IF you hit the primer when trying to start does it then start?

If it starts as described above does the Engine die when it uses up all the gas you gave it with the primer?

You prime in both carbs correct?

I don't think a single carb would help? I don't see any reason why it would be any different than running the duals that i am running now. they are sync'd and i just make any changes to both at the same time. There just has to be somthing that i am missing



my starting technique.

I give it 1 shot with the primer, i hit the key and it fires and dies instantly. If i prime it again it wont fire, it will act flooded. If i don't prime again it will crank and start to sputter and then fire, idf i don't prime again it will die.

Yes i prime both carbs, there is a line going from my primer to right between both carbs, and an equal amount of tubing goes to each carb to hpefully give each the same amount of fuel.

What if you gave it 2 shots of the primer before starting and no throttle ?

Where is your primer dumping in the gas?

it will spit and then crank and crank and crank until it starts to sorta half ass run and then once it starts to run die

I dropped my jets on the low end down to 67.5. seems to take care of most of the bog, but still feels slightly rich. I turned the needle out 3 turns because i figured it would be way lean but it seems to be a bit rich, so i will work the needle in a bit and see what i can come up with. It still will not idle, but i think that is due to it being rich. if i turn the idle up far enough to make it idle, after a rev it will stick at 3k. I think it i leaned it out a bit, it wouldn't have to have the butterflys open as far to idle so it would still return.

No clue here thought if I asked enough questions something might click in, using the primer you can tell if its lack of gas or too much gas problem sort of like using a choke on a regular Engine, can you take pics of your carb air cleaner intake tract setup I have read about these carbs being sensitive to intake changes like the flame arrestors on a PWC .

Try it with nothing on the carbs just open carbs? Does it act any different?
Try it with 50% of your intake system blocked off with duct tape any different?

Where are your primers dumping gas I installed mine at the very top of the carb so when I hit the primer its putting gas in ABOVE the throttle plate so when the Engine is started and is cold if it seems like its going to die I can give it another squirt and it slowly sucks the gas through the throttle plate if I crack the throttle plate and give it a squirt it usually almost floods itself.

Anyways play with giving it more gas to see if that's what its lacking at your low RPM bog problem area.

If it is in fact starving for gas figure out how to add more fuel at that throttle position.

Wish I could help more just throwing ideas at you.

Sorry i read your post and never replied.

my primers dump fuel right near the top of the carb. i believe the hole that it is installed in at one time was a butterfly choke setup? there is a plug on the far outside and then a nipple installed in the inner holes.

Ive been playing with it a little and got it to run better. It starts quite a bit better and the bog has almost been taken care of. When i go to start the Engine, i give it 3 pumps of the primer, it cranks for a second and fires and runs for a few seconds and then wants to die unless i give it another quick shot. sound about right for a cold Engine?

there is still one issue that i am having getting it to idle correct. If i turn the idle screw in to the point where the Engine will idle, once i rev the Engine it will not want to return from about 3k RPM. since i have my idle screw out quite a ways to keep it from sticking at 3k, i can hold it open and idling at about 1000rpm, and from there if i quickly stab the throttle it just falls on its face like it is getting too much fuel.

To correct the idle/not coming down from 3k with the idle set high enough to keep running before a rev, i don't know if i need to go up in jetting or down. I think it may be a bit too rich down low causing me to have to turn the idle up higher than it should be to get it to idle, but once i rev and it cleans out and tries to come back down the idle is set open too far and it does not want to come back down. Does this seem about right?

As far as falling on its face from a 1000rpm idle, this seems like it is because it is rich as well. im wondering if going down on the jets one size would clear some of these issues up. I wish i had a place local that had the jets so i could just stop by and grab a jet i think i may need, not just taking a shot in the dark. OR, i could raise the pop off pressure, would that achieve the same thing i am after without ordering a couple new jets? I am at 25psi at the moment and the next step up jumps me all the way to 32. i think that would be far too much?

let me know what you guys think. i am getting much much closer. I could probably take it on a ride now if ol faithful (the fl570) was not so faithful but the not idling would get old lol. Thanks

Thought the low adjust screw was for adjusting the mix at idle? Turn the screw in small increments at a time allow plenty of time for it to react.

