550 fuel vaccum issue

[Ryan Declark]

Trying to get my 550 to pull fuel. I just rebuilt the carb, and i did not use genuine, (amazon special) so i imagine this is problem number one. I also installed an aftermarket inline filter for the fuel and ripped the stock one out. I basically pulled the hose off the fitting of the carb, and sucked fuel pretty close to the top where the carb meets and i cant seem to get the fuel to the carb (i can visually see the fuel in the line not making it to the carb) even after getting it to fire by priming. If i had to take a swing at it id say i bought a bad carb kit and its not creating the correct vaccum it needs to pull fuel, but i want someone else to tell me im a cheap bastard too.

 

[fastgtfairlane]

Which carb is it? It sounds like you got the diaphragm on the metering side of the carb on backwards and it's not opening the needle and seat to pull fuel in. Did you change the spring for the needle and seat when you went through the carb? In my experience the cheaper carb kits work ok for a short time but the quality of the gaskets and diaphragms are not as good so they don't last very long. I don't think the kit is the main issue. Definitely re use the old spring for the needle and seat if you didn't already do so.

 

[Ryan Declark]

Ya old needle, spring and seat where all reused. Its the oem kawasaki 38mm carb. I feel like i some how messed it up. Im gonna take a look at another 550 i have just to see if iv got fuel routing right first. I also need another pop off tester.

 

[Ryan Declark]

iv checked compression on front cylinder 180 and rear cylinder at 173ish. i figure from what iv read this is good enough to run. my issue right now is that i know i have fuel flow as i see the fuel coming out of the return line from just cranking the engine over. iv gotten it to start 2 different ways now, buy using the primer which basically runs until the fuel from the prime burns but then after that, it cranks with no zing. off of a huntch i simulated choking the carb but putting my hand about 3/4 over the body of the carb intake and then it kinda wants to run properly. i took note of the amount of fuel that was coming out of the carb too which was more then i can see while just normally cranking with no simulated choke. here are the couple of things i have done so far to the ski and iv tried to do everything by the book. replace most fuel hose. tested hoses for leak all the way to the carb in fiting. iv rebuilt the carb with a genuine kit and excluding a few tiny orings i didnt replace because all the original stuff felt like it never had fuel in it to begin with and still seemed like a fresh kit. while i was in the carb i did also clean the jets with jet cleaning tool to ensure no blockages. so iv started by priming the carb to get initial fuel flow going as per the request of the manual. i also noticed that someone took the stock choke out of the body of the carb and replaced it with a fuel primer. iv set the low idle screw to "lighltly seated" as per the manual. i feel like im not pulling enough fuel through the carb to even get the ski to start and run on its on power which is frustrating. my hypothesis at this point as i am no expert is that either the choke is a vital part of the vaccum to pull fuel. HELP! PLEASE! iv spent to much time on this thing. also im fairly certain its a stock 38 bn.

 

[WFO Speedracer]

The choke is not needed to pull fuel, somewhere you have an air leak in the fuel system leading to the carb or you have a diaphragm installed wrong, without a popoff tester you are pissing in the wind trying to fix that carb , I am not that worried about the popoff , those carbs have a tendency to leak at the diaphragms , all of the gasket surfaces have to be spotlessly clean for the carb to seal up correctly, this is verified with the popoff tester , you have the low speed screw in way too far, on an unknown setup start at two full turns out and go in till it runs correctly.

The BN carbs are way different than the SBN's all the adjustment is in the high and low speed screws since the jets are fixed , the carb adjustment matters , a lot !

Vacuum pulse fuel pumps work directly opposite of a fuel pump in a car , on a car the pump is in the tank and it pushes fuel to the fuel rail, on a ski the pump is in the carb and it pulls fuel to the carb, if there is an air leak in the pickup, lines, filters or on the gaskets and diaphragms on a BN carb or anything else before the carb it will pull air , not fuel , the best example I can give you is its like sucking through a straw that has a hole in it, it just won't work.

