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  1. #1

    1991 Yamaha WRA650P running bad and bogging down

    Hello everyone, my name is Chris and I am new to this forum stuff but I have been reading a lot of posts for my problem but I still cant figure it out. So I need your expertise and it is greatly appreciated. So, I have a 1991 Yamaha WRA650P Waverunner 3 that is running like garbage and hard to start and just bogs down and has no power. I purchased it form a neighbor that has since moved away who said it ran perfect before we got it. So he converted it to pre-mix and said to always put in a ratio of 50:1 which I have done that. So we decided to take it out to the lake that was 50 miles away only to have it not run right. Also the guy we got it from, he tapped into the fuel lines and put a primer knob that squirts a little gas into the carb to get it to start. I think it is supposed to have a choke but there isnt unless he took it out and replaced it with the primer. But right away in the water, it ran bad. The idling is very rough like its missing or something and it just doesnt sound right. We try to ride it and it will go slowly but at say, 1/2 throttle to full throttle, it bogs down and usually dies and it just seems like there is a rev limiter cause at high throttle, it does the waa waa waa waa waa. Sorry its hard to explain. So I changed the plugs(dark and oil on them), rebuilt the carb(everything looked good and clean and no damage to the rubber gaskets and stuff and the little fuel filter is good), new fuel filter in line. Now I dont know how these carbs with the diaphrams and the fuel pump work so thats new to me. The needle and seat are all good. The inline fuel filter only has a little gas that passes through it when running so Im not sure ho much fuel gets pumped through it but its not very much. I also cleaned the fuel switch, checked the fuel hoses by blowing air through them one at a time. Also, Im confused as to what the 3 hose ports on the carb are for. There are 3, one says pulse,and the other 2 say nothing but I put the lines on as stated in the manual( I have one). That pulse line goes from the cover on the carb into the I believe the crank case engine. Not sure what the pulse means? The only thing I havent done was drain the gas out of the tank and clean that out but the hoses going into the fuel tank are good and clear so no blockages. So I have been trying to fix this issue for weeks now and its frustrating. Hopefully you guys can help me out here and give some suggestions for what to do. Thank you guys, Chris.

  2. #2

    Join Date
    Sep 2013
    Bennettsville, SC
    First thing is to check compression. The pulse line on the carb is the fuel pump fitting that receives the pulse signal from the crankcase. The two other lines should have directional arrows. One is fuel inlet, the other is fuel recirculation back to the tank. If your carb is clean did you set the screws to the factory settings? Ensure they are set correctly. Also, check the fuel tank vent check valve. Your fuel system should hold pressure. Good luck and let us know what you find out....and welcome to the Hulk!

  3. #3
    Hi butterbean, thank you for your reply. Im sorry it has been a while since I've been on here. Have been battling with chemo and everything else that goes with it. Anyways, I want to get back into getting my PWC running so I can enjoy it and have fun. SO I have checked compression, 136psi, and 134psi on cylinders. Both with in spec I believe and from my manual. SO I think Im good there. So I was able to replace all the fuel lines in the whole system, cleaned fuel selector, removed carb and cleaned and checked it over. I found out that there was supposed to be a check valve to the tank which there was none. Previous owner must have removed it. SO I got one for it and installed. Now it will hold pressure to help push fuel to carb. That still didnt help. Nothing has yet. Its weird though, sometimes when I am checking it and idling, all of the sudden, it will start to run great, revs up really high and sounds powerful like the problem was fixed. But then all of the sudden it will go back to bogging down at throttle. It sure does sound like it has a rev limiter or something. So I dont know. I set carb screws to factory and have tired so much to adjust those low and high speed screws and nothing, no change no matter what I adjust. I removed the thermoswitch and then I unplugged it all together from inside the electric box. No change. I have been running it on a garden hose to do these tests. I keep monitoring the temps also. It will idle great, just when you give it throttle, it bogs. And Im trying to understand that when its idling or when I throttle it up during the bogging down, it sounds real loud in the engine and has like knocking sounds sometimes off and on. Not sure if its normal. It does concern me though. Since compression is ok, does that mean the internal engine is ok? Or could there still be a problem? Is there a way to check the pulse line if its working correctly? I replaced the fuel lines with blue so I can see the flow. The flow when running is not great. It usually doesnt fill the clear fuel filter when running. But I dont know how much pressure it actually has. ANd there is a lot of air bubbles in both the lines to the carb. I tried pressurizing the fuel system also thinking it would help get fuel to the carb. It has the check valve so it always has some pressure build up correct? Seems like it should. I even tried bypassing the fuel selector, hooked the tank right to the carb and even tried taking the fuel filter out to try that. Nothing. How can I get all the air out? I read that pouring fuel in the carb to prime and fill the lines? Is that ok? I tried that and it didnt seem to fill the lines. Still lot of air. ANd then after that, it would not start because it seemed so flooded with all that gas in the carb. SO I maybe been doing it wrong. Please help you guys. Very frustrating. Does the waterbox or exhaust need cleaned? Im about to start taking apart the engine and see if I can find anything. Oh, I almost forgot. Could the timing be bad? Kind of seems like timing is off. Oh and when I checked for spark on both plugs, it had spark but it looked weak. Like blue white color. Im sorry this is so long. Thank yoj guys for all the help. Thank you.

  4. #4
    I want to perform a pop off pressure test. But Im not sure if that could b a problem. I dont know much about that. Can it be adjusted or cause the bogging down? I will try and perform that and I will update. Thanks

  5. #5

    Join Date
    Sep 2013
    Bennettsville, SC
    Lots of air bubbles in the fuel lines indicates a fuel leak that becomes a vacuum leak when the engine is running. Try removing the recirculation line from the carb, hold your finger over the carb nipple, and pressurize the fuel system by blowing in it. You have to sort of force as much air into the fuel line/system as you can possibly get. Any leak should be evident, by either hearing air, or seeing a fuel leak. I had this problem a few days ago on my wife's wave venture. It was a fuel/air leak on the outlet nipple of the fuel switch. A fuel/air leak will create a severe bog, especially when throttling up from idle.

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