Your Engine is made to idle at 1000 rpm? My 580 is 1800rpm idle...
if your idle is lower than recommended that will also contribute to full throttle off idle stumble/lack of response... Also it will take a lot longer for the Engine to come back down to that rpm after riding/cutting the throttle
Regards

Any updates?

well goOdy i missed your post.....damnit! your 580 idles at 1800 rpm? that seems a bit high? my Engine picks up running great at about 2500 so i wonder if the 670 is supposed to idle at that? i never had it running with the stock carbs because it had a bad crank, so i didnt get to hear it run. do you have a video of it at idle? i wonder if my tach isnt registering correct as well. it sounds like its running right when it shows about 1000rpm.

ive lowered the jetting to the point where it is starting to run shittier. so going back up one step it runs the best, but still wont idle, and has a low end bog. both of those things i can care less about at the moment. the damn thing still wont start. i can prime it, get it to fire one, and then it just crank crank crank and starts to sputter and fires. if i don't prime it after its running it will run out of fuel and die. once it is completely warmed up, i take it for a ride, i can hit the key and it instantly fires, and dies. i can crank it and it will eventually sputter and start to pick up. its running out of fuel down low, has to be. i think maybe raising the pop-off would help it get more fuel. that is the next thing i am going to try, it seems i have tried everything but changing that since the jetting has been lowered. I would really like it to run so i can actually take it on rides. but its been deemed the piece of shit... good thing i don't own a backhoe, or else i would have burried the damn thing. im starting to get tired of nothing helping at all. if the pop-off thing doesnt work i don't know what else to do, other than find a way to get the stock carbs fitted.

Was looking in the manual for my Engine type 454 the other day idle is suppose to be 1800-2000 RPM

I am working on it this weekend. It still wont idle, and it still wont start. Lowered the pop off pressure with the jetting that has it running the best it ever has, and i saw no change in the way it run. when i was driving it it really felt lean up high, and the plug read a little lean for my taste. Upped the high jets from 137.5 to 140, just one jet size, and the damn thing wont start at all. Why the hell would the high speed jet affect the timing? this has be baffled.

Anybody want to buy a pilot? lol

I don't know what is up, but im thinking the carburetors are junk. i just cant figured it out. I have gone from extremely rich, to extremely lean and everything in between and nothing helps. It is a complete animal when i can get it started, but why is it so damn hard to start?! at the moment if i could get it to start and idle i could care less if it even ran through the entire RPM range. By the time i get it started to take it for a test ride my damn battery is dead.

http://www.thecrankshopvt.com/product_i ... cts_id=155" .".. (first piece in the list down the page a ways) " 15 Degree Short Angled RV Cover Non Injection (limited qty discontinued part) "
I am tempted to buy this, throw the stock 670 sled carbs on it, mix my fuel and be done with the damn thing. just hard to spend $275 on a piece of aluminum if you cant 100% verify that the carbs are going to fit with it in there.

are the BNi 38s that i have too small of a carb? the 670HO came with 44mm slide carbs. I have also been looking at single 44bn setups and dual 44 setups. Again, hard to spend that kind of money if it isnt going to help me in the least. I know it isnt an Engine issue, i have compression tested it and i get about 145-150, and i have done a leakdown test and that is good.

any other suggestions before i dig a big ass hole and burry the whole thing? never had this much of a tuning nightmare in my life.

You tried the PWC sites their has to be a carb guru that can tell you whats up with your setup?

You mean one of these manifolds? ROTAX part number 912 570575 ? Dunno how big of carb this will accept without modifications it was used for 38mm carbs but I could send to you and you can see if their is anything you can do with it at least use it for mock up to see if carbs could clear the trans.

Personally I would search the web looking for super BN idle problems find a super BN guru I would think the 38mm carb would work on a 335cc cylinder just fine especially at low RPMs .

You still have the choke plates installed and can cut off some air at idle see if it helps? if not pull the filters and use your hands over the inlets of the carbs.

Anyone you can borrow a known good set of carbs from?

Tried a couple PWC sites but ive not gotten anything from them other than what the factory settings/jetting should be for the seadoo that the carbs came off of. That is really tons of help....

Hoser, i may take you up on borrowing that plate and see if it will work for me. I think it is exactly what i need but, i still don't think the carbs will clear the trans. I will go try and find a good pwc site that someone can maybe help me. Hell if i have to i wont say its on a sled Engine. shouldn't really matter either way. Im sure the Engine construction is the same basic setup from pwc/ski just different output shafts.

I do not have a choke plate, but cutting off the air does not seem to help. i will keep trying for a bit with these carbs. it is just extremely frustrating.

well these showed up today. they are from a 96 SEADOO SPX 717 . these carbs are CLEAN, they don't even appear to ever have been opened up. Still have the choke plates. My current carbs have been converted to primer, and have had someones grimey hands all over them.

picked this setup up for $100. I am not going to touch them. Bolt them on and see how far that gets me. hey are from a 717/720 so the jetting should be fairly close... Tomorrow i will see if they work. Just tired of my current carbs settings getting me nowhere. wish me luck... lol

Cant really see what you have their 38mm 44mm 48mm carbs? round or square bodied?

