This is a great video, I have my “carb”screwdriver never knew that it was metric just knew the guy that sold it to me said don’t use anything else, humbled again today
Awesome video! A few years ago when I was new to all this I had the exact question about which part the manual was calling the "body" of the carb. I wish this video existed then.
I saw your pop-off video while trying to learn how to rebuild my triple Mikuni BN 44's. Never done this before but found your video engaging and informative. My GP 1200 came with an owners manual for the Mikuni's and I will now give it special attention before I dive in on the rebuild. My GP is running sluggish and doesn't have the "hole shot" acceleration it used to, so I'm going to carburation after having pulled the motor to replace the rear oil seals and have now replaced the motor in the hull and test run it on the lake.
John, my 2 cents is that this is your best informative video yet. I felt you dove a little deeper into the topic than most of your others. I might of added , try an use only OEM Mikuni jets and springs and needle valve assy. Good job..keep it up.
I have my father in-laws old 1996 tiger shark montego. It ran good when I first had it and now it won't run at all I'm getting a kit with the needle and seat and the Springs to tune .The info you gave on the intake pressure's or vacuum is a big help because I know this would have been a problem.. I will be ordering a stock flame arrester and cover thanks
Thanks, I seen "pop off " mentioned on a FB group and was totally lost. Now that is out of the way, will visit your site as I will need parts here shortly. I have a Franken Jon and most likely will have to modify the carb to get more bottom end. 61 x is what I am installing as my 62 g and other 61 bit the bullets.
Recently got that same Vessel Impacta JIS screwdriver. Can't believe it took till 2022 for me to get my first JIS screwdriver lol, though I suppose the PZ driver bits in some large tool kits is about the same as far as not camming out of the screw head like what a Phillips driver does on a JIS screw.
Sounds like pop off pressure has many parallels to compression test results, where compression testers can vary some based on so many factors (altitude, length of tester rubber hose, gauge calibration, etc), meaning that one shouldn't get so hung up on the numbers, cause they're best used: A) As just a general ballpark figure (ie, are both cylinders at least kinda close) and, B) As a comparative diagnostic (ie, make notes of compression readings 1 hour after a fresh top end rebuild, then retest using the same compression tester every 10-20 hours and/or if suspecting issues). I've never messed with my stock '95 750sxi twin Keihins, but my buddy that raced 750s in the late 90s swears I need to swap a single Mikuni SBN on it. Sooner or later I'll give one a shot.
If im rebuilding the carbs and the ski was running well before, should I check what the pop off is at and make sure tobreturn it to the same psi? Thanks and great video!
I've tested 4 different springs from the kits, they all range from 36psi to 55psi. How can I adjust it lower than 36psi? Can you snip a spring slightly? I was trying to get to 30psi. 97 spx 787
You can change the size of the needle and seat, to lower pop off. The Mikuni tuning manual has a chart showing pop off numbers with all combinations of needle and seats, and springs.
Thank you for your comment. We don't make these kits, they come from Keihin in Japan. There should be 2 o-rings for under the needle and seat above the filter.
great video ! can you please tell me where i can get jetting specs for different altitudes as i am moving a 1986 js 550 from a colorado elevation of 5000’ to florida sea level elevation? thx a bunch
Thank you for watching. We sell jetting kits on our Watcon web site. Please give me all your specs in the notes section when ordering. I need to know what ski, what engine, what carb, any and ALL mods done, what impeller, and elevation where you ride.
I have a low hour bone stock 1996 WB2. I know I’m going about this backwards but when I rebuilt the carbs I failed to write down the carb numbers. I’m looking at the chart for the Mikuni SB44s and only one has a choke but it also doesn’t have extended shafts for a duals.
Sorry, I am unsure of your question? Are you looking for new carbs? Unless you order direct from Yamaha, any SBN 44 carbs you will find are just universal carbs. Please reach to me at the shop if I can help.
Are you talking about the metering diaphragm button? Like your diaphragm is in backwards? That is not good, or correct, and you should correct it, and then tune accordingly.
If the pop off pressure isn’t in sync on a twin carb will it only pull fuel from one carb? My twin carb 750 Kawasaki sts is only pulling from the front carb and not the back one I just rebuilt the carbs?
Need some advice. I have 3 1997 gtx seadoos. All have good compression they had sit for a couple years so I replaced fuel lines and rebuilt the twin sbn40i carbs on all using mikuni oem kits. I did not change the springs. They pop off at 24 to 26 lbs with my tester. Problem is they idle smooth and accelerate to 5000 rpm great but some lag there until they hit hard. I can interrupt the lag by cycling the throttles and off they go. Is this pop off or low speed adjustment arm height etc. Running them at 5500 foot msl.
My guage has a certificate from the government that says its accurate to within 0.01psi(digital). If im not paying attention to my guage, what am i looking at to determine if my popoff is set correctly?
Hi gusy, i have a problem and are serching for solution, -70cc reedvalv engien with a 24/28mm eba carb, Inthake manyfold meight be a lithe small, Proble: at WOT in LOW rpms it whill cut out when u dont let it rev up in 2-4sek (or at a hill or somthing) It wiLL NOT cut out in high enouh rpm, in very low rpm. when the engien can gain rpm fast enouh it works, It will get betther with so softer spring it will get bether but then in idle the fuel wil not vaporise and will just runn down the carb and bild a lithhle swamp