One more thing a piston port 550 would have to have had a ton shaved off the head or an aftermarket head to have those kinds of compression numbers , if it's a stock head you have to install thick head washers to get it to torque down, if it has stock head washers on a stock head your compression gauge is way , way off .

 

[waxhead]

Where do you have the fuel inlet hooked to ? the one you think would be the pulse is actually the fuel in on the bn carbs

 

[fastgtfairlane]

Take and post some pics of the ski, engine and carb you're working on. A good pic of the fuel line routing as well. Without any visual, we're all just guessing at this point.

 

[WFO Speedracer]

Where do you have the fuel inlet hooked to ? the one you think would be the pulse is actually the fuel in on the bn carbs

Yep fuel inlet is at the very end of the carb , the pulse line connects in the middle of the pump body, return is at the banjo fitting . also those older models had an oddball rev limiter plumbed into the return line , it used a solenoid and injected extra fuel into the carb to bring the revs back down , if you have removed it you have to put a restrictor into the return line.

You can also refer to that diagram to make sure you have all the gaskets and diaphragms in the right order .

They were bad about leaking at #50 and #51, #51 is plastic and they warped , the aftermarket ones were Aluminum .

 

[waxhead]

Yep fuel inlet is at the very end of the carb , the pulse line connects in the middle of the pump body, return is at the banjo fitting . also those older models had an oddball rev limiter plumbed into the return line , it used a solenoid and injected extra fuel into the carb to bring the revs back down , if you have removed it you have to put a restrictor into the return line.

You can also refer to that diagram to make sure you have all the gaskets and diaphragms in the right order .

They were bad about leaking at #50 and #51, #51 is plastic and they warped , the aftermarket ones were Aluminum .

Mikuni round body Bn Billet Fuel inlet

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[Ryan Declark]

The choke is not needed to pull fuel, somewhere you have an air leak in the fuel system leading to the carb or you have a diaphragm installed wrong, without a popoff tester you are pissing in the wind trying to fix that carb , I am not that worried about the popoff , those carbs have a tendency to leak at the diaphragms , all of the gasket surfaces have to be spotlessly clean for the carb to seal up correctly, this is verified with the popoff tester , you have the low speed screw in way too far, on an unknown setup start at two full turns out and go in till it runs correctly.

The BN carbs are way different than the SBN's all the adjustment is in the high and low speed screws since the jets are fixed , the carb adjustment matters , a lot !

Vacuum pulse fuel pumps work directly opposite of a fuel pump in a car , on a car the pump is in the tank and it pushes fuel to the fuel rail, on a ski the pump is in the carb and it pulls fuel to the carb, if there is an air leak in the pickup, lines, filters or on the gaskets and diaphragms on a BN carb or anything else before the carb it will pull air , not fuel , the best example I can give you is its like sucking through a straw that has a hole in it, it just won't work.

One more thing a piston port 550 would have to have had a ton shaved off the head or an aftermarket head to have those kinds of compression numbers , if it's a stock head you have to install thick head washers to get it to torque down, if it has stock head washers on a stock head your compression gauge is way , way off .

Good info. Gonna order another pop off tester as my last gauge broke due to the required popoff for a 94 wave raider stock psi requirement was higher then the gauge vould handle. I would imagine at this point i would pump 20 pounds into the carb and look for a leak with soapy water? What should stock pop off be?

As far as assembly and fuel line routing i have fuel in closes to the gunwall, vaccum mid section of carb and return closest to the engine. I know nothing is flipped as both the manual and the carb kit came with instructions on installation directions. One thing i didnt do is pressure test the carb.

If i cant get it to hold pressure would it be a decent idea to maybe get an aftermarket sbn?

 

[SUPERJET-113]

"Knights of the round pump" lol

I would ditch that ancient technology crap carb and get a SBN. You'll have to get a spacer kit to get to the SBN pump side away from the cylinder. The spacer kits are like $35 up to $60 for a kit on ebay and that comes with longer bolts and gaskets too. Or get a new manifold, but those are more $$$. Those old round pumper carbs are very temperamental even when they are working correctly.

