Backie Chan 850 BB need help bad....

d_moss

d_moss

Location
Rexburg, ID
MODS:
big bore 850 cr500 pistons/ported 180 psi ect ect
atp hx3 ignition
NEW kawi coil
ada super bore head
b pipe
stock intake no screens
hooker 11/17 solas mag pump
stock sbn 44s

Damn thing has always had dead spot right before you hit a wake and now that im really trying to fix it its even worse. You can pinch the throttle and it will just sit and blubber and not really rev up. If you gradually pull it on you can get it to rev out almost normal.

The only way i can get it to run is with the bottom screws like 3.5 turns out. no matter if it has a 115 pilot jet or a 125 pilot jet or 14 psi pop off or 30 psi.

Im starting to think its not carb related...........

Current jets

high 137.5
low 122.5
pop off 20 psi
top screw 1 turn
bottom screw 3 ish turnes out

it had

high 145? i think
low 115
pop off 30 psi
top 1 turn out
bottome 3.5 out



top end with 137.5 main and high screw 1 turn out is gnarly as soon as the ski blubbers and pukes and finally hits that upper power band it jumps out of the water. But it just doesnt brap brap brap crisp and snappy. its more bog bog bog bog.

I have a backie chan and all i can do is work on this stupid motor
 
TheBuzzard

TheBuzzard

Location
the jetski grave yard
you been dicking with this thing for a year now................ it still sounds either rich or lean on the bottom. if it runs best at 3 turns out as opposed to 1 turn out, it sounds lean. put in a bigger pilot jet. put in a 140 , 1 turn out.
 
Harbor

Harbor

Location
Stockton
Quote: as soon as the ski blubbers and pukes and finally hits that upper power band it jumps out of the water. But it just doesnt brap brap brap crisp and snappy. its more bog bog bog bog.

What flywheel are you running with that HX3 ?

The reason I ask is I had very similar symptoms that turned out to be caused by the aluminum charging flywheels reduced magnetic's. The HX3 was designed to work with a stock flywheels magnetic's.

Also what timing curve are you running ?

I also get sorta similar symptoms from too much timing early in the curve or a flat curve early before the timing ramps up later in the curve. Too much initial timing also made it pretty rough down low before the hit

The flywheel computability with the HX3 took awhile to figure out, once that was figured out I programmed the MSD enhancer curve into the Cdi to completely isolate both set of symptoms and verify the ski was back to normal.
 
d_moss

d_moss

Location
Rexburg, ID
140 pilot jet? do they even make them that big haha.

the flywheel is stock 62t and its what ever atp recommended with the 850 bb. I dont have a tuning cable. I should get one.

bigger pilot seems just what it needed but i feel like when i put in the 125 pilot it was to rich but i only had it in for 15 min and took it out. I cant remember if I messed with the bottom screw much. top and bottom screws should be set at 1 turn really and any changes should be made with jets.

I have a noise when its not running just after it shuts down. I think I can hear air going into maybe the fuel lines. and I always have to prime the line with the primer to get it to start for the day.
 
Harbor

Harbor

Location
Stockton
Well that's good you have the stock wheel........

I have ATPs curve they programmed for my 865, it's rough down low and not snappy, I ramped the curve in the lower rpm range to make it less rough, it's still pretty rough and sounds like poop but hits hard off my set up wake

So some of your symptoms are the timing curve, if you could get a cable and put the enhancer curve in you could eliminate that portion and you'd be left with whatever else you've got going on, jetting and air leaks and noises.

Edit: I added the rotary switch to mine so I can switch between curves depending on how I'am riding or two test out variations
 
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d_moss

d_moss

Location
Rexburg, ID
If I put a 140 pilot in wouldn't I need to put a smaller main jet in it? A lot of setups I see have smaller main jets and bigger pilots. Two 140 jets per carb seems like a lot of fuel for an 850.
 
4SeasonsPower

4SeasonsPower

Location
Ogden, Utah
Pilot and main jets overlap so if you add fuel by going with a larger pilot it will be richer on the top as well. You need to get your pilot right and then you can worry about leaning out your main. The larger pilot than main is reverse jetting.


Sent from my iPhone using Tapatalk
 
masterblaster

masterblaster

X-H2
your lean off bottom,bogs and revs out clean later in rpm,screws are 3 turns out,and still doesnt start easy. id look at the curve in the hx3 also,or put in a enhancer and verify ign is working right to begin with. The hx3 is still sensitive to other electronics that the enhancer will run fine with.
 
Harbor

Harbor

Location
Stockton
[QUOTE="d_moss, post: 1637832, member:

I have a noise when its not running just after it shuts down. I think I can hear air going into maybe the fuel lines. and I always have to prime the line with the primer to get it to start for the day.[/QUOTE]


This Noise you speak of is troubling as well, can you try to narrow it down and isolate the source of this noise/air leak ? Could it be a contributing factor in the fuel calculation/ratio/jetting delima

Airtime has the cables and rotary switches. I bought my HX without it to but I quickly realized the curve would need to be tuned
 
oside-tanner

oside-tanner

Location
Oceanside
Ok, that is why I asked, I'm running a 780cc, oem 44 manifold, oem dual 44 carbs, v-force 3 reeds, b-pipe, keep in mind the oem 44 carbs have a fine pitch thread on the low speed adjuster which means it's going to be open more turns than aftermarket carbs which all have the corse thread, your low speed adjuster should only be used to smooth out the idle, if your adjusting it to take care of the engine running rich or lean than your popoff is off or you are using the wrong jetting, my low speed screw is 2 open, I'm running a popoff of 17psi by using a 2.3 n/s and an 80g spring, any higher popoff my ski has a lean bog, you have to fill in the cross over, it helps the low speed fuel metering so much, it was the best thing I did to help my jetting issues(thanks waxhead), before I filled the crossover I was running 127.5 low speed jet, 115 high speed jet and 17 psi popoff, once I filled it in I'm now running 125 low speed jet, 105 high speed and still 17 psi popoff and every thing is great now, I just ordered an hx3 so we will see how much my jetting changes, for your ski do your self a favor, fill the crossover, get 2.3 or 2.5 n/s's, I would start off around 125 low speed jet and 115ish high speed jet, and put one or two screen's back in, good luck
 
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d_moss

d_moss

Location
Rexburg, ID
I ordered jets yesterday. Pilots 127.5 through 135 and main jets 115 through 130. We will see.... I think I have some putty left from my case porting to block off the intake
 
bobob729

bobob729

Location
wichita, ks
ok so i have 47full specks on my 850bb and i have 132.5 highs and 122.5 lows highs are 1/2 turn out and the lows are 7/8or a little over a full turn. 80gram black springs at 23 psi popoff and runs like a champ.
 
d_moss

d_moss

Location
Rexburg, ID
I have 132.5 low 120 Hi black spring at 20 psi pop off. One turn out hi low. Just need to plop it in the water if I get a chance. Revs good dry but that's doesn't mean anything
 
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