High revs, fuel issue - riva powerbomb, xs900rr

[doitfordale3]

Picked up my first freestyle ski this summer for a great price. Figured id be running into some issues with it though and sure enough they have began. First was a hole in the fuel tank, had that welded back up really nice and remounted so it doesn't happen again. After that I took it back out and the ski was still running rough. Like lugging hard anytime i touched the throttle. I made it back to the ramp and got it in the garage. Initially it didn't want to fire on the stand. I poured a little fuel in the carbs and got it running but it was revving quite high. Looking at the intake side I noticed a lot of gasket maker was used - thought maybe I had an air leak so I pulled the intake off. The first thing I found was the pulse nipple on the cases for my front carb had busted. It had previously been JB-Welded. I cleaned it up and applied some new JB-Weld - not ideal fix but it is still holding. I also found an odd combination of intake parts. X Scream intake manifold, a spacer, boysen reeds and the only paper gaskets were between the carb and speed plate. I want to have proper gaskets for all this right?

I had some concern with this manifold. The "ears" of the reed blocks (where the screws go) sat partially on the manifolds o rings. I figured this could be where my air leak was coming from. I emailed x scream and they agreed I wouldn't have a good seal with this setup. Onto of that, the thread holes for the reeds weren't even square on the manifold. I later found out that without the spacer, the reeds wont even fit in the cases due to the misalignment. My reeds are in great shape though so given all the concern I had with this manifold, I ordered a push ind. manifold that aligns and seals nicely with the boysen reeds.

After reassembling everything with new gaskets I dumped a little fuel in the carbs and fired it up and it still revved high. This time i noticed the inline fuel filter that goes to my front carb had no fuel in it. I pulled all the fuel lines going to that carb and blew them out with air. Checked the fuel pickup and it looks like its in good shape (sits about an inch above the bottom of the fuel tank). I pulled the carbs apart and everything looked pretty good to me. Im not an expert on these fuel pump carbs though so maybe i missed something. I connected the pulse line from this carb to the rear pulse fitting and cranked with plugs out and still no fuel. Ive checked idle, t-handles, Im thinking it would have to be a fuel pump issue at this point but looking for any other ideas. Ive had so much fun riding this ski but have found i have lots to learn!

 

[wiikstromm]

Make a proper rebuild of the carbs.

Total loss or charging system?

 

[doitfordale3]

Make a proper rebuild of the carbs.

Total loss or charging system?

Zeeltronic 760 ignition. Thanks tho I will start with carb rebuild

 

[DylanS]

After reassembly there is almost always pockets of air in the fuel system and this leads to the “high revving” on startup you’re talking about. It takes a little to fill that fuel filter as well. Not sure if you tried but putting your hands over one carb at a time and cranking the ski will help pull fuel into the system faster. On initial startup after removing fuel lines you may find it beneficial to back the idle adjustment all the way out until the throttle plates are closed entirely. Next use your hands to “prime” the carbs and use very small amounts of throttle to keep her running while the air bubbles sort out of the lines and system.
I would be curious to see how it behaves on the water again before we went diagnosing an unsolved issue that you may have already solved.
As mentioned above a good genuine rebuild kit for your carbs is an excellent start and never hurts.
As far as gaskets go you can shoot a message to @SUPERJET-113 and he will hook you up with some top quality stuff.

Post some pics of your setup when you get a chance.

 

[fastgtfairlane]

its always a good idea to prime the engine before first start up especially if the carbs have no fuel in them. hold your hand over each carb and crank the engine over while pressing the stop button so the engine wont start. do that for both carbs before trying to start for the first time. if you still have a high idle then you could have an air leak somewhere. give it 30-45 seconds to idle back down. do not attempt to rev the engine at that time, let it idle back down first.

 

[Pro-pulsion]

Try to get any play out of your throttle shaft before you go too crazy. It's the easiest thing to check, needs no disassembly and will tell you if you need a pair of throttle shaft rebuild kits. Most likely your air leak is coming from there, it's a very common wear item that well used carbs experience. The only catch is when they're aftermarket carbs like Novi or whatever, you can't buy original Mikuni throttle shaft kits because they don't make the butterflies larger than what comes in the original SBN46 carbs and the angles the butterflies are cut at to seal to the carb body is very specific to the aftermarket brand and modifications they did to the carbs. There shouldn't be any real play in the shafts, if there is the butterflies are worn out and most definitely the bushings are too. That's where your high rev issue will most likely be because unmetered air is getting into the carb passing through the air space left by the worn out bushings and/or butterflies. If you look down the carbs, look at the outer edge of the butterflies where they meet the shafts and look for little square indentations in the butterflies, try to move the shafts sideways and see if there is play there as well, you want to know if when you push left or right, does it move, how much, can you see an air gap open at the edge of the butterflies when you try this. If they're worn as mentioned with that little squaring off then you'll never tune that high idle out of it until you replace the shaft kits. Hopefully they still make replacement kits for those particular carbs, I encountered this issue too many times on obsoleted models or in the case of Novi, I don't think he's even in existence anymore and had to junk the carbs, the owners never like hearing that their once awesome carbs are spent and they don't make the rebuild parts for them anymore. They usually know that means either big bucks to replace them with new carbs or accept going with SBN46's and have a lifetime of replaceable parts support. Personally for me and just being a rec rider wave junkie, I'll stick with the original SBN46's