Super Jet 2009 Superjet - Off idle bog? Battery?

[spdtrpl]

Just bought a 2009 Superjet, it is totally stock, totally a blast to ride, and low hours... so far
Couple of questions:


Off idle bog?
It fires up immeduiately and runs great at anything over 1/4 throttle but hesitates/bogs just off idle - any ideas?
I suspect i need to lean out the low speed jetting, any advice and preferably pictures on how to access the low speed jets/adjustment would be great.

Battery?
As mentioned ski starts right up every time, starter turns the motor over fast, and open circuit voltage on the battery seems a healthy 13.7 volt. The thing that's weird is that I have 2 battery tenders that I know are working fine (as they work fine on my motorbikes) but connected to the ski they stay on red for 36-48 hours and never go green.. Normally a Battery Tender will get the battery up to 'good' in much less time. So is it time for a new battery?

Thanks for any advice!

 

[MikeyB]

It sounds like your running lean on the low speed adjuster. Backing out the screws with the letter 'L' stamped by them will richen the low speed (hesitation=lean, blubber=rich). Try pulling the spark plugs next time you have it out to see how the color looks on the ends of them. You want them to be brown.

From what I recall the low speed adjuster effects idle mixture, pop-off pressure/low speed jet effects idle to 1/4 throttle, high speed jet effects 1/3 to 3/4 throttle and the high speed adjuster effects 3/4 to wide open.

Here is the link to the sbn manual http://www.mikuni.com/pdf/sbn_manual.pdf

 

[fst89lx]

does it hesitate or bog??

If you have a lean hesitation, the ski will fall on its face, I had one that if I was running at 1/4 throttle or below and I pinned it it felt like the ski just shut off for a sec and then it would take off. The fix is to richen up the low speed circuit. I swapped in a different spring to lower the pop off pressure and the problem was solved.

with a bog you will still have a loss of power but it will sound and feel different than a hesitation. I don't really know how to describe it, you give it throttle and it seems like it takes a second or two for the RPM's to catch up and the ski to take off.

Now this may just be because I am a cheap ass but I would run the battery until it stops working Try leaving the battery tender off of it and see if the battery is holding its charge between riding days.

 

[RedTurboMr2]

Since you have a newer superjet, you'll have to remove the tamper caps on the carbs to access the low and high speed screws. I've tried two methods to remove the caps. First method was to drill a pilot hole, then put in a screw and use some vise grips to break it loose. That method only worked on one cap. I then drilled a bunch of pilot holes in a straight line, used a big flat head screw driver and broke the others loose. I recommend removing the stock adjusters and switching them for T adjusters.

 

[fst89lx]

It sounds like your running lean on the low speed adjuster. Backing out the screws with the letter 'L' stamped by them will richen the low speed (hesitation=lean, blubber=rich). Try pulling the spark plugs next time you have it out to see how the color looks on the ends of them. You want them to be brown.

From what I recall the low speed adjuster effects idle mixture, pop-off pressure/low speed jet effects idle to 1/4 throttle, high speed jet effects 1/3 to 3/4 throttle and the high speed adjuster effects 3/4 to wide open.

Here is the link to the sbn manual http://www.mikuni.com/pdf/sbn_manual.pdf

I agree with the bold text here. Don't try to tune this with the low speed adjuster, either a low speed jet or pop off change is needed.

 

[MikeyB]

[/B]

I agree with the bold text here. Don't try to tune this with the low speed adjuster, either a low speed jet or pop off change is needed.

I dont think it would hurt if he tried richening up the low speed a bit with the screw to see if that helps his problem, it just seems weird that he would have to change out popoff/jets on a stock ski unless hes at some weird elevation or it has aftermarket flame arrestors?

 

[spdtrpl]

Thanks for the replies - Ski was sold and used previously in Alaska (!) and I'm in sunny Houston, TX. Original owner tells me the ski is unmodified, but who knows if the Alaskan dealer jetted it for cold temps.
Guess I'll take the carbs off and remove the low/high speed cover plates and try small adjustments to the low speed first. Who sells T- top or longer adjustment screws?

 

[MikeyB]

Both of my skis had the caps on the adjustment screws, but I gently wiggled them off with a flat head without pulling the carbs or anything, maybe I got lucky

 

[fst89lx]

I dont think it would hurt if he tried richening up the low speed a bit with the screw to see if that helps his problem, it just seems weird that he would have to change out popoff/jets on a stock ski unless hes at some weird elevation or it has aftermarket flame arrestors?

