1996 Yamaha waveventure 700

[Josumrall]

I recently purchased a 96 waveventure 700. I have been having an issue with it where I have to choke the carbs to prevent it from bogging and dying out. I went through the carbs and rebuilt with genuine mikuni parts. I verified the pop off pressure is lowest possible with 32 psi for both carbs. It seems to idle fine however won’t rev over 1/4 throttle without the choke. Would it be correct for me to assume that it’s a fuel quantity issue making it run lean?
When I was rebuilding the cards I did notice that the red coating was worn off one of the diaphragms while the other carb’s diaphragm looked new. Could my issue be related to the lever height adjustment? If so, how do I properly adjust the lever to stock specs?

 

[orangefinger]

Fuel delivery

Same symptoms before you rebuilt carbs ?
> Yes > then I would be looking at , gas cap and gas cap seal, tank vent and fuel selector switch, fuel filter old / clogged
> No > then I would look at high and low setting ,start at 1.25 each u cant really go wrong with that, pop off seems high but i would have to verify oem pop off,
diaphragms in correctly ?

 

[bored&stroked]

Why do you want the lowest pop off pressure possible?

 

[Myself]

I went through the carbs and rebuilt with genuine mikuni parts. won’t rev over 1/4 throttle without the choke.

If they were genuine Mikuni kits it should be running correctly at stock or slightly richer carb settings.

If they were NOT Mikuni kits this symptom often occurs.

 

[WFO Speedracer]

Yor best bet is to hook a supply line directly from the reserve tank pickup to the carb, bypass everything , if it still acts the same it's in the carbs if not start adding stuff like the fuel filter and the petcock back into the mix till it acts up again.

Those fuel filers get old and crusty inside , always a good idea to replace them when doing carb work , the rubber piece inside the petcock gets messed up over the years alse , ethanol is not nearly as nice to those components as regular non ethanol fuels , I have also seen stuff in the pickup lines before , it might be worth it to pull the pickups and have a look.

One more tidbit Yamaha in their infinite wisdom ran the hose from the one way valve all the way to the back of the ski at the front of the rear seat, I have seen a few where that plastic piece was crushed or mangled not allowing proper tank ventilation, I have also seen damaged hoses that's a long way to run a fuel tank vent , I usually cut the hose and run it up under the cowling in the front somewhere.

 

[Josumrall]

Yes I would say it’s running slightly worse than compared to when I got it.
I have already bypassed the reserve switch, installed new clear fuel lines, installed new fuel filter and rebuilt with genuine mikuni kit.
I’m wondering if for some reason when I’m choking it, that is allowing it to create a stronger vacuum to overcome the pop off pressure resistance allowing it to run better.
I also realized last night that with the oil bypass, the feed holes in the carb intake were not plugged, would that leak in the intake be enough to cause an issue? Also is the needle lever supposed to be flush with the carb body?

 

[WFO Speedracer]

Yes the lever is flush with the carb body, I would say given the location of the oil feed holes the difference would be negligible , but try this next , locate the low speed screws, if the limiter caps are still on them pull them off , then turn them out about 1 1/2 turns from where they are right now, run it and report back , you will most likely have to turn the idle speed screw up some as well to get it to idle properly.

 

[Josumrall]

I worked on some more today. Yesterday while at the launch I was adjusting the low speed screw and checked it today and it was out about 1-3/4 turns, manual says 5/8 which is where I started at.
I broke the carbs back down tonight and from what I can tell it may still have original needle and seat with the exception of one needle. Could a leaky needle and seat cause issues similar to what I’m experiencing? When I rebuilt the carbs (with exception of needle/seat and spring/lever) the pop off was 32psi, tonight I put springs in from the rebuild kit and it lowered it to 23psi.

 

[WFO Speedracer]

A leaky needle and seat would make it run rich, not lean , if you are running stock flame arrestors there is no reason to lower the popoff .

 

[Myself]

Get your popoff back up to 45-60 on that Yamaha........that's where it would have been........which means somebody has been into them before.

Did you replace the anti siphon flapper on the backside of the jet covers?

 

[WFO Speedracer]

Get your popoff back up to 45-60 on that Yamaha........that's where it would have been........which means somebody has been into them before.

Did you replace the anti siphon flapper on the backside of the jet covers?

I didn't think of that , it will still run with those missing or damaged but it is a total dud till it get enough RPMs to get on the main jet.

Also check the reeds, bad or damaged reed valves will also cause serious running issues.
Easy check on the reeds, remove the flame arrestor cover, hold your hand over the top of the carbs about an inch away , if you feel any pressure coming back up through the carbs the reeds are toast.

 

[Josumrall]

I didn’t replace the flaps yet, reason being the person that was in it before me stripped out the screw for them and upon inspection it seamed to be laying flat with no creases and no cracks.

 

[Myself]

OK, I don't want to sound like an ass here but since you didn't replace those OR needles you did not "rebuild" the carbs.

See if you can take me a short, up close video of you using a paperclip or similar to push open and close the flapper.

 

[Josumrall]

Okay, understand now that I talk through it. I should have specified I replaced all carbs diaphragms, seals/gaskets, filters and verified the none of the jets were clogged. I did verify there was some resistance when pushing on the flaps yesterday, but I should be able to attach a short video this evening of that as well.
When testing the pop off the needle/seat did seal long enough to build pressure for the initial pop and every time after if I refilled it with WD40 and reapplied air pressure it would pop. But I feel that test might not be accurate in real world scenario when I would assume pressure on the seat is never completely void to allow it to reseat.

 

[Myself]

Many people worry way too much about popoff pressures. Most of these things will run fine anywhere from 25-65psi popoff. Maybe not as snappy out of the hole as it COULD be, but definately still everyday rideable. The real thing to look for doing a popoff is that there is no bubbling around the seat o'ring, OR leaking out from some other carb body gasket.

I feel like your issue is in that flapper. Get me a vid.

 

[bored&stroked]

I still wanna know why your attempting the lowest possible popoff? Aftermarket flame arrestors?

 

[Josumrall]

No, its utilizing stock flame arrestors, I was just leaning towards pop off due to the fact that the bogging issue gets better when the carbs are slightly choked thinking that’s creating a stronger vacuum to overcome the pop off pressure.
I’ll get a video of the flappers this evening. Also when doing the pop off test, when the first initial pop off occurred and there was still some residual wd40 left and air pressure was still applied I could see some bubbles around the needle. I wasn’t sure if that’s normal occurrence when the pressure was still constantly being applied with no small/minor drop in the air pressure.

 

[Myself]

Yes, bubbles are normal right after a pop and air pressure still applied.

 

[Josumrall]

Here is a video of the check valve flapper

Check valve

 

[WFO Speedracer]

It doesn't look like it ever fully closes to me , just saying