38 square pump carb. its a BNi38. bolted em on she Runs Okay. just won't start. hot or cold. I got it started and made it idle, but as soon as I shut it off and try to start it it will fire one time, then I have to crank other for a bit, then it will sputter and almost start then die. thos is fustrating. i don't know where to go from here. seadoo forums are no help, guus tell me the factory settings of a seadoo close to same size bit i can find that shit on my own. so back to square one. maybe i should find a different Engine to use..

how did this Engine run in the sled with the stock set up?

You can make this work don't give up, that Engine will run with any kind of carbs on it you just need to adjust the carbs to the Engine.

Back to the basics research hard starting and cold starting see what part of these carbs are responsible for proper cold and hot start problems regardless what application they are used in should be the same.

Its been so long since I read up on these carbs I would be no help, have you read all the carb info on the http://www.groupk.com I mean everything regardless what the topic or application read about the problems they discovered and the cures....

don't get too frustrated when site gurus cant help they probably don't have that much experience with these carbs other than making slight adjustments to compensate for minor mods they have made and those adjustments are probably suggested by the developer of of the mods heck look at me I am about clueless about these carbs because I was easily able to adapt the 580 carbs to my 440 and it runs, I read my piston wash after 40-50 hrs run time and the top of my piston was still about 100 clean so I know I am running really rich but not to the point of leaving a trail of blue smoke where ever I go and my plugs are not black and wet, I make more power than I need so I never bothered to lean it out.

Install the primer to use with the chokes during cold starting just for the hell of it ?

I would think with chokes and throttle plates closed it would suck more than enough fuel for a cold start that is if their is enough fuel present and available when cranking, if not and a shot of gas using the primer makes it start then I would look at delivery for that circuit, dirty or not large enough to supply enough gas for your application.

I would get it running then crank the idle up to 2500 RPM once the Engine is up to full temp (take for a ride get it hot) then see how it starts maybe the throttle plate is too closed when cranking when you open it up while cranking its open too much?

Good question, if compression and timing is good should run but I wonder if the rotary valve timing being way off could create the problems he is having?

You know any Super BN carb gurus their had to be some growing pains when they modified these carbs to work on the Briggs cars I remember at one of the races I went to in WI that Renni and Bob raced Renni had the carb off his and all apart looking at everything inside, I was just looking over his shoulder watching its been so long ago I cant remember what problem it was he was trying to solve.

You get your left turn issue resolved?

Yeah. Thought it was carb. It ended up having a large crack in the exhaust port allowing coolant into the exhaust then the pulse was pushing coolant into the cylinder. On a right handturn i never had to let off so on the straigh away I was able to get it to clear out and keep it reved up through the turn but on the left handers it was always after a jump so if I got out of the gas and back in it it would bogg out like it was super rich. (coolant acting like toooo much fuel and oil) The guy Can who did all the custom work to the Engine originally was able to weld it up and re-port it for me. I pressure tested the cooling system and got it all back together a month ago.
With nitros Engine I don't understand why its hard starting. With the bn carbs it should fire up easier.
Nitro have you done a leak test on the Engine? I know with nickrnrs twin it was a bitch to start he ended up having a bad seal on the flywheel side.

Read all of this one yet? http://www.mikuni.com/pdf/sbn_manual.pdf

Parts and info http://www.hotproductsusa.com/catalogs/ ... ection.pdf

Like to read?
http://www.pwctoday.com/showthread.php?t=110154

Found this while searching lol http://www.pwcforum.com/aftermarket-per ... oject.html

No clue. bought the sled real cheap, had a bad crank bearing that let go and twisted the crank on the PTO side lower wrist pin. Picked up a crank for it, assembled leakdown tested, new rings in the top end with fresh very light hone. cylinders werent bad, just wanted to freshen it up while i was there.

COuld the timing somehow be off with the CDI (Capacitor Discharge Ignition)? IF that was the case, wouldn't it run like hell once it got in the upper rpms? What baffles me is that it runs awesome once you get it started. Its just trying to get the damn thing started that i don't understand. if it runs great the rest of the time, why is starting so hard? Even when the damn thing is completely warm been rode around for 15 minutes. I came in, shut the key off. and instantly tried to fire it up.. it fired once and then back to cranking until it would spit and spit and spit and try to run.

How about the stator? Coil pickup? coil?