650SX Carb is killing me...Help please...LOL - PWC Forum: The best hang-out for Personal WaterCraft enthusiasts
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 16 (permalink) Old 08-01-2009, 12:49 PM Thread Starter
Junior Member
 
Join Date: Aug 2009
Posts: 9
650SX Carb is killing me...Help please...LOL

I have a 93 650SX which we have rebuilt the motor on, and in the process lost the original carb. After looking around I purchased a used carb and could never get it running... It would start but every time I gave it throttle it would go BWAA BWAA. After getting frustrated enough to chuck it in the trash I purchased a mikuni SBN-44 carb. Tuned it with original adjustment screw settings and it worked great. Took it to the lake, did a little fine tuning, rode it for about an hour, and left. Now I can't find my adjustment screw settings on carb or online, and it is doing the same thing it did in the first place, bwaa bwaa bwaaa lol.... I've about given up hope, but that ski is my favorite thing I own. Does anyone have any clue what could be causing this?? Or what a pretty accurate screw setting would be on that carb? BTW ski was bored out to around a 670 is what they said? I've though maybe it could be my primer creating a weird vacuum in there?? Thanks, I'd appreciate any help from this long, boring post.
bantamboxer is offline  
Sponsored Links
Advertisement
 
post #2 of 16 (permalink) Old 08-02-2009, 11:21 PM Thread Starter
Junior Member
 
Join Date: Aug 2009
Posts: 9
So now I've got it tuned where it seems to idle and run pretty good, but only with the hood off or the little pop out on the hood open. Obviously it seems like it get's starved for air when the hood is on.... Any suggestions or ideas why this could be? Thanks, I'd appreciate it!
bantamboxer is offline  
post #3 of 16 (permalink) Old 08-03-2009, 12:48 AM
Senior Member
 
Join Date: Dec 2007
Posts: 227
What's the pop off pressure of the carb needle? It really might take some tuning since the engine was bored over. Might need a few jet sizes larger, might need a lower pop off than stock. Borderline I would say on pop off is 25 psi. Fuel pump working ok? What's your compression?
fedorov5549 is offline  
Sponsored Links
Advertisement
 
post #4 of 16 (permalink) Old 08-03-2009, 01:09 AM Thread Starter
Junior Member
 
Join Date: Aug 2009
Posts: 9
I know the fuel pump works great, and compression in excellent.... Pop-off or jets very well could be the issue. I'm just not to familiar with tearing carbs apart myself. Jet's would be one thing, the pop-off I know nothing about. Any idea where i should even begin with that??
bantamboxer is offline  
post #5 of 16 (permalink) Old 08-03-2009, 02:00 PM
Senior Member
 
Join Date: Dec 2007
Posts: 227
The low speed adjuster, bypass holes and low speed jet work with the inlet needle pop=off pressure to transfer fuel when you go from low to high speed. You have to put a pressure pump with a guage on it to the inlet nipple on the carb/fuel pump. Take the cover off on the other side of the carb. Make sure the needle is wet. Pump the gauge up until it pops and adjust it by changing the spring under the needle arm.
fedorov5549 is offline  
post #6 of 16 (permalink) Old 08-04-2009, 08:42 AM Thread Starter
Junior Member
 
Join Date: Aug 2009
Posts: 9
Oh I see. Sounds like something I could do lol. I'll check that out thanks. I've heard a lot about the pop off pressure but it always passed right over my head. I took the ski out this weekend and had it sounding great at shore with the hood off. Put the hood back on, took it out on the lake and it died shortly after at about half throttle, so I popped the little hole cover in the hood off and it ran great. Flew across the water, so I pushed the cover back in and immediately it bogged down and did the same old thing. Took the little hole cover off and away we went again. Do you think this could be due to not enough air getting to the carb in that closed off hood, therefore making the thing way to rich??? Seems like soon as it get's some air it great....
bantamboxer is offline  
post #7 of 16 (permalink) Old 08-05-2009, 10:11 PM Thread Starter
Junior Member
 
Join Date: Aug 2009
Posts: 9
Has anybody else ever heard of a prob like this oir have any clue? Thanks
bantamboxer is offline  
post #8 of 16 (permalink) Old 08-11-2009, 12:29 AM
Junior Member
 
Join Date: Aug 2009
Posts: 5
i am maybe going through the same prob I have a js 440 that i rebuild and with the hood off it seems like its got more power. I might have to get different jets it has a super bn 38 on it with 107.5 main and a 65 piolit jet i don't know if that is to big or what because it take forever to get on plane does anyone know what the jets should be
raptor50 is offline  
post #9 of 16 (permalink) Old 08-12-2009, 12:14 AM
Junior Member
 
Join Date: Jun 2009
Posts: 20
There should be some sort of vent into the engine bay. Is that clear and clean? The engine bore should not affect the carb setting that much. Sounds like your not getting air to the filter. or putting your hand over the venturi/intake.
danhuffmans is offline  
post #10 of 16 (permalink) Old 08-21-2009, 12:01 PM Thread Starter
Junior Member
 
Join Date: Aug 2009
Posts: 9
I can only find two things that look like vents, and they just go right out the sides of the hood. Like an inlet and outlet for water. Guys at the lake have been saying there should be no holes in the hood whatsover because then water gets in the engine bay....Which makes sense, but how else are you going to get air to a hungry 2 stroke ya know. It's never gonna run right if it keeps choking out. They all say its something with ignition because it always stops a cylinder for a second after a hard landing. Anyone ever hear of that problem?
bantamboxer is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the PWC Forum: The best hang-out for Personal WaterCraft enthusiasts forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 2 (0 members and 2 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
seadoo rxpx 260 bov help im new lol superman5397 Sea-Doo Jetski 0 05-26-2015 07:08 PM
How do you see the trailer?? lol ontwowheels General PWC & Jetski Discussion 10 08-28-2009 05:32 PM
650 xs keeps killing cdi mlehman144 Kawasaki Jetski 3 06-29-2008 10:02 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome