Rebuilding Carbs on my LX210

[dordelli]

Last season my boat was stalling when applying full throttle from a dead stop, I am assuming I need a carb rebuild as I am pretty sure it has never been done to this boat. I have replaced my fuel filters and tried seafoam, still same symptons. My question is after watching a bunch of youtube videos, do I need to soak my carbs in carb cleaner, no one mentions this at all? And do most of you check the popoff or reuse the existing springs, how important is this step as I would need to buy a pop-off tester.

And lastly, after watching the online videos, looks pretty straight forward and quick job but anything to watch out for in removing and installing the carbs from the engine, do the carbs come off individually, are their additional gaskets needed to attach to the motor that are not included in the Mikuni rebuild kit?

Any advise or tips would be much appreciated. I am not a skilled mechanic but bought this boat knowing I'd have to do some work to it and learn as I go.

 

[Bruce]

How much SeaFoam did you use? I found that adding a can every time I filled up made a huge difference. That plus changing the fuel filters and spark plugs had the engines running perfectly.

Are you planning to change the oil lines while you have the carbs off?

I thought about rebuilding the carbs on my LX210 but never did it because of the need to make sure the mix was just right and the oil was flowing perfectly afterward. If I had I was going to hire a family friend who is a jet ski mechanic to help.

 

[4x15mph]

If you don't know when the carbs were last done, I would definitely rebuild them so they are clean and functional. Your problem could still be fuel delivery (fuel filter), fuel pickup, or other. Is it both engines? Have you replaced the plugs?

For carb replacement, my thoughts

• Use OEM Mikuni rebuild kits. Absolutely do this given everything I have read. Don't cut a corner here. There are 3 carbs in each rack (2) so you will need 6 carbs kits if you are doing both sides. I would advise doing one rack at a time so you can always refer to the other side on reassembly.
• Take pictures as you remove and break down the one rack.
• The kit will come with new springs. I would not advise using them since you will need to do pop-off testing and this is where it can be a disaster. Lots of lean or rich conditions and I blame the spring/jet changes that some people do. Just clean the jet needles.
• The carbs are joined together with fuel line that is secured by oetiker clamps. You will need to take the fuel lines off so have new fuel line and clamps or at least new clamps. I think it is a good time to replace the small runs of fuel line.
• I soaked the different carb parts in carb cleaner. I used a gallon container of Berryman Chem-dip carb cleaner. It came with a basket that you lower into the can. Worked great
• IMPORTANT - the service manual tells you the exact number of turns to use for the high speed and low speed screws. Use these! Some will say to count the number of screw turns when you take out each jet and while I would do this and record your number, I would only use that as a reference to see how different they are from the manual, suggested turns. Use the suggestion and tune from there
• IMPORTANT - Use all new gaskets when putting the carb racks back on the engine and when putting the flame arrestor back on top of the carb rack. You don't want air leaks. These gaskets (top/bottom of carb racks) do not come in the Mikuni carb kits that I am familiar with. I had to buy them separate the kit that i bought included other gaskets that I didn't need.

Are you using the GroupK air/fuel separator? My other advise would be to look at putting that in while doing this work. Easy starting and no air in the fuel lines when on an emptier tank or doing hard turns. Check it out

 

[Speedling]

The above post is spot on! Do not deviate!
It's not that hard to do but will take a little time to do right.

 

[dordelli]

@Bruce, yes I changed fuel filters and plugs, and used (I think) 3 cans of sea foam in a full tank, weird part was the stalls seemed more frequent after that treatment, maybe that showed it was working by breaking up deposits, not sure? Yes I may address the oil lines at same time. I know this is usually job one on these boats, but the lines do seem secure and have some slack and are not brittle.

 

[dordelli]

@4x15, thanks for the incredibly detailed tips, after reading ur posts was hoping to hear from you!
-Yes the issue is with both engines, one more than the other but don't recall if it was Port or Sb.
- Yes I did get the mikuni rebuild kits.
-I've watched videos of the Popoff test and the gauge is $50, I may buy one to have just in case. U have any idea what the expected reading should be?
-Yes will replace the short fuel lines and need to get the oetiker clamp. What size are these lines?
-On the soaking, It is weird that I watched about 10 different videos on rebuilding carbs and not one mentioned this step. None addressed the high speed and low speed screws either even the SBT video and this seems the most important step where u can F up the job.
-So I need 4 other gaskets, 2 for each side, one for the carb rack to engine and other for flame arrester?
- No I do not have a Group K air/fuel separator. Would love to fix the hard starting and may consider it, I installed the fuel primer bulbs and didn't seem to help at all.

