the bottom with the prok's on.

 

[jasonham41]

Ok so finally got the xpl out on the water,
It's now turning 7K or a touch over, which is an improvement of 200+ rpms.
The plugs aren't really colouring up, just a very light hint of brown on the porcelain, after a 15miniute ride, so I've upped the highs by half a turn. So now to see what that returns.

 

[Matt Braley]

Glad to hear your chasing it in the right direction. I've never heard of folks needing to go all the way up to 100 lows with stock carbs so you should be able to fine tune with the adjusters from here.

Where is Devon? It's getting a little chilly here I've been blowing off test rides but I know it will only get worse.

 

[jasonham41]

Thanks for the input, it doesn't seem like it's a million miles away now.
Devon is a county in the far south coast of England UK.
It's 6'centigrade above freezing today. Spent an hour or so out on the water before I couldn't feel my fingers anymore.

 

[snikwad003]

That is true 2 stroke seadoo dedication

 

[jasonham41]

Haha, wouldn't have it any other way!!

 

[jasonham41]

Upped the highs to 1 full turn, here is what I've got now. Seems to have lost a hundred rpms compared to last time out. The whiter of the two plugs is mag side.

 

[jasonham41]

Originally I thought I should richen the mag to match, now I'm thinking as the outer ring of the plug is good and wet I should lean the pto slightly? Aim to make some of the rpms back?
Your thoughts please?

 

[mikidymac]

I like to have mine a little darker than that.

 

[Matt Braley]

Sometimes it takes more time to establish the color. For an initial chop test you are looking for color on the porcelain way down in there.

When I'm tuning the high speed needles I start with them 2 turns out and then work them in in 1/4 turn intervals with WOT tests in between until you stop gaining rpm. Then I'll open the needles a little from there giving back about 50 rpm. This should put you on the rich side enough to be safe.

 

[jasonham41]

Thread update,
It's running pretty good now, I'd say it's a touch rich although the plugs never really get dark.
Waiting on another new coil at the moment, as its killed another. While the boats been off the water I've ordered a solas concord 15/20, along with a digital tach to get a proper rpm number.

 

[jasonham41]

Update.
We're back on the water thanks to Nick at west side.....
I've got the solas concord fitted and what a difference, A different machine compared to the skat-swirl that was in there before.
I was a little surprised at how easy it was turning the concord, knocked off a 100 rpm or so.
I came home after a full tank full of fuel was burned, and decided to compression test it just out of curiosity. 148-149 down each hole...... On what appears to be a stock head.
So a question for the gurus.. Should I be running premium pump gas with that compression?

 

[jasonham41]

So here we are today's fresh plug chop. What everyone's thoughts?
Currently turn 6800 +/- 40rpm with the concord.

 

[snikwad003]

Took the that right to the definition there.

 

[jasonham41]

Haha yes. It removes any doubt about the size and colour of that carbon ring.