Loading Up When Tilted To The Right, Novi 46mm

[robertg]

I was having this problem last year and didn't solve it yet. I have dual Novi 46mm carbs on a Superjet and it loads up when it is tipped on it's right side and not on the left. The carbs are mounted with the fuel pumps out so they are down when it does this.

I was going to email Novi but I figured I would try here first.

 

[waxhead]

its dripping fuel out the venture into the engine
i would cheak the small clear plastic part on the mettering block
you know the part that unscrews out and have the jets under
i would say you have ethier a broken one or somthing sitting under it allowing the fuel to drip past

 

[robertg]

I was thinking of that, I don't think fuel could come from anywhere else. They look good but changing them couldn't hurt.

 

[waxhead]

yeah change them and try it
sometimes that on its side thing can really test you
i chased it for ages one time and then found that
maybe a small air leak in the diaphram may cause that as well
check those

 

[robertg]

I was just checking and the little flapper is not available seperate. I hope the whole block is cheap. The diaphragms are only $3.50 in Canada. I am going to get new needle valves also.

 

[keefer]

its dripping fuel out the venture into the engine
i would cheak the small clear plastic part on the mettering block
you know the part that unscrews out and have the jets under
i would say you have ethier a broken one or somthing sitting under it allowing the fuel to drip past

The official name for the flapper valves is the "anti siphon valve". I have read somewhere that you can double them up but do not exceed 2 valves. I have experienced this problem with all SBN mikuni carbs if you exert enough g's by slamming the boat in a turn or landing on the side with the fuel pump side of the carbs down. I have never been able to get rid of it completely. Not that I would wish this problem on anyone, it is good to hear that someone else has experienced this and that I am not crazy. It took me a while before anyone had ever heard of this when I first noticed this problem several years ago. I also think it has something to do with lowering the pop off pressure and running bigger needle & seats. I have gone back to 2.0 NS and run about 23 pounds pop off. I still get it but it does not seem quite as bad. Thats my 2 cents worth. LMK how you make out solving this. And if anyone else has any ideas I would like to hear other solutions.

 

[Matt_E]

or landing on the side with the fuel pump side of the carbs down.

Thanks for explaining one of those unexplained phenomena about my ski to me. It would be all loaded up, not wanting to rev after hitting the water just right (or wrong) after a stab. Which just happens to be on the fuel pump side.

 

[keefer]

I was just checking and the little flapper is not available seperate. I hope the whole block is cheap. The diaphragms are only $3.50 in Canada. I am going to get new needle valves also.

I found the package with the anti siphon valves that I bought a few years ago. I don't remember where I bought them, Riva maybe, but I bet Paul at Jr. Magoo's can get them. http://www.jrmagoos.com/ The following is a Mikuni part number and should still be available.

N100-606-130 Anti Siphon Valve

 

[keefer]

Thanks for explaining one of those unexplained phenomena about my ski to me. It would be all loaded up, not wanting to rev after hitting the water just right (or wrong) after a stab. Which just happens to be on the fuel pump side.

No prob, this still drives me crazy sometimes when pulling stabs too. I just have to anticipate it and blip the throttle a few times to clean it out. If it happens too often I have even fouled plugs. I wonder if this happens only on the various mikuni body variant carbs or do some of the other billet body types have the same problem? Surely lots of other people have had this problem. I had asked several people some years ago but did not get much feeback.

 

[Matt_E]

It would mystify me....the motor would barely rev, making me wonder what was going on. Turn it off, wait a couple of secs, and it would run great.

 

[robertg]

I remember reading something about the anti-siphon valve, I think it was in the Mikuni manual. I will try to double them up also. If the valve caused too much restriction I guess it would starve the fuel supply.

 

[steve802cc]

Robert,
Try this.
Start you ski with the flame arresters off so you can see down the throat of the carb.
If you look down the throats at idle fuel SHOULD NOT be dripping from the bomb site(inner venturi). If it is then as others have said your pop-off is too low or fuel is leaking by your anti-siphon valve. This can sometimes be caused by a motor that vibrates a lot at idle.
Don't forget to check the condition of the needle.

I often double up on the anti-siphon valves and also tend to run higher pop-offs.

Good luck.
Steve

 

[robertg]

Robert,
Try this.
Start you ski with the flame arresters off so you can see down the throat of the carb.
If you look down the throats at idle fuel SHOULD NOT be dripping from the bomb site(inner venturi). If it is then as others have said your pop-off is too low or fuel is leaking by your anti-siphon valve. This can sometimes be caused by a motor that vibrates a lot at idle.
Don't forget to check the condition of the needle.

I often double up on the anti-siphon valves and also tend to run higher pop-offs.

Good luck.
Steve

I remember trying that last year but I didn't see any drops. It runs perfect when it is upright or lying on the left side so gravity must have something to do with it. I ordered two new anti siphon valves to go with the new diaphragms and needles. If it still does it I will raise my pop off and double my anti siphon valves

 

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