No bottom end on 701 single carb

W

Westcoaster

Location
Seattle, WA
First off, I've been using this forum for a year and its been an immense help solving problems and just learning about skis in general so thank you guys. I bought a non running SN for $1000 last year without ever stepping on a standup. I was hooked from the moment my buddy mentioned he had one.

Here's what I'm running:
701 single carb in a 93 SN
Tau Ceti F/A
Worx 201 intake
Jet Dynamics ride plate
Hooker 9/15
Solas 144 Mag
compression 135psi both cylinders (will be doing top end this winter)
Pilot 100
Main 135
Pop off 43psi

Ever since I've run this ski it has always had a low end bog from idle all the way to about 1/2 throttle. After 1/2 throttle it rips hard. Low end sucks harder than a stock 650 SN, but I've just been digging the whole stand up thing and just ridding it, now its really starting to bug me. I was meticulous about rebuilding the carb a year ago so I don't think anything was left out (no missing parts, new filter, check valves correct way). I feel my pop off is a bit high for after market FA and my pilot is a bit low (I think stock is 115). So if anything I should be a bit lean but when I tried a lower pop off of 28 and a bigger Pilot of 115 I bogged even harder to the point of stalling out.

I'm beginning to lean towards the pump to pump shoe seal (packing) or the midshaft seal. Hard to imagine I'd loose idle to 1/2 throttle just from cavitation but maybe. For some reason when I installed the mag pump I could not for the life of me engage the splines with the new pump packing, so I put the old one back in. Bog was there before and after pump and prop install. I did not use any grease or Ultra Black sealant on the packing.

Any ideas on? Pump packing, midshaft, carb, new gas lines, tank check valve? Thanks, appreciate the input...This site kicks arse.
 
BruceSki

BruceSki

Formerly Motoman25
Location
Long Island
Sounds like a jetting issue to me. You made a huge change in jetting too.

Should make small jetting changes to see results.
 
W

Westcoaster

Location
Seattle, WA
So while on the stand I tried the 115 pilot with the 95g spring and then the 115g spring. Both seemed like they were very rich, quite a bit of smoke, wouldn't idle without pulling the throttle and still sounded terrible no matter where I had the Low speed needle or where I had the throttle. While it was running it sounded kind of low pitch, like it was on the verge of dieing. Put the 100 pilot back in with 115g spring for poops and couldn't maintain idle, so reverted to my original 95g spring and ran it just like I have been...crappy low end until I hit half throttle. I realize this pilot is shockingly low, but it is the only setting I've found that seems to run half way decent.

When testing the jetting a noticeable amount of black fluid came out of the exhaust.

Gas was new, running 40:1 with Castor 927, both fuel filters clean, fuel tank check valve working.

Thoughts?
 
Mike W

Mike W

Infidel
Location
North Florida
I would check the reeds. If they check out fine, (If it were me) I would send the carb off to have it professionally rebuilt. Something is going on there.
 
WB1994

WB1994

Location
Amherst NH
Black fluid out the exhaust means your running rich. Do you have a popoff tester? Is your N/S arm set correctly? It could be too high and holding your N/S open. Also run 50:1.
 
Quinc

Quinc

Buy a Superjet
Location
California
Is the carb setup for a 650 and not a 701? Have you looked in the manual to see what the stock 61x jetting/pop off should be?
 
Harbor

Harbor

Location
Stockton
Have you noticed either of your pissers spitting with inconsistent flow during the bog then going to a normal pisser flow after the bog ?
 
W

Westcoaster

Location
Seattle, WA
Been using a Mikuni gage, 95g spring is at 43 psi. 1.5 N/S is new and holds pressure for at least a minute. Good point, I'll check the arm but seemed to be operating correctly by hand. Side note, I don't think I replaced the arm when I rebuilt it, could be bent I suppose.

Manual for the 94, 95 SN 701 single carb says 115 p, 135 main, 1.5 N/S.

I don't have pissers with this 1993 SN hull. The line from the head to the exhaust is not T'd off. Should it be? I have the stock exhaust.

Thanks again fellas.
 
W

Westcoaster

Location
Seattle, WA
Yeah I had new wires from JSS, good idea though.

Good news is I found the problem and now it runs with the 115 pilot, 135 main. Was user error on the carb rebuild haha, shocking I know. I had rebuilt the pump side wrong by using both the O-rings AND the two paper gaskets surrounding the clear diaphram o_O. Here's my explanation as to why I did this...The guy I bought it from had issues with the carb so I couldn't trust to just replace the parts exactly how they were, instead I tried following the directions on the pdf that came with the kit shown below. The kits instructions say to use the paper gaskets (item 1) on the SBN 44 so I did. But then I also saw grooves for the O-rings that were supposed to only be on the SBN 38, I used them as well...this is where I should have stopped and researched. The Mikuni SBN Manual written 20 years ago states on page 10 that the SBN 38 O rings are ALSO USED ON LATE MODEL SBN 44! Lesson learned...there are different models of the SBN44, early models took the paper gaskets (item 1) and late models took the O-rings (item 1a). If there are grooves for the O rings use the O rings and do not use the paper gaskets. Reference the Manual, not the rebuild kit.

Mikuni Rebuild kit pdf: http://www.docstoc.com/docs/94089795/SBN-Rebuild-Kitindd
http://www.docstoc.com/docs/94089795/SBN-Rebuild-Kitindd
Thanks for all of your help!
 
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