Having a low speed stumble on 13 SJ, how to clean carbs? Causing any damage?

Hey guys, I have an all stock 2013 Superjet that has really low hours and has not been used all that much before I got it. I have taken it out twice and noticed that at low speeds and throttle if you give it too much throttle it sputters and even dies at times if it is cold. Once I get it up to speed there is no issues running it at any speed or throttle level. Spark plugs are brand new on her. Is this like a low speed jet clog? Can I just shoott he carbs with some carb cleaner and will it fix it? Also is this operating condition causing any harm to the engine running it as is? A minor issue but overall the ski runs great!
 
Location
DC
Hey guys, I have an all stock 2013 Superjet that has really low hours and has not been used all that much before I got it. I have taken it out twice and noticed that at low speeds and throttle if you give it too much throttle it sputters and even dies at times if it is cold. Once I get it up to speed there is no issues running it at any speed or throttle level. Spark plugs are brand new on her. Is this like a low speed jet clog? Can I just shoott he carbs with some carb cleaner and will it fix it? Also is this operating condition causing any harm to the engine running it as is? A minor issue but overall the ski runs great!

saw it last weekend on a buddies ‘15. No clue what the solution is. From what I have read it sounds like a lean fuel issue.
 
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smoofers

Rockin' the SQUARE!!!!
Site Supporter
Location
Granbury, TX
To both of the above posters: Sounds like a fuel issue. I'd suggest both of you find somebody local to walk you through everything that needs to be checked. On a stock SJ it's pretty straight forward to get them to run properly. Verify jetting is correct. Properly rebuild your carbs, this includes verifying pop-off pressure. Set the screws back to factory settings, get pop-off close to stock, and you should be fine. If not, you did something wrong. Walk us through your process and we'll help you out.

EDIT: To add, again for both of you, read this. Learn it. Love it:

http://mikuni.com/pdf/sbn_manual.pdf
 
Location
DC
To both of the above posters: Sounds like a fuel issue. I'd suggest both of you find somebody local to walk you through everything that needs to be checked. On a stock SJ it's pretty straight forward to get them to run properly. Verify jetting is correct. Properly rebuild your carbs, this includes verifying pop-off pressure. Set the screws back to factory settings, get pop-off close to stock, and you should be fine. If not, you did something wrong. Walk us through your process and we'll help you out.

Rebuilt carbs properly with OEM mikuni parts and new needles and seats, jets, etc.
 
Last edited:

smoofers

Rockin' the SQUARE!!!!
Site Supporter
Location
Granbury, TX
You can build a tester easily. The pic below shows my setup for testing pop off and pressure testing cases. All you need is a pressure gauge with a decent enough resolution like the 0-60 psi one below (both gauges I found at tractor supply). You’ll also need a tee fitting, a schraeder valve (also available at TSC) a barb, some hose and a pump. I use a rock shox shock pump. The 0-100psi tester I just put together to measure pop off on a set of GP1200R carbs I just rebuilt (stock pop off is 75psi).

EF1FADE4-E9BF-4D82-BA30-CFB4A804DA70.jpeg
 
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