88 650sx troubleshooting

[KIDbilly]

I am new to jet ski lingo so apologies for potentially butchering part names.

I have an 88' 650sx which I do not have much history on, but the ski has ran recently and it ran great. However, it has some starting/idle issues and the bigger issue is about after 20 minutes or so (it varies each time) the ski will stop running out in the water.

I have done the following:

• Compression check - good
• cleaned and rebuilt carb
• tightened all exhaust clamps
• New fuel
• New cooling lines

I have noticed two things.

1. I am getting fuel into the haul of the ski now and it seems to be leaking from the front of the round body carb. Maybe this is causing the issue as it is losing fuel pressure? However, I have taken it back apart and cleaned around that plastic cap, but it is still leaking.
   
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2. The red double buddle exhaust "host", not sure what it is called, that connects the water box to the exhaust outlet never seems to sit properly. I am not sure what that does, but maybe replacing that with something better would ensure no exhaust leak is happening.
   
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Aftermarket parts that I know of are:

• PJS exhaust manifold and exhaust pipe
• Cylinder head
• Ride plate and potentially aftermarket pump.

Thanks and looking forward to your support.

 

[WFO Speedracer]

Two things a jet ski won't run correctly with are exhaust leaks and fuel leaks , each contaminates the air the ski is running on and makes it run extremely rich , an exhaust leak will make it cut off completely , the red thing is called an Aquamuff, it is a silencer , you can take it off and it will just be a tad louder as they never worked that well to start with , as for the fuel leak, ditch that carb and get an SBN Mikuni carb and your issues will go completely away .

A 44 carb off of a Yamaha 650 will work and it is already jetted really close , if not the specs are 140 main jet , 125 pilot 2.0 needle and seat and an 80 gram spring , you ,may have to tweak it a bit but that usually runs pretty well .

 

[KIDbilly]

Two things a jet ski won't run correctly with are exhaust leaks and fuel leaks , each contaminates the air the ski is running on and makes it run extremely rich , an exhaust leak will make it cut off completely , the red thing is called an Aquamuff, it is a silencer , you can take it off and it will just be a tad louder as they never worked that well to start with , as for the fuel leak, ditch that carb and get an SBN Mikuni carb and your issues will go completely away .

A 44 carb off of a Yamaha 650 will work and it is already jetted really close , if not the specs are 140 main jet , 125 pilot 2.0 needle and seat and an 80 gram spring , you ,may have to tweak it a bit but that usually runs pretty well .

Awesome, thanks for the info. If I remove the Aquamuff is there anything I need to replace it with? The ski is already loud even with that on.

Regarding the 44mm carb, will I need a different intake manifold as well?

 

[WFO Speedracer]

Does the top of that carb have three bolts or four , if it has four tou are good to go, if it has three you will need another manifold , I can't tell from the pics .

 

[Myself]

Why would anybody swap a round body carb ONTO a 650sx??

 

[KIDbilly]

Does the top of that carb have three bolts or four , if it has four tou are good to go, if it has three you will need another manifold , I can't tell from the pics .

The part of the carb that attaches to the intake manifold has 2 bolts. The top that connects to an air filter has 4.

Why would anybody swap a round body carb ONTO a 650sx??

Great question, wish I had more history on the ski.

 

[WFO Speedracer]

You are good to go , just swap the carb .

 

[KIDbilly]

You are good to go , just swap the carb .

Any suggestions on best spot to find the 44 carb off of a Yamaha 650, or a part number? Am I looking for one with the fuel pump on the carb itself or external fuel pump?

I see this one on ebay, but not sure what all I should be looking for it to have or not have. Super BN 44mm Carburetor 1990-1995

 

[Myself]

That's the right style. Just an FYI.........I've taken 2 of the cheapo aftermarket carbs OFF of customer skis this summer already. Customers did it themselves and ended up at my shop anyway. I couldn't EVEN make them run right. Rebuilt the oem carbs and all is well.

 

[KIDbilly]

That's the right style. Just an FYI.........I've taken 2 of the cheapo aftermarket carbs OFF of customer skis this summer already. Customers did it themselves and ended up at my shop anyway. I couldn't EVEN make them run right. Rebuilt the oem carbs and all is well.

Where can I find an true OEM one?

 

[WFO Speedracer]

OEM Yamaha carb off of any 650 or 701 61X motor .

 

[WFO Speedracer]

The PJS pipe and Mariner head should run quite well , the head was installed backwards, it will run just fine that way, just letting you know.

