650/X-2 Best carb for 650sx

[dbattersby20]

I bought my first jet ski last winter and I was looking to do some upgrades and rebuilding starting with the carb. What is the best carb to put on a 650sx? is a SBN-44 the best, how hard is it to fit one on?

 

[kevbo]

The best carb for any stock ported/stock ignition 650 is the stock 91-93 carb and manifold. You can use a 92-95 750sx carb with the 91 650 manifold if a low pitch prop is used. A 44sbn on an aftermarket manifold will tend to act too large (tuning wise) but lots of people have run them successfully.

 

[oldschooldrool]

I have a couple 650sx's and started with the stock 28mm and went to a sbn mikuni 44 from a superjet and aftermarker intake manifold. worked much better. then switched to a mikuni sbn 46. same topend power but i lost on the bottom end. boggy starts, not as snappy. then switched to a aftermarker dual intake manifold with dual sbn mikuni 38s. that has been the best setup yet. gained more bottom and midrange power and snap. good top speed. most people that i have ridden with are suprised by the power and speed. I should note that i have had improse reline my jet pump and and am running a 13-16 impros skat prop.

 

[dbattersby20]

What intake mani did you use to set up the dual 38's? and did you bore out your stock mani to fit the sbn-44 or is there a bolt-on aftermarket one?

 

[oldschooldrool]

What intake mani did you use to set up the dual 38's? and did you bore out your stock mani to fit the sbn-44 or is there a bolt-on aftermarket one?

the dual intake manifold is a west coast I think and the flame arrestors are prok for the dual 38s. there is a dual 38 setup on ebay right now with west coast velocity stacks for $209 that looks very simmilar. now the sbn 44 single carb I used with an aftermarket intake designed for mikuni it does not have a name. I like the ocean pro single intake but it is very rare and hard to find. did not use the stock manifold.

 

[dbattersby20]

Seeing as I've never even tried to tune a carb on a jet ski I'm hesitant to get the dual 38s. Do you think it would be a problem for me to set them up? or would it just be simpler to stick with a single 44?

 

[Wilke]

Get a single, duals are nice, but IMO the small benefit over a single isn't worth the extra effort to get them dialed in - especially if you don't have any prior tuning experience.

Get a 38mm keihin cdkII and you don't even need a new manifold, just bore out the stock one. And with the keihin if you get one that came off a 650 to start with (any 650 after '91 I think) you won't even need to re-jet.

 

[Zack22]

Does anyone have a 38mm from a 650? I have the crappy 28mm on my 89 650sx and I think it’s pooping out on me

 

[Zack22]

I know this is a very old thread but I think it’s worth a shot

 

[WFO Speedracer]

I am going to give you a word of advice here, take it or leave it , most peoiple don't know this but the carbs and exhaust are a matched set on 650SX's this is why a lot of people are disappointed when bolting on a 44 carb.

The skis that came with 28mm carbs also came with exhaust manifolds with small openings and no diverter and exhaust pipes with 1 7/8" exits, waterboxes were alos 1/7\8" the newer skis that had the 38 carbs had larger diverter style exhaust manifolds and 2" openings on the exhaust exits and on the waterbox , to get the best bang for the buck when installing the 44 carb you need to at the least change the exhaust manifold, and if you can swing it modify or replace the stock exhaust and waterbox.

Bolting a 44 carb on your ski is probably not going to do what you want it to do.,

 

[fastgtfairlane]

My 93 x2 with a silver, larger exhaust manifold, Westcoast pipe, r&d intake manifold with a sbn 44, and a hooker 9/15 impeller was a very solid little setup with the stock engine would go 43mph

 

[WFO Speedracer]

I would go with a 38 kehin if you don't want to change everything else, you can use the stock manifold and bore it to fit the 38 carb and it will run good like that, or just ifind a newer 650 intake and bolt it on, if you go with anything bigger the exhaust is going to hinder the performance of the ski badly.


There is a lot of good info on modifying a 650 SX in the thread below.

Turn your stock slow 37MPH 650SX into a respectable 47MPH SKI for around $200 - PWCToday

Here you can have a thread all to yourself, about whatever PWC build you are working on.

www.pwctoday.com

 

[Zack22]

Ok thank you I’m not looking too mod it too much right now so this is perfect I’m just looking on getting this dang 28mm keihin off so I can have fun with it because my ski runs and idles great but I can’t rev it up too full rpm’s it won’t even exceed 5mph in the water

 

[WFO Speedracer]

If it won't do better than 5MPH I would be checking other things out as well.

 

[sturat]

I always had great luck with dual sbn38 on dual singles. Super easy to dial in if you add a second pulse nipple to the cases and run each cylinder as an independent unit.

 

[Zack22]

If you have any clue why it runs like crap please let me know because I’ve rebuilt my stock carb and it still just won’t go. It runs and idles but when I give it some gas it sorta sounds like ringgg ringggg ringgg and from 1/4 throttle and up too full that’s all it does.

 

[WFO Speedracer]

I can't help you from that description, is it revving and not going anywhere or is it not revving ? If is revving then the carb is doing it's job and the pump is not sealed or the impeller is damaged or both. If it is not revving that could be either carb, reeds, ignition or low compression.

 

[Zack22]

Idles great, I just put a brand new stater on, and I have 147 psi on each cylinder, the reads look good to me but I am no expert but I’m not 100% sure. When I rebuild the engine, I took it to the water and took it for a ride After I let it warm up it was acting strange sometimes when I went on the gas, it would takeoff like it normally should and revved out completely and then I would ride it for five minutes Come back in and kill it. And the next time I go up to start it runs like crap and sounds like the carb is trying too clear itself out

 

[WFO Speedracer]

That counld be aq bad needle in the carb not seating or it could be a bad CDI- coil, run it and when it starts acting up turn the fuel knob to off, does it start to run better and pickup before it runs out of fuel, if it does it's the carb that needs help , if it doesn't it's probably the CDI - coil although I jhave seen stators do this as well, was it a used OEM stator or a new aftermarket stator ?

 

[Zack22]

It is an aftermarket stater because when I was a rebuilding the engine, I accidentally messed up and broke a bunch of wires while taking the flywheel off, but I’m not expecting the fly wheel because it was doing the exact same thing before I replaced it