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  1. #1

    1991 Waverunner WRA650P Bogging Down!! HELP!

    Hey guys! Please forgive me for the length of this post. I have been down and out battling these chemo treatments and being sick so I haven't had time to work on the ski but I want to get back to it. This forum has been so much help. So thank you for help. I have a 1991 Yamaha Waverunner III WRA650P ski. We purchased it from a neighbor that was a very good small engine mechanic and was very knowledgeable with this ski. Unfortunately he has since moved away. When we bought it, he had it set up to start on the garden hose which he taught me. So I have always followed the rule of 15 with out water. And also with the water on, I always start first, then turn water on, then turn water off then ski off. So Im good there. But I have had trouble with it. Took it to the lake, it starts right up but when throttle is pressed, it immediately bogs down. I have spent hours researching this and A LOT people have this problem but the fix is never clear at least for me. I have tried everything. Replaced all fuel lines, gas tank removed and old gas out, cleaned fuel selector valve. New fuel filter. It is very strange. When at the lake, it was having the problem so I was trying to tune the carb and tried it. There was a couple of times where the ski ran excellent, didnt bog at all, was very fast. But it only lasted for a few minutes and then back to bogging down. It acts as though there is a rev limiter on this thing. But theres not. I have adjusted the mixture screws to factory and played with them to see if it helped. Nothing. Unplugged the thermoswitch from the head and also tried unplugging it in the CDI box. No change. I did notice it didn't have a check valve in the lines so I put one in that only allowed air into the tank and nothing oput. It builds pressure fine. It is premix, sorry I forgot to mention that. But it is converted over to premix. I have also removed the carb and took it all apart and cleaned and checked everything. I dont know a whole lot about a carb but no tears in gaskets. The clear plastic was not flat, it was indented from the carb the shape of it, the thin rubber was formed from the carb. Not sure if everything is supposed to be flat but it all looked ok to me. My next thing is getting a rebuild kit for it. But I dont know what size needle and seat or if I need new jets. I was finally able to do the pop off pressure test and it didn't go too well. It seemed to take a lot of pressure to pop it but it would not hold barely any pressure due to a leak. But when I kept pumping my pump for air pressure, I did it pretty fast ansd it was somewhat over 30psi. SO I decided to put it in my bath tub under water to find the leak because I thought it was my bike pump. But it wasn't, that was all sealed great. But, it did have bad leaks on the fuel pump side. Air bubbles coming out of the gaskets and stuff on that side. Im hoping this is my problem and I just need to rebuild the carb. I will be ordering it tomorrow but I dont know what one I need. Do I need a new needle and seat also? Or just the kit. And would it come with those little clear plastic check valve things and all gaskets? I dont see those little clear plastic round things in the rebuild kit. DO those wear out also? SO I will post back with the results of my carb rebuild. But during that time, any help is greatly appreciated. I want to get bcak to fixing this and having fun with it. I havent been able to do much battling these chemo treatments and stuff. Thanks guys. Oh and one last thing. I have been running the ski on the garden hose that is connected to the bottom of the head and piston area. It also has another garden hose hook up farther underneath that one that is connected with a tee fitting that runs from the bottom of the engine area and it runs to the back of the ski. Not sure if I should be using one, or which one, or both running it on a hose? I will post pics. Thank you guys so much. I will try and add a few pics into my account or somewhere for everyone mto check out. Thanks. SO the pic is of the garden hose connection. The blue hose that is the light green line I made, is the hose Im hooking my garden hose to. Is that correct? The placxe where I circled red, was the place I was thinking that is where I hook a garden hose to. SO Im not sure. And also, I took another pic of the other garden hose hook up. The red hose is for a garden hose also? It goes to a tee fitting that one end goes to the back of the ski where the exhaust is. Not sure if I need to be running water in that hose also. Maybe a dual Y hose setup? ANd I also uploaded other pics of my carb and the diaphragm and gaskets that are mis shaped or whatever. Thanks guys.
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  2. #2
    Here are other pics
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  3. #3
    quadzilla's Avatar
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    Hey there Stretch,

    First things first..
    - sorry to hear about your health issues.

    It's good you have a little distraction with this ski project..

    OK Then:.
    When you order the carb rebuild kit,
    - DON'T scrimp on the few bucks extra that a proper Mikuni kit costs.
    - (can't stress this highly enough There's probably a thousand posts on here alone where people have bought a cheaper kit only to regret it)
    - Take a few images of the actual carb body so we can identify exactly what you have there..
    - from your images the carb components are tired out. (gaskets that is)

    As for the needle and seat.
    - Yeah it's fairly certain the needle will be fubar'd.! (after 24 years. )
    - I'm not 100% on what size seat goes in the 650 though it'll either be a 1.5 or a 1.2.

    Now then.
    - the running on the hose thing.. That is fine but just not for too long.
    - (the pump bearings can overheat if the ski is operated out of the water too long. NO cooling water is supplied to them. there is some back-flow from the flush line into the pump, but it's limited to say the least.!)

    Get some more images posted up of where these two flush lines are being tied into.?
    - (you shouldn't need two lines, not on a 650 anyway)
    - Seems unusual someone would add another line.??