I can't tell which exhaust manifold you have but you might want to pull the pipe and look at the diameter of the head pipe and the manifold and see how well they match , the manifold can be opened up a bit with a drill mounted sanding drum to better match the pipe if needed but , make sure it is a diverter type manifold , they run a lot better , also the later model silver manifolds have a larger diameter exit to match the larger diameter exhaust and tubing on the later model skis, they do make more power .

On the 650's the manifold and the carb were a matched set , the early model came with small 28 Kehin carbs and a smaller exit on the exhaust manifolds, those manifolds were non diverter style manifolds, on the later models they went to the diverter style manifolds and enlarged the carb to 38mm , when they did that they also enlarged the exhaust exit size on the manifolds and the exhaust hoses went from 1 7/8 to 2 " , they also went to rear exhaust .

A lot of guys bolt on stuff on 650's then wonder why it doesn't run all that well , the mismatch on the exhaust manifolds is a big reason why some modded 650's have disappointing results and others run very well, most people don't know this information , I have been modding 650's for nearly 40 years now .

The K&N filter , I am in the minority in that I like them but they only work well if they are kept dry, if you start fdoing a lot of tricks and getting water insdeie of the ski you will have issues with that filter , once they get wet they take a while to dry back out and work correctly, they do make covers for them called outerwears or K&N calls it a drycharger , at in rate if K&N made a wrap to go around the filter io keep it dry , you know there was an issue keeping those filters dry , I would suggest getting one on it at minimum .

44 BN carbs, they were bad about leaking at that spot , the plastic fuel inlet piece warps over time and you will never get it to seal after that, a lot of the aftermarket carbs from Jetsport and Westcoast had Aluminum fuel inlets they installed to alleviate that issue , you won't even find a mention of that now because all of that stuff predated the internet by many years.

 

[KIDbilly]

The PJS pipe and Mariner head should run quite well , the head was installed backwards, it will run just fine that way, just letting you know.

I can't tell which exhaust manifold you have but you might want to pull the pipe and look at the diameter of the head pipe and the manifold and see how well they match , the manifold can be opened up a bit with a drill mounted sanding drum to better match the pipe if needed but , make sure it is a diverter type manifold , they run a lot better , also the later model silver manifolds have a larger diameter exit to match the larger diameter exhaust and tubing on the later model skis, they do make more power .

On the 650's the manifold and the carb were a matched set , the early model came with small 28 Kehin carbs and a smaller exit on the exhaust manifolds, those manifolds were non diverter style manifolds, on the later models they went to the diverter style manifolds and enlarged the carb to 38mm , when they did that they also enlarged the exhaust exit size on the manifolds and the exhaust hoses went from 1 7/8 to 2 " , they also went to rear exhaust .

A lot of guys bolt on stuff on 650's then wonder why it doesn't run all that well , the mismatch on the exhaust manifolds is a big reason why some modded 650's have disappointing results and others run very well, most people don't know this information , I have been modding 650's for nearly 40 years now .

The K&N filter , I am in the minority in that I like them but they only work well if they are kept dry, if you start fdoing a lot of tricks and getting water insdeie of the ski you will have issues with that filter , once they get wet they take a while to dry back out and work correctly, they do make covers for them called outerwears or K&N calls it a drycharger , at in rate if K&N made a wrap to go around the filter io keep it dry , you know there was an issue keeping those filters dry , I would suggest getting one on it at minimum .

44 BN carbs, they were bad about leaking at that spot , the plastic fuel inlet piece warps over time and you will never get it to seal after that, a lot of the aftermarket carbs from Jetsport and Westcoast had Aluminum fuel inlets they installed to alleviate that issue , you won't even find a mention of that now because all of that stuff predated the internet by many years.

Awesome information, thanks @WFO Speedracer!

The exhaust manifold it also PJS, thought I do feel like the grommet (or whatever you would consider the rubber collar) that connects the head to the exhaust manifold is not great. I have tried putting new worm clamps on to get a nice tight fit, but I can't say I am 100% sold on its connections. Added some pictures.

Is there another filter you'd recommend vs the K&N. I will look into those drycharger.

Interesting about the head as it lined up with the cylinder coolant jackets that way, could the cylinder also run bi directionally?

 

[WFO Speedracer]

It will run either way , just an observation, I would leave it alone for now , a stock Yamaha flame arrestor of any 650 or 701 62T engine would work great .

Figer out the size and order a silicone coupler to replace that hose .

WWW.SILICONEINTAKES.COM.

 

[KIDbilly]

I should have asked this eariler, but which lines go where on the 44 carb? I assume the top one in the out/return, the bottom on is In/fuel in from cockpit, but what goes to the pulse? The line from the crankcase?

 

[WFO Speedracer]

Yes you have it correct