VR not running well in 4th and 5th gear

[Guest mtwhitford]

Help, This my first post and question. I have a "02" Venture with 33K miles. It just started running bad and missing in 4th and 5th gear. 1st thru 3rd is fine, but when I go to 4th and pull the throtle back it spit ans spudders like its going to die. I have cleaned and sink'd the carbs, new sparkplugs, replace all fuel.

 

I'm beginning to think it may be in the electrical system since it just started and only in 4th and 5th gear.

 

Any ideas?

[muffinman]

Mark it sounds like you might have water in the carbs Did you get a bad tank of gas?

Does it eventually run better in 4th gear under heavy load?(wide open throttle)

put a can of seafoam in it and run hard till its empty then refuel and ride it to see if its any better.

Jeff

[Rick Haywood]

Man I went through that with mine for a long time and not sure what I did to fix it but I finally got it right. Two things that really helped were. The air box had come off of the top of one of the carbs and I assume was letting in to much air so I put it back on but the biggest thing I had done was had the card Color Tuned. This is were they set the air/fuel ratio on each carb and do it by the color of the combustion in each cylinder. I replaced the fuel filter also which made a difference. When I replaced the fuel filter I rerouted it and put an in-line under the seat so I could replace it more often and without all the hassle of replacing the OEM. Good Luck with it.

 

ps, I also forgot to mention that mine also started to run different just a few days before the ignition switch failed.

[Guest mtwhitford]

The engine is worse under heavy load (full Throttle). Local Yamaha shop doesn't understand it either, calling Yamaha next week.

[djh3]

So will it do it in all gears? Or is it only in 4th and 5th @ about what speed? If its say 45 or so in 4th what if you run it up to say about 50 in third and shift to 4th.

[skydoc_17]

Hey Mark,

I would suspect that the fuel pump is on it's way out. Do you ever have a hard starting issue. In other words, do you have to crank the engine for a while after it has been run and warmed up. The front two cylinders will run up to mid speed due to gravity feed from the gas tank, the back two cylinders will not run without the fuel pump. After you run the new plugs for about a week, pull them and look for the black, sooty, fouled pair, (usually in the back cylinder head) If this is the case, then your fuel pump diaphragm will keep the bike running at idle, but when fuel demand increases under load, (4th and 5th gear) the fuel pump can't keep up. Eventually the pump will fail completely, and the trouble shooting will be much simpler.

Earl

[Guest mtwhitford]

It runs fine in 3rd, when you shift to 4th and pull on the throttle it starts missing and fells like it running out of fuel. Same for 5th

[Guest mtwhitford]

We have check the fuel pump, I suspected it right off figured the bowls were fuel through 3rd gear and the pump count not keep up in 4th and fifth. I think I may try to replace the pump with a used on I have available and see if that is it. Thanks

[LilBeaver]

Hey Mark,

I would suspect that the fuel pump is on it's way out. Do you ever have a hard starting issue. In other words, do you have to crank the engine for a while after it has been run and warmed up. The front two cylinders will run up to mid speed due to gravity feed from the gas tank, the back two cylinders will not run without the fuel pump. After you run the new plugs for about a week, pull them and look for the black, sooty, fouled pair, (usually in the back cylinder head) If this is the case, then your fuel pump diaphragm will keep the bike running at idle, but when fuel demand increases under load, (4th and 5th gear) the fuel pump can't keep up. Eventually the pump will fail completely, and the trouble shooting will be much simpler.

Earl

 

Earl, I am a little confused as to your statement here. I do not understand how our 4 separate carburetors with ONE fuel input and only two fuel level manifolds could actually produce the symptoms you described here. Additionally, if I recall correctly, the two left carbs share a manifold and the two right carbs share the other fuel manifold both of which are nominally the same distance from the input line [one is a little further, but not by much] -- again, I do not understand how our bike's configuration could behave as you described.

I am no expert mechanic and am certainly not trying to rustle any feathers here, I just want to improve my understand and of course anyone else that reads this too [obviously help the O.P. as well].

[LilBeaver]

mtwhitford: Have you tried draining the carbs [via the drains on the float bowls] and looking at the fuel to see how it looks?

 

As others suggest, it sounds like changing out that fuel filter and some fresh gas are a good place to start.

[MikeWa]

Fuel pump & filter. And Or coil #4.

 

Mike

[skydoc_17]

Hey Beave,

Without fuel pump pressure, and the fuel tank above the Carbs. the fuel "dribbles" down the fuel manifolds and is pulled into the front two Carbs. by the engine vacuum, leaving very little for the rear two Carbs. With FULL fuel pump pressure, ALL four Carbs. are supplied with fuel equally. MikeWA has brought up a very good point about the rear coils on these bikes as well. Mark, if you have a good used fuel pump, that would certainly remove any doubt about the fuel delivery system. With that variable removed, you could move on to the coils next.

Earl