I dont know exactly what is going on with my bike. Some days it's fine, others, it runs out of gas to the carbs. It is getting progressively worse/more often. It'll start fine, then seems to run the bowls dry and of course starve for gas and die. I let it sit, as it happens when Im going to work, and by the time I get home to fix it, it works like normal. I took the tank and petcock apart last time it happened and all seemed fine. The spring looked and functioned ok, the rubber diaphram looked fine, the vacume hose from the engine to the petcock looks to be good. Any ideas? I need to get this bitch fixed, season is coming to a close. Thanks in advance for any help guys.

 

Why do you think that the petcock is the issue? I thought that the petcock was for the reserve fuel, unless I'm mistaken. ( still getting familiar with my 99)

 

The petcock controls all fuel flow via a vacume tube connected to the petcock on one end, and the other to the cylinders. If it's shut off, no fuel will flow, if it's on, it still needs vacume to build pressure to move the diaphram so fuel can flow, weather it's in on or reserve. Reserve only pulls fuel from another tube, lower in the tank, but through the same meathod and the same petcock.

 

A few posts in this forum talk about fuel problems for the 900rr. My 98 seems to have a glitch, it will run fine but when hammered on it seems to cut out (like no fuel delivery). It happens at all different times all different gears and sometimes it doesnt happen at all. The only thing at this point I can think to be the problem is similar to another post where the fuel pump leads where shorting out/loose. Check the wires to your fuel pump as well. Let us know!!
Also there are the filters inside the tank you might want to check also.

 

Only the earlier 900s had fuel pumps. The '98 and '99 do not, and perhaps a couple other years. The fuel is just gravity fed.

So you took the petcock assembly apart and everything looked good. So for now, we'll cross that off the list. The fuel tube doesn't look clogged and the inners are fine, right? If that's all good, the first thing that would come to mind would be that the petcock is closing off fuel flow as a result of the vacuum signal. The petcock is opened via vacuum signal from the #3 intake runner below the carb. So I would double check that vacuum tube for cracks and a tight, snug fit on both the petcock and the fitting below the carb. I would also check that the fitting is secure and not loose, therefore able to allow the vacuum signal to leak past. Possibly teflon tape it if you suspect it isn't sealing. Then I would double check the carburetor boots to make sure that they are all secure, primarily #3 in this situation. If the #3 carb is loose, then that could be leaking your vacuum signal rather than it forming suction to keep the petcock open.

That's about all I've got for now, aside from suspecting that there is something wrong with the petcock or fuel lines themselves.

You know you can modify the petcock so that it no longer needs a vacuum signal, right? Just don't forget to turn it off when you get off the bike, though I think the carb floats should seal off the bowls from fuel leaks/overflows. I did this on mine so that my high pressure pump couldn't suck the petcock closed and so that the petcock wouldn't close when under boost instead of the normal vacuum. If you've taken it apart, you can figure out how to modify it. I don't remember the specifics at the moment, but I cut some things off the rubber seal and mainly just kept the seal in place so that the petcock couldn't leak. I think I also moved the plastic piece over onto the other side of the rubber piece, but I don't remember. Take a look, and you can figure it out. It wasn't rocket science.

Good luck.

 

I was thinking on gutting it and doing just as you said. It shouldnt be rocket sceince, agreed. I just wasnt sure if the petcock would actually stop fuel flow from leaking a bit out of the bowls. But as you stated, should be fine. Thanks for your help gentlemen.

 

Sorry didnt know about the fuel pump thing! But now I do and thats why I am here to learn!! Thanks for the advice everyone. One more question though, I ran across a set of flat slide carbs I was thinking of installing on my 98.... any suggestions or bail on the idea??

 

I'm not sure if gutting a petcock is the best thing to do, it still doesn't resolve the initial reason for it's malfunction. I think it's a temporary resolvement like placing a band aid. On the long run, you're letting more then enough gas sit in your carbs when you start the bike. I say test the pressure on the vaccuum tube coming off the Cylinder #3. See if it meets specs. It could be as simple as replacing the vaccuum hose (it's over 7 years old, plenty of Armor All will soften hoses.)

 

True, I started it yesterday to go to work, and it was fine. I left the petcock in the on position from the last time I had it running normal. I have not experienced a problem since leaving it this way. (took it on 4 rides, all starting from a "cold" engine). Perhaps I missed something when I took the petcock apart. All seemed normal, will probably just get a new vacume line, (cheap enough) and a rebuild kit is $32 from my local Honda dealer. That should fix any issues. Thank you for your help guys. I will rebuild it and let you know if anything is ammuck.

 

Well, I found the issue today. It finally happened when I had time to work on it more thouroghly. I looked closer at the diaphram and noticed it was tearing in the center, under the spring and the spring spacer. Apparently it would seal sometimes, and others, not at all. So, a kit is on order. Thanks for the help guys.