I've got a 95 900RR I'm having a weird issue with. It runs fine when I first start it up and let it warm up. Once I throw a leg over it, it runs great for the first quarter mile or so then the power starts to go away a little at a time, it begins to miss, then it misses worse until ultimately its stops running altogether. The feeling is that of loosing a cylinder at a time until towards the end it feels like I am only on one, then it cuts out. If I sit for about ten minutes I can then start it back up but it feels like its only two cylinders, then the cycle repeats.

I have de-varnished the carbs, replaced the coils (at first I thought it was a coil overheating problem), replaced the plugs and wires, replaced the rectifier (needed to be done, I had a burnt terminal), tested that the stator resistance is correct, and checked that the tank breather is not clogged. Im getting 14v at the battery when the bike is running.

It should be noted that I have bypassed the fuel pump because it stopped pumping altogether. The condition still happens on a full tank of gas.

Any advice would be great. This has been one thing after another for the past three months and I'm to the point of throwing it on down the road.

 

Have you checked to see that the fuel tank is venting? If the vents are clogged then the gas tank will slowly create vacuum within the fuel tank as the fuel is pulled out of your tank. At a certain point that vacuum would technically start to make it hard for the fuel to be pulled and this is especially worrisome if you have a gravity system with no pump. The two vent lines can probably be checked by blowing air through them and see if you here the air going into the tank. Or ride carefully without leaning your bike hard with the gas cap on loosely. This will allow full air flow and if you have no problem then you have found your issue.

 

Checked that over the weekend and it seems fine. I can blow air into the tank through the vent tube. The tank seems to pressurize then blows the air back at me through the tube. Also tried taking it for a spin with the cap open just to be sure.

I'm wondering if the gravity feed setup just isn't sufficient to keep the bowls from drying out. Given what I have replaced in the electrical system is there even a possibility that it could still be related to that?

I'm thinking that I have a bad fuel cut relay and that is why my pump stopped working. I'm going to get another one of those an take the fuel pump issue out of play entirely. After that, I'm completely out of ideas.

 

by passing the fuel pump sounds to me almost like you are flooding the system... TRY REPLACING YOUR FUEL PUMP RELAY ($100) AND SEE IF THAT HELPS TO GET YOUR FUEL PUMP WORKING AGAIN. If your drowning the bike in gas it will bog down until it completelly dies just as you've explaned. it can only burn so much fuel at a time even if it wide open.

 

Logically wouldn't it flood out while idling too if that were the case? I tend to think that if this is a fuel issue it would be more of a starved condition, but either way it points to having the fuel pump back in the circuit. BTW it feels more like a starved condition than a bogging condition when it starts to go away, if that means anything.

Ron Ayers has the cut relay for $50.

 

you can't really flood a system that has floats. They are made to cut fuel to the bowls when the level gets to a certain height and maintain that level. Also, are you sure that your choke isn't sticking, cause that would cause the issues your having as the bike warmed up. Even if the pull **** looks good check to see if the mechanism at the carbs is returning all the way.

 

Got my answer from fireblades.org. It was leaning out because when applying the throttle the filter was not letting enough fuel through it (when gravity feeding) to keep the float bowls from drying up. That is why it would start right back up after sitting for a bit.

I am ordering a fuel cut relay (it tested bad) from Ron Ayers tonight and I will put it on this weekend. I get to ride to work tomorrow! I've been waiting for that early morning blast of fresh air for several months now.

Thanks all for your efforts!