Hi everyone,

I need some help. I went to sync my carbs after a ride today (temp today was above freezing!). Previously I installed a hose to the front vacuum port beneath the carb boot so it would be easier to sync the carbs (also installed a T on the rear vacuum port/hose for easier syncing). When I removed the cap from the hose going to the front vacuum port, fuel starting dripping out. Not a lot, maybe 5 ml or so. So I removed the tank and airbox to get a better look at things. I noticed the gasket between the top of the carb and airbox was wet with fuel. There seemed to be some fuel in the airbox, but not much at all. No fuel coming out of the overflow hoses on either carb. The bike seemed to run fine. Pulled the front spark plug and it looked fine, not wet with oil/fuel.

I cleaned and properly jetted the carbs (48, 178/180, shimmed front needle 0.03" and back 0.04", front mixture screw to 2.25 out and rear to 2.5 out. Drilled out previously filled hole on the front slide and replaced the K&N filter with a HiFlo). I set the TPS to 500. Float heights checked. Before installing the carbs I verified the needle valve was working properly and shutting off when the float was raised. I also verified the petcock was working properly. Everything seemed to be in order.

So, I'm stumped. My buddy seemed to think the needle valve was the culprit but admitted he wasn't sure. Any idea what might be causing this?

 

Check the petcock. If it's leaking, the float valves are are also most likely leaking. Check the oil for fuel.

 

Thanks for the reply. I “bench tested” the petcock and it seemed to function properly, but I know they are prone to failure. It might be worth rebuilding it anyway.

When I rebuilt the carbs I used the needle valves that came with the kit but they weren’t the rubber tipped ones. I wonder if they aren’t sealing properly, but I did bench test them as well and they seemed to be working properly.

No evidence of fuel in the oil but I’ll probably swap it out anyway as a precaution.

I feel like I’ve checked the usual culprits but I may have missed something.

 

It can only be one or both of the two fuel delivery points. Failed petcock is somewhat common. If it looks like a duck, quacks like a duck......
Unless there is a proven, reliable, known good replacement after market part, I only use Honda parts.

 

I agree, so it’s time start eliminating possibilities. I ordered the petcock parts 16953–ML0-034 last night. We’ll try that and see what happens. I’ll report back. Thanks!

 

It looks like a needle problem that closes badly, even if you checked it before installation. Maybe a small piece of debris or a worn seat that lets a little gas through. Otherwise, a slightly too high float level could also explain this. Any other opinions?