No, its not gonna hurt anything but I don't think it'll solve his problem. Also We still don't know if its a rich or lean condition he is experiencing.

At the bottom of pg 13, going on into pg 14 in the mikuni manual, it explains the low speed adjuster. I would advise him to read that, and this from group K's website:

LOW SPEED ADJUSTMENT 0% to 35% throttle range - In 90% of all cases, the low speed mixture screw can be accurately set without riding the machine. Secure the boat on a submerged trailer or standing in about three feet of water. With the engine completely warmed up, set the carb up to a slightly higher than normal steady idle. Turn the low speed mixture screw in or out in 1/4 turn increments. As you get closer to the ideal setting, the engine rpm's will increase. If the idle speed is increased by this mixture adjustment, turn the idle speed adjustment screw down and continue the same process in 1/8 turn increments. At the ideal mixture setting, 1/8 turn in a richer or leaner direction will cause a very un-steady idle and cause the engine to die. To confirm your perfect low speed mixture setting, touch the kill button during idling...and then touch the start button about ten seconds later. The engine should restart instantly and idle steadily without touching the throttle.

Now you're done with the low speed screw and if the machine is still not right then its time to change jets or springs.

 

[aramis]

Be careful when talking about what adjustment affects what, and at what % of throttle...there is a big difference between what an adjustment AFFECTS, and the ORDER in which to make the adjustments.

the low speed screw should be adjusted first to get a good idle...but it is then in play ALL THE WAY TO FULL THROTTLE. Pop-off comes into play just off idle, but it is then in play ALL THE WAY TO FULL THROTTLE. High speed jet starts to have an affect at 1/3 throttle, but then...you guessed it...it is in play ALL THE WAY TO FULL THROTTLE.

Once any adjustment kicks in, it then has a contribution all the way up to and including full throttle. Everybody seems to miss this.

For example, this is why you can somewhat fix a pop-off issue by opening the low speed screw, but then it may load up at idle...and may be too rich at the top too.

Again, follow the tuning ORDER that mikuni recommends...and tune that throttle position range accordingly...but remember that an adjustment doesn't ever stop having an AFFECT once it kicks in. Tuning became much more obvious once I realized this.

The fuel flow chart in the SBN manual is very clear about this.

 

[fst89lx]

I know what you are saying about the different circuits having an effect all the way up to full throttle, and I agree with you. However I would like to point out that the Mikuni tuning manual does state that "The low speed adjuster has no effect past 1/3 throttle" and "The regulator portion has no tuning effect past 1/4 throttle, although it continues to control the fuel supply"

So in this case you can have the low speed screw all the way out to (as rich as possible) and past 1/3 throttle it won't make any difference.

Either way, like I said earlier set the low speed adjuster so his idle is good, and then see if the problem is still there. If it is, progress into jet/spring changes.

Also, I would imagine that the ski was at some point jetted for cold temps, and possibly elevation. If it was jetted for cold weather in Alaska, it will be rich in hot weather in Texas (cold air is more dense than warm air so your A/F ratio goes lean and you must richen the jets to compensate)

Be careful when talking about what adjustment affects what, and at what % of throttle...there is a big difference between what an adjustment AFFECTS, and the ORDER in which to make the adjustments.

the low speed screw should be adjusted first to get a good idle...but it is then in play ALL THE WAY TO FULL THROTTLE. Pop-off comes into play just off idle, but it is then in play ALL THE WAY TO FULL THROTTLE. High speed jet starts to have an affect at 1/3 throttle, but then...you guessed it...it is in play ALL THE WAY TO FULL THROTTLE.

Once any adjustment kicks in, it then has a contribution all the way up to and including full throttle. Everybody seems to miss this.

For example, this is why you can somewhat fix a pop-off issue by opening the low speed screw, but then it may load up at idle...and may be too rich at the top too.

Again, follow the tuning ORDER that mikuni recommends...and tune that throttle position range accordingly...but remember that an adjustment doesn't ever stop having an AFFECT once it kicks in. Tuning became much more obvious once I realized this.

The fuel flow chart in the SBN manual is very clear about this.