Yamaha 1200 year 2004 triple carb. D plate installed. Jet ski on acceleration bogs down. After it clears up when you pull the triger a few times it runs fine. Soon as you slow down to idle, the same problem. Bogs down sometimes it stops. Spark plugs coming out blackish but not fouled. Eliminated D plate chip, reconnected exhause sensor, still the same chip or no chip. I believe my carbs need rebuilding. Advise
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Only of you have ran the engine out of oil...Sounds like the carbs may not be set correctly.. .Did a professional do the rebuild?..What exactly was "rebuilt".. were any parts replaced?
Sounds like the low speed (pilot jets/air screw passages may not be clean as they need to be??)
Please check the compression on each cylinder..remove the spark plugs... hold the throttle (carbs) wide open when you check this.. spin the motor for 5-8 seconds... you should get 120psi. minimum..(and less than 10psi difference).. if less, it might be time to actually rebuild the top end..(new pistons/rings/hone cyl.).. only bore it if absolutely necessary.. get it measured..
There are only 3 parts in a two-cycle carb that ever need to be replaced,,(unless they are actually broken) The needle and seat assy., the jet needle and the needle jet. ..see pic... parts # 41 = needle and seat assy. #6 = jet needle, #37 = needle jet.
The needle and seat regulate the flow of gas into the carb as the floats rise and fall..,, if they are damaged or leaking the carb will overflow with gas., the needle jet is a orifice with a specific size..The jet needle has a specific size, taper, and length..== The jet needle and needle jet work in unison to regulate the flow of gas from right off idle all the way to WFO..the needle jet/jet needle WILL wear over time causing the fuel/air mixture to become richer and richer and start fouling spark plugs..(this is more pronounced on 4-cycle ATV's)...
I hope this has shed some light on your carb situation...
exploded view of mikuni carb Google Search
there are no gears just a direct drive from the crank to a jet pump ! if theres no propultion of water it could be several things !
1. plastic bag etc in the intake to impellor pump assy !
2. impellor gap to housing too much ie worn impellor !
3. impellor not turning because splines on either the shaft or impellor worn !
4. drive coupler damaged and spinning on shaft !
Try running on a hose pipe and look at rear of engine ( remove plastic cover so you can see the 2part coupler and drive shaft ) .
Check the impellor assy !
Hi, Anonymous it should be noted that your performance issues are not electrical ie. faulty charging system, battery condition, and connections etc. If your fuel system (gas tank, filters, fuel valve and carburetor) is contaminated with ethanol sludge, varnish, rust, dirt, water etc. or your bike has been sitting for months or years without running these components must be "PROPERLY" cleaned and reassembled "CORRECTLY" before any adjustments can be made. Tuning your carburetor is fairly simple once you understand the basic principals. You engine is a simple airbox sucking air in and blowing it out, it is finely tuned at the factory for maximum performance once you upset that delicate balance by changing air filters, camshafts or exhaust systems your performance may go down the and the engine may run poorly, you need to compensate the air-fuel mixture in the carburetor in order for the engine to run smoothly and at peak performance. If you are running multi carburetors you need to sync them first and make sure your air cleaner element is clean and dry for paper elements or lightly oiled for foam and meshed elements and properly installed. Here is how and where you compensate trouble: "TIP" if your engine "BOGS" your not getting enough fuel.
1. Closed to 1/8 throttle is managed by the air screw and pilot/slow jet.
2. 1/8 to 1/4 throttle is managed by the air-screw, pilot/slow jet, and throttle slide.
3. 1/4 to 1/2 throttle is managed by the throttle slide and jet needle.
4. 1/2 to 3/4 throttle is managed by the jet needle, needle jet, main jet, and air jet.
5. 3/4 to wide open throttle is managed by the main jet and air jet.
6. Wide open throttle is managed by the main jet.
If you are running lean, spark plug electrode color is white, engine runs hot and feels like it is starving for fuel you need to go up on the jet size or move the c-clip down one notch. If you are running rich, spark plug color is black or dark gray, engine runs cool, and bogs down when accelerating you need to go down on jet size or move the c-clip up one notch. When your carburetor is properly tuned for maximum performance your spark plug electrode will be a light tan color like coffee with cream. If you prefer fuel economy over performance you can go down on main jet sizes until a satisfactory level of lower performance is acceptable versus MPH, your spark plug color will be whiter and your engine will run warmer. These tuning adjustments will only make improvements if your intake and exhaust system have no air leaks or sealing issues and the entire electrical system is in proper working order and you have no mechanical issues. For more information about your issue and valuable "FREE" downloads that you will need please click on the websites below. Good luck and have nice a day. How To 4 Stroke MX Fuel Screw Adjustment YZF CRF KXF RMZ FCR Part 1 of 2 Easy Carb Tuning Installing Fuel Screw YAMAHA YZ250F Owner Service Manual OEM parts for Yamaha http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals
I had a similar experience with that model. It turned out to be a mouse nest in the water box. However , in this case i think you just have some moisture corrosion on the rubber tipped needle in the carburetor. Clean that part of the carb and do not alter the tiny spring in any way. If that does not work open the electronics box, if it is wet , dry it out , and seal it back up. Those are the three things I know of that will cause your problem. Start with the carb.
Our 1996 waverunner has been running great until this weekend. It seems to bog down after 3 minutes of running at full speed. If you keep it at 3/4 speed no problem, it runs steady. Tried carb cleaner but it still runs the same....What repairs are we looking at. thanks.....