Sorry for so many questions, I bought this boat from original owner and who never did any upgrades let alone regular maintenance. I paid a great price knowing I would need to get my hands dirty especially in the engine compartment at some point. Last year I basically rebuilt the trailer (new hubs, new winch, jack, receiver, lights, sagging fenders and a spare). Then inside the boat, new radio, Bimini top, horn, fuel gauge, plug fix and the two tone Hydro Turf was a dramatic change. Still left to do, carbs, oil lines and the slow water leak on the port engine (new bearing housings) also need to get into the bilge and check out the pump as I am sure it's stock and with the leak, need it to be reliable.

Thanks for all the advice!!

 

[4x15mph]

@dordelli
- I don't recommend changing the springs so you would not need a pop-off tester. If you decided to go that route, I will not be any help there.
- I don't know the size of each piece of fuel line that runs betwen the carbs. It is a couple of inches so I just bought a couple of feet and cut what I needed. You can probably read the type on the existing fuel line which is what I did. I then visited a west marine store to buy the fuel line. Coast guard approved line is expensive as you will find.
- Yes, on the gaskets.
- PM me if you have specific questions and we can even set up a time for you to call me. I could be in my boat and help answer any additional specifics.

 

[dordelli]

Looking at this parts diagram, do I need gasket #15 and 2x of #17 for each engine? Or do I need #16 as well?

http://www.yamahasportsplaza.com/oemparts/a/yam/50039e75f870021f60a11436/repair-kit-1

 

[dordelli]

Thanks @4x15mph, really appreciate your help on this forum and the offer to talk on the phone, super cool of you! I think I should be able to figure out the carbs, but may pick your brain when I am ready to tackle the bearing housings.

 

[itsdgm]

Hi @dordelli i just saw your post and realized that you're in OC too. I rebuilt the mikuni carbs in my previous (sea doo) boat. I found some valuable info on mikuni's website regarding how to tune/jet them and how to fix issues based on the engines rpm when the issue happens. Also, I found a great shop in our area, pm me if you have any questions.

 

[4x15mph]

Looking at this parts diagram, do I need gasket #15 and 2x of #17 for each engine? Or do I need #16 as well?

http://www.yamahasportsplaza.com/oemparts/a/yam/50039e75f870021f60a11436/repair-kit-1

#16 gasket is not required.

 

[dordelli]

Hi @dordelli i just saw your post and realized that you're in OC too. I rebuilt the mikuni carbs in my previous (sea doo) boat. I found some valuable info on mikuni's website regarding how to tune/jet them and how to fix issues based on the engines rpm when the issue happens. Also, I found a great shop in our area, pm me if you have any questions.

Nice to meet you Dennis, I'm in Fountain Valley! Yeah I guess the Mikuni website would prob be a good place to start, I'll check it out! And a good shop is hard to find, where do u go?

Don't know any other jetboaters in OC, so where do you boat mostly? We go to Laughlin/Mohave a few times a year and have launched out of Newport and Long Beach a couple times (but my boat is not a great ocean boat) but that's it so far..

 

[4x15mph]

Mikuni carb manual attached - I reviewed this along with the service manual before tackling.

 

[itsdgm]

Nice to meet you Dennis, I'm in Fountain Valley! Yeah I guess the Mikuni website would prob be a good place to start, I'll check it out! And a good shop is hard to find, where do u go?

Don't know any other jetboaters in OC, so where do you boat mostly? We go to Laughlin/Mohave a few times a year and have launched out of Newport and Long Beach a couple times (but my boat is not a great ocean boat) but that's it so far..

We go to Laughlin a couple of times a year and are usually on the water 3-4 days each trip. Some years I'll do a pre-season shakedown at Elsinore.

Over all of my years of owning skis and jet boats I've only physically taken things into a shop (other than minor warranty/dealer work) twice. One was a Mikuni SBN carb for technical advice and more recently dropping off an engine to have it diagnosed for having zero compression in a cylinder (pretty sure it's either a sticky valve or piston ring) That being said, the shop that I've used Both times is Jet Works in Newport Beach. Robert is the owner/operator. He really takes the time to get to know your situation and has been there for about 25 years. Tell him Dennis sent you

 

[4x15mph]

This was another great reference that I used, thanks to SBT.

http://www.shopsbt.com/pdfs/mikunisbn.pdf

 

[heloskick]

Hello,

Does anyone have or know the proper adjustment to the carbs for a LX2000? Aka number of turns for both the high speed and low speed screw adjustments.

Thanks!

 

[the MfM]

Low 1.25, all

High .75, #1&3 cylinders .... 1 for #3

I think I set pop off pressure @50psi