 

[Ryan Declark]

"Knights of the round pump" lol

I would ditch that ancient technology crap carb and get a SBN. You'll have to get a spacer kit to get to the SBN pump side away from the cylinder. The spacer kits are like $35 up to $60 for a kit on ebay and that comes with longer bolts and gaskets too. Or get a new manifold, but those are more $$$. Those old round pumper carbs are very temperamental even when they are working correctly.

What do you do with the vaccum line if you install a sbn? Also 38 or 44?

 

[Ryan Declark]

Also ill take to pictures at the end of the day.

 

[WFO Speedracer]

"Knights of the round pump" lol

I would ditch that ancient technology crap carb and get a SBN. You'll have to get a spacer kit to get to the SBN pump side away from the cylinder. The spacer kits are like $35 up to $60 for a kit on ebay and that comes with longer bolts and gaskets too. Or get a new manifold, but those are more $$$. Those old round pumper carbs are very temperamental even when they are working correctly.

38's actually worked pretty well, the BN 44's were absolute garbage IMHO

 

[WFO Speedracer]

Good info. Gonna order another pop off tester as my last gauge broke due to the required popoff for a 94 wave raider stock psi requirement was higher then the gauge vould handle. I would imagine at this point i would pump 20 pounds into the carb and look for a leak with soapy water? What should stock pop off be?

As far as assembly and fuel line routing i have fuel in closes to the gunwall, vaccum mid section of carb and return closest to the engine. I know nothing is flipped as both the manual and the carb kit came with instructions on installation directions. One thing i didnt do is pressure test the carb.

If i cant get it to hold pressure would it be a decent idea to maybe get an aftermarket sbn?

Yes get an SBN44 and intake, it will run and crank much better.

 

[SUPERJET-113]

38's actually worked pretty well, the BN 44's were absolute garbage IMHO

I only ever messed with a 44 round pump a long time ago, so I no nothing about the round 38. I figured it was a POS too...lol

 

[WFO Speedracer]

I only ever messed with a 44 round pump a long time ago, so I no nothing about the round 38. I figured it was a POS too...lol

All the 440's came with 38 BN's 440's never had starting issues like the 550's did , the 1986 models had severe hot starting issues with the 44BN's , fuel would leak out of the low speed circuit on the carb into the intake manifold when the engine was warm making them damn near impossible to start, Kawasaki fixed the issue on the 87's but they did not do a recall so owners of 86 models were just SOL, , we didn't have SBN's yet much less intake manifolds or spacers for SBN's so there was no fix for the hard starting on 86's.

I ran dual 38BN's for years on my reed valve 550 engine never any issues there , I did eventually swap to 38 Kehins and it ran better on the Kehins than on the BN's.

 

[Ryan Declark]

Btw if i was to switch to a sbn44 is there a certain model or brand i should go with. I see alot of different mikuni 44s but idk what one is going to work best for my application. Is it a direct mount with the spacer plate in place? Also what happens to the oem vaccum line? also dont pay any mind to the hoses. i plan to get them all the same color i was just trying to get her vrooming first before i start making the hoses and the routing better. also it seems as though alot people bypass the selector switch as it goes bad but mine seems to be okay not pulling any air.

 

[Pro-pulsion]

The selector switches can be rebuilt very easily. Just remove the screw from the knob and retaining nut holding it to the hull, remove it from the hull, remove the screw in the back of the selector, it pulls apart, cleanup all surfaces if needed and replace the o-ring. I've done it to my 650sx and my SuperJet, never had an issue with air getting drawn in the system but definitely seen fuel leak out of it. After a cleaning up and fresh o-ring it was back in full service. Both have been going reliably for over 10 years since I rebuilt them.

 

[Ryan Declark]

btw this is most of the work, really a paint job for anyone curious about the ski in depth.

Was given a 550 The General Lee

Long story short, when i try to start it, it sounds like it has a dead battery and its slow to turn over, i had a 1000 cca battery hooked up. By hand the motor turns over but feels "stiff" My assumtion is that it sat so long that either the crankshaft bearings are seized or the piston rings...

www.x-h2o.com