RX sputters off idle and stalls after decel

[95won]

Hi guys, I was given a 2000 RX carb ski. Replaced the tempo fuel lines, vent lines, and accelerator pump lines, eliminated the fuel selector, installed in line filters, thoroughly cleaned the carbs and rebuilt them with Mikuni kits, replaced spark plugs, cut back spark plug wires for fresh connection.....basically everything that needs done based on the information I've received from this forum. I took the ski out on the lake last Saturday and it started immediately. It bogged real bad when trying to take off from idle but as soon as it got going it ripped. I couldn't believe how fast it is! I could be on and off the throttle without any problems. The only issue I'm having is that when I'm flying around and then let off the gas completely for a while it will stall unless I work and baby the throttle to keep it running. If it does stall it starts right back up and I repeated this process many times.

Two possible problems that I am in the process of fixing are that I didn't know the Mikuni kit didn't come with the gasket between the carb and intake manifold so I reused the old ones, they were not in great shape. I since have them on order and they will be here Friday. The other possible issue is that I didn't have the special exhaust tool so the bottom nut was left loose. I have since ordered that and will be here Friday as well. Is it possible these are my problems?

I've read about the check valve on the Super BN carbs, they are new as they came in the kit, I'm skeptical that I need to double or triple them up as the ski is completely stock.

I greatly appreciate any thoughts or ideas, it's going back together Friday so I'd hate to miss something by then.

Tom

 

[mikidymac]

First off if you replaced the accelerator pump hose you might have lost the restrictor orifice. The symptom you are describing is exactly how it will act of the accelerator pump isn't working. Without the restrictor the pump will not fill properly.

I also do not believe in in-line fuel filters as I feel they can cause a restriction and are not a water separator and the stock strainer works just fine.

What do you mean "double or tipple up" the check valves?

 

[95won]

Thank you for the reply mikidymac. I am very surgical when I work on things like this and take great care to ensure no pieces go missing and everything gets laid out on a white table top in the direction and pattern that it was removed. First thing I checked last night was that both accelerator pump jets are working properly and they are, they both shoot fuel in a solid stream into the carb.

I certainly accept your opinion on the inline fuel filters, I purchased large volume premium filters and highly doubt that they are restricting fuel based on how well and fast it ran on the high RPM end which is when the engine would of required the most fuel. Please correct me if I'm wrong. As far as not being a water separator I can't argue with that.

In the Super BN manual there is a troubleshooting section that says if you have a bogging problem after a long decel you can double and triple up the anti-siphon valves. That makes perfect sense mechanically but on a stock ski I don't see why it would be required. Maybe it is, I just don't see it. I have attached a picture of that paragraph from the manual.



Any other ideas? Any thoughts on my intake gasket and loose exhaust nut concerns?

Thank you for all the help.

 

[mikidymac]

Never seen that before and no, on a stock ski nothing needs to be modified.
What they are describing is it loading up with fuel whereas yours is more than likely lean if it hesitates.
What is your in the water idle rpm set at?

If your carb gasket are leaking air it will runaway when you start it out of the water. If isn't doing that they probably aren't the issue but still should never be reused.

 

[95won]

I agree with all of that. Unfortunately I don't know my RPM as my gauge needs replaced. It does idle good though and moves through the water about 3 mph under idle. I guess ill build a pop off gauge this weekend to check that. I used the springs from the rebuild kit and have since learned that I should of used the stock springs. I'll also double check the carbs to make sure it's as clean as I think it is. Besides that I'm running out of ideas. I'm afraid I'll put it back together and be no better off.

 

[95won]

I should also mention I found that my low speed adjusters were 1/4 turn out from stock. I doubt this is the problem but I wanted to mention it.

 

[mikidymac]

I would check your pop off.

You have to use the factory springs in these no questions asked.

The 46i genuine Mikuni kits are supposed to come with the correct springs but I have always reused the factory springs.

The springs are specific to the Seadoo 951.

To verify you have the correct springs they will measure 16.4 mm in length for the 951 95 gram springs.
The wrong 95 gram springs will measure 15.85 mm.

Also when you have the carbs off make sure you get 3 strong jets of cleaner from the 3 small holes in the body of the carb. They will squirt int the venturi. If these are not clear it will also bog at take off.

I would also set the adjustment screws to stock and bump your idle up to 5 mph since you don't have a tach. The tinytachs or TTO tachs are cheap.