    We'll get you going with this for sure..
    - It might be a good idea to do a quick compression test while you're in about the motor/carb.
    - Just to confirm the motor's soundness.!

    Other than that get well soon.

    .

  4. #4
    Hey quadzilla, thank you for the help and quick reply. Appreciate it very much. And yeah for sure I am trying to distract myself with this little project. I try and keep all those thoughts out of my mind. So I took some more pics of the carb body and that other line I cant figure out. That red hose goes straight down to a connection that has a small clamp like right under neath the engine. Then it tee's off down and through the ski to the back to where it dumps the water on the impeller I think. Maybe he could have put another line on it to run both hoses connected to a garden hose maybe to keep the impeller cool also? I dont know. But I did a compression test and one cylinder was 136psi, and the other is 138psi. SO I think thats good? And for sure I will buy a good Mikuni kit. No aftermarket for me! But here are some other pics and if you need me to take anymore or whatever, I can. Thanks again for your quick reply. Have a good night. ThanksClick image for larger version. 

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  5. #5
    I also wanted to add that when I do the pop off test, it doesnt really hold pressure and its leaking all the air out of all the gaskets and rubber parts on the fuel pump side. Just leaks it out the gaskets where the pump assembly bolts to the carb. ANd also the needle really doesnt hold pressure either. I will be doing a carb rebuild kit soon. Thanks

  6. #6
    quadzilla's Avatar
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    Quote Originally Posted by stretchallen25 View Post
    I also wanted to add that when I do the pop off test, it doesnt really hold pressure and its leaking all the air out of all the gaskets and rubber parts on the fuel pump side. Just leaks it out the gaskets where the pump assembly bolts to the carb. ANd also the needle really doesnt hold pressure either. I will be doing a carb rebuild kit soon. Thanks
    Hey again Stretch..

    Ok then from what you say, It would seem that the carb is long long overdue that overhaul..

    From the images it would appear to be an early SBN44
    - The good news is it looks to be in fairly good condition.

    You should download a copy of the Mikuni service manual if you don't have it already.
    Here:. http://www.mikuni.com/pdf/sbn_manual.pdf
    - Some good advice and guidance in it..

    From your earlier post.
    - The compression seems to be good and even which is also good news. (it may be a touch low.? I'm not 100% on what the 650 motor should read, could just be your gauge.?)

    I'll have a study of your images and try to figure out the second flush/cooling line.?
    - Maybe get you to take a few more images.?

    For now pop the needle and seat out..
    - see what size is stamped on the seat and get one of those on your shopping list (again don't scrimp the couple of bucks by not getting OEM)
    - The carb rebuild kit comes with a couple of new springs so the correct one should be in there..?
    We'll get this sucker up and running right in no time at all..

    Might be an idea to slightly modify your original post as it's a little hard on the eyes.. (as in Dammmmn hard)
    - Pretty certain some of the other guys will chip in some advice soon..

  7. #7
    butterbean_29512's Avatar
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    With the flush fitting, it is probably an add on. Yamaha used a PITA push in type years ago that always leaked, sprayed water, and always lost the o ring. But you can flush from either connection. And quad is right, that carb is in good shape. Don't skimp on cheap parts. Also, you can change over the 8 outside screws to SS capscrews. It's a nice little upgrade.

  8. #8
    Oh ok, thats what I kind of was thinking. It looked like it was tied in together where they join together in the engine. Thanks for that. And for sure I wont skimp on cheap ass crap, thats one thing I learned scouring these forums. I will for sure get a genuine Mikuni kit. I just need to figure out what size needle and seat to get. I will be taking my carb apart and get those out and try and find the size on the seat. Quad said it should be stamped on it somewhere. As for jets, will mine be ok still? Do they wear out? Can I get better ones to run better? Cause the ski is all stock. The only thing it has is a K/N air filter. Just mainly ride it with the family for fun. Thanks guys for the help!

  9. #9
    Hey quad, I just noticed your post reply, lol. I only noticed butterbeans up there. Sorry, lol. And your definitely right about how hard my post is on thee eyes! Sorry guys. Wont happen again, lol. Haha, you guys are great though. Appreciate all the help. But anyways I will get that carb pulled off today and check for that stamped size and add it on the list. Yeah I thought the carb guts were very worn also. They look way tired like you said. So until I get that done, its pretty difficult to test and tune. So that will be done today hopefully. I have to call this place here in town to see if he has or can get one. Might have to order it from Amazon. We'll see. I will let you guys know. And sorry Quad for the pics of the other flush line. I will get my camera down in there and get you a few other good pics and post them. I'll get back at it and post my next findings. Thanks guys.

  10. #10
    Oh and I took the water box out and was going to take apart to clean but like you said, I didnt do it. It looks like its all sealed a d glued shut so I wasnt going to mess with it. And I will do some more research on my compression and according to my manual the spec is 134psi for my WRA650. So I thinks its spot on? Oh and I couldnt find the grease zerk on the bearing? Not sure where it is. I removed the plastic gaurd also. I just looked in the manual and it doesnt show any grease zerks?

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