Jet Ski Carburetors: A Deep Dive on both Keihin and Mikuni Performance

Dive into the world of jet ski carburetors with the one and only Jet Ski Jim!
🌊 In this exclusive video, Jim shares his wealth of knowledge on carburetors, focusing on the renowned Keihin and Mikuni models. Whether you're a seasoned jet ski enthusiast or a newbie looking to fine-tune your watercraft, this video is a must-watch.
🚀 What to Expect:
• In-depth explanation of how carburetors work in jet skis.
• Detailed breakdown of Keihin and Mikuni carburetor components.
• Tips and tricks for optimal carburetor performance.
• Common issues and troubleshooting techniques.
• Insights on tuning for maximum power and efficiency.
Jet Ski Jim's expertise shines as he demystifies the intricacies of these carburetors, empowering you to take control of your jet ski's performance. Don't miss out on this invaluable information - hit play now and ride the waves with confidence! 🌊💨 #JetSkiCarburetors #Keihin #Mikuni #JetSkiJim #PerformanceTuning #WatercraftMaintenance
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[@steven.h0629]

Dang Jimmy.. whatever field you came from took a huge loss when you left 👍😎✊

[@neilfromclearwaterfl81]

I think it was easier for us old timers since the jets were adjustable having knobs on the engine cowlings of our 1940's/50's/60's outboards now considered antiques. If you were traveling and launched at a different elevation, season, load, etc you adjusted the idle jet at the ramp and then fine tuned the high speed jet with the second adjusting knob. You used the computer between your ears to fine tune things in real time to match any changes in conditions. If you mixed the fuel a little too thick that was easy to fix with the turn of a few knobs that you could often deal with even while wearing gloves and without taking anything apart. Best!

[@douglasbasinger2513]

Thanks Jim, I think it is funny hearing guys say, "I am so glad it is fuel injected cause carbs suck". A little patience and actually assessing how the engine is running will always result in great carburetion. My experience is that folks sell carbed motorcycles cheaper so I have more fun for less money. Love the content keep it coming.

[@M4rky71]

This was most helpful, thanks Jim. I’m in the UK where we seem to be seeing somewhat of a resurgence in popularity of older jetski’s. The issue here is the shortage of parts. I have a TS and a 550, and I’m having so much fun I can’t tell you. Having had larger, boat-like, SeaDoo’s in the past, I’m enjoying the involvement and challenge of riding the older stuff. Keep the content coming Jim, your wise words are gratefully received by us newbies.

[@robbymyer3615]

Great info here Jim. Thanks for sharing.

[@ryanc6574]

Super informative - I did not know pre-mix vs. oil injection would affect the carb's fueling and also did not know Kawasaki redesigned them to compensate for this. I have a '95 SXi, which was factory oil injection but it has the larger 1.6 needle/seat.

[@AtimatikArmy]

You should have mentioned you can look at your spark plug color to get an idea of where you are at in your jetting... rich/lean, etc.

[@Kristof-Kay]

Jim, your knowledge is 2nd to none, everydays a school day, thanks for sharing

[@havasubooo8840]

How do I know if I need to change my carburetor jet?

[@bozly209]

Man this is some great information thank you for getting me excited about carburetion

[@user-sy9mo5yx9x]

Very cool and easy to follow along thanks Jimmy!

[@brianzysset4946]

Way to keep up the brand 😎👍🏻👍🏻

[@danscomp66]

Saving his videos

[@jnew3755]

Thank you so much again for the information. I'm getting and old 650sx going for my 11 year old. He already rides an SXR 800 with me but after watching the 650 videos I wanted to get this hull damaged ski going. As far as I know it is totally stock, in very good shape under the hood with 150-155 on the compression gauge here in Montana between 2000 and 3000 feet of elevation. Parts on the way for the fuel pump and 28mm as well as a block off plate if we decide to delete the injection. If we do that can we ask for the beginning numbers for carburetion based on what information I've provided? It appears I will be doing the water box mod, crankcase drain bolt etc at some point. Needs straighter bars, kill tether and finger throttle first I think. So awesome you did these videos. Very much appreciated

[@duncanellico1398]

SCR Scott Clough Racing Pasadena Ca use to build my Mikunis He built fast skis back then 440super stocks and 550 mods wish I still had my skis

[@ozzielinkin]

Great info

[@ghfgh6150]

I still love the 2 strokes. I got to admit I hadn't thought about all those factors. And as far as the measuring, Iv'e been doing it wrong for years. I thought my wife was joking this whole time!

[@deadengine]

I've got a 1989 650SX with the stock tiny 28mm carburetor. I've read that bigger carbs really help the 650SX. I found a used Keihin 38mm carb from a Polaris (SL900 or SLTX). I've got two actually. One has an accelerator pump on it, but I can swap parts off the other one to get rid of the accelerator pump. Should I keep the pump, or ditch it? I ported the stock intake manifold to match the 38mm carb. I also bought a Mariner exhaust off Ebay and a milled head from Groaty. Where should I start my jetting at?

[@ozzielinkin]

Thx , great info !!

