94 Yamaha Wave Raider 700 problem

[flowmasterman]

Hey all, got a problem on this thing I can't figure out? A friend of mine just bought this over the weekend, took it to the lake, wouldn't hardly run, so determined it was a fouled plug, we put a new set of plugs in it, and it ran great like it supposed to for about 45 minutes or so, then it started acting up again, tried changing the plugs again, and no luck this time. What it is doing is when you try to go anything over 1/4 throttle it bogs down, but it sounds almost identical so like it would sound when the rev limiter kicks in? I don't understand what is going on, because like I said after changing the plugs the initial time it ran great. Even right now you can breathe on the start button and it fires right up, idles, but anything over 1/4 throttle and it sounds like the rev limiter is on. Anyone have any ideas on where to start? I have pulled the plugs and verified they are both getting fire, it even does the same thing on the trailer out of the water, can breathe on the start button, when get over 1/4 throttle and it like it hits the rev limiter.

 

[flowmasterman]

Any ideas guys?

 

[Dennis]

Sounds like the overheat sensor is triggering the rev limiter. The sensor is mounted on the cylinder head towards the front. Is the engine overheating? If not then I would disconnect the sensor connector inside the electrical box and see if it's OK then. If OK then replace sensor.

 

[flowmasterman]

Ok that makes sense, I will try that and see what happens, definitely sounds like it could be that, because you can tell it is limited revving, not just a miss or stumble or something. Am I going to have to undo that box from the rear of she ski or does it plug in somewhere else I hope, looks like a pain in the butt.

 

[Dennis]

It's a pain. The connection is inside the box. It's a 2 wire sensor. You could just cut 1 of the wires of the sensor outside of the box to see if that is the problem. Use a razor to strip back some of the insulation that is around both wires.

 

[flowmasterman]

Well I went ahead and unplugged the wires from the box, and started it up and it is doing the same thing? I also checked compression and was 140 on both cylinders. Anything else that could trigger the rev limiter?

 

[Dennis]

No, that's it. Next I would remove the air box on top of the carbs. Crank engine (with plug wires disconnected) and see if you feel air being pushed back up thru the carbs. if so then you have bad reeds. Post results.

 

[flowmasterman]

Any ideas why it ran so good then started doing that all of a sudden though? Would having bad reeds only affect the engine at higher speeds or all speeds? Because like even right now I can go outside when the motor is cold and just breathe on the start button and it starts. I will do that test and see what I can find out, should I be putting my hands over the carbs or just close to them to try and feel for air?

 

[Dennis]

Just put your hand close to the carbs. If it seems OK then I would start the ski and watch the carbs when I reved it. Look for air/fuel blowing back up. Don't stare down into the carbs in case of a backfire. Bad reeds can effect all RPM's.

 

[flowmasterman]

If that test checks out ok, where should I go from there?

 

[Dennis]

Would help if you could post a video of what it's doing. I sent you a P.M.

 

[flowmasterman]

Ok I am at work right now, is that a cell #? And I will send a video of it when I have time tomorrow before work maybe.

 

[Dennis]

Yea, my cell.

 

[flowmasterman]

pretty much all I can do a video of is starting it up, and then give it gas, and it just revs so high and sounds like it hitting off the rev limiter, but does the same thing in the water. I wi.lll try and send one tomorrow