 

[95won]

I really appreciate all the help. The kit I bought is the genuine Mikuni 46. It says it came with 95 gram springs. I'm going to pull them out tonight and measure them. I'm sure they're wrong though like you said. If so I'll be ordering new springs. I really appreciate all the help. I'll let you know what I find.

 

[Coastiejoe]

I really appreciate all the help. The kit I bought is the genuine Mikuni 46. It says it came with 95 gram springs. I'm going to pull them out tonight and measure them. I'm sure they're wrong though like you said. If so I'll be ordering new springs. I really appreciate all the help. I'll let you know what I find.

If you have the springs that came out, and they measure properly on the pop-off, they are the best to use. Most replacement springs, OEM or otherwise, are an issue.

 

[95won]

Unfortunately I don't. I'm the complete opposite of a hoarder. Any suggestions on what to do going forward?

 

[Coastiejoe]

This is just one of those items that you don't touch if they are good. Same goes for OEM starters as compared to aftermarket starters. You are MUCH better off buying a used starter and installing brushes and NEVER buy an aftermarket starter.

 

[95won]

Turns out I have the 15.85 mm spring. I also just remembered the rebuild kit didn't come with a new needle and seat. What do I do?

 

[mikidymac]

You will need to get new springs and I strongly suggest you get new needle and seats.
The spring part number is Mikuni 730-03034 Seadoo 270500313

The needle and seats are Mikuni 786-35018-2.0 Seadoo 270500208
[MENTION=41828]Minnetonka4me[/MENTION] here can also hook you up.

You are also need the restrictor jet in the accelerator pump hose if you threw that away and minnetonka has those too.

 

[benjilafouine]

[MENTION=53237]mikidymac[/MENTION] Do you remember my ski in 2015 when the acceleration sucked after the BRP dealer rebuilt it? I ended up buying a new carb in the end and I remember we talked about the dealer taking some springs or needle out of the kit while he had to keep the original ones. Which parts it was?

My ski had acceleration issues after that. I would have to be at full throttle or at very low speed. Nothing in between. So maybe the OP has the wrong parts in his carb rebuild.

Benji.

 

[1of500]

The jet is in a small hose from the carb to the pump

 

[1of500]

This is the jet that gets lost

 

[mikidymac]

Yes 1of500. He threw it away. But he also has the wrong needle arm springs.

Multiple issues.

It would be so much better if Mikuni didn't give us new springs in the kits.

Honestly the accelerator hoses never go bad so nobody should be replacing them.

 

[1of500]

This one had a split had to order tygon hence the zip ties holding the jet

 

[95won]

I appreciate the responses guys. I'm going to call the Sea Doo dealer when they open this morning and hope that they have the springs and needle and seat. If not I guess I'll be ordering them. As far as the jet in the accelerator pump line: I've read multiple threads of people removing them or others that simply don't have them. Is this something that I really need to replace? I wouldn't even bother to ask but my accelerator pump nozzles are squirting fuel like they should.

 

[mikidymac]

Good luck with the dealer, most don't stock any of the 2 stroke stuff anymore.

Yes, you need that jet as it limits the fuel going into the pump, seadoo put it there for a reason.

 

[scortpower]

what did you set the low speed adjuster too? I had similar issues to you which was solved by a carb rebuild and setting the pop off pressure. It ran great on the last trip out apart from a fouled plug which I need to fine tune the carbs as its a little too rich.

 

[mikidymac]

A 2000 RX should have the lows at 1-1/2 turn out and the high at 0.

 

[95won]

Just wanted to update y'all on where I'm at with this. I made a pop-off gauge on Friday, tore the carbs back out and ended up with 24 psi on each carb. This being 1 psi over spec I decided to run with it. I cleaned the carb up again just so I was absolutely certain that isn't the problem. I put it all back together with the new intake gasket, exhaust gasket and the ability to tighten the exhaust pipe nut. I took it out to the lake Sunday and it starts right up and runs great except when I am putting around at real low RPM and then open the throttle up slowly. Based on my understanding of how these carbs work I have two theories, the pop-off psi is too high therefor causing it to starve for fuel until I create enough RPM to open them up, or since I don't have that jet in the accelerator pump inlet line I understand that can cause fuel delivery problems at low RPM as well. I plan to purchase the OEM pop-off springs and new needle/seats and put them in soon, as well as the jet (anybody know the part number for this?), until then i'm very happy with how it turned out and had a blast on Sunday. Thank you all again for all the help, I really appreciate it, hopefully I can return the favor.