[@christianthejetskiguy]

Hey Jim love your videos, good info in here to help keep the old school ski world alive. I think you may have made a mistake though in talking about the keihin carbs with the measurements, I have all 4 models here in my shop and decided to measure them , while the 28 cdk1 measures at around 34mm at the flange like you said , I've found the other cdk2 models to measuring properly + about 1/2 mm at the flange and not behind the butterfly , with 38 measuring at 38.45mm at the flange and the 40 measuring at 40.40mm at the flange and my sudcos measuring at about 42.52mm at he flange. All 3 oem models 28,38, and 40 had a 2mm diameter step right above the butterfly at the throat which gets conically smaller the closer you get to the bombsight at an unknown rate (4mm shrink rate for the 28)that would make the throat measurements for the 38 and 40 , 36.45mm and 38.40mm respectively at the step and 32.45mm and 34.40mm at the smallest point near the bombsight if applying the same conical shrink rate as a 28mm carb. The only exception to these rules was the sudco 42 with smaller size step after the butterfly, I didnt have one disassembled without a butterfly to measure unfortunately.

[@americonoffroadadventures8132]

Great explanation. Thanks

[@mazevx2451]

That's the same as with suspension tuning, you really need to see the whole picture and understand how it works.

[@harveystephens6115]

Interesting Jimmy!

[@Trikekid84]

It seems like skis always run fine on the hose, but then won’t idle high enough or have other issues once in the water. Can you explain why or give tips? I also have a good test spot, a quarry, no other boaters in my way as I tune and take it in and out of the water. Working on a 93 sea doo spx 587.

[@danscomp66]

What jet are you puting in I think I remember you saying 55 Main is what you change too when you go too premix?

[@jetskijim007]

No. It was the pilot jet we changed. Yes 55 sounds right.

[@spacenut708]

i have a 750sx that i rebuilt carb on and it has 2 jets (main and low). i bought a parts 750sx that had a big pin installed and a single carb and intake. i noticed the carb was different because it had the oil injection inlet on the carb. pulled carb apart to clean and noticed that it had 3 jets. what is the difference performance wise? how would u jet one of these carbs? dont remember jet size off hand but two of them were close so i was thinking those two were the low speed while the other was a high speed?

[@cbh148]

Yeah I think a lot of those Kawi 750 engines were equipped w/ the 3 jet Keihin carbs. My understanding is that it was mostly on the twin carb Keihin 750s, like my '95 750sxi with the dual 38mm setup (1 year only as the next year went to twin Mikunis). I believe most of the sit down 750's got them too, albeit w/ 40mm versions in some models, but I think I recall reading a small number of them were still 2 jet. Never known much about the single carb Keihin 750 setups, so maybe some of those were 3 jet as well. I think it's just the addition of a mid jet rather than only being a low (pilot) and high (main). Generally speaking, everybody seems to prefer the Mikunis over the Keihins, be it in stock form or aftermarket racing carb form, and I think this is all the more true when the Keihin being considered is a 3 jet version as that only adds to the confusion with another variable in the mix. Also, with the Mikunis having been substantially more popular all these decades, the knowledge/experience base out there is a lot more dialed in for baseline jetting predictions and parts support. Knock on wood, my twin carb Keihins are still working fine after 14 years with this ski (I am 2nd owner) including swapping another 750 engine in once the original engine died from the oil injection lines splitting during a ride. So despite having the engine and carbs out, I haven't taken the carbs apart out of fear of screwing something up and needing some part that's discontinued. For whatever it's worth, I haven't missed a winter without winterizing the ski with Stabilt added to the fuel tank.

[@FastFlash-dg2fc]

What rebuild brand do you recommend for the CDK2?

[@jetskijim007]

Keihin only. They are pricey, but they wipl last many years of trouble free service.

[@trussell3669]

Hey Jimmy, I have a question for you. I have a 2013 JK that I'm doing hemi swap in. I bought a 2022 392 with 8 speed transmission out of a Durango SRT. Using a Jeep Speed shop swap kit. I'm disabled and am going to tackle it myself. If you happen to need a project. I can't think of anyone I'd rather have do it and I'm in Minneapolis.I could throw in the engine and transmission with 95k miles on them. I know it's a long shot but hell.I'm hoping I can manifest it lol. Thanks Trent

[@ozzielinkin]

Second time watching the video.

[@jetskijim007]

Right on. Yeah, i packed a lot of info in that video. :-)

[@ruffpizza]

Was rebuilding the carbs for my 96 spx and I have a couple questions…I got the pop off set correctly but it seems like both needles slowly leaked over the course of ten mins or so and never held pressure. My carb kit didn’t come with a new needle and seat. Should I get new ones? Also, on the pto side I didn’t have to plug the fuel return line to test the pop off…is this right? I feel like my return line is clogged somehow…

[@jetskijim007]

yes, the factory mikuni carb kits come with a new needle. The seats don't usually wear out though, but they are replaceable as well. You are correct on the return line being plugged. :-)

[@philipsweet71]

I have a 2005 Yamaha AR210. Has twin 135hp 2stroke 3 cylinder motors. I’m a 1st time boat and 2stroke owner. Believe it has mikuni carbs stock. Looking for best reccomendation for carb rebuild kits(stock)

[@jetskijim007]

Get the Actual Mikuni brand rebuild kits, you will end with headaches if you don't. The chinese kits come close, but they are not near as good quality.

[@philipsweet71]

Well, I’ve found it very hard to find parts for this boat. I dont have a service manual but can rebuild a carb. Any idea what model or size mikuni’s come on these motors? There’s 3 carbs/motor